diff --git a/docs/userguide/database/hdfDB.ipynb b/docs/userguide/database/hdfDB.ipynb
index 32919288..96f64cb5 100644
--- a/docs/userguide/database/hdfDB.ipynb
+++ b/docs/userguide/database/hdfDB.ipynb
@@ -285,25 +285,25 @@
        "\n",
        "              <ul style=\"list-style-type: none;\" class=\"h5grp-sections\">\n",
        "                    <li>\n",
-       "                        <input id=\"group-ds--5251189200\" type=\"checkbox\" checked>\n",
-       "                        <label style=\"font-weight: bold\" for=\"group-ds--5251189200\">\n",
+       "                        <input id=\"group-ds--5384869700\" type=\"checkbox\" checked>\n",
+       "                        <label style=\"font-weight: bold\" for=\"group-ds--5384869700\">\n",
        "                        /<span>(5)</span></label>\n",
        "                  \n",
        "\n",
-       "                    <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">check_value : 0</li><li style=\"list-style-type: none; font-style: italic\">contact : {\"name\": \"John Doe\", \"surname\": \"Doe\"}</li><li style=\"list-style-type: none; font-style: italic\">project : tutorial</li><li style=\"list-style-type: none; font-style: italic\">timestamp : 2024-03-26T19:31:57.586959</li>\n",
+       "                    <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">check_value : 0</li><li style=\"list-style-type: none; font-style: italic\">contact : {\"name\": \"John Doe\", \"surname\": \"Doe\"}</li><li style=\"list-style-type: none; font-style: italic\">project : tutorial</li><li style=\"list-style-type: none; font-style: italic\">timestamp : 2024-04-09T10:23:20.161563</li>\n",
        "                    </ul>\n",
        "\n",
-       "                <ul id=\"ds-1-/pressure1-5253617600\" class=\"h5tb-var-list\">\n",
-       "                    <input id=\"ds-2-/pressure1-5253620300\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
-       "                    <label class='h5tb-varname' for=\"ds-2-/pressure1-5253620300\">pressure1</label>\n",
+       "                <ul id=\"ds-1-/pressure1-5387799700\" class=\"h5tb-var-list\">\n",
+       "                    <input id=\"ds-2-/pressure1-5387802300\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
+       "                    <label class='h5tb-varname' for=\"ds-2-/pressure1-5387802300\">pressure1</label>\n",
        "                    <span class=\"h5tb-dims\">(10) [float64]</span>\n",
        "                <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">check_value : -140.3</li><li style=\"list-style-type: none; font-style: italic\">standard_name : pressure</li><li style=\"list-style-type: none; font-style: italic\">units : Pa</li>\n",
        "                </ul>\n",
        "                </ul>\n",
        "\n",
-       "                <ul id=\"ds-1-/velocity-5254243000\" class=\"h5tb-var-list\">\n",
-       "                    <input id=\"ds-2-/velocity-5254247600\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
-       "                    <label class='h5tb-varname' for=\"ds-2-/velocity-5254247600\">velocity</label>\n",
+       "                <ul id=\"ds-1-/velocity-5388263300\" class=\"h5tb-var-list\">\n",
+       "                    <input id=\"ds-2-/velocity-5388265500\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
+       "                    <label class='h5tb-varname' for=\"ds-2-/velocity-5388265500\">velocity</label>\n",
        "                    <span class=\"h5tb-dims\">(3) [int32]</span>\n",
        "                <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">check_value : 14.2</li><li style=\"list-style-type: none; font-style: italic\">standard_name : velocity</li><li style=\"list-style-type: none; font-style: italic\">units : m/s</li>\n",
        "                </ul>\n",
@@ -311,17 +311,17 @@
        "\n",
        "              <ul style=\"list-style-type: none;\" class=\"h5grp-sections\">\n",
        "                    <li>\n",
-       "                        <input id=\"group-ds-group1-5254734500\" type=\"checkbox\" >\n",
-       "                        <label style=\"font-weight: bold\" for=\"group-ds-group1-5254734500\">\n",
+       "                        <input id=\"group-ds-group1-5388578700\" type=\"checkbox\" >\n",
+       "                        <label style=\"font-weight: bold\" for=\"group-ds-group1-5388578700\">\n",
        "                        group1<span>(1)</span></label>\n",
        "                  \n",
        "\n",
        "                    <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">check_value : 0</li>\n",
        "                    </ul>\n",
        "\n",
-       "                <ul id=\"ds-1-/group1/velocity-5255716000\" class=\"h5tb-var-list\">\n",
-       "                    <input id=\"ds-2-/group1/velocity-5255718500\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
-       "                    <label class='h5tb-varname' for=\"ds-2-/group1/velocity-5255718500\">velocity</label>\n",
+       "                <ul id=\"ds-1-/group1/velocity-5389201800\" class=\"h5tb-var-list\">\n",
+       "                    <input id=\"ds-2-/group1/velocity-5389204200\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
+       "                    <label class='h5tb-varname' for=\"ds-2-/group1/velocity-5389204200\">velocity</label>\n",
        "                    <span class=\"h5tb-dims\">(5) [int32]</span>\n",
        "                <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">standard_name : velocity</li><li style=\"list-style-type: none; font-style: italic\">units : m/s</li>\n",
        "                </ul>\n",
@@ -331,33 +331,33 @@
        "\n",
        "              <ul style=\"list-style-type: none;\" class=\"h5grp-sections\">\n",
        "                    <li>\n",
-       "                        <input id=\"group-ds-group2-5256028000\" type=\"checkbox\" >\n",
-       "                        <label style=\"font-weight: bold\" for=\"group-ds-group2-5256028000\">\n",
+       "                        <input id=\"group-ds-group2-5389453900\" type=\"checkbox\" >\n",
+       "                        <label style=\"font-weight: bold\" for=\"group-ds-group2-5389453900\">\n",
        "                        group2<span>(3)</span></label>\n",
        "                  \n",
        "\n",
        "                    <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">check_value : 0</li>\n",
        "                    </ul>\n",
        "\n",
-       "                <ul id=\"ds-1-/group2/pressure2-5257217300\" class=\"h5tb-var-list\">\n",
-       "                    <input id=\"ds-2-/group2/pressure2-5257219500\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
-       "                    <label class='h5tb-varname' for=\"ds-2-/group2/pressure2-5257219500\">pressure2</label>\n",
+       "                <ul id=\"ds-1-/group2/pressure2-5390440500\" class=\"h5tb-var-list\">\n",
+       "                    <input id=\"ds-2-/group2/pressure2-5390443100\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
+       "                    <label class='h5tb-varname' for=\"ds-2-/group2/pressure2-5390443100\">pressure2</label>\n",
        "                    <span class=\"h5tb-dims\">(10) [float64]</span>\n",
        "                <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">check_value : -10.3</li><li style=\"list-style-type: none; font-style: italic\">standard_name : pressure</li><li style=\"list-style-type: none; font-style: italic\">units : kPa</li>\n",
        "                </ul>\n",
        "                </ul>\n",
        "\n",
-       "                <ul id=\"ds-1-/group2/velocity-5257559900\" class=\"h5tb-var-list\">\n",
-       "                    <input id=\"ds-2-/group2/velocity-5257562100\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
-       "                    <label class='h5tb-varname' for=\"ds-2-/group2/velocity-5257562100\">velocity</label>\n",
+       "                <ul id=\"ds-1-/group2/velocity-5390806700\" class=\"h5tb-var-list\">\n",
+       "                    <input id=\"ds-2-/group2/velocity-5390809000\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
+       "                    <label class='h5tb-varname' for=\"ds-2-/group2/velocity-5390809000\">velocity</label>\n",
        "                    <span class=\"h5tb-dims\">(5) [float64]</span>\n",
        "                <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">check_value : 30.2</li><li style=\"list-style-type: none; font-style: italic\">standard_name : velocity</li><li style=\"list-style-type: none; font-style: italic\">units : m/s</li>\n",
        "                </ul>\n",
        "                </ul>\n",
        "\n",
-       "                <ul id=\"ds-1-/group2/z-5257908600\" class=\"h5tb-var-list\">\n",
-       "                <input id=\"ds-2-/group2/z-5257910900\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
-       "                <label class='h5tb-varname' for=\"ds-2-/group2/z-5257910900\">z</label>\n",
+       "                <ul id=\"ds-1-/group2/z-5391128000\" class=\"h5tb-var-list\">\n",
+       "                <input id=\"ds-2-/group2/z-5391131800\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
+       "                <label class='h5tb-varname' for=\"ds-2-/group2/z-5391131800\">z</label>\n",
        "                <span class=\"h5tb-dims\">5.4 [m] (float64)</span>\n",
        "                <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">standard_name : z_coordinate</li><li style=\"list-style-type: none; font-style: italic\">units : m</li>\n",
        "                </ul>\n",
@@ -367,12 +367,12 @@
        "\n",
        "              <ul style=\"list-style-type: none;\" class=\"h5grp-sections\">\n",
        "                    <li>\n",
-       "                        <input id=\"group-ds-h5rdmtoolbox-5258242600\" type=\"checkbox\" >\n",
-       "                        <label style=\"font-weight: bold\" for=\"group-ds-h5rdmtoolbox-5258242600\">\n",
-       "                        h5rdmtoolbox<a href=\"https://schema.org/SoftwareSourceCode\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"Image 1\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">@type: https://schema.org/SoftwareSourceCode</span></a><span>(0)</span></label>\n",
+       "                        <input id=\"group-ds-h5rdmtoolbox-5391546300\" type=\"checkbox\" >\n",
+       "                        <label style=\"font-weight: bold\" for=\"group-ds-h5rdmtoolbox-5391546300\">\n",
+       "                        h5rdmtoolbox<a href=\"https://schema.org/SoftwareSourceCode\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"IRI_ICON\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">@type: https://schema.org/SoftwareSourceCode</span></a><span>(0)</span></label>\n",
        "                  \n",
        "\n",
-       "                    <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">__h5rdmtoolbox_version__<a href=\"https://schema.org/softwareVersion\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"Image 1\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://schema.org/softwareVersion</span></a> : 1.2.3a2</li><li style=\"list-style-type: none; font-style: italic\">codeRepository<a href=\"https://schema.org/codeRepository\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"Image 1\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://schema.org/codeRepository</span></a> : <a href=\"https://github.com/matthiasprobst/h5RDMtoolbox\">https://github.com/matthiasprobst/h5RDMtoolbox</a></li>\n",
+       "                    <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">__h5rdmtoolbox_version__<a href=\"https://schema.org/softwareVersion\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"IRI_ICON\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://schema.org/softwareVersion</span></a> : 1.2.3a2</li><li style=\"list-style-type: none; font-style: italic\">code_repository<a href=\"https://schema.org/codeRepository\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"IRI_ICON\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://schema.org/codeRepository</span></a> : <a href=\"https://github.com/matthiasprobst/h5RDMtoolbox\">https://github.com/matthiasprobst/h5RDMtoolbox</a></li>\n",
        "                    </ul>\n",
        "</li>\n",
        "</ul>\n",
@@ -767,7 +767,7 @@
     {
      "data": {
       "text/plain": [
-       "[<matplotlib.lines.Line2D at 0x27439c18cd0>]"
+       "[<matplotlib.lines.Line2D at 0x243ca0741c0>]"
       ]
      },
      "execution_count": 11,
@@ -1061,30 +1061,30 @@
        "\n",
        "              <ul style=\"list-style-type: none;\" class=\"h5grp-sections\">\n",
        "                    <li>\n",
-       "                        <input id=\"group-ds--6454791000\" type=\"checkbox\" checked>\n",
-       "                        <label style=\"font-weight: bold\" for=\"group-ds--6454791000\">\n",
+       "                        <input id=\"group-ds--6356740700\" type=\"checkbox\" checked>\n",
+       "                        <label style=\"font-weight: bold\" for=\"group-ds--6356740700\">\n",
        "                        /<span>(2)</span></label>\n",
        "                  \n",
        "\n",
        "                    <ul class=\"h5tb-attr-list\">\n",
        "                    </ul>\n",
        "\n",
-       "                <ul id=\"ds-1-/u-6456257500\" class=\"h5tb-var-list\">\n",
-       "                    <input id=\"ds-2-/u-6456260500\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
-       "                    <label class='h5tb-varname' for=\"ds-2-/u-6456260500\">u</label>\n",
+       "                <ul id=\"ds-1-/u-6357345000\" class=\"h5tb-var-list\">\n",
+       "                    <input id=\"ds-2-/u-6357347300\" class=\"h5tb-varname-in\" type=\"checkbox\" >\n",
+       "                    <label class='h5tb-varname' for=\"ds-2-/u-6357347300\">u</label>\n",
        "                    <span class=\"h5tb-dims\">(4) [int32]</span>\n",
-       "                <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">standard_name<a href=\"https://matthiasprobst.github.io/ssno#hasStandardName\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"Image 1\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://matthiasprobst.github.io/ssno#hasStandardName</span></a> : coeff<a href=\"https://matthiasprobst.github.io/pivmeta#piv_correlation_coefficient\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"Image 1\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://matthiasprobst.github.io/pivmeta#piv_correlation_coefficient</span></a></li><li style=\"list-style-type: none; font-style: italic\">units : m/s</li>\n",
+       "                <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">standard_name<a href=\"https://matthiasprobst.github.io/ssno#hasStandardName\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"IRI_ICON\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://matthiasprobst.github.io/ssno#hasStandardName</span></a> : coeff<a href=\"https://matthiasprobst.github.io/pivmeta#piv_correlation_coefficient\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"IRI_ICON\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://matthiasprobst.github.io/pivmeta#piv_correlation_coefficient</span></a></li><li style=\"list-style-type: none; font-style: italic\">units : m/s</li>\n",
        "                </ul>\n",
        "                </ul>\n",
        "\n",
        "              <ul style=\"list-style-type: none;\" class=\"h5grp-sections\">\n",
        "                    <li>\n",
-       "                        <input id=\"group-ds-h5rdmtoolbox-6456672500\" type=\"checkbox\" >\n",
-       "                        <label style=\"font-weight: bold\" for=\"group-ds-h5rdmtoolbox-6456672500\">\n",
-       "                        h5rdmtoolbox<a href=\"https://schema.org/SoftwareSourceCode\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"Image 1\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">@type: https://schema.org/SoftwareSourceCode</span></a><span>(0)</span></label>\n",
+       "                        <input id=\"group-ds-h5rdmtoolbox-6357852200\" type=\"checkbox\" >\n",
+       "                        <label style=\"font-weight: bold\" for=\"group-ds-h5rdmtoolbox-6357852200\">\n",
+       "                        h5rdmtoolbox<a href=\"https://schema.org/SoftwareSourceCode\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"IRI_ICON\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">@type: https://schema.org/SoftwareSourceCode</span></a><span>(0)</span></label>\n",
        "                  \n",
        "\n",
-       "                    <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">__h5rdmtoolbox_version__<a href=\"https://schema.org/softwareVersion\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"Image 1\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://schema.org/softwareVersion</span></a> : 1.2.3a2</li><li style=\"list-style-type: none; font-style: italic\">codeRepository<a href=\"https://schema.org/codeRepository\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"Image 1\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://schema.org/codeRepository</span></a> : <a href=\"https://github.com/matthiasprobst/h5RDMtoolbox\">https://github.com/matthiasprobst/h5RDMtoolbox</a></li>\n",
+       "                    <ul class=\"h5tb-attr-list\"><li style=\"list-style-type: none; font-style: italic\">__h5rdmtoolbox_version__<a href=\"https://schema.org/softwareVersion\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"IRI_ICON\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://schema.org/softwareVersion</span></a> : 1.2.3a2</li><li style=\"list-style-type: none; font-style: italic\">code_repository<a href=\"https://schema.org/codeRepository\" target=\"_blank\" class=\"tooltip\"> <img class=\"size_of_img\" src=\"https://github.com/matthiasprobst/h5RDMtoolbox/blob/dev/h5rdmtoolbox/data/iri_icon.png?raw=true\" alt=\"IRI_ICON\" width=\"16\" height=\"16\" /> <span class=\"tooltiptext\">https://schema.org/codeRepository</span></a> : <a href=\"https://github.com/matthiasprobst/h5RDMtoolbox\">https://github.com/matthiasprobst/h5RDMtoolbox</a></li>\n",
        "                    </ul>\n",
        "</li>\n",
        "</ul>\n",
@@ -1123,55 +1123,55 @@
       "    \"foaf\": \"http://xmlns.com/foaf/0.1/\",\n",
       "    \"hdf5\": \"http://purl.allotrope.org/ontologies/hdf5/1.8#\",\n",
       "    \"m4i\": \"http://w3id.org/nfdi4ing/metadata4ing#\",\n",
-      "    \"prov\": \"http://www.w3.org/ns/prov#\",\n",
-      "    \"rdfs\": \"http://www.w3.org/2000/01/rdf-schema#\",\n",
-      "    \"schema\": \"https://schema.org/\"\n",
+      "    \"schema\": \"https://schema.org/\",\n",
+      "    \"standard_name\": \"https://matthiasprobst.github.io/ssno#hasStandardName\"\n",
       "  },\n",
       "  \"@graph\": [\n",
       "    {\n",
-      "      \"@id\": \"_:N000e46de92cc458a879014828b600138\",\n",
-      "      \"@type\": \"hdf5:Group\",\n",
-      "      \"hdf5:name\": \"/\"\n",
-      "    },\n",
-      "    {\n",
-      "      \"@id\": \"_:Nd3cce22a8a8f466d95bb22236121ff43\",\n",
+      "      \"@id\": \"_:N5f9799ded58e4fde9bbcf249ac8b769e\",\n",
       "      \"@type\": \"hdf5:Dataset\",\n",
       "      \"hdf5:attribute\": [\n",
       "        {\n",
-      "          \"@id\": \"_:N76cdaad12ad0436587a082b5fdd0c333\"\n",
+      "          \"@id\": \"_:Nbd1baad6115d4ddc8a75f1fe6aa2bad7\"\n",
       "        },\n",
       "        {\n",
-      "          \"@id\": \"_:Nd3338c47158240f1b80b7299b0f96ed7\"\n",
+      "          \"@id\": \"_:Nbe20474443cf471db750a63b0dbab125\"\n",
       "        }\n",
       "      ],\n",
       "      \"hdf5:datatype\": \"H5T_INTEGER\",\n",
       "      \"hdf5:name\": \"/u\",\n",
       "      \"hdf5:size\": 4,\n",
-      "      \"https://matthiasprobst.github.io/ssno#hasStandardName\": {\n",
+      "      \"hdf5:value\": {\n",
+      "        \"@id\": \"https://matthiasprobst.github.io/pivmeta#piv_correlation_coefficient\"\n",
+      "      },\n",
+      "      \"standard_name\": {\n",
       "        \"@id\": \"https://matthiasprobst.github.io/pivmeta#piv_correlation_coefficient\"\n",
       "      }\n",
       "    },\n",
       "    {\n",
-      "      \"@id\": \"_:N76cdaad12ad0436587a082b5fdd0c333\",\n",
+      "      \"@id\": \"_:Nbd1baad6115d4ddc8a75f1fe6aa2bad7\",\n",
       "      \"@type\": \"hdf5:Attribute\",\n",
       "      \"hdf5:name\": \"standard_name\",\n",
       "      \"hdf5:value\": \"coeff\"\n",
       "    },\n",
       "    {\n",
-      "      \"@id\": \"_:Nd3338c47158240f1b80b7299b0f96ed7\",\n",
+      "      \"@id\": \"_:Nbe20474443cf471db750a63b0dbab125\",\n",
       "      \"@type\": \"hdf5:Attribute\",\n",
       "      \"hdf5:name\": \"units\",\n",
       "      \"hdf5:value\": \"m/s\"\n",
       "    },\n",
       "    {\n",
-      "      \"@id\": \"_:N6618ee04b2f640b4a446fe8139a3de3c\",\n",
-      "      \"@type\": \"hdf5:Group\",\n",
+      "      \"@id\": \"_:N72771d3b53cb4faea05d2e0f53af5839\",\n",
+      "      \"@type\": [\n",
+      "        \"hdf5:Group\",\n",
+      "        \"schema:SoftwareSourceCode\"\n",
+      "      ],\n",
       "      \"hdf5:attribute\": [\n",
       "        {\n",
-      "          \"@id\": \"_:N8c88e5db8d664e48b9aa549937960425\"\n",
+      "          \"@id\": \"_:Nb4ec9a01835748a79001db648bf2f508\"\n",
       "        },\n",
       "        {\n",
-      "          \"@id\": \"_:Nb738cf2cec9247ff9efe63dac83dd66e\"\n",
+      "          \"@id\": \"_:N5dc0aea57e2f495e9097e5174591d778\"\n",
       "        }\n",
       "      ],\n",
       "      \"hdf5:name\": \"/h5rdmtoolbox\",\n",
@@ -1182,19 +1182,23 @@
       "      \"schema:softwareVersion\": \"1.2.3a2\"\n",
       "    },\n",
       "    {\n",
-      "      \"@id\": \"_:N8c88e5db8d664e48b9aa549937960425\",\n",
+      "      \"@id\": \"_:Nb4ec9a01835748a79001db648bf2f508\",\n",
       "      \"@type\": \"hdf5:Attribute\",\n",
       "      \"hdf5:name\": \"__h5rdmtoolbox_version__\",\n",
       "      \"hdf5:value\": \"1.2.3a2\"\n",
       "    },\n",
       "    {\n",
-      "      \"@id\": \"_:Nb738cf2cec9247ff9efe63dac83dd66e\",\n",
+      "      \"@id\": \"_:N5dc0aea57e2f495e9097e5174591d778\",\n",
       "      \"@type\": \"hdf5:Attribute\",\n",
-      "      \"hdf5:name\": \"codeRepository\",\n",
+      "      \"hdf5:name\": \"code_repository\",\n",
       "      \"hdf5:value\": {\n",
       "        \"@type\": \"http://www.w3.org/2001/XMLSchema#anyURI\",\n",
       "        \"@value\": \"https://github.com/matthiasprobst/h5RDMtoolbox\"\n",
       "      }\n",
+      "    },\n",
+      "    {\n",
+      "      \"@id\": \"_:Na95070c707e84ab0a5b40219a355e0fe\",\n",
+      "      \"@type\": \"hdf5:Group\"\n",
       "    }\n",
       "  ]\n",
       "}\n"
@@ -1345,18 +1349,7 @@
    "execution_count": 22,
    "id": "bb53a466-6571-450f-8cfd-a386314d9c4d",
    "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "'/h5rdmtoolbox'"
-      ]
-     },
-     "execution_count": 22,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "outputs": [],
    "source": [
     "find_attribute_from_name(h5.hdf_filename, 'codeRepository', 1)"
    ]
diff --git a/h5rdmtoolbox/_cfg.py b/h5rdmtoolbox/_cfg.py
index bc69439c..0800b0a9 100644
--- a/h5rdmtoolbox/_cfg.py
+++ b/h5rdmtoolbox/_cfg.py
@@ -32,7 +32,7 @@ def is_valid_logger_level(level: Union[str, int]):
     'expose_user_prop_to_attrs': True,
     'add_provenance': False,
     'ignore_set_std_attr_err': False,
-    'auto_create_h5tbx_version': True,  # automatically creates the group h5rdmtoolbox with the version attribute
+    'auto_create_h5tbx_version': False,  # automatically creates the group h5rdmtoolbox with the version attribute
     'uuid_name': 'uuid',  # attribute name used for UUIDs
     # if a standard attribute is defined and cannot be retrieved because the value is invalid, ignore it:
     'ignore_get_std_attr_err': False,
diff --git a/h5rdmtoolbox/_user.py b/h5rdmtoolbox/_user.py
index 08b8b073..5e3b1386 100644
--- a/h5rdmtoolbox/_user.py
+++ b/h5rdmtoolbox/_user.py
@@ -1,12 +1,11 @@
+import appdirs
+import importlib_resources
 import pathlib
 import shutil
 import time
 from itertools import count
 from typing import Tuple
 
-import appdirs
-import importlib_resources
-
 _filecounter = count()
 _dircounter = count()
 
@@ -89,16 +88,28 @@ def _get_dir(self, name: str) -> pathlib.Path:
 
         return self.user_dirs[name]
 
-    def clear_cache(self, delta_days: int):
+    def clear_cache(self, delta_days: int, utime: bool = False):
         """Clear the cache directory. The delta_days arguments will be used
-        to delete files older than delta_days days. This is only applied to files"""
+        to delete files older than delta_days days. This is only applied to files
+
+        Parameters
+        ----------
+        delta_days : int
+            The number of days to keep the files in the cache.
+        utime : bool
+            If True, the file access time will be used to determine the age of the file.
+            Otherwise, the file creation time will be used.
+        """
         if delta_days == 0:
             shutil.rmtree(self.user_dirs['cache'])
             return
         if self.user_dirs['cache'].exists():
             for f in self.user_dirs['cache'].iterdir():
                 # get the file creation time
-                fct = f.stat().st_ctime
+                if utime:
+                    fct = f.stat().st_atime
+                else:
+                    fct = f.stat().st_ctime
                 dt = _now - fct
                 if dt > delta_days * 86400:
                     f.unlink()
diff --git a/h5rdmtoolbox/database/hdfdb/filedb.py b/h5rdmtoolbox/database/hdfdb/filedb.py
index 9418268b..2c77b434 100644
--- a/h5rdmtoolbox/database/hdfdb/filedb.py
+++ b/h5rdmtoolbox/database/hdfdb/filedb.py
@@ -2,8 +2,8 @@
 import pathlib
 from typing import Union, Generator, List
 
-from .objdb import ObjDB
 from .nonsearchable import NonInsertableDatabaseInterface
+from .objdb import ObjDB
 from .. import lazy
 from ..template import HDF5DBInterface
 
@@ -12,16 +12,14 @@ class FileDB(NonInsertableDatabaseInterface, HDF5DBInterface):
     """A database interface for an HDF5 file, where the filename is given."""
 
     def __init__(self, filename: Union[str, pathlib.Path]):
-        self.filename = pathlib.Path(filename)
+        self.filename: str = str(filename)
         self.find = self._instance_find  # allow `find` to be a static method and instance method
         self.find_one = self._instance_find_one  # allow `find_one` to be a static method and instance method
 
     @staticmethod
-    def find_one(file_or_filename, *args, **kwargs) -> lazy.LHDFObject:
+    def find_one(filename: Union[str, pathlib.Path], *args, **kwargs) -> lazy.LHDFObject:
         """Please refer to the docstring of the find_one method of the ObjDB class"""
-        if isinstance(file_or_filename, (h5py.Group, h5py.Dataset)):
-            return ObjDB(file_or_filename).find_one(*args, **kwargs)
-        with h5py.File(file_or_filename, 'r') as h5:
+        with h5py.File(str(filename), 'r') as h5:
             return ObjDB(h5).find_one(*args, **kwargs)
 
     def _instance_find(self, *args, **kwargs):
@@ -81,16 +79,15 @@ def find_one(self, *args, **kwargs) -> lazy.LHDFObject:
         contains the object, the first one is returned. If you want to find one per file,
         call find_one_per_file instead."""
         for filename in self.filenames:
-            with h5py.File(filename, 'r') as h5:
+            with h5py.File(filename, mode='r') as h5:
                 ret = ObjDB(h5).find_one(*args, **kwargs)
                 if ret:
                     return ret
-        return
 
     def find(self, *args, **kwargs) -> Generator[lazy.LHDFObject, None, None]:
-        all_results = []
+        """Call find on all the files"""
         for filename in self.filenames:
             with h5py.File(filename, 'r') as h5:
                 ret = ObjDB(h5).find(*args, **kwargs)
-                all_results.extend(ret)
-        return all_results
+                for r in ret:
+                    yield r
diff --git a/h5rdmtoolbox/database/hdfdb/objdb.py b/h5rdmtoolbox/database/hdfdb/objdb.py
index 7e5f5184..3d95960a 100644
--- a/h5rdmtoolbox/database/hdfdb/objdb.py
+++ b/h5rdmtoolbox/database/hdfdb/objdb.py
@@ -158,7 +158,6 @@ def _h5find(h5obj: Union[h5py.Group, h5py.Dataset], qk, qv, recursive, objfilter
 
     """
     found_objs = []
-
     if qk in query.value_operator:
         # user wants to compare qv to the value of the object
 
@@ -301,7 +300,7 @@ def _h5find(h5obj: Union[h5py.Group, h5py.Dataset], qk, qv, recursive, objfilter
                         if query.operator[ok](objattr, ov):
                             found_objs.append(hv)
                     except Exception as e:
-                        raise Exception(f'Error while filtering for "{qk}" with "{ok}" and "{ov}"') from e
+                        raise Exception(f'Error while filtering for "{qk}" with "{ok}" and "{ov}": {e}')
     return found_objs
 
 
@@ -420,8 +419,20 @@ def __init__(self, obj: Union[h5py.Dataset, h5py.Group]):
             self.src_obj = h5py.Dataset(obj.id)
         else:
             raise TypeError(f'Unexpected type: {type(obj)}')
+        self.find = self._instance_find  # allow `find` to be a static method and instance method
+        self.find_one = self._instance_find_one  # allow `find_one` to be a static method and instance method
+
+    @staticmethod
+    def find_one(obj: Union[h5py.Dataset, h5py.Group], *args, **kwargs) -> lazy.LHDFObject:
+        """Please refer to the docstring of the find_one method of the ObjDB class"""
+        return ObjDB(obj).find_one(*args, **kwargs)
+
+    @staticmethod
+    def find(obj: Union[h5py.Dataset, h5py.Group], *args, **kwargs) -> lazy.LHDFObject:
+        """Please refer to the docstring of the find_one method of the ObjDB class"""
+        return ObjDB(obj).find(*args, **kwargs)
 
-    def find_one(self,
+    def _instance_find_one(self,
                  flt: Union[Dict, str],
                  objfilter=None,
                  recursive: bool = True,
@@ -452,7 +463,7 @@ def find_one(self,
                 ignore_attribute_error=ignore_attribute_error)
         )
 
-    def find(self,
+    def _instance_find(self,
              flt: Union[Dict, str],
              objfilter=None,
              recursive: bool = True,
diff --git a/h5rdmtoolbox/database/hdfdb/query.py b/h5rdmtoolbox/database/hdfdb/query.py
index 6f2a649c..ef725db6 100644
--- a/h5rdmtoolbox/database/hdfdb/query.py
+++ b/h5rdmtoolbox/database/hdfdb/query.py
@@ -1,3 +1,4 @@
+"""query module"""
 import logging
 import numpy as np
 import re
@@ -59,9 +60,12 @@ def _regex(value, pattern) -> bool:
         except UnicodeDecodeError:
             warnings.warn(f'could not decode {value}', UserWarning)
             return False
+
     if isinstance(value, bytes):
         value = value.decode()
 
+    value = str(value)
+
     match = re.search(pattern, value)
     if match is None:
         return False
diff --git a/h5rdmtoolbox/layout/core.py b/h5rdmtoolbox/layout/core.py
index 06485745..d7456c1e 100644
--- a/h5rdmtoolbox/layout/core.py
+++ b/h5rdmtoolbox/layout/core.py
@@ -66,7 +66,7 @@ class SpecificationResult:
 
     def __init__(self, target):
         self.target = target
-        self.target_name = target.name
+        self.target_name = target if isinstance(target, str) else target.name
         self.target_type = 'Dataset' if isinstance(target, h5py.Dataset) else 'Group'
         self.validation_flag = VALIDATION_FLAGS.UNCALLED.value
         self.res = []
@@ -575,13 +575,13 @@ def validate(self, filename_or_root_group: Union[str, pathlib.Path, h5py.Group])
         """Validate the layout by passing a filename or an opened root group"""
         self.reset()
 
-        if isinstance(filename_or_root_group, (str, pathlib.Path)):
-            with h5tbx.File(filename_or_root_group, mode='r') as h5:
-                return self.validate(h5)
+        # if isinstance(filename_or_root_group, (str, pathlib.Path)):
+        #     with h5tbx.File(filename_or_root_group, mode='r') as h5:
+        #         return self.validate(h5)
 
-        if isinstance(filename_or_root_group, h5py.Group):
-            if not filename_or_root_group.name == '/':
-                raise ValueError('If passing an HDF5 group, a root group must be passed')
+        # if isinstance(filename_or_root_group, h5py.Group):
+        #     if not filename_or_root_group.name == '/':
+        #         raise ValueError('If passing an HDF5 group, a root group must be passed')
 
         # first reset all specs (n_calls = 0, _n_fails = 0, failed = None)
         for spec in self.specifications:
diff --git a/h5rdmtoolbox/layout/core_depr.py b/h5rdmtoolbox/layout/core_depr.py
deleted file mode 100644
index 5bc9a4e3..00000000
--- a/h5rdmtoolbox/layout/core_depr.py
+++ /dev/null
@@ -1,563 +0,0 @@
-"""Layout validation module"""
-import enum
-import h5py
-import logging
-import pathlib
-import types
-import uuid
-import warnings
-from typing import Dict, Union, List, Protocol, Optional
-
-import h5rdmtoolbox as h5tbx
-
-logger = logging.getLogger('h5rdmtoolbox')
-
-
-class VALIDATION_FLAGS(enum.Enum):
-    """Validation flags used in layout validation"""
-    UNCALLED = 0
-    SUCCESSFUL = 1
-    FAILED = 2
-    ALTERNATIVE_CALLED = 4  # an alternative spec succeeded
-    INVALID_NUMBER = 8
-    OPTIONAL = 16  # if a spec is optional, it is successful independent of the number of results
-
-
-def _replace_callables_with_names(dict_with_callables: Dict) -> Dict:
-    """Replace all callables in a dictionary with their names plus '()'
-    Used by __repr__ of LayoutSpecification"""
-    dict_with_callables = dict_with_callables.copy()
-    for key in dict_with_callables.keys():
-        if callable(dict_with_callables[key]):
-            dict_with_callables[key] = f'{dict_with_callables[key].__name__}()'
-        elif isinstance(dict_with_callables[key], dict):
-            _replace_callables_with_names(dict_with_callables[key])
-    return dict_with_callables
-
-
-class QueryCallable(Protocol):
-    """Protocol class for classes passed to the LayoutSpecification class.
-
-    Those classes must implement the method find()
-    """
-
-    def find(self, target: Union[str, pathlib.Path, h5tbx.Group], **kwargs): ...
-
-    def __call__(self, *args, **kwargs) -> List: ...
-
-
-def is_single_result(res) -> bool:
-    """Return True if the result is a single result. This is the case if the result is not an iterable object."""
-    if res is None:
-        return False
-    return not isinstance(res, (types.GeneratorType, tuple, list))
-
-
-class SpecificationCallResult:
-    """Stores the result of a specification call"""
-
-    def __init__(self):
-        self.validation_flag = VALIDATION_FLAGS.UNCALLED.value
-        self.res = []
-
-    @property
-    def n_res(self) -> int:
-        """Number of found objects (results)"""
-        return len(self.res)
-
-
-class LayoutSpecification:
-    """Specification for a layout
-
-    Parameters
-    ----------
-    func: QueryCallable
-        Callable query according to protocol class QueryCallable to be called on the hdf5 file.
-        The first argument of the function will be an opened h5py.File or h5py.Group or h5py.Dataset object.
-    kwargs: Dict
-        Keyword arguments passed to the func.
-    n: Union[int, None, Dict]
-        Number of matches or condition. Only applicable if query function (`func`) returns an iterable
-        object. None means that the number can be zero as well, which makes the specification optional.
-        Example: n=1 means that the specification is successful if the query function returns exactly one.
-        If n is a dictionary, the key must be a comparison operator (e.g. '$eq', '$gt', '$lt', '$gte', '$lte'),
-        e.g. {'$eq': 1} means that the query function must return exactly one result.
-        {'$gt': 1} means that the query function must return more than one result.
-    description: Optional[str]
-        Optional description explaining the specification
-    parent: Optional[LayoutSpecification]
-        Parent specification. If the specification is a conditional one, it has a parent.
-        If this is the case, the function `func` is called on the parent's results.
-        If the parent's specification fails, the specification is not applied.
-        If `parent` is None, the specification has no parent and is applied to the
-        hdf5 root group.
-    """
-
-    def __init__(self,
-                 func: QueryCallable,
-                 kwargs,
-                 n: Union[int, None, Dict],
-                 description: Optional[str] = None,
-                 parent: Optional["LayoutSpecification"] = None):
-        self.func = func
-        self.kwargs = kwargs
-
-        if n is None:
-            self.number_of_result_comparison = lambda x, y: True
-            self.n = None
-        else:
-            if isinstance(n, int):
-                if n < 1:
-                    raise ValueError('n must be greater than 0')
-                n = {'$eq': n}
-            if not isinstance(n, dict):
-                raise TypeError(f'n must be an integer or dictionary, but got {type(n)}')
-
-            from ..database.hdfdb import query
-            assert len(n) == 1, 'n must be a dictionary with exactly one key'
-            for k, v in n.items():
-                self.number_of_result_comparison = query.operator.get(k)
-                assert isinstance(v, int), 'n must be an integer'
-                self.n = v
-
-        self.id = uuid.uuid4()
-        self.specifications: List[LayoutSpecification] = []
-        self.alt_specifications: List[LayoutSpecification] = []
-        self.parent: Optional["LayoutSpecification"] = parent
-        self.description: str = description or ''
-        # self.validation_flag = VALIDATION_FLAGS.UNCALLED.value
-        # self._n_res = 0
-        # self._n_calls = 0
-        # self._n_fails = 0
-        self.results: List[Optional[SpecificationCallResult]] = []
-
-    def __eq__(self, other) -> bool:
-        """A specification is equal to another if the ID is identical or the
-        function, kwargs, description and parent are identical."""
-        if not isinstance(other, LayoutSpecification):
-            return False
-        if isinstance(other, Layout):
-            return False
-        same_id = self.id == other.id
-        if same_id:
-            return True
-        same_parent = self.parent == other.parent
-        same_comment = self.description == other.description
-        same_kwargs = self.kwargs == other.kwargs
-        same_func = self.func == other.func
-        same_n = self.n == other.n
-
-        return all([same_parent, same_comment, same_kwargs, same_func, same_n])
-
-    @property
-    def failed(self) -> bool:
-        """Return True if the specification failed"""
-        return self.validation_flag & VALIDATION_FLAGS.FAILED.value == VALIDATION_FLAGS.FAILED.value
-
-    @property
-    def n_calls(self) -> int:
-        """Return number of calls"""
-        return len(self.results)
-
-    @property
-    def n_fails(self) -> int:
-        """Return number of failed calls"""
-        return self._n_fails
-
-    def reset(self) -> None:
-        """Reset the specification and all its children"""
-        self._n_calls = 0
-        self._n_fails = 0
-        for spec in self.specifications:
-            spec.reset()
-
-    @property
-    def called(self) -> bool:
-        """Return True if the specification has been called at least once.
-        This is determined by the number of calls."""
-        return self.n_calls > 0
-
-    @property
-    def n_successes(self):
-        """Return number of successful calls"""
-        if self.n_calls == 0:
-            raise ValueError('Not called')
-        return self.n_calls - self._n_fails
-
-    def __repr__(self):
-        _kwargs = _replace_callables_with_names(self.kwargs)
-        if self.description:
-            return f'{self.__class__.__name__}(description="{self.description}", kwargs={_kwargs})'
-        return f'{self.__class__.__name__}(kwargs={_kwargs})'
-
-    def __call__(self, target: Union[h5py.Group, h5py.Dataset]):
-        if isinstance(target, h5tbx.database.lazy.LHDFObject):
-            with target as _target:
-                return self.__call__(_target)
-
-        scr = SpecificationCallResult()
-
-        if self.n is None:
-            # per definition successful since n is None
-            scr.validation_flag = VALIDATION_FLAGS.SUCCESSFUL.value + VALIDATION_FLAGS.OPTIONAL.value
-
-        # self._n_calls += 1
-        # logger.debug(f'calling spec (id={self.id}) with func={self.func.__module__}.{self.func.__name__} and '
-        #              f'kwargs {self.kwargs}')
-
-        res = self.func(target, **self.kwargs)
-        if res is None or is_single_result(res):
-            res = [res]
-            if self.n is None:
-                self.n = 1
-
-        if not is_single_result(res) and res is not None:
-            res = list(res)
-
-        scr.res = res
-
-        if not res:
-            # first assume failure unless n=None. There might be an alternative spec registered though.
-            # The following will update `res`
-            if self.n is None:  # query is optional!
-                scr.validation_flag = VALIDATION_FLAGS.SUCCESSFUL.value + VALIDATION_FLAGS.OPTIONAL.value
-            else:
-                scr.validation_flag = VALIDATION_FLAGS.FAILED.value
-
-            # If alternative specifications exist, try them. This will only be performed if self.n is not None
-            if len(self.alt_specifications) > 0 and self.n is not None:
-                alt_spec_successes = []
-                res = []
-                for alt_spec in self.alt_specifications:
-                    alt_res = alt_spec.func(target, **alt_spec.kwargs)
-
-                    if not is_single_result(alt_res):
-                        alt_res = list(alt_res)
-
-                    if alt_res:
-                        alt_spec.validation_flag = VALIDATION_FLAGS.SUCCESSFUL.value
-                        alt_spec_successes.append(True)
-                    else:
-                        alt_spec.validation_flag = VALIDATION_FLAGS.FAILED.value
-                        alt_spec_successes.append(False)
-
-                    res.extend(alt_res)
-
-                # failed = not any(alt_spec_successes)
-                if any(alt_spec_successes):
-                    logger.debug('An alternative succeeded!')
-                    if self.validation_flag & VALIDATION_FLAGS.FAILED.value:
-                        self.validation_flag -= VALIDATION_FLAGS.FAILED.value
-                    self.validation_flag += VALIDATION_FLAGS.ALTERNATIVE_CALLED.value
-                else:
-                    self._n_fails += 1
-                    logger.error(f'Applying spec. "{self}" on "{target}" failed.')
-                    self.validation_flag = VALIDATION_FLAGS.FAILED.value + VALIDATION_FLAGS.ALTERNATIVE_CALLED.value
-
-        # now, for successful results, let's apply the sub-specifications if exist
-        # and check how many results we have and if the number of results is correct (if n is specified)
-        if is_single_result(res):
-            # as there is a result, the specification is successful as n=1 is implicit
-            scr.validation_flag = VALIDATION_FLAGS.SUCCESSFUL.value
-
-            # check sub-specifications
-            for sub_spec in self.specifications:
-                sub_spec(res)
-
-            self.results.append(scr)
-            return
-
-        n_res = len(res)
-        if res:  # if no alternative was defined, res may still be None!
-            # continue here if res is an iterable object
-            for r in res:
-                if not r:  # first result failed
-                    logger.error(f'Applying spec. "{self}" on "{target}" failed.')
-                    self._n_fails += 1
-                else:
-                    # if it was successful, we can check the sub-specifications
-                    for sub_spec in self.specifications:
-                        logger.debug(f'Calling spec {sub_spec} to hdf obj {r}.')
-                        sub_spec(r)
-
-        # logger.debug(f'Validation {self} found {n_res} results from which {self._n_fails} failed.')
-        # If the number of successful results is not specified, it means, that
-        # the spec is optional. so it is successful in any case!
-        if self.n is not None:
-            if self.number_of_result_comparison(n_res, self.n):
-                scr.validation_flag = VALIDATION_FLAGS.SUCCESSFUL.value
-            else:  # if self.n != n_res:
-                self._n_fails += 1
-                scr.validation_flag = VALIDATION_FLAGS.FAILED.value + VALIDATION_FLAGS.INVALID_NUMBER.value
-                logger.error(f'Applying spec. "{self}" failed due to not '
-                             f'matching the number of results: {self.n} != {n_res}')
-        self.results.append(scr)
-
-    def add(self,
-            func: QueryCallable,
-            *,
-            n: Union[int, None, Dict],
-            description: Optional[str] = None,
-            **kwargs):
-        """
-        Add a specification by providing a callable query obj. Optionally, the
-        number of exact matches can be provided as well as the a description string.
-        The kwargs are passed to the callable
-
-        Parameters
-        ----------
-        func: Callable
-            Function to be called on the hdf5 file
-        n: int
-            Number of matches or query dictionary. None indicates optional specification.
-        description: Optional[str]
-            Optional description explaining the specification
-        kwargs: Dict
-            Keyword arguments passed to the func
-
-        Returns
-        -------
-        LayoutSpecification
-
-        Examples
-        --------
-        >>> from h5rdmtoolbox.database import FileDB
-        >>> lay = LayoutSpecification()
-        >>> spec1 = lay.__set_meta_field__(hdfdb.FileDB.find, flt={'$name': '/u'}, n=1)
-        >>> spec2 = lay.__set_meta_field__(...) # add another spec to layout
-        >>> spec_sub1 = spec1.__set_meta_field__(...)  # add spec to `spec1` if it succeeds and apply to all results of `spec1`
-        """
-        new_spec = LayoutSpecification(func=func,
-                                       kwargs=kwargs,
-                                       n=n,
-                                       description=description,
-                                       parent=self)
-        for spec in self.specifications:
-            if spec == new_spec:
-                warnings.warn(f'Specification "{new_spec}" already exists. Skipping.',
-                              UserWarning)
-                return spec
-        self.specifications.append(new_spec)
-        return new_spec
-
-    def add_alternative(self,
-                        func: QueryCallable,
-                        *,
-                        n: Union[int, None, Dict],
-                        description: Optional[str] = None,
-                        **kwargs):
-        """Add an alternative specification by providing a callable query obj. Optionally, the
-        number of exact matches can be provided as well as the a description string.
-        The kwargs are passed to the callable
-        Either the parent or the alternative specification must be successful.
-
-        .. note::
-
-            An alternative query can only added to specifications which have a number of expected results (n!=None).
-
-        Parameters
-        ----------
-        func: Callable
-            Function to be called on the hdf5 file
-        n: Union[int, None, Dict]
-            Number of matches or query dictionary. None indicates optional specification.
-        description: Optional[str]
-            Optional description explaining the specification
-        kwargs: Dict
-            Keyword arguments passed to the func
-
-        """
-        if self.n is None:
-            raise ValueError('Parent specification must not be an optional specification. Please provide a number of '
-                             'expected results.')
-        new_spec = LayoutSpecification(func=func,
-                                       kwargs=kwargs,
-                                       n=n,
-                                       description=description,
-                                       parent=self)
-        for spec in self.alt_specifications:
-            if spec == new_spec:
-                warnings.warn(f'Specification "{new_spec}" already exists. Skipping.',
-                              UserWarning)
-                return spec
-        self.alt_specifications.append(new_spec)
-        return new_spec
-
-    def is_valid(self):
-        """Return True if the specification is valid"""
-        if self.n_calls == 0:
-            print(f'{self} has not been called yet')
-            return False
-        if self.failed:
-            print(f'{self} failed')
-            return False
-        return all(spec.is_valid() for spec in self.specifications)
-
-    def get_valid(self) -> List['LayoutSpecification']:
-        """Return all successful specifications"""
-        if self.n_calls == 0:
-            return []  # has not been called yet, thus cannot be valid
-
-        valid: List[LayoutSpecification] = []
-
-        if not self.failed and self.n_calls > 0 and not self.failed:
-            valid.append(self)
-
-        if self.specifications:
-            for spec in self.specifications:
-                valid.extend(spec.get_valid())
-        return valid
-
-    def get_failed(self) -> List['LayoutSpecification']:
-        """Return a list of failed specifications"""
-        if self.failed is True:
-            return [self]
-        failed = []
-        if self.failed:
-            failed.append(self)
-        if self.specifications:
-            failed.extend(spec.get_failed() for spec in self.specifications)
-            # flatten list:
-            return [item for sublist in failed for item in sublist]
-        return failed
-
-    def get_summary(self, exclude_keys: Optional[List] = None) -> List[Dict]:
-        """return a summary as dictionary"""
-        explanations = []
-
-        def _get_flag_explanations(flag):
-            explanations = []
-            for i in VALIDATION_FLAGS:
-                if flag & i.value:
-                    explanations.append(i.name)
-            return ', '.join(explanations)
-
-        data = []
-        for res in self.results:
-            data.append({'id': self.id,
-                         'called': len(self.results) > 0,
-                         # 'n_calls/n_res/n_fails': f'{self.n_calls}/{n_res}/{self.n_fails}' if self.called else '-(-)',
-                         'flag': res.validation_flag,
-                         'flag description': _get_flag_explanations(res.validation_flag),
-                         'description': self.description,
-                         # '_n_fails': self._n_fails,
-                         'func': f'{self.func.__module__}.{self.func.__name__}',
-                         'kwargs': self.kwargs,
-                         })
-
-        if exclude_keys is None:
-            exclude_keys = []
-        for key in exclude_keys:
-            # pop keys from dict:
-            data[0].pop(key)
-
-        for spec in self.specifications:
-            data.extend(spec.get_summary(exclude_keys))
-        return data
-
-
-class LayoutResult:
-    """Container for the result of a layout validation. It only contains a list of failed specs."""
-
-    def __init__(self, specifications: List[LayoutSpecification]):
-        self.specifications: List[LayoutSpecification] = specifications
-
-    def get_failed(self) -> List[LayoutSpecification]:
-        """Return a list of failed specifications"""
-        failed = [spec.get_failed() for spec in self.specifications]
-        # flatten list:
-        return [item for sublist in failed for item in sublist]
-
-    def get_valid(self) -> List[LayoutSpecification]:
-        """Return a list of valid specifications"""
-        valid_specs = [spec.get_valid() for spec in self.specifications]
-        # flatten list:
-        return [item for sublist in valid_specs for item in sublist]
-
-    def is_valid(self) -> bool:
-        """Return True if the layout is valid, which is the case if no specs failed"""
-        return len(self.get_failed()) == 0
-
-    def get_summary(self, exclude_keys: Optional[List] = None) -> Dict:
-        """return a summary as dictionary"""
-        data = []
-        for spec in self.specifications:
-            data.extend(spec.get_summary(exclude_keys=exclude_keys))
-        return data
-
-    def print_summary(self, exclude_keys: Optional[List[str]] = None):
-        """Prints a summary of the specification. Requires the tabulate package."""
-        try:
-            from tabulate import tabulate
-        except ImportError:
-            raise ImportError('Please install tabulate to use this method')
-        print('\nSummary of layout validation')
-        print(tabulate(self.get_summary(exclude_keys), headers='keys', tablefmt='psql'))
-
-
-class Layout(LayoutSpecification):
-    """A layout is a collection of specifications that can be applied to an HDF5 file or group.
-
-    The class is inherited from LayoutSpecification. Some methods are overwritten.
-
-    Examples
-    --------
-    >>> from h5rdmtoolbox import layout
-    >>> lay = layout.Layout()
-    >>> spec_all_dataset = lay.__set_meta_field__(
-    >>> hdfdb.FileDB.find,  # query function
-    >>>     flt={},
-    >>>     objfilter='dataset'
-    >>> )
-    >>>
-    >>> # all datasets must be compressed with gzip (conditional spec. only called if parent spec is successful)
-    >>> spec_compression = spec_all_dataset.__set_meta_field__(
-    >>>     hdfdb.FileDB.find_one,  # query function
-    >>>     flt={'$compression': 'gzip'}  # query parameter
-    >>> )
-    >>>
-    >>> # the file must have the dataset "/u"
-    >>> spec_ds_u = lay.__set_meta_field__(
-    >>>     hdfdb.FileDB.find,  # query function
-    >>>     flt={'$name': '/u'},
-    >>>     objfilter='dataset'
-    >>> )
-    >>> lay.validate('path/to/file.h5')
-    """
-
-    def __init__(self):
-        self.specifications: List[LayoutSpecification] = []
-
-    def __eq__(self, other):
-        if not isinstance(other, Layout):
-            return False
-        return self.specifications == other.specifications
-
-    def validate(self, filename_or_root_group: Union[str, pathlib.Path, h5py.Group]) -> LayoutResult:
-        """Validate the layout by passing a filename or an opened root group"""
-        if isinstance(filename_or_root_group, h5py.Group):
-            if not filename_or_root_group.name == '/':
-                raise ValueError('If passing an HDF5 group, a root group must be passed')
-
-        # first reset all specs (n_calls = 0, _n_fails = 0, failed = None)
-        for spec in self.specifications:
-            spec.reset()
-
-        for spec in self.specifications:
-            spec(filename_or_root_group)
-
-        return LayoutResult(self.specifications)
-
-    def __call__(self, *args, **kwargs):
-        raise RuntimeError('Layout cannot be called. User `.validate()` to validate')
-
-    def is_valid(self) -> bool:
-        """Return True if all specifications are valid.
-        A specification is valid it is has been called and has not been failed"""
-        return all(spec.is_valid() for spec in self.specifications)
-
-    def get_failed(self) -> List[LayoutSpecification]:
-        """Return a list of failed specifications"""
-        failed = [spec.get_failed() for spec in self.specifications]
-        # flatten list:
-        return [item for sublist in failed for item in sublist]
diff --git a/tests/conventions/test_ontology.py b/tests/conventions/test_ontology.py
index 53223e0e..7e036be7 100644
--- a/tests/conventions/test_ontology.py
+++ b/tests/conventions/test_ontology.py
@@ -1,11 +1,11 @@
 """Testing the standard attributes"""
 import json
 import pathlib
+import rdflib
 import unittest
 
 import h5rdmtoolbox as h5tbx
-import rdflib
-from h5rdmtoolbox.convention.ontology import HDF5, Attribute, Dataset, Group, File
+from h5rdmtoolbox.convention.ontology import Attribute, Dataset, Group, File
 
 __this_dir__ = pathlib.Path(__file__).parent
 
@@ -27,9 +27,15 @@ class TestOntology(unittest.TestCase):
     def setUp(self):
         h5tbx.use(None)
 
+        self.curr_auto_create_h5tbx_version = h5tbx.get_config('auto_create_h5tbx_version')
+        h5tbx.set_config(auto_create_h5tbx_version=True)
+
+    def tearDown(self):
+        h5tbx.set_config(auto_create_h5tbx_version=self.curr_auto_create_h5tbx_version)
+
     def test_Attribute(self):
         attr = Attribute(name='standard_name',
-                                      value='x_velocity')
+                         value='x_velocity')
         print(attr.model_dump_jsonld())
 
     def test_Dataset(self):
@@ -37,7 +43,7 @@ def test_Dataset(self):
             name='/grp1/grp2/ds1',
             attribute=[
                 Attribute(name='standard_name',
-                                       value='x_velocity')],
+                          value='x_velocity')],
             size=100)
         print(ds.model_dump_jsonld())
 
@@ -46,25 +52,25 @@ def test_Group(self):
             name='/grp1/grp2',
             attribute=[
                 Attribute(name='standard_name',
-                                       value='x_velocity')],
+                          value='x_velocity')],
             member=[
                 Dataset(
                     name='/grp1/grp2/ds1',
                     attribute=[
                         Attribute(name='standard_name',
-                                               value='x_velocity')],
+                                  value='x_velocity')],
                     size=100),
                 Group(
                     name='/grp1/grp2/grp3',
                     attribute=[
                         Attribute(name='standard_name',
-                                               value='x_velocity')],
+                                  value='x_velocity')],
                     member=[
                         Dataset(
                             name='/grp1/grp2/grp3/ds2',
                             attribute=[
                                 Attribute(name='standard_name',
-                                                       value='x_velocity')],
+                                          value='x_velocity')],
                             size=100)])])
         print(grp.model_dump_jsonld())
 
@@ -73,25 +79,25 @@ def test_RootGroup(self):
             name='/',
             attribute=[
                 Attribute(name='standard_name',
-                                       value='x_velocity')],
+                          value='x_velocity')],
             member=[
                 Dataset(
                     name='/ds1',
                     attribute=[
                         Attribute(name='standard_name',
-                                               value='x_velocity')],
+                                  value='x_velocity')],
                     size=100),
                 Group(
                     name='/grp1',
                     attribute=[
                         Attribute(name='standard_name',
-                                               value='x_velocity')],
+                                  value='x_velocity')],
                     member=[
                         Dataset(
                             name='/grp1/ds2',
                             attribute=[
                                 Attribute(name='standard_name',
-                                                       value='x_velocity')],
+                                          value='x_velocity')],
                             size=100)])])
         print(grp.model_dump_jsonld())
 
@@ -104,7 +110,7 @@ def test_File(self):
             name='/',
             attribute=[
                 Attribute(name='version',
-                                       value='1.0.0')]
+                          value='1.0.0')]
         )
 
         file = File(
@@ -184,7 +190,7 @@ def test_jsonld_to_hdf(self):
             resolve_keys=True
         )
         json_dict = json.loads(jsonld_str)
-        print(jsonld_str)
+
         i = 0
         for g in json_dict['@graph']:
             if isinstance(g['@type'], list) and 'prov:Person' in g['@type']:
diff --git a/tests/database/test_hdfDB.py b/tests/database/test_hdfDB.py
index fccf09f5..ff2e1443 100644
--- a/tests/database/test_hdfDB.py
+++ b/tests/database/test_hdfDB.py
@@ -20,6 +20,65 @@ def test_insert(self):
             with self.assertRaises(NotImplementedError):
                 gdb.insert_group(None)
 
+    def test_dtype_char(self):
+        # find a string dataset
+        with h5tbx.File() as h5:
+            ds = h5.create_string_dataset('a string ds', data=['one', 'two', 'three'])
+            gdb = hdfdb.ObjDB(h5['/'])
+            res = gdb.find_one({'$dtype': {'$regex': 'S*'}},
+                               objfilter='dataset',
+                               recursive=False)
+            self.assertEqual(res, ds)
+            ds_name = ds.name
+        fdb = hdfdb.FileDB(h5.hdf_filename)
+        fdb.find_one({'$dtype': {'$regex': 'S*'}},
+                     objfilter='dataset',
+                     recursive=False)
+        self.assertIsInstance(res, h5tbx.database.lazy.LDataset)
+        self.assertEqual(res.name, ds_name)
+
+        with self.assertRaises(FileNotFoundError):
+            hdfdb.FileDB.find_one('invalid_filename.filename',
+                                  {'$dtype': {'$regex': 'S*'}},
+                                  objfilter='dataset',
+                                  recursive=False)
+
+        res = hdfdb.FileDB.find_one(h5.hdf_filename,
+                                    {'$dtype': {'$regex': 'S*'}},
+                                    objfilter='dataset',
+                                    recursive=False)
+        self.assertIsInstance(res, h5tbx.database.lazy.LDataset)
+        self.assertEqual(res.name, ds_name)
+
+        res = hdfdb.FileDB.find(h5.hdf_filename,
+                                {'$dtype': {'$regex': 'S*'}},
+                                objfilter='dataset',
+                                recursive=False)
+        # res is a generator
+        self.assertIsInstance(res, types.GeneratorType)
+        res = list(res)
+        self.assertIsInstance(res, list)
+        self.assertIsInstance(res[0], h5tbx.database.lazy.LDataset)
+        self.assertEqual(res[0].name, ds_name)
+
+        res = hdfdb.FileDB(h5.hdf_filename).find({'$dtype': {'$regex': 'S*'}},
+                                                 objfilter='dataset',
+                                                 recursive=False)
+        self.assertIsInstance(res, list)
+        self.assertIsInstance(res[0], h5tbx.database.lazy.LDataset)
+        self.assertEqual(res[0].name, ds_name)
+
+        # find a string dataset
+        with h5tbx.File() as h5:
+            h5.create_string_dataset('a string ds', data=['one', 'two', 'three'])
+            ds = h5.create_dataset('num', data=2.4)
+            print(str(ds.dtype))
+            gdb = hdfdb.ObjDB(h5['/'])
+            res = gdb.find({'$dtype': {'$regex': '^(?!\|S|\|).*'}},  # does not starts with "|S" or "|"
+                           objfilter='dataset',
+                           recursive=False)
+            self.assertEqual(list(res), [ds, ])
+
     def test_value_find(self):
         with h5tbx.File(mode='w') as h5:
             ds_random = h5.create_dataset('random', data=np.array([1, 2, 3]))
@@ -64,7 +123,7 @@ def test_find_shape(self):
             res = gdb.find({'$ndim': {'$gte': 0}}, recursive=True)
             self.assertListEqual(sorted([r.name for r in res]), sorted([ds_random.name, ds_half.name]))
 
-    def test_distint_props(self):
+    def test_distinct_props(self):
         with h5tbx.File(mode='w') as h5:
             ds_random = h5.create_dataset('random', data=np.array([1, 2, 3]))
             ds_half = h5.create_dataset('half', data=0.5)
@@ -78,85 +137,86 @@ def test_distint_props(self):
             self.assertListEqual(sorted(res), [0, 1])
 
     def test_find_one(self):
-        with h5py.File(h5tbx.utils.generate_temporary_filename(suffix='.hdf'),
-                       'w') as h5:
-            h5.attrs['long_name'] = 'root group'
-            grp = h5.create_group('grp')
-            grp.attrs['a'] = 1
-            grp.attrs['long_name'] = 'a group'
-            ds = h5.create_dataset('dataset', shape=(2, 3), dtype='float64')
-            ds.attrs['a'] = 1
-            ds.attrs['b'] = 2
-            grp.create_dataset('sub_grp_dataset', shape=(4,))
-
-            dsdb = hdfdb.ObjDB(h5)
-
-            res_only_dataset = dsdb.find({'$dtype': {'$exists': True}})
-            self.assertEqual(len(list(res_only_dataset)), 2)
-
-            del grp['sub_grp_dataset']
-
-            grpdb = hdfdb.ObjDB(h5['grp'])
-            res_is_dataset = grpdb.find_one({'$dtype': {'$exists': True}}, recursive=False)
-            self.assertTrue(res_is_dataset is None)
-
-            dsdb = hdfdb.ObjDB(h5['dataset'])
-            res_is_dataset = dsdb.find_one({'$dtype': {'$exists': True}})
-            self.assertTrue(res_is_dataset is not None)
-
-            res = dsdb.find_one({'$dtype': np.dtype('<f8')}, objfilter='dataset')  # is float64
-            self.assertEqual(res, ds)
-            res = dsdb.find_one({'$dtype': np.dtype('<f4')}, objfilter='dataset')  # is float64
-            self.assertEqual(res, None)
-
-            gdb_grp = hdfdb.ObjDB(h5['grp'])
-            res = dsdb.find_one({'$name': '/dataset'}, recursive=False)
-            with res as res_ds:
-                self.assertEqual(res_ds, ds)
-
-            res = dsdb.find_one({'units': {'$exists': True}}, recursive=False)
-            self.assertTrue(res is None)
-
-            ds.attrs['units'] = 'invalid units'
-
-            res = dsdb.find_one({'units': {'$exists': True}}, recursive=False)
-            self.assertFalse(res is None)
-
-            single_res = gdb_grp.find_one({'a': 1}, recursive=False)
-            self.assertIsInstance(single_res, database.lazy.LGroup)
-            self.assertEqual(single_res.basename, 'grp')
-
-            gdb_root = hdfdb.ObjDB(h5['/'])
-            single_res = gdb_root.find_one({'a': 1}, objfilter=h5py.Dataset)
-            self.assertIsInstance(single_res, database.lazy.LDataset)
-            self.assertEqual(single_res.basename, 'dataset')
-
-            gdb_root = hdfdb.ObjDB(h5['/'])
-            single_res = gdb_root.find_one({'a': 1}, objfilter='dataset')
-            self.assertIsInstance(single_res, database.lazy.LDataset)
-            self.assertEqual(single_res.basename, 'dataset')
-
-            single_res = gdb_root.find_one({'b': 2}, recursive=True)
-            self.assertIsInstance(single_res, database.lazy.LDataset)
-            self.assertEqual(single_res.basename, 'dataset')
-
-            # check $exists operator:
-            single_res = gdb_root.find_one({'long_name': {'$exists': True}},
-                                           recursive=True)
-            self.assertIsInstance(single_res, database.lazy.LGroup)
-            self.assertTrue(single_res.basename in ('grp', ''))
-
-            single_res = gdb_root.find_one({'long_name': {'$exists': False}},
-                                           recursive=True)
-            self.assertIsInstance(single_res, database.lazy.LDataset)
-            self.assertEqual(single_res.basename, 'dataset')
-
-            # check $gt, ... operators:
-            single_res = gdb_root.find_one({'a': {'$gt': 0}}, recursive=True)
-            self.assertTrue(single_res.attrs['a'] > 0)
-
-            single_res = gdb_root.find_one({'a': {'$gte': 0}}, recursive=True)
-            self.assertTrue(single_res.attrs['a'] >= 0)
+        with h5tbx.set_config(auto_create_h5tbx_version=False):
+            with h5py.File(h5tbx.utils.generate_temporary_filename(suffix='.hdf'),
+                           'w') as h5:
+                h5.attrs['long_name'] = 'root group'
+                grp = h5.create_group('grp')
+                grp.attrs['a'] = 1
+                grp.attrs['long_name'] = 'a group'
+                ds = h5.create_dataset('dataset', shape=(2, 3), dtype='float64')
+                ds.attrs['a'] = 1
+                ds.attrs['b'] = 2
+                grp.create_dataset('sub_grp_dataset', shape=(4,))
+
+                dsdb = hdfdb.ObjDB(h5)
+
+                res_only_dataset = dsdb.find({'$dtype': {'$exists': True}})
+                self.assertEqual(len(list(res_only_dataset)), 2)
+
+                del grp['sub_grp_dataset']
+
+                grpdb = hdfdb.ObjDB(h5['grp'])
+                res_is_dataset = grpdb.find_one({'$dtype': {'$exists': True}}, recursive=False)
+                self.assertTrue(res_is_dataset is None)
+
+                dsdb = hdfdb.ObjDB(h5['dataset'])
+                res_is_dataset = dsdb.find_one({'$dtype': {'$exists': True}})
+                self.assertTrue(res_is_dataset is not None)
+
+                res = dsdb.find_one({'$dtype': np.dtype('<f8')}, objfilter='dataset')  # is float64
+                self.assertEqual(res, ds)
+                res = dsdb.find_one({'$dtype': np.dtype('<f4')}, objfilter='dataset')  # is float64
+                self.assertEqual(res, None)
+
+                gdb_grp = hdfdb.ObjDB(h5['grp'])
+                res = dsdb.find_one({'$name': '/dataset'}, recursive=False)
+                with res as res_ds:
+                    self.assertEqual(res_ds, ds)
+
+                res = dsdb.find_one({'units': {'$exists': True}}, recursive=False)
+                self.assertTrue(res is None)
+
+                ds.attrs['units'] = 'invalid units'
+
+                res = dsdb.find_one({'units': {'$exists': True}}, recursive=False)
+                self.assertFalse(res is None)
+
+                single_res = gdb_grp.find_one({'a': 1}, recursive=False)
+                self.assertIsInstance(single_res, database.lazy.LGroup)
+                self.assertEqual(single_res.basename, 'grp')
+
+                gdb_root = hdfdb.ObjDB(h5['/'])
+                single_res = gdb_root.find_one({'a': 1}, objfilter=h5py.Dataset)
+                self.assertIsInstance(single_res, database.lazy.LDataset)
+                self.assertEqual(single_res.basename, 'dataset')
+
+                gdb_root = hdfdb.ObjDB(h5['/'])
+                single_res = gdb_root.find_one({'a': 1}, objfilter='dataset')
+                self.assertIsInstance(single_res, database.lazy.LDataset)
+                self.assertEqual(single_res.basename, 'dataset')
+
+                single_res = gdb_root.find_one({'b': 2}, recursive=True)
+                self.assertIsInstance(single_res, database.lazy.LDataset)
+                self.assertEqual(single_res.basename, 'dataset')
+
+                # check $exists operator:
+                single_res = gdb_root.find_one({'long_name': {'$exists': True}},
+                                               recursive=True)
+                self.assertIsInstance(single_res, database.lazy.LGroup)
+                self.assertTrue(single_res.basename in ('grp', ''))
+
+                single_res = gdb_root.find_one({'long_name': {'$exists': False}},
+                                               recursive=True)
+                self.assertIsInstance(single_res, database.lazy.LHDFObject)
+                self.assertEqual(single_res.basename, 'dataset')
+
+                # check $gt, ... operators:
+                single_res = gdb_root.find_one({'a': {'$gt': 0}}, recursive=True)
+                self.assertTrue(single_res.attrs['a'] > 0)
+
+                single_res = gdb_root.find_one({'a': {'$gte': 0}}, recursive=True)
+                self.assertTrue(single_res.attrs['a'] >= 0)
 
     def test_find_dict_attr(self):
         with h5tbx.File(mode='w') as h5:
@@ -322,6 +382,13 @@ def test_filesDB_find_one(self):
         self.assertIsInstance(single_res, database.lazy.LDataset)
         self.assertEqual(single_res.filename, filename2)
 
+        multi_res = filesdb.find({'d': 4}, recursive=True)
+        self.assertIsInstance(multi_res, types.GeneratorType)
+        multi_res = list(multi_res)
+        self.assertEqual(len(multi_res), 1)
+        self.assertIsInstance(multi_res[0], database.lazy.LDataset)
+        self.assertEqual(multi_res[0].filename, filename2)
+
     def test_filesDB_insert_filename(self):
         filename1 = h5tbx.utils.generate_temporary_filename(suffix='.hdf')
         filename2 = h5tbx.utils.generate_temporary_filename(suffix='.hdf')
diff --git a/tests/layouts/test_core.py b/tests/layouts/test_core.py
index 9645dc51..3cda34b2 100644
--- a/tests/layouts/test_core.py
+++ b/tests/layouts/test_core.py
@@ -111,8 +111,8 @@ def test_is_single_result(self):
         self.assertEqual(is_single_result(None), False)
 
         lay = layout.Layout()
-        spec = lay.add(hdfdb.FileDB.find_one, flt={'$name': '/u'}, n=None)
-        sub_spec = spec.add(hdfdb.FileDB.find, flt={'$shape': (3, 4)}, n=None)
+        spec = lay.add(hdfdb.ObjDB.find_one, flt={'$name': '/u'}, n=None)
+        sub_spec = spec.add(hdfdb.ObjDB.find, flt={'$shape': (3, 4)}, n=None)
 
         self.assertFalse(spec.is_valid())
         self.assertFalse(sub_spec.is_valid())
@@ -148,7 +148,7 @@ def test_print_summary(self):
         out = StringIO()
         sys.stdout = out
         lay = layout.Layout()
-        spec = lay.add(hdfdb.FileDB.find_one, flt={'$name': '/u'}, n=None)
+        spec = lay.add(hdfdb.ObjDB.find_one, flt={'$name': '/u'}, n=None)
         with h5tbx.File(name=None, mode='w') as h5:
             ds = h5.create_dataset('u', shape=(3, 4), dtype='float32')
             res = lay.validate(h5)
diff --git a/tests/test_user.py b/tests/test_user.py
index 42070dbf..3f22ca13 100644
--- a/tests/test_user.py
+++ b/tests/test_user.py
@@ -1,5 +1,8 @@
 """test h5rdmtoolbox.user.py"""
+import datetime
+import os
 import shutil
+import time
 import unittest
 
 import h5rdmtoolbox as h5tbx
@@ -12,6 +15,26 @@ class TestUser(unittest.TestCase):
     def setUp(self) -> None:
         clean_temp_data(full=True)
 
+    @classmethod
+    def tearDownClass(cls) -> None:
+        cache_dir = (h5tbx.UserDir['cache'].exists(), h5tbx.UserDir['cache'])
+        convention_dir = (h5tbx.UserDir['convention'].exists(), h5tbx.UserDir['convention'])
+        snt_dir = (h5tbx.UserDir['standard_name_tables'].exists(), h5tbx.UserDir['standard_name_tables'])
+        layouts_dir = (h5tbx.UserDir['layouts'].exists(), h5tbx.UserDir['layouts'])
+        tmp_dir = (h5tbx.UserDir['tmp'].exists(), h5tbx.UserDir['tmp'])
+
+        h5tbx.UserDir.reset()
+        if cache_dir[0]:
+            assert not cache_dir[1].exists(), 'UserDir.reset() failed to remove cache directory'
+        if convention_dir[0]:
+            assert not convention_dir[1].exists(), 'UserDir.reset() failed to remove convention directory'
+        if snt_dir[0]:
+            assert not snt_dir[1].exists(), 'UserDir.reset() failed to remove standard_name_tables directory'
+        if layouts_dir[0]:
+            assert not layouts_dir[1].exists(), 'UserDir.reset() failed to remove layouts directory'
+        if tmp_dir[0]:
+            assert not tmp_dir[1].exists(), 'UserDir.reset() failed to remove tmp directory'
+
     def test_user_dir(self):
         self.assertListEqual(sorted(h5tbx.UserDir.names),
                              sorted(('root', 'tmp', 'layouts', 'standard_name_tables', 'cache', 'convention')))
@@ -23,6 +46,25 @@ def test_user_dir(self):
 
         self.assertTrue(h5tbx.UserDir['cache'].exists())
 
+        # create cache with file from the past
+        cache_dir = h5tbx.UserDir['cache']
+        filename = cache_dir / 'test.txt'
+        with open(filename, 'w') as f:
+            f.write('test')
+        timestamp = datetime.datetime.now() - datetime.timedelta(days=2)
+        epoch_time = time.mktime(timestamp.timetuple())
+        os.utime(filename, (epoch_time, epoch_time))
+        self.assertTrue(cache_dir.exists())
+        h5tbx.UserDir.clear_cache(delta_days=1, utime=True)
+        self.assertFalse(filename.exists())
+
+        with open(filename, 'w') as f:
+            f.write('test')
+        os.utime(filename, (epoch_time, epoch_time))
+        h5tbx.UserDir.clear_cache(delta_days=3, utime=True)
+        self.assertTrue(filename.exists())
+        filename.unlink()
+
         with self.assertRaises(ValueError):
             h5tbx.UserDir._get_dir('invalid')
         if h5tbx.UserDir.user_dirs['standard_name_tables'].exists():