fix issue #505: Effective boolean value is not defined for a sequence…

… of two or more items starting with a boolean

src/main/resources/xml/schema/2020-1/nordic2020-1.sch

@@ -551,7 +551,7 @@
             <let name="always-allowed-types" value="('abstract', 'acknowledgments', 'afterword', 'answers', 'appendix', 'assessment', 'assessments', 'bibliography', 'z3998:biographical-note', 'case-study', 'chapter', 'colophon', 'conclusion', 'contributors', 'copyright-page', 'credits', 'dedication', 'z3998:discography', 'division', 'z3998:editorial-note', 'epigraph', 'epilogue', 'errata', 'z3998:filmography', 'footnotes', 'foreword', 'glossary', 'dictionary', 'z3998:grant-acknowledgment', 'halftitlepage', 'imprimatur', 'imprint', 'index', 'index-group', 'index-headnotes', 'index-legend', 'introduction', 'keywords', 'landmarks', 'loa', 'loi', 'lot', 'lov', 'notice', 'other-credits', 'page-list', 'practices', 'preamble', 'preface', 'prologue', 'z3998:promotional-copy', 'z3998:published-works', 'z3998:publisher-address', 'qna', 'endnotes', 'revision-history', 'z3998:section', 'seriespage', 'subchapter', 'z3998:subsection', 'toc', 'toc-brief', 'z3998:translator-note', 'volume')"/>
             <let name="document-components" value="('z3998:pgroup', 'z3998:example', 'z3998:epigraph', 'z3998:annotation', 'z3998:introductory-note', 'z3998:commentary', 'z3998:clarification', 'z3998:correction', 'z3998:alteration', 'z3998:presentation', 'z3998:production', 'z3998:attribution', 'z3998:author', 'z3998:editor', 'z3998:general-editor', 'z3998:commentator', 'z3998:translator', 'z3998:republisher', 'z3998:structure', 'z3998:geographic', 'z3998:postal', 'z3998:email', 'z3998:ftp', 'z3998:http', 'z3998:ip', 'z3998:aside', 'z3998:sidebar', 'z3998:practice', 'z3998:notice', 'z3998:warning', 'z3998:marginalia', 'z3998:help', 'z3998:drama', 'z3998:scene', 'z3998:stage-direction', 'z3998:dramatis-personae', 'z3998:persona', 'z3998:actor', 'z3998:role-description', 'z3998:speech', 'z3998:diary', 'z3998:diary-entry', 'z3998:figure', 'z3998:plate', 'z3998:gallery', 'z3998:letter', 'z3998:sender', 'z3998:recipient', 'z3998:salutation', 'z3998:valediction', 'z3998:postscript', 'z3998:email-message', 'z3998:to', 'z3998:from', 'z3998:cc', 'z3998:bcc', 'z3998:subject', 'z3998:collection', 'z3998:orderedlist', 'z3998:unorderedlist', 'z3998:abbreviations', 'z3998:timeline', 'z3998:note', 'z3998:footnotes', 'z3998:footnote', 'z3998:verse', 'z3998:poem', 'z3998:song', 'z3998:hymn', 'z3998:lyrics')"/>
             <let name="allowed-types" value="($always-allowed-types, $document-components)"/>
-            <assert test="tokenize(@epub:type, '\s+') = $allowed-types">[nordic211] Sections inside a part must also have one of the allowed epub:type values allowed for such sections. <value-of select="concat('&quot;', (tokenize(@epub:type, '\s+')[not((. = 'part', 'volume'))], '(missing type)')[1], '&quot; is not an allowed type in a part)')"/> <value-of select="$context"/></assert>
+            <assert test="tokenize(@epub:type, '\s+') = $allowed-types">[nordic211] Sections inside a part must also have one of the allowed epub:type values allowed for such sections. <value-of select="concat('&quot;', (tokenize(@epub:type, '\s+')[not(. = ('part', 'volume'))], '(missing type)')[1], '&quot; is not an allowed type in a part)')"/> <value-of select="$context"/></assert>
         </rule>
     </pattern>