Merge pull request #3 from doublebyte1/def

Added information about OGC building blocks.

_pages/overview/whatis.md

@@ -6,4 +6,10 @@ An Building Block is a way of packaging a component of a **specification** that
 
 For various reasons specifications have often made statements in text regarding how they relate to other specifications, and created implementation artefacts such as schemas that may not make these intentions explicit. The following diagram shows how Building Blocks form a value-added packaging option for such specification elements that can then be exploited as part of a comprehensive knowledge base to support discovery and re-use (FAIR principles).
 
-![Overview](https://lucid.app/publicSegments/view/266abfd3-ed51-43a8-a9b0-8e3251c28b54/image.png)
+![Overview](https://lucid.app/publicSegments/view/266abfd3-ed51-43a8-a9b0-8e3251c28b54/image.png)
+
+Many OGC Standards contain reusable building blocks that can be used in other OGC Standards. The Standards themselves can also be structured with modular sets of requirements that collectively function as a reusable building block (see image bellow).
+
+[![Usage](/assets/api-bblocks.png)](/assets/api-bblocks.png)
+
+To facilitate the discovery of these building blocks by other Standards and applications, once they are identified their definition should be published in the [OGC Register](https://opengeospatial.github.io/bblocks/register/). Normative information about the OGC Standards building blocks can be found in the [Technical Committee Policies and Procedures](https://docs.ogc.org/pol/05-020r29/05-020r29.html#building-bloocks)