Update README.md

tools/py/pipeline/README.md

@@ -1,7 +1,38 @@
-Versa pipeline
-==============
+This Versa pipeline library provides  a toolkit for constructing data transformation pipelines for Versa models.
 
-Tools for constructing data transformation pipelines for Versa models
+# Overview and example
+
+A Versa pipeline transforms one graph's patterns and vocabularies to another, based on a set of declared rules for pattern matching and output graph construction.
+
+Take the following pair of graphs:
+
+![Black Star graph](http://gonzaga.ogbuji.net/~uche/tech/2021/blackstar1.jpg)
+
+The left hand side is the input graph, based on the [Black Star test example](https://raw.githubusercontent.com/uogbuji/versa/pipeline_uni/test/resource/schemaorg/blackstar.md), which is based on [Schema.org MusicAlbum](https://schema.org/MusicAlbum). The right hand is the output graph, based on the [MusicBrainz schema](https://musicbrainz.org/doc/MusicBrainz_Database/Schema).
+
+Here is the input graph in Versa literate format:
 
 ```
-```
+<!-- 
+# @docheader
+
+* @iri:
+    * @base: http://example.org/records/
+    * @schema: https://schema.org/
+
+# black-star [MusicAlbum]
+
+* name: Mos Def & Talib Kweli Are Black Star
+* byArtist: <md>
+* byArtist: <tk>
+* release:
+    * catalogNumber: RWK 1158-2
+
+# md [Person]
+
+* name: Mos Def
+
+# tk [Person]
+
+* name: Talib Kweli
+* ```