docs: brief documentation

README.md

@@ -1,5 +1,26 @@
 # Schema
-TEI schema for project documents
+TEI schemas for project documents
+
 This repo contains the schema and annotated template files to be used to enter new data while a proper form is prepared.
 
-The schema is generated with ROMA from a ODD specification (tei-betamesaheft.xml).
+## Contents
+
+- The main ODD specification is `tei-betamesaheft.xml`. 
+- `tei-betamesaheft-expanded.odd` is derived ODD (that uses `tei-betamesaheft.xml` as its source) and it’s meant to validate the expanded files generated in the app as well as file generated by other project.
+- Both RELAXNG schemas, `tei-betamesaheft.rng` and`tei-betamesaheft-expanded.rng` are generated through the [TEIGarage](https://github.com/TEIC/TEIGarage) API.
+- The main ODD specification is validated on CI. Also, the RELAXNG schemas are continuously updated on CI.
+
+## Build requirements
+
+- [ant](http://ant.apache.org/) version: 1.10.7 (for building from source)
+
+## Build instructions
+
+To create a XAR file with the schemas run
+
+```
+ant
+```
+
+
+