update readme and add more compact image

README.md

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 The OntoUML Metamodel repository contains the metamodel of the OntoUML language. Unlike the UML profile, this version is independent of UML and presents only the concepts officially supported in the language. This metamodel covers the abstract and concrete syntaxes of the language and serves as the reference for all projects in the [OntoUML as a Service (OaaS)](https://ceur-ws.org/Vol-2969/paper29-FOMI.pdf) ecosystem, including its different model serializations.
 
-![](./diagrams/Metamodel%20Summary%20Diagram.png)
+## Abstract Syntax Summary
 
+![](./diagrams/Abstract%20Syntax%20Summary.png)
+
+## Concrete Syntax Summary
+
+![](./diagrams/Concrete%20Syntax%20Summary.png)
 
 ## Repository Organization
 
@@ -14,15 +19,15 @@ The OntoUML Metamodel repository contains the metamodel of the OntoUML language.
 
 ## Related Projects
 
-- [OntoUML Schema](https://github.com/OntoUML/ontouml-schema): the JSON serialization of OntoUML models that supports the exchange of models over HTTP in microservice architectures.
+- [OntoUML Schema](https://w3id.org/ontouml/schema): the JSON serialization of OntoUML models that supports the exchange of models over HTTP in microservice architectures.
 
-- [OntoUML Vocabulary](https://github.com/OntoUML/ontouml-vocabulary): the Turtle serialization of OntoUML models that supports querying model datasets in knowledge graphs.
+- [OntoUML Vocabulary](https://w3id.org/ontouml/vocabulary): the Turtle serialization of OntoUML models that supports querying model datasets in knowledge graphs.
 
-- [OntoUML Plugin for Visual Paradigm](https://github.com/OntoUML/ontouml-vp-plugin): a [Visual Paradigm](https://www.visual-paradigm.com/) plugin that provides OntoUML-specific features and enables access to OaaS services (e.g., export models in the JSON format in compliance with the ontouml-schema).
+- [OntoUML Plugin for Visual Paradigm](https://w3id.org/ontouml/vp-plugin): a [Visual Paradigm](https://www.visual-paradigm.com/) plugin that provides OntoUML-specific features and enables access to OaaS services (e.g., export models in the JSON format in compliance with the ontouml-schema).
 
-- [OntoUML JSON2Graph Decoder](https://w3id.org/ontouml/json2graph): a model transformation service from JSON ([ontouml-schema](https://github.com/OntoUML/ontouml-schema)) to a graph format (OntoUML Vocabulary).
+- [OntoUML JSON2Graph Decoder](https://w3id.org/ontouml/json2graph): a model transformation service from an OntoUML Schema-compliant JSON to an OntoUML Vocabulary-compliant graph representation (e.g., in Turtle).
 
-- [OntoUML/UFO Catalog](https://github.com/OntoUML/ontouml-models): a FAIR open-source model catalog that contains hundreds of OntoUML and UFO ontologies.
+- [OntoUML/UFO Catalog](https://w3id.org/ontouml-models/git): a FAIR open-source model catalog that contains hundreds of OntoUML and UFO ontologies.
 
 
 ## Contributors