simplified some sentences

.gitignore

@@ -20,3 +20,4 @@ yarn-debug.log*
 yarn-error.log*
 
 .idea/
+openaire-graph-docs.iml

docs/data-model/data-model.md

@@ -11,12 +11,12 @@ The latest version of the JSON schema can be found on [Bulk downloads](../downlo
 The figure above, presents the graph's data model. 
 Its main entities are described in brief below:
 
-* [Results](entities/result) represent the outcomes of research activities.
+* [Results](entities/result) represent the outcomes (or products) of research activities.
-* [Data Sources](entities/data-source) are the resources used to collect metadata for the graph objects
+* [Data Sources](entities/data-source) are the sources from which the metadata of graph objects are collected 
 * [Organizations](entities/organization) correspond to companies or research institutions involved in projects,
 responsible for operating data sources or consisting the affiliations of Product creators.
-* [Projects](entities/project) are research projects funded by a Funding Stream of a Funder.
+* [Projects](entities/project) are research project grants funded by a Funding Stream of a Funder.
-* [Communities](entities/community) are groups of people with a common research intent.
+* [Communities](entities/community) are groups of people with a common research intent (e.g. research infrastructures, university alliances)
 
 :::note Further reading
 

docs/data-model/pids-and-identifiers.md

@@ -1,8 +1,8 @@
 # PIDs and identifiers
 
-One of the challenges towards the stability of the contents in the OpenAIRE Graph consists of making its identifiers and records stable over time.
+Ensuring the stability of the records and their identifiers in the OpenAIRE Graph is a challenge.
-The barriers to this scenario are many, as the Graph keeps a map of data sources that is subject to constant variations: records in repositories vary in content,
+Data sources from which OpenAIRE collects metadata records are subject to constant variations: records in repositories vary in content,
-original IDs, and PIDs, may disappear or reappear, and the same holds for the repository or the metadata collection it exposes.
+original IDs, and PIDs, may disappear or reappear, and the same holds for the data source itself or the metadata collection it exposes.
 Not only, but the mappings applied to the original contents may also change and improve over time to catch up with the changes in the input records.
 
 ## PID Authorities