- add DataArchitectureDiagram.md

DataArchitectureDiagram.md

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+![Image](./data_diagram.drawio.svg)
+

Database.md

@@ -106,6 +106,14 @@ In addition, the relation types (the kind of relationship) are precisely defined
 ## TETHYS lookup tables
 ![title](./tethys_lookup.png)
 
-* **document_xml_cache**:
+* **document_xml_cache**: all of the dataset's relations are stored in an internal XML format with a timestamp. Once the internal XML file has been created, it could be parsed and transformed into various output formats, including OAI-PMH (dublin core and datcite protocols used for OAI queries) and DOI registration data. These output formats would likely include information about the dataset itself (such as title, author, abstract, subjects, language, collection and publication date), as well as information about its relationships to other records in the repository. This metadata could then be used by other systems or services to facilitate discovery and access to the published dataset:
+
+    * 'xml_data': stores the internal TETHYS xml.
+    * 'xml_version': if the database model changes, the version of the internal xml must be increased.
+    * 'server_date_modified': timestamp of dataset publication or doi update date
 * **mime_types**:
-* **languages**:
+    * 'name': this attribute holds the mime-type. e.g. 'text/csv', 'application/x-sqlite3', 'image/jpeg'
+    * 'file_extension': all allowed file extension for a mime-type: e.g. jpg|jpeg|jpe for the mime-type 'image/jpeg'
+    * 'enabled': defines if the mime-type is enabled for TETHYS
+    * timestamp attributes 'cretaed_at' and 'updated_at'
+* **languages**: 

tethys_acl.png:Zone.Identifier

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-[ZoneTransfer]
-ZoneId=3
-HostUrl=about:internet