- describe file metadata

Database.md

@@ -50,15 +50,29 @@ Many research repositories allow you to filter content based on specific criteri
 * **dataset_subjects** with pivot table link_dataset_subjects: This table stores all the keywords. Until now only uncontrolled keywords are possible (attribute type is default 'uncontrolled')
 
 * **datset_abstracts**: This table stores all the descriptions to an uploaded dataset. Allowed values for an abstract type are: 'Abstract', 'Methods', 'Series_information',  'Technical_info', 'Translated' and 'Other'. 
+
 * **persons**: All dataset authors and contributors are stored inside this table. The table includes fields for the user's name, email address, and other contact information. \
 In the pivot table there are attributes for:
     * sort_order: sorting the authors and contributors 
     * allow_email_contact: if the email contact is allowed 
     * contributor_type: 'ContactPerson', 'DataCollector', 'DataCurator', 'DataManager', 'Distributor', 'Editor', 'HostingInstitution', 'Producer', 'ProjectLeader', 'ProjectManager', ProjectMember', 'RegistrationAgency', 'RegistrationAuthority', 'RelatedPerson', 'Researcher', 'ResearchGroup', 'RightsHolder', 'Sponsor', 'Supervisor', 'WorkPackageLeader' and 'Other'
+
 * **coverage**:  The spatial search functionality in Tethys allows users to find and access geospatial data that are relevant to their research or analysis by specifying a geographic extent that matches their area of interest. The 'x_min' and 'x_max' values represent the minimum and maximum x-coordinates (usually longitude) of the bounding box, while 'y_min' and 'y_max' represent the minimum and maximum y-coordinates (usually latitude). By specifying these coordinates, users can filter datasets based on their geographic location, making it easier to find relevant data for their analysis. Additionaly there are attributes for the elevation, depth and time coverage.
-* **projects**: When a user uploads data to TETHYS, they can assign them to one project. These projects could represent research studies, experiments, collaborations, or any other relevant grouping of data.
+* **projects**: When a user uploads data to TETHYS, they can assign them to one project. These projects could represent research studies, experiments, collaborations, or any other relevant grouping of data. Once the data have been assigned to a project, users can then filter the datasets in TETHYS based on the project they are associated with.
-* **collections**: 
+
+* **collections**: ...
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 <br />
 
 ## Tables for file metadata and file checksums:
+![title](./tethys_file.png)
+* **document_files**: TETHY stores the following metadata attributes for every uploaded file:
+    * path_name: path to the file on the harddisk
+    * label: name of the file presented aon the web frontend
+    * comment: optional comments to files are possible
+    * mime_type:
+    * file_size
+    * visible_frontdoo: is the file visible on the web frontend
+    * visible_oai: is the file vissible iin the oai response
+* **file_hashvalues**:
+TETHYS RDR calculates internal checksums during the ingestion workflow. These checksums ensure that ingested data has not been altered or damaged. A checksum is a short sequence of bits or bytes that is calculated from the data using an algorithm. If even a single bit of the data changes, the checksum will also change, indicating that the data has been changed unintentionally on the file store. During the file upload, TETHYS calculates and stores md5 and sha512-checksums for each file.