EDITED to make the question more clear
I have the same desire, as the original poster of this this question.
I was also able, to add my desired fields to bibers data modell and voila: running biber --tool does not yield a warning on my additional fields any more. So far so good.
As described in that self answering question, I copied the data model file from biber (i.e. biber --tool-config) and added my fields.
<config>
<!-- skipped 383 lines -->
<datamodel>
<!-- skipped "constants" and "entrytypes" -->
<fields>
<!-- skipped all predefined fields -->
<field fieldtype="field" datatype="literal">source</field>
<field fieldtype="field" datatype="literal">copyright</field>
</fields>
<entryfields>
<field>source</field>
<field>copyright</field>
<!-- skipped remainder of file -->
</entryfields>
</datamodel>
</config>
Now my question: is there any chance, to write my custom fields to an additional date model config file, so that it enhances whatever data model will be used by future versions of biber?
Chapter 3.1.2 describes, that biber uses "user-level maps", which could be declared by a LaTeX command or in a config file. The manual states, that the sourcemap option could be used, to "Add new fields to an entry", which is exactly my desire.
This would be the best solution. It would ensure, that the default data model in its latest revision, will always be loaded as default model and by additionally loading my fields via a second, additional config file, all fields are available. I don't have to check regularly, if the biber team updated the data model and thus have to insert also the recent changes into my enhanced and file.
What content must be defined in a file to be loaded with the --sourcemap=<extension-config> to extend the default data map with my custom fields?
biber --toolwith the manipulated data model. BUT: when the biber authors change the biber data model, I have to update my enhanced file. What I want: define only the additional fields in an config file. Whenbiberis run in tool mode, it will read its default data model and than will add my extra definitions to it. Therefore, I always use the most recent version of the data model and requested config file adds only those fields, which are missing. – Jan Dec 26 '23 at 17:19biber --tool. – gusbrs Dec 26 '23 at 17:54