VO-DML <-> database schema

[Paul Harrison]

> On 2020-05 -14, at 14:47, Gerard Lemson <glemson1 at jhu.edu> wrote:
> 
> Short follow up:
> Would be nice to represent the mapping as a votable with empty tables, annotated with the data model.
> But there are some substantial complications with a relational mapping caused by freedoms allowed in VO-DML wrt VO-URP.
> Such as data type inheritance and attributes/references with cardinalities > 1.


For that sort of thing, I think that the JPA annotations do a fairly good job - it might be nice to adopt a similar set of annotation concepts - TBH in the past, when I wanted to create data models, I have tended to hand write Java POJOs and then JPA and JAXB annotate them to produce DDL and XML schema. I liked the way that the Java annotations were “close” to the related data items, but I cannot think of a way of doing that directly with the VO-DML, so I agree that a separate mapping document is needed - I am not sure that I am keen on your VOTable suggestion though, as it effectively requires annotating the whole model rather than just having to write the (hopefully) few rules where the “default” behaviour is not sufficient or decidable.

Cheers,
	Paul.


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