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[EP-tech] Re: Associating eprints with other entities

Tim Brody wrote:

On Thu, 30 Aug 2012 21:37:39 +0200, Jan Ploski<jpl@plosquare.com>  wrote:

Hi,

I'd like our eprints to be searchable using attributes of other,
associated entities. Specifically, we want to be able to search for
eprints that were published in journals that match certain criteria
(e.g. show all eprints published in OpenAccess journals). The attribute
values of journals may of course change in time and such changes should
be reflected immediately for all associated eprints.

The quickest and most primitive approach would be to reproduce the
desired journal attributes as metadata fields on eprints themselves and
set the values whenever an eprint is saved. But that would call for some
mechanism to ensure consistency when the journals themselves change
(e.g. if a journal becomes OpenAccess, update all eprints that were
published in it accordingly, to support search; perhaps through a db
trigger).

Furthermore, the direct approach of just storing the journal title in a
text field (rather than some stable foreign key) seems bad for ensuring
referential integrity (journal titles might change, too).

So I was wondering whether it would be proper to model the journals as a
new dataset and use itemref type fields to refer to them, or whether
there are other recommended approaches. Do you know of any examples that
might point me into the right direction?


Hi,

You can create a separate journals dataset and use itemref to tie the
journal into the eprint. There are some business-process issue with that
approach - how do users supply unlisted journal titles, who manages that
data etc.

Any other approach will require building an extension onto EPrints. You can
control how searches happen by creating a custom 'MetaField' e.g. by
returning a condition that queries a separate table.

No simple solutions I'm afraid, at least until we get further along with
adding support for CRIS-like features.


Tim,
Thanks for the clarifications. For the time being I decided to address the problem at database level with triggers, by keeping redundant data between the custom journals table and eprint, translating the user-entered journal titles into foreign keys on save, and writing back changed journal attributes into associated eprints.
The trouble I saw with itemref in 3.0.5 was that there was apparently no way to search eprints linked by itemref to journals with particular attributes. I think that your comment about MetaField with separate table is true for the current version (where I saw a search on userid.username), but not for 3.0.5... which we'll have to stick with at least for a short while. 

Regards,
Jan Ploski