Support for Multiple Schemas
A simple enhancement proposal to add support for multiple (flat) schemas.
Current assignee: Martin Hald. Basic implemenation complete, alpha version available as http://sourceforge.net/tracker/index.php?func=detail&aid=1242663&group_id=19984&atid=319984 a patch on SourceForge.
The basic idea is to generalise the code and DB tables around Dublin Core. Conceptually speaking, a new column is added to
, and the same mechanisms used for Dublin Core may be used for other schemas. I believe Jim+Downing has already implemented something along these lines.
Backwards compatibility is important and not actually too difficult. Most of the 'under the hood' changes can be made with no need to change any UI code or other code in
From a backwards-compatibility point of view, keeping the table names the same might be easiest. However, changes to table names are masked from most code through the org.dspace.content.Item API. We may be able to use D views for other cases. There would need to be refactoring in a couple of other areas, but from an architectural consistency and code manageability / understandability viewpoint, I think this would be worth it. So that's what I've assumed below.
A new table,
is added, and
and modified to relate to the schema registry. Note the UNIQUE constraint on element / qualifier is removed (can easily see >1 schema having "title").
would be renamed to
, but remain the same. (Note that
is removed since it's an architectural relic.)
We can create a view
for backwards compatibility:
We could define '1' as a special value for
for Dublin Core. (Can we make
? Not that it probably matters.)
By definition anything in the DSpace application/interface layer
won't be affected as it is using the
method. Of course additional functionality will be needed in the UI (administration UI etc.) to realise the schema support but everything should work as before when the relevant changes are made elsewhere. Care will be needed to do everything in a way that doesn't impact performance. (Don't want to add to ScalabilityIssues1.4!)
. Very much along the lines of existing
and other DSpace Java objects. _Maybe belongs in
needs updating (see below).
Maybe create a backwards-compatible class
- will need a few changes. etc. need to work exactly as before. Not difficult. It will also need some extra get/set methods for the (and maybe ?).
- New class : identical to , except with a value. Can make a subclass of for backwards-compatibility.
Will work with DC with no changes as it uses APIs and not direct D access. Will need to be modified to use new metadata schema values.
search parameters can be changed to index new schemas, e.g.:
Code and table views will need alteration.
- Format of will need to be altered. (Perhaps even can use XSLT for backwards-compatilibity )
- Custom submission form stuff could be extended to take advantage of this new stuff
- Batch importer/exporter – should be easy to retain backwards compatilibity (with " " clearly indicating Dublin Core, can use different filename for other metadata)
- History system??
- UI changes to item display page