[okfn-help] vdm: primary keys question

Thu Aug 19 16:18:53 BST 2010

Hi there,

Thanks for the feedback!

On Mon, Aug 16, 2010 at 8:21 PM, Rufus Pollock <rufus.pollock at okfn.org> wrote:

>> (I'll have to think the pending story through a bit more. it's very
>> important to my use case, including pending relations and the ability
>> to revert pending items)
>
> Indeed, and reverting with vdm is very easy: you just delete (really
> delete!) the relevant 'revision'

One use case that might occur is the following:

* the database is being edited (the published version remains unaffected)

* the user makes a modification to a particular record (or set of records)

* the user also makes other modifications

* someone else comes by to review these changes

* the reviewer wants to publish some changes, but revert back others

Alternatively:

* the user makes 3 changes

* the user wants to revert one of them

The way I have this in the UI of an app is that you can revert a
particular operation on a particular record. This fits vdm less well,
as vdm works on whole revisions. I guess with vdm you could model this
as a more general undo facility. But I imagine you can't undo a
revision that has later revisions stacked on top of it, correct?

I'm going to actively play with vdm in a project to see how far I can
get it, and I'll keep an eye out for documentation issues.

Regards,

Martijn