RDF merge (Re: [Gzz] PR)

[Tuukka Hastrup]

On Mon, 31 Mar 2003, Tuomas Lukka wrote:
> > Hmm... could this be possible after we have Loom working also as RDF 
> > editor? How much the final xml-file would change between loading, editing 
> > and saving? I mean, is it at any way possible to have a CVS shared RDF 
> > files for our project management?

If we save as alphabetically sorted triples or such, CVS would notice the 
smallest change set. But there could still be CVS merge problems, and we 
don't want to deal with them. Or maybe if the conflict remover proves to 
be a simple sed-script that removes the duplicated parts of CVS conflict 
syntax...

> Hmm... actually, with RDF, the first way of merging changes would be to just
> take the space to be the set of triples. 
> 
> CVS wouldn't do it right, but it wouldn't be too hard to make a real
> merge tool that you could trust enough to know what it would do in a
> given situation.

As long as we save into CVS, we will have some kind of conflict problems, 
I think. But how far are we from using Mediaserver architecture again? If 
our append-only format for RDF is simply additions and deletions of 
triples, could we load the document as all blocks some pointer has ever 
pointed to, sorted by date (ie. don't care about multiple "current" 
blocks, and use obsoleting only to determine loading order)?

Nodes are never created or deleted. A triple cannot be deleted if it 
wasn't there, so it can't be both deleted and created at the same time. Or 
here's one problem: A triple exists in version O. In version A1(O) it's 
deleted and further added back in version A2(A1). On the other hand, in 
version B1(O) it's just deleted. When we load the set with all O, A1, A2, 
B1; the triple might be deleted or be re-created.


Anyway, I hope the conflicts should be easier to solve than previously.

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