Yes but we need tons of warning in case properties are deleted.
If class are deleted this is even more problematic as this can make a
lot of deletion.
For versioning, what we do is we store in the XML of each object the
definition of the class at the time the object was saved. This means we
can build the class as it was before we actually load the object.
Now I'm pretty sure we don't really make use of that.
Ludovic
Pascal Voitot wrote:
> That's what I think...
> In a ideal world, removing a class or a property should imply removing
> associated instances naturally...
> Another idea...One question: are classes and properties versioned as
> documents? I mean, if you modify a class, is it possible to keep the
> previous version and keep existing objects as instantiations of the
> older version and then new objects will be instantiations of the newer
> version of the class? We could also propose an object to be
> translated into the newer version with some risks.
> In this case, it could be simple to modify or remove properties of a
> class even if it would bring some complexity also...
> Then the last problem would be class deletion which would be more
> violent and would need some strong warnings because objects would be
> deleted definitely... in this case, a kind of temporary bin could be
> interesting...
>
> Pascal
>
> On Tue, Mar 18, 2008 at 10:56 AM, Sergiu Dumitriu <sergiu@xwiki.com
> devs@xwiki.org <mailto:devs@xwiki.org>> <mailto:sergiu@xwiki.com>> wrote:
>
> Pascal Voitot wrote:
> > This might seem stupid but what are the limitations in class/object
> > deletion?
> >
>
> We don't know what to do with the data. Adding a property is simple,
> existing objects will not have a property and it will be added
> when the
> object is saved. But when you delete a property, what do we do?
> Leave it
> there? Delete it from all the objects?
>
> If we keep it there, it will be "shadowed", as the persistence layer
> will not know that it exists. More, if we add back that property with
> the same name and another type, we'll have errors because we'll
> have two
> instances with the same identifier in two places (this is what
> happened
> when switching number types or the multiselect metaproperty of a list
> property).
>
> If we remove it, then we'll completely remove a lot of data. And is a
> warning enough for that? Probably we need a mass rollback utility that
> is able to revert bulk changes.
>
> My take is that we should remove the data, but what do others think?
> --
> Sergiu Dumitriu
> http://purl.org/net/sergiu/
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Ludovic Dubost
Blog: http://blog.ludovic.org/
XWiki: http://www.xwiki.com
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