> Ludovic
>
> Pascal Voitot wrote:
>> ok I see
>> But do we agree that we shall have a class/mechanism deletion
>> somewhere? (in fact I agree with myself about that at least because
>> I'm frustrated not to be able to delete the classes I don't need
>> anymore :))
>>
>> I'm not sure about something: did you intend to give to the concept of
>> "class" about the same "generic" extend as the concept of "class" in
>> any OO language? Is a class a kind of descriptor of entities with
>> their own properties and relations to other entities? or is a class
>> only a convenience for gathering properties and creating objects with
>> these properties?
>> If XWiki classes are real classes (I think they are) then it would be
>> nice to push the concepts as far as possible... Moreover, with XE
>> (that I don't have installed yet), it would be nice to be able to
>> manage classes directly and to have refactoring features :)...
>>
>> Pascal
>>
>>
>> On Tue, Mar 18, 2008 at 12:52 PM, Ludovic Dubost <
ludovic@xwiki.org
>> <mailto:
ludovic@xwiki.org>> wrote:
>>
>>
>> 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 <mailto:
sergiu@xwiki.com>
>> > <mailto:
sergiu@xwiki.com <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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