[xwiki-devs] why hasn't the class deletion been implemented?

[Ludovic Dubost]

We have thought about the capability of having class heritage.. but it's 
not so easy to implement..
Want to work on it ?

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 at xwiki.org 
> <mailto:ludovic at 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 at xwiki.com <mailto:sergiu at xwiki.com>
>     > <mailto:sergiu at xwiki.com <mailto:sergiu at 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/
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-- 
Ludovic Dubost
Blog: http://blog.ludovic.org/
XWiki: http://www.xwiki.com
Skype: ldubost GTalk: ldubost