Re: EAV (Re: Object-relational impedence)
Date: Sat, 29 Mar 2008 15:37:13 GMT
"Dmitry A. Kazakov" <mailbox_at_dmitry-kazakov.de> wrote in message
> On Sat, 29 Mar 2008 04:47:01 GMT, Brian Selzer wrote:
>> There is a table for attributes that are common to all
>> possible widgets, and a table for each set of attributes that are common
>> to all possible widgets, but rather to a subset of all possible widgets.
> It is interesting to see people reinventing the wheel (class). The set of
> "all possible widgets having attributes T, U, V" is a class.
That depends upon how you define what is a class. The set of all possible widgets having attributes T, U, V, such that T and U have the same sign is a different class. The set of all possible widgets having attributes T, U, V such that T and V have the same sign is also a different class. Under this definition, a widget may be a member of all three classes, right?
> But that is not my point. The problem with widgets hierarchy is that there
> are three axes of widget relations. You were discussing only one of them
> attributes, which is usually directly mapped to types. This is not that
> deal. More difficult are other two:
> 2. Visual containment. Widgets can consist of / contain other widgets.
If a widget consists of other widgets, then it must have attributes that are also widgets. If a widget contains other widgets, then it either has one attribute for each contained widget or an attribute that is a set of widgets. Visual containment can be defined in terms of attributes, so I don't understand why it is a problem.
> 3. Signal handing. Handlers of widget events are composed in a certain
> hierarchical way.
> Dmitry A. Kazakov
Received on Sat Mar 29 2008 - 16:37:13 CET