[PEAK] peak.model and mappings?

[Bob Ippolito]

On Feb 23, 2004, at 8:35 PM, Bob Ippolito wrote:

> On Feb 23, 2004, at 8:12 AM, Phillip J. Eby wrote:
>
>> At 08:35 PM 2/22/04 -0500, Bob Ippolito wrote:
>>> How are you supposed to define a mapping with peak.model?  I'm 
>>> looking for something that would be used like this, in theory:
>>>
>>> from peak.api import *
>>>
>>> class MyElement(model.Element):
>>>
>>>     class elementToStringMapping(model.Mapping):
>>>         referencedKeyType = 'MyElement'
>>>         referencedType = model.String
>>
>> There isn't such a feature type at present, I'm afraid.  But if you 
>> look at peak.metamodels.MOF131.Namespace, you'll see an 
>> implementation of an "indexed" relationship whereby a sequence of 
>> objects is also indexed in a mapping.  It's not quite the same thing, 
>> but for some applications it's actually better, since it also retains 
>> sequence information.  If your value objects don't reference their 
>> keys, use a tuple as the target type.  IOW, if your feature's 
>> singular name is 'mapping':
>>
>> anElement.addMapping((key,value))
>>
>> would add the key-value pair.  You can define additional verbs of 
>> course that do this in a cleaner-seeming way, according to your app's 
>> needs.
>>
>> Or you can completely override the standard stuff and do it your own 
>> way altogether.
>
> Ah I see.  Basically, what I was trying to do was more of a metamodel, 
> like building tables in SQL (not triggers, stored procedures, etc).. 
> model the data, not its behavior, so I wanted to put as much metadata 
> in there as possible.  I think I will try and develop my own 
> "model.Mapping" to go along with this style, because I don't want to 
> tie myself to python dicts, or ZODB BTrees, or what have you, and I do 
> need to know what kind of objects are used for keys, and what for 
> values.
>
> Basically, I want to define the specification and decide what the 
> implementation is going to be later, or even use the specs to 
> implement a storage for me (i.e. design SQL tables based upon my 
> Element classes and their StructuralFeatures).

Here is my first pass at extending StructuralFeature and friends to 
support mappings...

It would be great if someone (PJE, preferably) could take a look at it 
and let me know if I'm going in the right direction here.. I'm still 
new to PEAK :)

-bob

-------------- next part --------------
A non-text attachment was scrubbed...
Name: model_support.py
Type: application/octet-stream
Size: 9164 bytes
Desc: not available
Url : http://www.eby-sarna.com/pipermail/peak/attachments/20040224/4654fd5c/model_support.obj
-------------- next part --------------
A non-text attachment was scrubbed...
Name: test_model_support.py
Type: application/octet-stream
Size: 1322 bytes
Desc: not available
Url : http://www.eby-sarna.com/pipermail/peak/attachments/20040224/4654fd5c/test_model_support.obj