[Zope3-dev] schema initial documentation

[Craeg K Strong]

We have been having email problems.  If this is a duplicate
post, my apologies...

--Craeg

Craeg K Strong wrote:
> 
> 
> R. David Murray wrote:
> 
>> On Sun, 28 Apr 2002, Craeg K Strong wrote:
>>  
>>
>>> in the sort of metamodeling issues you are discussing.   My question is
>>> this: will the
>>> metamodel be reified?  That is, will it be captured as actual code and
>>> classes such that models
>>> could be generated automatically from it?    This is Goodness for many
>>> reasons
>>> (which we can get into in case it is not obvious to everybody).
>>>   
>>
>>
>> I guess it's not obvious to me, probably because I don't know a lot
>> about modeling tools.  In my visualization (which may or may not
>> be shared by Martijn and Jim), there will be "generic" views and
>> components that can use Schemas to automatically generate display
>> and edit forms, possibly using additional meta-data provided by
>> companion objects defined at the same level of abstraction as
>> the Schemas.  Does your requirement go beyond that kind of thing?
>>  
>>
> I think I am a little confused.   I was looking at the XML-Schema 
> specification
> on w3.org and it includes lots of ways of specifying rules that could be
> used for validation.  For example, you might define a regular expression 
> that specifies
> what a valid string input field value should look like, or set a maximum 
> for the number
> of a certain sequence (e.g. no more than 100 items can be entered on a 
> purchase order), etc.
> 
> I can imagine how one might generate an XML-Schema from a python class, 
> properly
> annotated with other metadata.  I can further imagine how an HTML form 
> might be generated from the
> XML-Schema.  As a matter of fact, isn't that what the w3.org X-Forms 
> standard is all
> about?  I believe you define an XML-Schema that defines the data types, 
> constraints,
> and validation rules, and then a mapping (using X-Forms UI language) 
> that specifies
> how the actual form GUI should look.
> 
> But what you are talking about is creating a new kind of Schema, 
> implemented in Python.
> I wonder-- are you going to going to end up replicating the work done in 
> XML-Schema?
> Or is the idea to put together something from which one could optionally 
> _generate_
> an XML-Schema, if one wished?  That way you could stay python-centric 
> but have a nice integration path.
> Either way, I would think you would want to examine the XML-Schema spec 
> and define
> a specification (aka meta model) of your own that is similar in 
> semantics as much as makes sense.
> 
> The metamodel will define the things that can exist: for example, a 
> Schema can have Features,
> Features can either be Associations, Mutators or Accessors.  A Factory 
> is automatically generated for a Schema.
> Mutators can define Validators..... etc. etc.   and then you would 
> describe the class hierarchy
> of Validators: primitives or types or classes.   StringValidators can 
> define regular expressions..etc.
> 
> Then you could programmatically query the metamodel if you wanted.  For 
> example, in
> my business logic/python layer, I could find out what validation rules 
> would be applied
> if I were to enter a social security number.   This kind of capability 
> is convenient for
> a) multiple types of UIs:  wireless, web, Tkinter/fat client  or b) EAI 
> -- interfacing with
> legacy systems that contain old data that may or may not be compliant 
> with today's business rules.
> 
> Sorry for the rambling email, but I have hopefully explained a bit more 
> about the sort
> of requirements I am thinking about.    Your thoughts?
> 
> --Craeg