Re: [xml-dev] Processing instruction to designate a schema as subset of

[Stephen Green <stephengreenubl@gmail.com>]

I note too that it would be handy to have a way to associate the
prose instructions corresponding to an XML processing instruction
(PI) with that PI - perhaps all PIs should at some time in the future
contain a reserved attribute which points to the resolvable URL with
their actual instructions. How about 'pi-href'?

e.g.
 <?xml-subset superset-loc="http://www.acme.example/acmeschema.xsd";
superset-ns="acme:example:acmeschema-0-1"
 type="lax"
pi-href="http://lists.xml.org/archives/xml-dev/200908/msg00318.html";?>

---
Stephen D Green




2009/8/27 Stephen Green <stephengreenubl@gmail.com>:
> And in most cases there would not even be a need to process a second
> artifact:
>
>
> =======================
>
> Instructions corresponding to processing instruction:
>
> <?xml-subset superset-loc="<<url>>" [superset-ns="<<uri>>"]
> type="strict | lax"?>
>
> are:
>
>
> 'xml-subset' the schema with this processing instruction constrains XML such
> that all so constrained XML instances are also valid instances of a superset
> schema
>
> 'superset-loc' - a url (or filenpath/filename) resolving to the
> location of the superset
> schema
>
> 'superset-ns' - optional - the namespace of the superset schema (if not supplied
> then this is the same as the namespace, if any, of the subset)
>
> 'type' - values either 'strict' or 'lax', instructions as follows
>
> A) If type="lax":
>
> In effect (that is the outcome should be the same as doing the following)
>
> 1. try to locate superset schema and use it to validate the instance, handling
> any errors as if this were the primary schema for the instance but if no schema
> could be located then skip this validation step
>
> (It could be an optional processing step to check that the subset is in fact
> a true subset of the superset, that is, logically, that every valid instance for
> the subset schema is also a valid instance for the superset schema.)
>
> 2. if there are no errors from logical step 1) or if step 1) was skipped then
> validate document using subset schema (the schema containing this processing
> instruction) and handle errors as normal.
>
> A) If type="strict":
>
> Just perform validation according to the subset schema and handle errors as if
> this were the primary schema.
>
>
> ========================
>
>
> So you see that it is a matter of trying to locate the superset schema but there
> is no actual dependency on it. In cases where it cannot be located the
> PI functions
> merely as a note about the intent of the schema as a subset of some other schema
> and a reminder that there may be valid instances for the namespace
> which are not
> valid accoring to the subset schema.
>
>
> Stephen D Green
>
>
>
>
>> Well 'standalone' is part of the XML declaration; I was thinking of
>> a processing instruction (relevant only to a schema) like:-
>>
>> <?xml-subset superset-loc="http://..."; superset-ns="http://..."; type="strict"?>
>>
>> where 'superset-loc' would be a url to the location of the superset schema,
>> 'superset-ns' would be the namespace of the superset schema (optional,
>> without it being the same namespace as the subset) and 'type' would specify
>> whether the validation is to allow nodes only found in the superset and not
>> in the subset (values perhaps 'strict' and 'lax' for 'don't allow' and
>> 'do allow' such nodes respecively).
>>
>> ---
>> Stephen D Green
>>
>> PS 'xml-subset' is probably not appropriate enough a PI name
>> maybe 'xml-subset-schema' a little better
>>>
>>>
>>>
>>> 2009/8/27 mozer <xmlizer@gmail.com>:
>>>> Do you mean something like standalone="yes/no" ?
>>>>
>>>> Xmlizer
>>>>
>>>> On Wed, Aug 26, 2009 at 8:48 PM, Stephen Green<stephengreenubl@gmail.com> wrote:
>>>>> Would it be feasible to use a processing instruction at the
>>>>> top of an xml schema to designate it as a subset of another
>>>>> schema (in the sense Rick Jelliffe recently mentioned on this
>>>>> list of all instances valid by the subset schema being also
>>>>> valid by the superset schema)? How would one go about
>>>>> defining such a processing instruction? Would it have to be
>>>>> something like DSDL - via ISO? I noticed Rick's mention of
>>>>> the need for specifying a schema and/or namespace as a
>>>>> subset of another schema and/or namespace and thought
>>>>> maybe the problem could get critical mass of interest sufficient
>>>>> to solving it. I have found the problem exists not only when
>>>>> the subset schema has a different namespace; it was tricky
>>>>> to find a way to define a subset without changing the
>>>>> namespace when first working on subsets for the Universal
>>>>> Business Language and I think people eventually just wrote
>>>>> a second schema with the same namespace but without any
>>>>> way other than an accompanying prose spec to show it as
>>>>> defining a subset of a superset (the Standard UBL schemas).
>>>>>
>>>>> Maybe to solve this a processing instruction could be defined
>>>>> which specifies within a subset schema that it is a subset of
>>>>> schema at location ABC, either same namespace or
>>>>> namespace XYZ. There might also need to be a way to tell
>>>>> tools (if feasible, I've no idea) that they should either allow
>>>>> nodes of just the superset or not when the subset schema is
>>>>> given as the schema for the instance. How then to get such
>>>>> a PI or set of PIs specified and supported?
>>>>>
>>>>> Otherwise it might be that one has to stick with prose and/or
>>>>> accompanying (test) assertions such as those of Schematron
>>>>> or (work-in-progress) OASIS TAG TC's Test Assertion Markup
>>>>> Language (shameless plug).
>>>>> ---
>>>>> Stephen D Green
>>>>>
>>>>> _______________________________________________________________________
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>>>>>
>>>>
>>>
>>
>