Thanks for your info, and I will use that for benchmarking. 

Best Regards
Yongnian
-----Original Message-----
From: Boris Kolpackov [mailto:boris@c...] 
Sent: 2007=C4=EA5=D4=C214=C8=D5 2:45
To: Le, Yongnian
Cc: Michael Kay; xmlschema-dev@w...; Jones, Kevin; Yu, Zhiqiang
Subject: Re: is there any formal commercial identity constraint cases

Hi Yongnian,

Le, Yongnian <yongnian.le@i...> writes:

> That's a pity that there is no real application having identity
> constraints, maybe because that feature is quite advanced.

I did a quick search over our schema repository. The following
two "real" schemas appear to use identity constrains:

3DXML                                             =
http://www.3ds.com/3dxml
Open Vulnerability and Assessment Language (OVAL) http://oval.mitre.org/


> 1.     Identity constraint processing creates dependence between
> validations in different SAX events, which make it hard for further
> advanced optimization; while regular expression in schema validation
> can be processed in a single SAX event validation.

This is not entirely correct. SAX can deliver content for an element
or attribute over several calls to characters().

> 2.     Identity constraint requires typed based comparison, which
> might involve a lot of table/value-object/memory management, type
> conversion and string operations during validation;

That's another reason why it is a good idea to do validation and
data extraction as one step. Luckily the element/attribute that is
specified in the field declaration should be of a simple type. This
way you only need to handle a handful of built-in XML Schema simple
types when it comes to comparing the values. Figuring out if types
are related by inheritance could be tricky though.

[Yongnian] identity constraint validation requires that simple value of =
previous qualified nodes are kept for future comparison and searching =
based on simple type (not necessary atomic, could be union or list). =
Only data extraction seems not enough for validation.

hth,
-boris


-- 
Boris Kolpackov
Code Synthesis Tools CC
http://www.codesynthesis.com
Open-Source, Cross-Platform C++ XML Data Binding

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