Thanks a lot.
It is clear now.
Shlomo.
From:
noah_mendelsohn@us.ibm.com [mailto:noah_mendelsohn@us.ibm.com]
Sent: â 20
îøõ 2007 21:57
To: Shlomo Yona
Cc: xml-dev@lists.xml.org
Subject: RE: [xml-dev] xsd:anyType
and xsd:any
Shlomo
Yona writes:
> OK. So,
both xsd:any and xsd:anyType refer to a subtree. While the
> default parseContents for xsd:any is
"strict" the parseContents for
> xsd:anyType is "skip"?
I'm
afraid you are still confused. As I said before, one of these is a
"type". The architectural purpose of a type in XML schema is to
be a constraint on what you're calling a subtree, I.e. independent of the name
of an element, what are its legal contents.
xsd:any
is not a type, but it's usable as a term of a particle. It doesn't
directly constrain a subtree at all. Particles are things like the
references to elements A and C in the following.
<xsd:complexType name="T">
<xsd:sequence>
<xsd:element ref="A"/>
<xsd:any />
<xsd:element ref="C"/>
</xsd:sequence>
</xsd:complexType>
You will
note that these references are to the >name< of an element (will,
literally to the declaration). The particles in the sequence, in this
example, tell what element >names< may appear as >immediate
children< of the element of type T. They also do get you started on
validating those elements, because they get you to the element declarations,
which in turn have types, which in turn constrain the contents of those
elements, perhaps by having groups such as sequences, which have
particles....and the whole thing is thus recursive. The <xsd:any>
here is just a special type of particle that matches any name. >It is
NOT a type!< There are controls you can put on the xsd:any to make it match
only names in certain namespaces, etc., as I assume you've read in the schema
Recommendation [1].
There is no
such thing as parseContents, but there is processContents on the wildcards.
Since the wildcard can match elements of any name, there's a possibility
that some such elements will have (global) declarations in the schema and some
won't. In case that's of concern to the schema author, processContents
merely tells whether it's an error not to have such declaractions, whether they
are to be ignored even if present, or whether they are to be used if available
to validate the content, but not cause an error if missing.
As I said in
my first note, the built in type named xsd:anyType behaves as if it had a
wildcard in it for elements (and another for attributes, by the way.)
anyType is magic in some ways, but it's a useful approximation for some
purposes to assume the wildcard is there. As you will see at [2], the
Recommendation says:
"There
is a complex type definition nearly equivalent to the ·ur-type definition·
present in every schema by definition. It has the following properties:"
(in this, ur-type definition means xsd:anyType -- don't ask!) If
you look at that, you will see that its particles property is defined as:
{particles}
a list containing one particle with the following properties:
So,
there's your answer: it's lax. (There is something funny going on
there, because this is the root of the type hierarchy, yet lax will reject some
things that skip will accept. We had extensive discussions for Schema 1.1
about doing something to fix that, but my somewhat vague recollection is that
we didn't come up with anything sufficiently satisfactory to propose as a
change. So, that's a glitch if I'm remembering correctly.)
Noah
[1]
http://www.w3.org/TR/2004/PER-xmlschema-1-20040318/#Wildcards
[2]
http://www.w3.org/TR/2004/PER-xmlschema-1-20040318/#d0e9210
--------------------------------------
Noah Mendelsohn
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------
|
|
"Shlomo Yona"
<S.Yona@F5.com>
03/20/2007 12:29 PM
|
To: <noah_mendelsohn@us.ibm.com>
cc: <xml-dev@lists.xml.org>
Subject: RE: [xml-dev]
xsd:anyType and xsd:any
|
Hello,
and thanks for your detailed answer.
Actually, reading the references that you listed
got me into this confusion...
OK. So, both xsd:any and xsd:anyType refer to a
subtree. While the default parseContents for xsd:any is "strict" the
parseContents for xsd:anyType is "skip"?
How can I tell the default parseContents of such
"joker" or "wildcard" definitions?
Thanks.
Shlomo.
-----Original Message-----
From: noah_mendelsohn@us.ibm.com
[mailto:noah_mendelsohn@us.ibm.com]
Sent: â 20 îøõ 2007 17:36
To: Shlomo Yona
Cc: xml-dev@lists.xml.org
Subject: Re: [xml-dev] xsd:anyType and xsd:any
Shlomo Yona asks:
> I was not able to fully understand the
difference between an xsd:any
> and an element with a type xsd:anyType.
Very different. xsd:anyType is a type, like
xsd:integer (though
xsd:anyType is special in that it can act as a
simple or complex type, and
it places essentially no restrictions on the tree
that it validates --
thing of it loosely as the Schema language's
analog of java.lang.Object).
A sample use would be:
<xsd:element
name="e" type="xsd:anyType"/>
This would mean that elements named <e> can
have any content, any
attributes, etc.
xs:any is a wildcard, usable as a term in a
content model. For example:
<xsd:complexType
name="T">
<xsd:sequence>
<xsd:element ref="A"/>
<xsd:any
/>
<xsd:element ref="C"/>
</xsd:sequence>
</xsd:complexType>
Elements of type T must have content
<A/><???/><C/>, where <???> can be
any named element. Now, if you look really
closely there is an
approximation to the definition of xsd:anytType
given for reference in the
Recommendation, and it uses an xsd:any wildcard as
the means of saying
that it allows any elements.
I hope you'll see that most of your questions are
answered once you get
the above straight. I would encourage you to
carefully read the schema
primer [1], or some of the good books on W3C XML
Schema (Priscilla
Walmsley's is among the one's that's very well
respected. [2]).
Noah
[1] http://www.w3.org/TR/xmlschema-0/
[2]
http://www.amazon.com/Definitive-XML-Schema-Priscilla-Walmsley/dp/0130655678/ref=sr_1_1/103-2086530-8739813?ie=UTF8&s=books&qid=1174404823&sr=8-1
--------------------------------------
Noah Mendelsohn
IBM Corporation
One
Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------
"Shlomo Yona" <S.Yona@F5.com>
03/20/2007 11:08 AM
To:
<xml-dev@lists.xml.org>
cc: (bcc:
Noah Mendelsohn/Cambridge/IBM)
Subject:
[xml-dev] xsd:anyType and xsd:any
Hello,
I was not able to fully understand the difference
between an xsd:any and
an element with a type xsd:anyType.
Is there any difference?
Do both wildcard methods refer to any child
element(s) or does one or both
refer to a wildcard subtree?
What should be the parse mode (parserContents) for
processing xsd:anyType?
Should is be same as xsd:any’s “skip” or “lax” or
“strict” or perhaps to
something else?
The section 3.4.7 Built-in Complex Type Definition
(in
http://www.w3.org/TR/xmlschema-1/) says, if I
understand correctly, that
the subtree should be processed in “lax”. Is that
so?
What’s the difference, if any between the
following wildcard definitions
(with regards to the depth of subtree they refer
to, the processing mode
and any other issue):
· xsd:any
· element definition
with type=”xsd:anyType”
· a complexContent
that has a restriction base=”xsd:anyType” with
an xsd:anyAttribute namespace=”##other” and
processorContents=”lax”
· a complexContent
that has a restriction base=”xsd:anyType” with
an xsd:anyAttribute namespace=”##other” and
processorContents=”skip”
Thanks.
Shlomo.
