Hi,
I've got a question on namespaces. After reading http://www.w3.org/TR/xml-names11 I still don't understand how namespaces are
applied to attributes - particularly in regard to how processing
applications are supposed to determine the proper validation DTD.
In the following XML:
-------------
<?xml version="1.0" ?>
<root xmlns="http://www.w3.org/TR/REC-html40"
xmlns:html="htt p://www.w3.org/TR/REC-html40">
<a href="page1.htm l" html:href="page 2.html">
<html:a href="page1.htm l" html:href="page 2.html">
</root>
-------------
How is an application supposed to interpret these attributes?
TIA,
Axel Dahmen 13  2527 
In article <eg**********@o nline.de>,
Axel Dahmen <NO*****@NoOneK nows.invalidwro te:
><root xmlns="http://www.w3.org/TR/REC-html40"
xmlns:html="htt p://www.w3.org/TR/REC-html40">
<a href="page1.htm l" html:href="page 2.html">
<html:a href="page1.htm l" html:href="page 2.html">
</root>
How is an application supposed to interpret these attributes?
The <aand <html:aelemen ts are both in the http://www.w3.org/TR/REC-html40
namespace. The href attributes are in no namespace, and the html:href
attributes are in the http://www.w3.org/TR/REC-html40 namespace.
The interpretation of attributes in no namespace depends on the element
they're on, so the interpretation of the href attributes is given by
the HTML spec.
>After reading
http://www.w3.org/TR/xml-names11 I still don't understand how namespaces are
applied to attributes - particularly in regard to how processing
applications are supposed to determine the proper validation DTD.
Namespaces have nothing to do with determining the DTD. On the other
hand, namespaces *are* used to choose an XML Schema for validation.
The schema definition of the html:href attribute (if such a thing
exists) should appear in the HTML schema, because it's in the HTML
namespace. The definition of the href attribute should also appear
there, because it's on an element in the HTML namespace.
-- Richard
Richard Tobin schrieb:
The schema definition of the html:href attribute (if such a thing
exists) should appear in the HTML schema, because it's in the HTML
namespace. The definition of the href attribute should also appear
there, because it's on an element in the HTML namespace.
And, of course, the HTML 4 specification does not define or use a
namespace, because HTML is no XML application.
--
Johannes Koch
Spem in alium nunquam habui praeter in te, Deus Israel.
(Thomas Tallis, 40-part motet)
In article <45************ ***********@aut hen.yellow.read freenews.net>,
Johannes Koch <ko**@w3develop ment.dewrote:
>And, of course, the HTML 4 specification does not define or use a
namespace, because HTML is no XML application.
I was talking theoretically :-)
-- Richard
This looks awfully like a homework problem. If so, shame on you. But
it's a common point of confusion, so it's worth explaining in detail
whether or no.
Attributes are bound to a namespace *only* if their names use a prefix.
Unlike elements, they are not affected by an inherited default
attribute, nor do they pick up the namespace of their element.
<?xml version="1.0" ?>
<root xmlns="http://www.w3.org/TR/REC-html40"
xmlns:html="htt p://www.w3.org/TR/REC-html40">
These two attributes, of course, default the default namespace and the
html: prefix respectively. Since the default is defined, the <root>
element itself is in the namespace http://www.w3.org/TR/REC-html40 ...
which may not be what was intended.
<a href="page1.htm l" html:href="page 2.html">
Since the default namespace is set, the <aelement is in that
namespace. Since html:href has a prefix, it is in the namespace bound to
that prefix (which also happens to be http://www.w3.org/TR/REC-html40).
Since href does not have a prefix, is is *NOT* in that namespace -- it's
in the "no namespace" namespace. The fact that the element is namespaced
has no effect on the attributes.
<html:a href="page1.htm l" html:href="page 2.html">
html: is bound, so html:a is an a element in that namespace.
The attributes are as discussed before; the fact that the element is
namespaced has no effect on the attributes..
--
() ASCII Ribbon Campaign | Joe Kesselman
/\ Stamp out HTML e-mail! | System architexture and kinetic poetry
Thanks, Richard, I'm still trying to understand XML, so your information is quite appreciated!
After reading
http://www.w3.org/TR/xml-names11 I still don't understand how namespaces are
applied to attributes - particularly in regard to how processing
applications are supposed to determine the proper validation DTD.
Namespaces have nothing to do with determining the DTD. On the other
hand, namespaces *are* used to choose an XML Schema for validation.
I don't understand... Let's keep XML Schema out of focus for a minute.. From the XML Spec., DTDs are used by XML parsers to validate an XML document. So, DTDs are to XML what header files are to C++, aren't they?
For an XML parser being able to validate an XML document it uses DTDs. If I want to create an XML document being compiled from several DTDs (e.g. XHTML1.0), I add a reference to the corresponding DTDs to my XML document. For an XML parser being able to determine the correct DTD from a given set of DTDs at the beginning of an XML document, namespaces are used then. Aren't they?
Thanks a lot, Joe. Like I said in my previous post, I'm currently learning XML and your information is QUITE appreciated!
This looks awfully like a homework problem. If so, shame on you. But
it's a common point of confusion, so it's worth explaining in detail
whether or no.
No no, I'm just learning for myself... Look at me.. would I EVER cheat? ;-)
In my other life I'm a software engineer, but admittedly this XML specification is too hard for me to grasp.
I understand how attributes are saved and stored in a tree considering namespaces. What I don't understand is how an application is supposed to determine a valid attribute to apply to an element:
Imagine there's an application being able to render XML/XSL and XHTML1.0. Let's call it XaPP...
From what I understand, DTDs are to XML what header (.h) files are to C++, so in a document to render both, some proprietary XML and some embedded XHTML, I'd add 2 DTDs:
<?xml version="1.1"?>
<!DOCTYPE greeting SYSTEM "hello.dtd" >
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://...dtd">
Next, I'd assign a namespace to the XHTML DTD: (To stress my point, I'll add the default namespace to XHTML as well)
<body xmlns="http://www.w3.org/TR/REC-html40"
xmlns:html="htt p://www.w3.org/TR/REC-html40">
Then I'd add nodes to the tree:
...
<a href="page1.htm l" html:href="page 2.html">
<html:a href="page1.htm l" html:href="page 2.html">
</body>
Three questions arise:
a) Which element declaration do I have to add to "hello.dtd" to allow for foreign (XHTML) elements to appear in the XML tree?
b) When the XaPP application reaches the <a(or <html:a>) element, which href / html:href attribute will it use to render the hyperlink?
c) Shouldn't at least two of the href / html:href attributes be interpreted as invalid by the parser as they are not mentioned in the appropriate DTD?
Thanks a lot for helping me to understand!! (Which I unfortunately don't yet..)
Regards,
Axel Dahmen
These two attributes, of course, default the default namespace and the
html: prefix respectively. Since the default is defined, the <root
element itself is in the namespace http://www.w3.org/TR/REC-html40 ...
which may not be what was intended.
Oops, my fault... ;)
Axel Dahmen schrieb:
For an XML parser being able to validate an XML document it uses DTDs.
Only one DTD per document.
If I want to create an XML document being compiled from several DTDs (e.g. XHTML1.0),
compiled?
I add a reference to the corresponding DTDs to my XML document. For an XML parser being able to determine the correct DTD from a given set of DTDs at the beginning of an XML document,
There is no set of DTDs at the beginning of an XML document. There is
only _one_ document type declaration which references _one_ document
type definition.
namespaces are used then. Aren't they?
No.
DTDs don't know namepaces. They are older than XML namespaces. For a DTD
an element foo:bar is not an element named bar from a namespace with the
prefix foo, but an element named foo:bar.
--
Johannes Koch
Spem in alium nunquam habui praeter in te, Deus Israel.
(Thomas Tallis, 40-part motet)
Axel Dahmen wrote:
What I don't understand is how an application is supposed to determine a valid attribute to apply to an element:
Remember, the attributes have specific meanings to applications.
Therefore, they're generally hardcoded into the application.\
So the decision's made by the programmer.
From what I understand, DTDs are to XML what header (.h) files are to C++
so in a document to render both, some proprietary XML and some
embedded XHTML, I'd add 2 DTDs:
No. As others have said, one DTD per document, made up of an External
Subset and an Internal Subset. If you want to intermix other structures,
you either need a DTD which leaves some areas unvalidated (using ANY),
or you need to move to schemas. Note that XHTML *IS* intended to be
primarily schema-based rather than DTD-based.
Next, I'd assign a namespace to the XHTML DTD
No. Again as others have said: DTDs don't do namespaces. In fact, DTDs
are pretty darned nearly INCOMPATABLE with namespaces. If you're working
with namespaced documents, do not waste time studying DTDs; go directly
to schemas, or drop back to well-formed rather than validated.
--
() ASCII Ribbon Campaign | Joe Kesselman
/\ Stamp out HTML e-mail! | System architexture and kinetic poetry
compiled?
^= combined
Thanks to all of you for your valuable help.
Regards,
Axel Dahmen
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