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Do attributes have scope? Are attributes metadata?
- From: "Costello, Roger L." <costello@mitre.org>
- To: "xml-dev@lists.xml.org" <xml-dev@lists.xml.org>
- Date: Wed, 29 Feb 2012 13:07:45 +0000
Hi Folks,
Do attributes have scope?
Consider this:
<Document classification="unclassified">
<Para>...</Para>
<Para>...</Para>
<Para>...</Para>
</Document>
(1) Is it correct to say, "The scope of the classification attribute is from the Document start-tag to its end-tag" or, more casually, "The Document and its content are unclassified"
Conversely, consider the same document where the attribute is replaced with a namespace declaration:
<Document xmlns="http://www.example.org">
<Para>...</Para>
<Para>...</Para>
<Para>...</Para>
</Document>
(2) Is it correct to say, "The scope of the namespace declaration is from the Document start-tag to its end-tag"
Are attributes metadata?
Consider this:
<altitude units="feet">12000</altitude>
(3) Is it correct to say, "The units attribute provides metadata about the altitude element's value" or, more casually, "The attitude is 12000 feet"
I will attempt to answer my questions.
First, the XML specification defines attributes as:
Attributes are used to associate name-value pairs
with elements.
Wow!
That's all. It says nothing about scope or metadata.
Second, the Namespace specification *does* talk about scope:
... these declarations are scoped by the elements on
which they appear ...
So, here are my answers to my questions:
(1) Attributes do not have scope.
(2) Namespace declarations *do* have scope. In the example above, the scope of the http://www.example.org namespace is from the Document start-tag to its end-tag.
(3) Attributes are not metadata.
Do you agree?
/Roger
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