ak117 at freenet.carleton.ca
Mon Feb 23 17:15:51 GMT 1998
Michael J. Suzio writes:
> What I wonder is, how does SAX decide what is ignorable
> whitespace and what is significant? I'm not clear on how that
> works, and the role xml:space plays in defining that.
> Ignoring whitespace is one of the most tedious things I keep doing
> in my XML parsing apps, I'd prefer to have to explicitly *work* to
> keep whitespace.
SAX itself is not a program, but its interface allows DTD-driven
parsers to make the distinction described in clause 2.10 (AElfred
takes advantage of the distinction):
2.10 White Space Handling
In editing XML documents, it is often convenient to use "white space"
(spaces, tabs, and blank lines, denoted by the nonterminal S in this
specification) to set apart the markup for greater readability. Such
white space is typically not intended for inclusion in the delivered
version of the document. On the other hand, "significant" white space
that should be preserved in the delivered version is common, for
example in poetry and source code.
An XML processor must always pass all characters in a document that
are not markup through to the application. A validating XML processor
must also inform the application which of these characters constitute
white space appearing in element content.
Note that this has nothing to do with the `xml:space' attribute -- it
is your application, rather than the XML parser, that is allowed to
act on that one.
> What I don't understand is, given something like this in a DTD:
> <!ELEMENT QUOTE (SOURCE?|LINE+|KEY+)>
> Why wouldn't *any* character data located within
> <QUOTE></QUOTE> (and not inside one of it's child
> elements) be ignorable? I'd expect a parser seeing this:
> <SOURCE href="http://www.quotesrus.com/">
> <LINE>This is line 1 of the quote</LINE>
> To ignore those carriage returns and extraneous spaces within the
> QUOTE element, and just give me the SOURCE and LINE elements and
> their content.
Absolutely correct. If your XML parser is DTD-driven (as AElfred is),
it should somehow flag the carriage returns and leading spaces in your
example as ignorable. It is a major pain having to deal with this
kind of thing yourself, if your parser is not DTD-aware.
All the best,
David Megginson ak117 at freenet.carleton.ca
Microstar Software Ltd. dmeggins at microstar.com
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