White Space

John Cowan cowan at locke.ccil.org
Mon Aug 16 19:48:38 BST 1999

David Brownell wrote:

> Hmm, the XML spec never quite seemed clear about that to me.  It didn't
> quite include a definition of the term "ignorable whitespace".

No, it doesn't.  But the kind of whitespace that SAX calls "ignorable"
is the kind mentioned in the first sentence of Clause 3.2.1.  It must
be passed to the app, but is ignored for validation, and will often
be ignored by apps as well (since it appears only in elements that
are expected to have only element content), hence the name "ignorable".

> What about an empty element "<EMPTY>  <!-- spaces!! --> </EMPTY>" ...
> isn't that "ignorable" whitespace as well?  It "must be" passed to the
> app, and clearly isn't regular character text.

Note that this element is not empty: it contains three spaces.
If the DTD says that elements named "EMPTY" (as opposed to those
declared EMPTY) have some kind of optional element content
(for example, a content model like (FOO?)), then the whitespace
would be ignorable.  Otherwise not.

> FWIW I concluded "ignorable" whitespace is within elements that have a
> content model that's not "ANY" or a mixed content model.

Or EMPTY either.  EMPTY elements can't have *anything* between
start-tag and end-tag; see clause 3.1.

> Where "application" is a fuzzy notion:  everything above the XML processor,
> which could primarily consist of library code that doesn't want to give
> such options to its callers.

"Application" in the context of the XML Rec means "everything above
the XML processor".

	John Cowan	http://www.ccil.org/~cowan	cowan at ccil.org
Schlingt dreifach einen Kreis um dies! / Schliesst euer Aug vor heiliger Schau,
Denn er genoss vom Honig-Tau / Und trank die Milch vom Paradies.
			-- Coleridge / Politzer

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