Subject: Re: [xsl] Trimming (formatting-only) leading tabs/spaces from XSLT - issues?|
From: Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>
Date: Tue, 07 Jun 2011 14:46:21 -0400
In XML (and SGML, including SGML-conformant HTML), I think this means you can follow a schema -- significant whitespace is anywhere character data is permitted. Regrettably, this means that all whitespace (outside tags) is significant when there is no schema. (Whether you can take a schema to be implicit when it is not given is another problem.)
Whether XML (or HTML) fragments embedded in XSLT can be taken to reference a schema depends, I'm afraid, on the XSLT: it won't always be true. Conservatively, we might say it's never definitively true except when a schema is specifically assigned using xsl:import-schema and xsl:result-document/@validation='strict'. But I suppose an application might also let a user declare such a binding by other means.
Yes, schema-binding within the XSLT is critical to the editor's features and the rest of the system, and is performed externally, mainly because this (hypothetical product) is a batch-processing system, with an editor for convenience. I've found issues in the 'non schema-aware' scenario, because literal-result elements, don't have full context (though there may be some ancestor element to provide an interrupted validation 'path' that is exploited if available) and can be ambiguous unless defined globally in the schema. This (incomplete) PSVI data is currently only used for partial validation of literal-result elements/attributes and auto-completion, but it makes sense to exploit this for trimming purposes, when available.
Finally, I think it's important to distinguish between whitespace handling in tag-formatting applications from the way whitespace may, or may not, be collapsed, re-flowed or munged for display in a receiving application. These are two different issues that are frequently confused. The fact that some tag-formatting applications may (usefully) reformat whitespace in some places where it is not entirely stripped -- perhaps on the grounds that receiving applications will be doing likewise, so it doesn't matter -- makes for another set of troublesome blurry cases.
I think I follow you (though I may have read this wrong!). So in this case, the tag-formatting is the stripping of whitespace and the receiving application is the editor's display and the hardcopy-rendering system for printing (both of which use line-by-line margins, not characters to auto-indent - which is why such characters must be removed first).
A developer can then, by changing the view (in the receiving application), choose a preferred indentation style or select none at all without affecting a single character. Hopefully there isn't a blurry case once you can say that all characters in the XSLT are there on merit (though some will still fulfill a text formatting role, say for XPath), not because an XML 'pretty-print' system needs them (I hope this doesn't sound emotional - its not meant to).
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