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xom-interest - Re: [XOM-interest] Problem with "Missing scheme in absolute URI reference"

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Subject: XOM API for Processing XML with Java

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  • From: Peter Murray-Rust <pm286 AT cam.ac.uk>
  • To: elharo AT metalab.unc.edu
  • Cc: xom-interest AT lists.ibiblio.org
  • Subject: Re: [XOM-interest] Problem with "Missing scheme in absolute URI reference"
  • Date: Thu, 01 Jan 2009 17:30:47 +0000

Elliotte Harold wrote:
Peter Murray-Rust wrote:

I accept this (reluctantly). Could not XOM parse the standalone="yes" message and so not pass the DTD address to Xerces?). I still don't understand where the error message comes from but it must be somewhere in the DTD structure on the W3C pages. I don't understand why a DTD has to reference a namespaceURI at all and why the error is generated in the way it is. Is Xerces producing a misleading error message? And is the W3C spec in error (it validates on their pages) or does Xerces report a spurious error?

I still have to look at where that error is coming from. I agree it does sound misleading.

Thanks;

The problem with standalone='yes' is that there's limited guarantee that it's accurate. What is a parser/XOM supposed to do when it hits an undeclared entity reference after not reading the DTD?

Also, standalone='yes' actually has a very technical meaning. In practice, standalone='yes' is wrong for almost every document with a DTD:

The standalone document declaration MUST have the value "no" if any external markup declarations contain declarations of:

* attributes with default values, if elements to which these attributes apply appear in the document without specifications of values for these attributes, or
* entities (other than amp, lt, gt, apos, quot), if references to those entities appear in the document, or
* attributes with tokenized types, where the attribute appears in the document with a value such that normalization will produce a different value from that which would be produced in the absence of the declaration, or
* element types with element content, if white space occurs directly within any instance of those types.

If we were redesigning XML from scratch today, I think the standalone document declaration would be one of the first things to go (right after the internal DTD subset).

Understood. And I agree that you/XOM have to support XML as it is, rather than how we would like it to be. It's because of that, that I in my own language (CML) I have a lightweight approach to all XML (whether text-oriented or data-oriented). I avoid DTDs, entities - except explicit numeric ones, mixed content, default values, types other than CDATA. Validation is through Schematron and (for chemistry) bespoke code. It's probably off topic, but I could see the value of a lightweight subset of XML - and we had ideas of that sort back in 1998-2000.

P.






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