Re: Argh...Entities

At 08:49 PM 5/11/99 +0000, Noah_Mendelsohn/CAM/Lotus@lotus.com wrote:
>The more difficult case, I think, is default values for attributes.  These 
>too affect content (and in the case of default values for namespace 
>attributes can affect the deeper meaning of the document structure.) 
>Anyway, we've heard strong opinions expressed that (1) default values for 
>attributes are an important feature of any replacement for DTDs and (2) 
>that it would be very cumbersome to define the default values somewhere 
>that is far removed from the declaration of the attribute itself.  The 
>natural place to introduce a default does seem to be on the attribute 
>declaration.

I agree that separating defaulting declarations from the 'main'
declarations for attributes is ugly and feels unnatural... However, I don't
think that's necessarily a disaster.

>So, depending on how you feel about that analysis of attribute values, 
>pandora's box is then open.  The schema can afffect the contents of a 
>standalone=no document.  Having, with regrets, crossed that bridge, does 
>that change the net tradeoff on entities?  Maybe.   The standalone=no 
>document is already potentially dependent on the schema for other reasons, 
>I.e. attribute defaults.  Now the question is:  be a proper superset of 
>DTD, including questionable features, or leave out entities?

You might want to take a look at my proposal for XML Processing Description
Language (XPDL) - http://purl.oclc.org/NET/xpdl.  One of the key things I
did there was make it possible to separate processing for constraints from
processing for default attributes.  You can make constraints checking
optional, while requiring the processor to collect default attribute
values.  You can leave the material in the same schema, while providing a
way for documents to get any combination of constraints and defaults that
is appropriate from a schema.

Simon St.Laurent
XML: A Primer / Building XML Applications (June)
Sharing Bandwidth / Cookies
http://www.simonstl.com

Received on Wednesday, 12 May 1999 10:31:04 UTC