Re: combine

[Norman Walsh <ndw@nwalsh.com>]

/ James Clark <jjc@jclark.com> was heard to say:
| Right.  We could have a restriction on combine="group" that you can't use it
| in a way which makes order significant (eg combining two <element>
| patterns).  On the other hand that would rule out using combine="group" to
| provide functionality similar to derivation of complex types by extension in
| XML Schema (adding things on to the end of a content model).

Making order insignificant would be nice, but I think it would be a
mistake to lose the ability to mutate content models this way.

| I wonder whether one could attach a priority to definitions to allow
| combination without order dependence (like xsl:template).  With
| combine="replace", the pattern with the highest priority would be the one
| used.  With combine="group", the patterns would be grouped in order of
| priority.  You wouldn't be able to mix different kinds of combine for a
| single pattern.

Sounds interesting. A "computationally non-trivial nice-to-have" would
be combine="restrict". This would be the same as replace, but it would
be an error if the new content model was not a strict subset of the
current content model.

                                        Be seeing you,
                                          norm

-- 
Norman.Walsh@Sun.COM   | If today was a fish, I'd throw it back in.
XML Standards Engineer |
Technology Dev. Group  | 
Sun Microsystems, Inc. |