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Re: unrecognized actiontype in maction

From: David Carlisle <davidc@nag.co.uk>
Date: Tue, 29 May 2012 14:03:49 +0100
Message-ID: <4FC4C935.2060508@nag.co.uk>
To: Frédéric WANG <fred.wang@free.fr>
Cc: www-math@w3.org
On 29/05/2012 12:58, Frédéric WANG wrote:
>> That would be an incompatible (but not necessarily impossible) change to
>> the spec, since it currently says unknown values should be ignored.
> Yes, unknown values are ignored but what about the case when the
> actiontype is not specified? The actiontype is declared "required"

Ah. Sorry so per current spec not having it is an error.
> I'm thinking about
> http://www.w3.org/TR/MathML/chapter2.html#interf.error
> I don't see anything about how to handle the "required" value here:
> http://www.w3.org/TR/MathML3/chapter2.html#fund.defaults

> However, I'm not sure that this requirement is specified by the relax ng
> schema:
> http://www.w3.org/TR/MathML3/appendixa.html#parsing_maction.attributes

the relax ng (which is mostly automatically generated from the tables in 
the spec) makes it optional. Arguably that's a bug in the schema 
although of course the schema never claims to encode _all_ requirements 
of the spec.
> (BTW, I see that if no selected sub-expression exists it should also be
> handled as an error. But that's not what Firefox currently does.)

So in summary what I think the spec says is

* a missing actiontype is an an error (not detected by the schema) but 
any value should be accepted

* If the actiontype is known by the processor then the it may ignore any 
selection attribute and may have other requirements on the number of 
children required for that action

* If the actiontype is not known then the child identified by the 
selection attribute (or 1 by default) should be rendered.

Does that sound like reasonable behaviour or should we be considering an 
errata to change something?


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Received on Tuesday, 29 May 2012 13:04:20 UTC

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