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Suggested rewording in'3.8 Particle Details'

From: Smith, Michael K <michael.smith@eds.com>
Date: Mon, 8 May 2000 13:59:09 -0500
Message-ID: <F34B81CA6A55D21187A800A02461E9040674F5DE@USPLM207>
To: www-xml-schema-comments@w3.org
Cc: "Smith, Mike" <mksmith@aus.edsr.eds.com>
In '3.8 Particle Details':

The 'either' preceding paragraphs 1.1.1 through 1.1.3 (see below) and
1.2 is confusing.  It initiallly appears that 1.1.1 through 1.1.3 are
modified by the 'either', while upon further reading they must be
joined by an implicit 'and' and the 'either' relates the implicit 1.1
to 1.2.  I don't know what the best solution to this might be, perhaps
parenthesis or an explict 1.1 with an 'and' conjoining its children.
Perhaps your notational introduction explained this, but I didn't see
it.

> A sequence (possibly empty) of element information items is
> schema-valid with respect to a particle if either 
> 1.1.1 The length of the sequence is greater than or equal to the {min
occurs}; 
> 1.1.2 If {max occurs} is a number, the length of the sequence is less than
        or equal to the {max occurs};
 
One aspect of this separation of 1.1.1 and 1.1.2 that seems less than
optimal is that it makes it easy to define a schema that cannot be
satisfied.  E.g. minOccurs = 2 and maxOccurs = 1.  (Such schemas 
might be generated mechanically, say from database entries.)  Whereas if
1.1.1
and 1.1.2 were combined we could at least have a schema that could be
satisfied by instances that did not contain the excluded element.

  1.1.1 Let range = [{min occurs}...{max occurs}].  If range is empty
        then the sequence must be empty, otherwise the length of the
        sequence must be contained in the range. 

Hope this has not already be asked and answered elsewhere, but
I can't find it in the correspondence.

 Michael K. Smith		       	michael.smith@eds.com
 EDS CIO Services 2000			512 404-6683
 98 San Jacinto Blvd. Suite 500	512 404-6655 (fax)
 Austin, TX 78701
Received on Monday, 8 May 2000 14:59:47 UTC

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