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RE: Implementation issues with the VoiceXML 2.0 LCWD (20020424) XML Schemas

From: Scott McGlashan <scott.mcglashan@pipebeach.com>
Date: Fri, 23 Aug 2002 13:38:24 +0200
Message-ID: <2764A29BE430E64A92EB56561587D2E7107EF0@se01ms02.i.pipebeach.com>
To: "Dave Burke" <david.burke@voxpilot.com>, <www-voice@w3.org>

thank you for your input. Similar problems with the schemas have already
been reported to the group and they will be fixed in the next version. I
will add the issues you note to our change requests.  

 -----Original Message-----
From: Dave Burke [mailto:david.burke@voxpilot.com]
Sent: Monday, August 19, 2002 22:25
To: www-voice@w3.org
Subject: Implementation issues with the VoiceXML 2.0 LCWD (20020424) XML

I have recently noticed a number of issues with the XML schema strategy
for VoiceXML 2.0 (20020424) and SRGS CR (20020626) and SSML WD
(20020405). Obviously I have missed the LCWD call for comments by a
considerable amount but did not notice any relevant CRs and think my
comments could be of some benefit for a future draft.
I must add the disclaimer that I only have limited Schema experience. In
addition, I should note that the issues outlined below were provoked by
attempting to use Java Xerces 1.4.4 (which only has beta Schema
Recommendation support and is not necessarily a reference implementation
- although in general I find the C++ and Java parsers excellent...). 

Hope this is of some use,
David Burke BE MEngSc
Chief Architect
Voxpilot Ltd
Quantum House
Temple Road
Blackrock, Co. Dublin
Mobile: +353 86 6055086
Office: +353 1 2091922
email: david.burke@voxpilot.com <mailto:david.burke@voxpilot.com> 

Issue 1
+ Synopsis: 
The files, grammar-adapter.xsd and synthesis-adapter.xsd, should not
<include> the schemas they 
+ Suggested solution: 
Remove - inclusion is implicit in the <redefine> element.

Issue 2
+ Synopsis:
The prefix vxml: is not required (and undefined) in grammar-adapter.xsd
and synthesis-adapter.xsd 
+ Suggested solution: 
Omit as it is implicit via the default xmlns in each of these documents.

Issue 3
+ Synopsis:
It *seems* the <redefine> element can only employ extension or
restriction of base types - not both.
+ Suggested solution:
Verify this to be true and maybe consider using a
grammar-adapter-extension.xsd and grammar-adapter-restriction.xsd with 
vxml.xsd including the later, which in turn redefines a restiction the
former, which in turn redefines an extension of grammar-core.xsd.
Issue 4
+ Synopsis:
<redefine> can only perform limited redefinition by extension or
restriction. Specifically this 
means that omitting parent elements/attributes is not possible nor is
loosening restrictions
in redefined types. This affects, at least:
- grammar-adapter.xsd attempt to make SRGS 'version' attribute to
optional - not possible as it is not
more restrictive than its base which is 'required'
- synthesis-adapter.xsd attempt to use a union of types for the 'type'
attribute of say-as - again not
more restrictive

+ Suggested solution:
Make base types more general - this might mean changing SRGS and SSML

Issue 5
+ Synopsis:
The grammar-adapter.xsd and synthesis-adapter.xsd files should start
with the usual xml prolog.
+ Suggested solution:
Add the XML prolog and use consistent encoding across all VBWG
specifications e.g. VoiceXML 2.0 LCWD 
and SRGS CR use different encodings (UTF-8 and ISO-8859-1 respectively).

Issue 6
+ Synopsis:
In vxml.xsd the simpleType 'Boolean.datatype' uses enumeration with
xsd:boolean, which is illegal.
(ref. Section 2.1 W3C XML Schema Part 0: Primer)
+ Suggested solution:
Use xsd:string and 'true' and 'false' enumerated values.

Issue 7
+ Synopsis:
In grammar-adapter.xsd 'grammar-header' and 'grammar-body' groups are
+ Suggested solution:
Omit - not required if doing an <extension> or <restriction> of base

Issue 8
+ Synopsis:
The <redefine> element must contain <extension> or <restriction>
grandchildren. This is
a problem with grammar-adapter.xsd and synthesis-adapter.xsd.
(ref. Section 4.2.2 W3C XML Schema Part 1: Structures)
+ Suggested solution:
Add <extension> or <restriction> as necessary.

Issue 9
+ Synopsis:
In vxml.xsd the anonymous complexType child of element should allow
mixed content.
Suggested solution:
Add mixed="true"
Received on Friday, 23 August 2002 07:38:27 UTC

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