Fwd: Issues with the What section of the VOEvent-1.1 schema

[Rob Seaman]

Hola,

I will forward three messages from Bob Denny regarding the VOEvent  
schema.  These seem like issues for the whole working group to chew  
on.  We can fold any related changes into the v2.0 efforts, which  
should be picking up again as Hotwired II approaches.

Rob
---

Begin forwarded message:

> From: Bob Denny <rdenny at dc3.com>
> Date: February 3, 2009 5:01:34 PM GMT-07:00
> To: Rob Seaman <seaman at noao.edu>, Roy Williams  
> <roy at cacr.caltech.edu>,  Andrew Drake <ajd at cacr.caltech.edu>
> Subject: Issues with the What section of the VOEvent-1.1 schema
>
> Rob (et al.) --
>
> I've been living with some validation warnings on the VOEvent-1.1  
> schema versus the actual messages that are running around out there.  
> After touching on this with Roy and Andrew, they encouraged me to  
> report this to you for consideration in future VOEvent schemata.
>
> Here's the issue... at present (VOEvent-1.1), <What> is written like  
> this:
>   <!-- What: Event Characterization -->
>   <xs:complexType name="What">
>     <xs:choice maxOccurs="unbounded">
>       <xs:element name="Param" />
>       <xs:element name="Group" />
>       <xs:element name="Description" type="Description" />
>       <xs:element name="Reference" />
>     </xs:choice>
>   </xs:complexType>
>   <xs:complexType name="Param">
>     <xs:attribute name="name" type="xs:token" />
>     <xs:attribute name="ucd" type="xs:token" />
>     <xs:attribute name="value" type="xs:string" />
>     <xs:attribute name="unit" type="xs:string" />
>   </xs:complexType>
>   <xs:complexType name="Group">
>     <xs:choice maxOccurs="unbounded">
>       <xs:element name="Param" />
>       <xs:element name="Description" type="Description" />
>       <xs:element name="Reference" />
>     </xs:choice>
>     <xs:attribute name="name" type="xs:string" />
>     <xs:attribute name="type" type="xs:string" />
>   </xs:complexType>
> Graphically, it looks like this:
>
>
>
> While Param is defined as to its attributes (name, ucd, value, and  
> unit), neither What/Param nor Group/Param are typed as Param, so the  
> validator cannot find any schema information for either one (Despite  
> Param being a defined type in the Schema). The same sort of problem  
> exists for What/Group, which is not typed as Group, as well as What/ 
> Reference, and What/Group/Reference (there is already a Reference  
> typealso). In contrast, What/Description and What/Group/Description  
> are already typed as Description, and thus they can be validated.
>
> The problem has a simple solution, shown in bold below:
>   <!-- What: Event Characterization -->
>   <xs:complexType name="What">
>     <xs:choice maxOccurs="unbounded">
>       <xs:element name="Param" type="Param" />
>       <xs:element name="Group" type="Group" />
>       <xs:element name="Description" type="Description" />
>       <xs:element name="Reference" type="Reference" />
>     </xs:choice>
>   </xs:complexType>
>   <xs:complexType name="Param">
>     <xs:attribute name="name" type="xs:token" />
>     <xs:attribute name="ucd" type="xs:token" />
>     <xs:attribute name="value" type="xs:string" />
>     <xs:attribute name="unit" type="xs:string" />
>   </xs:complexType>
>   <xs:complexType name="Group">
>     <xs:choice maxOccurs="unbounded">
>       <xs:element name="Param" type="Param" />
>       <xs:element name="Description" type="Description" />
>       <xs:element name="Reference" type="Reference" />
>     </xs:choice>
>     <xs:attribute name="name" type="xs:string" />
>     <xs:attribute name="type" type="xs:string" />
>   </xs:complexType>
> Here's the result graphically, showing that the links for Param and  
> Group/param are made and the validator can work all the way through  
> the XML. The same goes for the Reference nodes, which I typed in  
> bold above (but didn't expand in the diagram):
>
>
>
> I've circled the 5 changes in this diagram so you can see that the  
> effect is to complete the path from What all the way down to Param,  
> using the already defined Param type in the schema.
>
> I hopes this proves to be useful for future schemata.
>
>   -- Bob
>

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