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PROV-ISSUE-572: What constraints should we have on ordering of elements within the main complexTypes? [XML Serialization]

From: Provenance Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Thu, 11 Oct 2012 12:49:14 +0000
Message-Id: <E1TMICQ-0007x3-Oa@tibor.w3.org>
To: public-prov-wg@w3.org
PROV-ISSUE-572: What constraints should we have on ordering of elements within the main complexTypes? [XML Serialization]


Raised by: Curt Tilmes
On product: XML Serialization

(Caution, the word "attributes" is overloaded between PROV-N and
XML -- consider context for the meaning of that word.)

Within the PROV-N specification for most of our types, the syntax is
something like this:

something(id; a, b, c, attrs);


* a,b,c are either required or optional fields and

* attrs are optional attributes to be specified as a set of
  attribute-value pairs

Thoat attributes can include specified prov:* fields like
prov:location, prov:role, etc. or other fields in some other

The current approach to developing the XML complexType for 
each of those is to:

* make prov:id an attribute of the type

* make each of the a,b,c, XML elements and to require they be
  specified in the same order as the PROV-N

* also make the attributes XML elements, require that they be
  after the primary a,b,c fields, but they can be specified in
  any order.

The XML schema for the type becomes something like this:

  <xs:complexType name="something">
      <xs:element name="a" type="..."/>
      <xs:element name="b" type="..."/>
      <xs:element name="c" type="..." minOccurs="0"/> (optional)
      <xs:choice minOccurs="0" maxOccurs="unbounded">
        <xs:element name="location"/>
        <xs:element name="role"/>
        <xs:element name="label"/>
        <xs:element name="type"/>
        <xs:any namespace="##other"/>
    <xs:attribute ref="prov:id"/>

So, for example:

used(a1, e1, 2011-11-16T16:00:00, [ ex:parameter="p1" ])


    <prov:activity prov:ref="a1"/>
    <prov:entity prov:ref="e1"/>

There is some concern over the constraint on the ordering, either
to make it more strict, or less strict.

Here are a few options (there are others and hybrids):

A: Leave it the way it is now.

   This can allows mixing attributes so e.g. you can specify a
   prov:type, then a prov:location, then another prov:type.

   It also allows mixing prov: namespace attributes with
   non-prov: namespace attributes in any order.

B: Require all prov: namespace attributes to precede all
   non-prov: namespace attributes, but still don't require a
   specific prov:* attribute order.

C: Require strict ordering of the prov: namespace attribute
   fields in addition to strict ordering of the other elements.

   So, e.g. if you including a prov:type and a prov:label field,
   you must put the prov:label prior to the prov:type, and you
   get a validation error if you specify them in the wrong order.

D: Remove all ordering

   You could, e.g. specify a prov:type prior to the activity or
   entity elements.
Received on Thursday, 11 October 2012 12:49:19 UTC

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