[Nml-wg] Review of the XSD schema

[Roman Łapacz]

Hi Freek,

Thanks for the comments. I'll look at them closer in 2013 :) (next week).

Happy New Year,
Roman

W dniu 2012-12-28 02:34, Freek Dijkstra pisze:
> Here is my review of the XSD schema. Since I'm less verbose in XSD, it's
> mostly a series of questions.
>
> First of all I really like to compliment Roman -- you have been able to
> even add rather complex constructs like implicit and explicit relations.
> I also now understand the pros and cons of XSD much better (after having
> read parts of the primer http://www.w3.org/TR/xmlschema-0/, as well as
> the discussion
> http://www.imc.org/ietf-xml-use/mail-archive/msg00217.html and rebuttal
> http://www.imc.org/ietf-xml-use/mail-archive/msg00261.html -- see
> further follow-ups for a nice cozy flamewar which may keep you warm
> during the long cold nights during this winter season.)
>
> General questions and remarks:
> ------------------------------
>
> * Where does it specify that all NML descriptions should start with
> nml:Topology as the root element?
>
> * In the current schema, the order of child elements is very strict --
> it is a sequence of elements in particular order. For example, a
> relation element MUST occur before a Location element. If relation
> occurs after a Location, the document is invalid.
>
> Here is an excerpt for the schema:
>
>>    <xs:complexType name="NetworkObject">
>>      <xs:sequence>
>>        <xs:element  name="name"       type="xs:string"          minOccurs="0"  maxOccurs="1"/>
>>        <xs:element  name="relation"   type="nml:RelationType"   minOccurs="0" />
>>        <xs:element  name="Location"   type="nml:LocationType"   minOccurs="0"  maxOccurs="1"/>
>>        <xs:element  name="parameter"  type="nml:ParameterType"  minOccurs="0"/>
>>        <!-- .... -->
>>      </xs:sequence>
>>      <!-- .... -->
>>    </xs:complexType>
> Instead, I would suggest to use xs:all:
>
>>    <xs:complexType name="NetworkObject">
>>      <xs:all>
>>        <xs:element  name="name"       type="xs:string"          minOccurs="0"  maxOccurs="1"/>
>>        <xs:element  name="relation"   type="nml:RelationType"   minOccurs="0" />
>>        <xs:element  name="Location"   type="nml:LocationType"   minOccurs="0"  maxOccurs="1"/>
>>        <xs:element  name="parameter"  type="nml:ParameterType"  minOccurs="0"/>
>>        <!-- .... -->
>>      </xs:all>
>>      <!-- .... -->
>>    </xs:complexType>
> In XSD 1.0, this would limit the maxOccurs to 1, but XSD 1.1 no longer
> has that restriction. Given that XSD 1.0 and XSD 1.1 use the same
> namespace, perhaps it is good to make this explicit:
>
>>    <xs:complexType name="NetworkObject">
>>      <xs:all>
>>        <xs:element  name="name"       type="xs:string"          minOccurs="0" maxOccurs="1" />
>>        <xs:element  name="relation"   type="nml:RelationType"   minOccurs="0" maxOccurs="unbounded" />
>>        <xs:element  name="Location"   type="nml:LocationType"   minOccurs="0" maxOccurs="1" />
>>        <xs:element  name="parameter"  type="nml:ParameterType"  minOccurs="0" maxOccurs="unbounded" />
>>        <!-- .... -->
>>      </xs:all>
>>      <!-- .... -->
>>    </xs:complexType>
> * I don't really understand how you are trying to deal with implicit and
> explicit relations.
> This seems at first very powerful (meaning: either use implicit or
> explicit):
>
>>        <xs:choice>
>>          <xs:element  name="lifetime"     type="nml:LifeTimeType"     minOccurs="0"  maxOccurs="1"/>
>>          <xs:element  name="existDuring"  type="nml:ExistDuringType"  minOccurs="0"  maxOccurs="1"/>
>>        </xs:choice>
> In fact there are four ways to represent implicit relations:
>
> 1.
>
> <nml:Node id="...">
>    <nml:name>My Device</nml:name>
>    <nml:Location>
>      <nml:name>Somewhere</nml:name>
>    </nml:Location>
> </nml:Node>
>
> 2.
>
> <nml:Node id="...">
>    <nml:name>My Device</nml:name>
>    <nml:Relation type="http:....nml/base#locatedAt">
>      <nml:Location>
>        <nml:name>Somewhere</nml:name>
>      </nml:Location>
>    </nml:Relation>
> </nml:Node>
>
> 3.
>
> <nml:Node id="...">
>    <nml:name>My Device</nml:name>
>    <nml:Location id="..." />
> </nml:Node>
> <nml:Location id="...">
>    <nml:name>Somewhere</nml:name>
> </nml:Location>
>
> 4.
>
> <nml:Node id="...">
>    <nml:name>My Device</nml:name>
>    <nml:Relation type="http:....nml/base#locatedAt">
>      <nml:Location id="..." />
>    </nml:Relation>
> </nml:Node>
> <nml:Location id="...">
>    <nml:name>Somewhere</nml:name>
> </nml:Location>
>
> Currently, for Location/locatedAt only the form 1 seems allowed.
> For LifeTime/existDuring only forms 1 and 3 seem allowed.
>
> Is this on purpose? (I presume it is on purpose that the explicit
> variants are not listed, but that the missing form #3 for Location is a
> omission.)
>
> * To iterate on existsDuring: It seems that the described form it even
> slightly different:
>
> <nml:Node id="...">
>    <nml:name>My Device</nml:name>
>    <nml:existDuring idRef="..." />
> </nml:Node>
>
> (thus without the <nml:LifeTime> wrapper)
>
> Is that interpretation correct?
>
> * The RelationType lists all possible relation URIs as values for the
> type attribute. Is it permitted to use a URI not listed here? Thus, is
> is possible to define a new relation in nml-experimental, without
> changing nml-base?
>
> Specific remarks:
> -----------------
>
>>      <xs:attribute  name="idRef"    type="xs:anyURI"        use="optional"/>
> Remove line 32, as idRef is no longer used:
>
>>        <xs:element  ref="nml:Port"  minOccurs="1"/>
> Remove minOccurs on line 40:
> (perhaps the minOccurs should be listed elsewhere?)
>
>>      <xs:attribute  name="version"  type="xs:unsignedInt"   use="optional"/>
> version type should be a dateTime on line 33:
>
> For readability, I suggest to put xsd:attribute before xsd:elements, in
> particular for NetworkObject and RelationType. (Simply because
> attributes also come earlier in a document).
>
>>        <xs:element  name="relation"   type="nml:RelationType"   minOccurs="0" />
> * relation: should be capitalized as Relation on line 23:
>
> Missing relation (lines 48-55):
> - canProvidePort
> (I assume that the implicit relations are not listed on purpose)
>
>>           <xs:element  name="duration"  type="xs:duration"  minOccurs="0"  maxOccurs="1"/>
> LifeTime does not have a duration (only a end):
>
> LifeTime should not have an id attribute.
>
> Location should have an id attribute.
>
>
>
> Note: I have not yet looked at the cardinalities (minOccurs and
> maxOccurs) yet, and only reviewed about the first 100 lines, so this is
> an incomplete list of remarks.
>
> Freek
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