Review of convention for representing CF cell methods and associating with FTs

[ko23]

Follow on from ticket:465 and discussion between Bryan and myself.

dgStructuredKeyword allows multiple sub-terms. The original idea was to allow grouping of terms from a single namespace. However, this can be reused to bring together terms from different namespaces in a manner similar to a parameter group... (whoops!)

A CF standard name really requires at least the option to have cell methods and feature type attached. These last 2 are also terms, but from different namespaces.

Given the above, it is possible to store the method and ft under the standard name, but it would be easier to parse if this structure, which is likely to be common and important within the NDG, is formalised.

To this end, we're proposing a convention under MOLES 1.2.5 that CF standard names can have sub-terms from the cell method and ft namespaces, and that they should occur in this order, if present.

If agreed and the structure is successful, then this will become a distinct structure/type in MOLES 1.3.

A made-up example (will make it more realistic later):

<dgStdParameterMeasured>
   <dgValidTerm>cf std name</dgValidTerm>
   <dgValidTermID>
      <ParentListID>cf std name namespace</ParentListID>
      <TermID>1</TermID>
   </dgValidTermID>
   <dgValidSubterm>
      <dgValidTerm>example cell method</dgValidTerm>
      <dgValidTermID>
         <ParentListID>cell method namespace</ParentListID>
         <TermID>10</TermID>
      </dgValidTermID>
      <ListLevel>1</ListLevel>
   </dgValidSubterm>
   <dgValidSubterm>
      <dgValidTerm>example feature type</dgValidTerm>
      <dgValidTermID>
         <ParentListID>feature type catalogue namespace</ParentListID>
         <TermID>10</TermID>
      </dgValidTermID>
      <ListLevel>1</ListLevel>
   </dgValidSubterm>
   <ListLevel>0</ListLevel>
</dgStdParameterMeasured>

[lawrence]

Some of the key relationships are encapsulated in the following diagram, and a few words about it are  here.

[rkl]

CF cell methods have now been implemented as a vocabulary in the vocabulary server (P151) and consequently may now be referenced in the same ways as any of the other vocabularies.

[rkl]

Ball passed to CF extension proposal headed by Frank Tourant.