[Nml-wg] Discussion on identifiers for relations

[Freek Dijkstra]

Roman, Jeroen,

While we're here together I still like a short discussion on identifiers
for relations.

Currently, it is just a string in XML. e.g. "isSink", "hasPort"
However, it is a full URL in RDF, e.g.
"http://schemas.ogf.org/nml/2013/10/relation#isSink",
"http://schemas.ogf.org/nml/2013/10/relation#hasPort".

So the translation is to simply prefix the XML-identifier with a fixed
(special-purpose) URI. So far I used
"http://schemas.ogf.org/nml/2013/10/relation#".

However, as we found at the previous OGF, this is a problem when a new
version of NML is defined in the future, with possibly more relations.
Eg.: "http://schemas.ogf.org/nml/2016/08/relation#isSink". In that case,
it is no longer clear which URL should be prepended to the base name
("isSink").

I can see two solutions:
1. Append the namespace of the element when translating.
E.g.
<nml:Topology xmlns:nml="http://schemas.ogf.org/nml/2013/10/base#">
...
  <nml:Relation type="isSink">
becomes "http://schemas.ogf.org/nml/2013/10/base#isSink"

(thus not "http://schemas.ogf.org/nml/2013/10/relation#isSink")

2. Don't translate relation identifier between XML and RDF, and use full
URI in XML (yes, it's ugly, but it's simple):
<nml:Relation type="http://schemas.ogf.org/nml/2016/08/relation#isSink">

Can we talk this over during a break today?

Freek