LINK VOTable element for DATALINK

[Patrick Dowler]

(appendix section numbers from VOTable-1.3 doc)

I woud like to add to this that the appendix of VOTable contains all 
kinds of interesting twists and ideas. The proposed structure for a
<RESOURCE type="service"> we are discussing actually combines the ideas 
in A.2 (VOTable query: uses FIELD to describe query params of a URL) and 
A.4 (uses child LINK to indicate that the value for a FIELD comes from 
someplace else...

 > *So my question: is this third emerging extension of LINK usage not
 > clash with the two previous usages.*
 > For instance, until now, the "value" attribute can be used for
 > alternative link text. And in this third usage, the "value" attribute
 > is used as a kind of "ref" attribute.

(note: as per previous messages, value was mistakenly used when it 
should have been href).

In the PARAM-LINK proposal, we use a PARAM to describe a service input 
parameter and a child LINK to say that the value comes from someplace 
else. In this case, the href is restricted to a fragment so it is always 
someplace else in the same document. So no: I don't see this as clashing 
with those possible uses.

In A.2 specifically, I am interested to hear why FIELD was chosen over 
PARAM to describe essentially a service API? Is it just because PARAM 
was originally designed as a constant value? and requires the value 
attribute? It seems that conventions for using PARAM and the general 
understanding of the term have gone the other way...

If we really want to use PARAM-LINK instead of FIELD-LINK, what should 
we do about the required value attribute?

VOTable-1.3 section 3.5 does say that other standards can/should define 
values for content-role (otherwise doc-like may be assumed). So it looks 
like DataLink should in fact define a content-role for these LINKs since 
they are relative URIs to something not doc-like.


-- 

Patrick Dowler
Canadian Astronomy Data Centre
National Research Council Canada
5071 West Saanich Road
Victoria, BC V9E 2E7

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