Avoid proliferation of links in resources

[aaime]

When linking to a related resource, some implementations provide a full set of links, targeting every supported representation of the target resource. This can cause the size of documents to grow significantly.

Possible approaches:

• Provide a format-less link in HTML resources, and a full set of links in the machine oriented representations (this is done, with some variations, by both GeoServer and Cubewerx)
• Just link without the format, and allow content negotiation to take place

The second approach is based on the assumption that the client will just provide a list of supported/preferred formats in the Accept header. In case the client actually wants to find out which representations are supported, then:

• Either HEAD or OPTIONS should be implemented by the server
• The links to alternate representation are returned in the response to the above requests (links should be there regardless, as per Commons requirements)

It is to be noted that Commons currently provides no indication about the usage of those two methods, while OGC API Features recommends implementing HEAD.

[cmheazel]

This is the sort of information we try to capture in the Users Guide. That suggests two actions: 1) Add a section to the Users Guide and populate it 2) Add a reference to that content in the Common Part 2 standard.