RE: Link relation type to link to discover LDP

On 22 Jun 2015 at 09:59, Ruben Verborgh wrote:
>>> That's not possible due to patterns like
>>>   ?x foaf:knows ?x
>> 
>> Does the server need to know about that? Isn't it enough if the client
knows
>> about this restriction?
> 
> It's a triple pattern, so it could/should be supported.

Strictly speaking it is not necessary but obviously it makes certain queries
more efficient. Is that increased efficiency necessary or can we move this
"feature" to the client? In other words, can we replace

   ?x foaf:knows ?x

queries with

    __ foaf:knows __

___ is a completely arbitrary value, i.e., the server returns all triples
that contain foaf:knows in the predicate position.


>>> No, there is currently no interpretation for ?var.
>>> The string "?var" is represented as "?var" in explicit representation.
>>> ?var would be a URI (because no quotes),
>>> but relative URIs are not meaningful in this context anyway.
>> 
>> Hmm.... I have to say I really don't like this.
> 
> Could you clarify?

We have variables and bind them to values. The VariableRepresentation
"specifies how to serialize variable values into strings". Variable values
are RDF terms [1]. RDF terms have no notion of placeholders or variables.
That would introduce a completely new concept and expand the value space.
Also, in most cases, it wouldn't make much sense to allow variables. We
don't want to require servers to be able to accept variables in IriTemplates
in general.


> It seems like a good thing for me:
> there currently is no interpretation for ?var,
> so no confusion can be caused.

We have to keep other applications in mind as well. Variables are a special
case in a very specific application.


>>> Does hydra:search have any formal meaning at all then?
>> 
>> Depends on what you mean by "formal meaning".
> 
> Is there anything at all a machine can derive if we use hydra:search?
> (Other than "it involves something with these parameters (but don't know
how)".)

Yes, that it can query the collection (or something else) by some parameters
or a freetext query. It is a fuzzy search - similar to popular web search
engines. My assumption is that for a lot of applications, that (vague)
contract should be enough.


[1] http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-term


--
Markus Lanthaler
@markuslanthaler

Received on Monday, 22 June 2015 19:32:16 UTC