Re: Profiles in Linked Data

On 5/11/15 11:54 AM, Svensson, Lars wrote:
> Kingsley,
>
> On Saturday, May 09, 2015 12:07 AM, Kingsley Idehen wrote:
> [...]
>>> So to repeat my question in another mail: I have an entity described by a
>>> (generic) URI.
>> You have an entity identified by a IRI in RDF. If you are adhering to Linked Open
>> Data principles, said IRI would take the form of an HTTP URI.
>>
>>
>>>   Then I have three groups of documents describing that entity, the first uses
>>> schema.org, the second group uses org ontology and the third uses foaf.
>> You have an entity identified by an HTTP URI. The dual nature of this kind of
>> URI enables it function as a Name. The fundamental quality (attribute,
>> property, feature) of a Name is that its interpretable to meaning ie., a Name
>> also has a dual (denotation and connotation feature) which is what an HTTP URI
>> is all about, the only different is that denotation->connotation (i.e. name
>> interpretation) occurs in the hypermedia medium provided by an HTTP network
>> (e.g. World Wide Web). Net effect, the HTTP URI resolves to and document at a
>> location on the Web (i.e, a document at a location, which is the URL aspect of
>> this duality).
> OK. I have an http URI that denotes an entity. Depending on the server configuration and what accept-headers I provide, the http dereferencing function returns a document at a location.
>
>>> All documents are available as RDF/XML, Turtle and xhtml+RDFa. How does a
>>> client that knows only the generic URI for the resource tell the server that it
>>> prefers foaf in turtle and what does the server answer?
>> It can do stuff like this:
>>
>> curl -L -H "Accept: text/xml;q=0.3,text/html;q=1.0,text/turtle;q=0.5,*/*;q=0.3" -
>> H "Negotiate: *" -I http://dbpedia.org/resource/Analytics
> OK, I can see how setting the Accept-header negotiates the media type. If I understand correctly, the Negotiate-header gives the server and intermediate proxies a carte blanche to negotiate things any way they prefer. I don't see any header that tells the server what profile/shape/vocabulary the client prefers.

That's about a client negotiating different types of document content 
using a preference algorithm which in integral to Transparent Content 
Negotiation. It has nothing to do with a preferred vocabulary of terms 
e.g., dcterms vs schema.org in regards to terms used to describe 
something using RDF Language bases sentences/statements.

If you want an RDF based entity description, where the terms used come 
from a specific vocabulary, that's where you could leverage a query 
language e.g., SPARQL. Of course, there are those that don't want to use 
SPARQL which could then lead to yet another kind of "profile" relation 
object, but ultimately such use will only be the equivalent of ignoring 
the existence of "multiplication" and "division" in regards to 
arithmetic operations.

Conclusion: if folks want to build "profile" relations for selecting RDF 
content constructed using terms from a specific vocabulary, that's fine 
too, even though its  utility would simply boil down to navigating 
politics.
>
>> HTTP/1.1 303 See Other
>> Date: Tue, 05 May 2015 16:01:06 GMT
>> Content-Type: text/turtle; qs=0.35
>> Content-Length: 0
>> Connection: keep-alive
>> Server: Virtuoso/07.20.3213 (Linux) i686-generic-linux-glibc212-64  VDB
>> TCN: choice
>> Vary: negotiate,accept
>> Alternates: {"/data/Analytics.atom" 0.500000 {type application/atom+xml}},
>> {"/data/Analytics.jrdf" 0.600000 {type application/rdf+json}},
>> {"/data/Analytics.jsod" 0.500000 {type application/odata+json}},
>> {"/data/Analytics.json" 0.600000 {type application/json}},
>> {"/data/Analytics.jsonld" 0.500000 {type application/ld+json}},
>> {"/data/Analytics.n3" 0.800000 {type text/n3}}, {"/data/Analytics.nt" 0.800000
>> {type text/rdf+n3}}, {"/data/Analytics.ttl" 0.700000 {type text/turtle}},
>> {"/data/Analytics.xml" 0.950000 {type application/rdf+xml}}
> Given this Alternates-header: how can  a client figure out what those representations look like (except for their media type)?

Your Web Browser (a client) understands text/html. A Browser and other 
HTTP clients apply the same content handling rules to other content 
types (e.g., those related to images, sound, and video etc..) .


>
>> Link:
>> <http://mementoarchive.lanl.gov/dbpedia/timegate/http://dbpedia.org/resour
>> ce/Analytics>; rel="timegate"
>> Location: http://dbpedia.org/data/Analytics.ttl
>> Expires: Tue, 12 May 2015 16:01:06 GMT
>> Cache-Control: max-age=604800
> Best,
>
> Lars


-- 
Regards,

Kingsley Idehen 
Founder & CEO
OpenLink Software
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