rdf_http_plugin.pl -- RDF HTTP Plugin

This module allows loading data into the semantic web library directly from an HTTP server. The following example loads the RDF core data into the RDF database.

:- use_module(library(semweb/rdf_db)).
:- use_module(library(semweb/rdf_http_plugin)).

    ...,
    rdf_load('http://www.w3.org/1999/02/22-rdf-syntax-ns')

rdf_db:rdf_open_hook(+Scheme, +URL, +HaveModified, -Stream, -Cleanup, -Modified, -Format, +Options) is semidet[multifile]

Load hook implementation for HTTP(S) URLs.

Arguments:

`HaveModified`	- is bound to a timestamp (number) if we already have a copy and that copy was modified at `HaveModified`.
`Modified`	- is bound to `unknown`, `not_modified` or a timestamp.

rdf_content_type(?MediaType:atom, ?QualityValue:between(0.0,1.0), ?Format:rdf_format) is nondet[multifile]

Quality values are intended to be used in accordance with RFC 2616. Quality values are determined based on the following criteria:

Label	Criterion	Value
A	Supported RDF parser	0.43
B	RDF-specific content type	0.33
C	Official content type	0.23

For example, text/turtle has quality value 0.99 because it is an official content type that is RDF-specific and that has a parser in Semweb.

This intentionally allows the user to add another content type with a higher Q-value (i.e., >0.99).

Deduce the RDF encoding from the mime-type. This predicate is defined as multifile such that the user can associate additional content types to RDF formats.

See also: - Discussion http://richard.cyganiak.de/blog/2008/03/what-is-your-rdf-browsers-accept-header/; - N-Quadruples http://www.w3.org/ns/formats/N-Quads; - N-Triples http://www.w3.org/ns/formats/N-Triples; - N3 http://www.w3.org/ns/formats/N3; - RDFa http://www.w3.org/ns/formats/RDFa; - TriG http://www.w3.org/ns/formats/TriG; - Turtle http://www.w3.org/ns/formats/Turtle; - XML/RDF http://www.w3.org/ns/formats/RDF_XML
bug: - The turtle parser only parses a subset of n3. (The N3 format is treated as if it were Turtle.)