1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2006-2015, University of Amsterdam 7 VU University Amsterdam 8 All rights reserved. 9 10 Redistribution and use in source and binary forms, with or without 11 modification, are permitted provided that the following conditions 12 are met: 13 14 1. Redistributions of source code must retain the above copyright 15 notice, this list of conditions and the following disclaimer. 16 17 2. Redistributions in binary form must reproduce the above copyright 18 notice, this list of conditions and the following disclaimer in 19 the documentation and/or other materials provided with the 20 distribution. 21 22 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 30 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 32 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 POSSIBILITY OF SUCH DAMAGE. 34*/ 35 36:- module(rdf_http_plugin, []). 37:- use_module(library(http/http_open)). 38:- use_module(library(http/http_header)). 39:- use_module(library(semweb/rdf_db), []). % we define hooks for this 40:- use_module(library(date)). 41:- use_module(library(error)). 42:- use_module(library(lists)). 43:- use_module(library(option)).
60:- multifile 61 rdf_db:rdf_open_hook/8, 62 rdf_db:url_protocol/1, 63 rdf_content_type/3. 64 65rdf_dburl_protocol(http). 66rdf_dburl_protocol(https). 67 68 69% define `rdf_format` as a type. 70:- multifile error:has_type/2. 71errorhas_type(rdf_format, Term):- 72 error:has_type(oneof([nquads,ntriples,rdfa,trig,turtle,xml]), Term).
When given, option format(+atom) is used in order to prioritize
the corresponding RDF content types.
84rdf_extra_headers([ cert_verify_hook(ssl_verify),
85 request_header('Accept'=AcceptValue)
86 ], Options) :-
87 option(format(Format), Options, _VAR),
88 rdf_accept_header_value(Format, AcceptValue).102rdf_dbrdf_open_hook(https, SourceURL, HaveModified, Stream, Cleanup, 103 Modified, Format, Options) :- 104 rdf_db:rdf_open_hook(http, SourceURL, HaveModified, Stream, Cleanup, 105 Modified, Format, Options). 106rdf_dbrdf_open_hook(http, SourceURL, HaveModified, Stream, Cleanup, 107 Modified, Format, Options) :- 108 modified_since_header(HaveModified, Header), 109 TypeHdr = [ header(content_type, ContentType), 110 header(last_modified, ModifiedText) 111 ], 112 rdf_extra_headers(Extra, Options), 113 append([Extra, TypeHdr, Header, Options], OpenOptions), 114 catch(http_open(SourceURL, Stream0, 115 [ status_code(Code) 116 | OpenOptions 117 ]), E, true), 118 ( Code == 200 119 -> ( open_envelope(ContentType, SourceURL, 120 Stream0, Stream, Format) 121 -> Cleanup = close(Stream), 122 ( nonvar(ModifiedText), 123 parse_time(ModifiedText, ModifiedStamp) 124 -> Modified = last_modified(ModifiedStamp) 125 ; Modified = unknown 126 ) 127 ; close(Stream0), 128 domain_error(content_type, ContentType) 129 ) 130 ; Code == 304 131 -> Modified = not_modified, 132 Cleanup = true 133 ; var(E) 134 -> throw(error(existence_error(url, SourceURL), 135 context(_, status(Code,_)))) 136 ; throw(E) 137 ). 138 139:- public ssl_verify/5.
145ssl_verify(_SSL,
146 _ProblemCertificate, _AllCertificates, _FirstCertificate,
147 _Error).If-modified-since if we have a version with the given
time-stamp.154modified_since_header(HaveModified, []) :- 155 var(HaveModified), 156 !. 157modified_since_header(HaveModified, 158 [ request_header('If-modified-since' = 159 Modified) 160 ]) :- 161 http_timestamp(HaveModified, Modified).
168open_envelope('application/x-gzip', SourceURL, Stream0, Stream, Format) :- 169 rdf_db:rdf_storage_encoding(_, gzip), 170 !, 171 ( var(Format) 172 -> file_name_extension(BaseURL, _GzExt, SourceURL), 173 file_name_extension(_, Ext, BaseURL), 174 rdf_db:rdf_file_type(Ext, Format) 175 ; true 176 ), 177 stream_pair(Stream0, Read, _), 178 rdf_zlib_plugin:zopen(Read, Stream, []). 179open_envelope(_, _, Stream, Stream, Format) :- 180 nonvar(Format), 181 !. 182open_envelope(ContentType, SourceURL, Stream, Stream, Format) :- 183 major_content_type(ContentType, Major), 184 ( rdf_content_type(Major, _, Format) 185 -> true 186 ; Major == 'text/plain' % server is not properly configured 187 -> file_name_extension(_, Ext, SourceURL), 188 rdf_db:rdf_file_type(Ext, Format) 189 ). 190 191major_content_type(ContentType, Major) :- 192 sub_atom(ContentType, Pre, _, _, (;)), 193 !, 194 sub_atom(ContentType, 0, Pre, _, Major). 195major_content_type(Major, Major).
200rdf_accept_header_value(Format, AcceptValue) :- 201 findall(AcceptValue, accept_value(Format, AcceptValue), AcceptValues), 202 atomic_list_concat(['*/*;q=0.001'|AcceptValues], ',', AcceptValue). 203 204accept_value(Format, AcceptValue) :- 205 rdf_content_type(MediaType, QValue0, Format0), 206 ( Format == Format0 207 -> QValue = 1.0 208 ; QValue = QValue0 209 ), 210 format(atom(AcceptValue), '~a;q=~3f', [MediaType,QValue]).
| 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.
247rdf_content_type('application/n-quads', 0.99, nquads ). %ABC 248rdf_content_type('application/n-triples', 0.99, ntriples). %ABC 249rdf_content_type('application/rdf', 0.76, xml ). %AB 250rdf_content_type('application/rdf+turtle', 0.76, turtle ). %AB 251rdf_content_type('application/rdf+xml', 0.76, xml ). %AB 252rdf_content_type('application/rss+xml', 0.66, xml ). %AC 253rdf_content_type('application/trig', 0.99, trig ). %ABC 254rdf_content_type('application/turtle', 0.76, turtle ). %AB 255rdf_content_type('application/x-trig', 0.76, trig ). %AB 256rdf_content_type('application/x-turtle', 0.76, turtle ). %AB 257rdf_content_type('application/xhtml+xml', 0.66, rdfa ). %AC 258rdf_content_type('application/xml', 0.66, xml ). %AC 259rdf_content_type('text/html', 0.66, rdfa ). %AC 260rdf_content_type('text/n3', 0.56, turtle ). %BC (N3) 261rdf_content_type('text/rdf', 0.76, xml ). %AB 262rdf_content_type('text/rdf+n3', 0.33, turtle ). %B (N3) 263rdf_content_type('text/rdf+xml', 0.76, xml ). %AB 264rdf_content_type('text/turtle', 0.99, turtle ). %ABC 265rdf_content_type('text/xml', 0.66, xml ). %AC 266rdf_content_type('application/x-gzip', 0.23, gzip ). %C
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')*/