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(semweb/rdf_db), []). % we define hooks for this 38 39:- autoload(library(date),[parse_time/2]). 40:- autoload(library(error),[domain_error/2]). 41:- autoload(library(lists),[append/2]). 42:- autoload(library(option),[option/3]). 43:- autoload(library(http/http_header),[http_timestamp/2]). 44:- autoload(library(http/http_open),[http_open/3]).
61:- multifile 62 rdf_db:rdf_open_hook/8, 63 rdf_db:url_protocol/1, 64 rdf_db:rdf_storage_encoding/2, 65 rdf_db:rdf_file_type/2, 66 rdf_content_type/3. 67 68rdf_dburl_protocol(http). 69rdf_dburl_protocol(https). 70 71 72% define `rdf_format` as a type. 73:- multifile error:has_type/2. 74errorhas_type(rdf_format, Term):- 75 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.
87rdf_extra_headers([ cert_verify_hook(ssl_verify),
88 request_header('Accept'=AcceptValue)
89 ], Options) :-
90 option(format(Format), Options, _VAR),
91 rdf_accept_header_value(Format, AcceptValue).105rdf_dbrdf_open_hook(https, SourceURL, HaveModified, Stream, Cleanup, 106 Modified, Format, Options) :- 107 rdf_db:rdf_open_hook(http, SourceURL, HaveModified, Stream, Cleanup, 108 Modified, Format, Options). 109rdf_dbrdf_open_hook(http, SourceURL, HaveModified, Stream, Cleanup, 110 Modified, Format, Options) :- 111 modified_since_header(HaveModified, Header), 112 TypeHdr = [ header(content_type, ContentType), 113 header(last_modified, ModifiedText) 114 ], 115 rdf_extra_headers(Extra, Options), 116 append([Extra, TypeHdr, Header, Options], OpenOptions), 117 catch(http_open(SourceURL, Stream0, 118 [ status_code(Code) 119 | OpenOptions 120 ]), E, true), 121 ( Code == 200 122 -> ( open_envelope(ContentType, SourceURL, 123 Stream0, Stream, Format) 124 -> Cleanup = close(Stream), 125 ( nonvar(ModifiedText), 126 parse_time(ModifiedText, ModifiedStamp) 127 -> Modified = last_modified(ModifiedStamp) 128 ; Modified = unknown 129 ) 130 ; close(Stream0), 131 domain_error(content_type, ContentType) 132 ) 133 ; Code == 304 134 -> Modified = not_modified, 135 Cleanup = true 136 ; var(E) 137 -> throw(error(existence_error(url, SourceURL), 138 context(_, status(Code,_)))) 139 ; throw(E) 140 ). 141 142:- public ssl_verify/5.
148ssl_verify(_SSL,
149 _ProblemCertificate, _AllCertificates, _FirstCertificate,
150 _Error).If-modified-since if we have a version with the given
time-stamp.157modified_since_header(HaveModified, []) :- 158 var(HaveModified), 159 !. 160modified_since_header(HaveModified, 161 [ request_header('If-modified-since' = 162 Modified) 163 ]) :- 164 http_timestamp(HaveModified, Modified).
171open_envelope(ContentType, SourceURL, Stream0, Stream, Format) :- 172 ( ContentType == 'application/x-gzip' 173 ; ContentType == 'application/octet-stream', 174 file_name_extension(_, gz, SourceURL) 175 ), 176 !, 177 rdf_db:rdf_storage_encoding(_, gzip), 178 !, 179 ( var(Format) 180 -> file_name_extension(BaseURL, _GzExt, SourceURL), 181 file_name_extension(_, Ext, BaseURL), 182 rdf_db:rdf_file_type(Ext, Format) 183 ; true 184 ), 185 stream_pair(Stream0, Read, _), 186 rdf_zlib_plugin:zopen(Read, Stream, []). 187open_envelope(_, _, Stream, Stream, Format) :- 188 nonvar(Format), 189 !. 190open_envelope(ContentType, SourceURL, Stream, Stream, Format) :- 191 major_content_type(ContentType, Major), 192 ( rdf_content_type(Major, _, Format) 193 -> true 194 ; Major == 'text/plain' % server is not properly configured 195 -> file_name_extension(_, Ext, SourceURL), 196 rdf_db:rdf_file_type(Ext, Format) 197 ). 198 199major_content_type(ContentType, Major) :- 200 sub_atom(ContentType, Pre, _, _, (;)), 201 !, 202 sub_atom(ContentType, 0, Pre, _, Major). 203major_content_type(Major, Major).
208rdf_accept_header_value(Format, AcceptValue) :- 209 findall(AcceptValue, accept_value(Format, AcceptValue), AcceptValues), 210 atomic_list_concat(['*/*;q=0.001'|AcceptValues], ',', AcceptValue). 211 212accept_value(Format, AcceptValue) :- 213 rdf_content_type(MediaType, QValue0, Format0), 214 ( Format == Format0 215 -> QValue = 1.0 216 ; QValue = QValue0 217 ), 218 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.
255rdf_content_type('application/n-quads', 0.99, nquads ). %ABC 256rdf_content_type('application/n-triples', 0.99, ntriples). %ABC 257rdf_content_type('application/rdf', 0.76, xml ). %AB 258rdf_content_type('application/rdf+turtle', 0.76, turtle ). %AB 259rdf_content_type('application/rdf+xml', 0.76, xml ). %AB 260rdf_content_type('application/rss+xml', 0.66, xml ). %AC 261rdf_content_type('application/trig', 0.99, trig ). %ABC 262rdf_content_type('application/turtle', 0.76, turtle ). %AB 263rdf_content_type('application/x-trig', 0.76, trig ). %AB 264rdf_content_type('application/x-turtle', 0.76, turtle ). %AB 265rdf_content_type('application/xhtml+xml', 0.66, rdfa ). %AC 266rdf_content_type('application/xml', 0.66, xml ). %AC 267rdf_content_type('text/html', 0.66, rdfa ). %AC 268rdf_content_type('text/n3', 0.56, turtle ). %BC (N3) 269rdf_content_type('text/rdf', 0.76, xml ). %AB 270rdf_content_type('text/rdf+n3', 0.33, turtle ). %B (N3) 271rdf_content_type('text/rdf+xml', 0.76, xml ). %AB 272rdf_content_type('text/turtle', 0.99, turtle ). %ABC 273rdf_content_type('text/xml', 0.66, xml ). %AC 274rdf_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')*/