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) 2007-2018, University of Amsterdam 7 All rights reserved. 8 9 Redistribution and use in source and binary forms, with or without 10 modification, are permitted provided that the following conditions 11 are met: 12 13 1. Redistributions of source code must retain the above copyright 14 notice, this list of conditions and the following disclaimer. 15 16 2. Redistributions in binary form must reproduce the above copyright 17 notice, this list of conditions and the following disclaimer in 18 the documentation and/or other materials provided with the 19 distribution. 20 21 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 29 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 31 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 32 POSSIBILITY OF SUCH DAMAGE. 33*/ 34 35:- module(rdf_history, 36 [ rdfh_transaction/1, % :Goal 37 rdfh_assert/3, % +S,+P,+O 38 rdfh_retractall/3, % +S,+P,+O 39 rdfh_update/3, % +S[->NS],+P[->NP],+O[->[NO] 40 rdfh_db_transaction/3, % ?DB, +Condition, ?Transaction 41 rdfh_triple_transaction/2, % +Triple, -Transaction 42 rdfh_transaction_member/2 % ?Action, +Transaction 43 ]). 44:- use_module(library('http/http_session')). 45:- use_module(library(lists)). 46:- use_module(library(record)). 47:- use_module(library(error)). 48:- use_module(library(debug)). 49:- use_module(library('semweb/rdf_persistency')). 50:- use_module(library('semweb/rdf_db')).
75 /******************************* 76 * DECLARATIONS * 77 *******************************/ 78 79:- module_transparent 80 rdfh_transaction/1. 81 82:- rdf_meta 83 rdfh_assert(r,r,o), 84 rdfh_retractall(r,r,o), 85 rdfh_update(t,t,t). 86 87:- multifile 88 rdfh_hook/1. 89 90:- record 91 rdf_transaction(id:integer, 92 nesting:integer, 93 time:number, 94 message, 95 actions:list, 96 other_graphs:list). 97 98 99 /******************************* 100 * MODIFICATIONS * 101 *******************************/
108rdfh_transaction(Goal) :-
109 rdfh_user(User),
110 transaction_context(Context),
111 rdf_transaction(Goal, log(rdfh([user(User)|Context]), User)).
119rdfh_assert(S,P,O) :-
120 ( rdf_active_transaction(log(rdfh(_), User))
121 -> rdfh_time(Time),
122 rdf_assert(S,P,O,User:Time)
123 ; throw(error(permission_error(assert, triple, rdf(S,P,O)),
124 context(_, 'No rdfh_transaction/1')))
125 ).One of the problems we are faced with is that a retract action goes into the journal of the user whose triple is retracted, which may or may not be the one who performed the action.
139rdfh_retractall(S,P,O) :-
140 ( rdf_active_transaction(log(rdfh(_), _User))
141 -> rdf_retractall(S,P,O)
142 ; throw(error(permission_error(retract, triple, rdf(S,P,O)),
143 context(_, 'No rdfh_transaction/1')))
144 ).
Current simple-minded approach is to turn an update into a
retract and assert. The S,P,O specifications are either a ground
value or of the form Old -> New. Here is an example:
rdfh_update(Work, Style, wn:oldstyle -> wn:newstyle)
163rdfh_update(S,P,O) :- 164 ( rdf_active_transaction(log(rdfh(_), User)) 165 -> update(S,P,O, rdf(RS, RP, RO), rdf(AS, AP, AO)), 166 must_be(ground, RS), 167 must_be(ground, RP), 168 must_be(ground, RO), 169 rdfh_time(Time), 170 rdf_retractall(RS, RP, RO), 171 rdf_assert(AS, AP, AO, User:Time) 172 ; throw(error(permission_error(retract, triple, rdf(S,P,O)), 173 context(_, 'No rdfh_transaction/1'))) 174 ). 175 176update(Ss, Ps, Os, rdf(S0, P0, O0), rdf(S,P,O)) :- 177 update(Ss, S0, S), 178 update(Ps, P0, P), 179 update(Os, O0, O). 180 181update(From->To, From, To) :- !. 182update(Value, Value, Value).
191transaction_context(Context) :-
192 ( rdfh_session(Session)
193 -> Context = [session(Session)]
194 ; Context = []
195 ).201rdfh_session(Session) :- 202 rdfh_hook(session(Session)), 203 !. 204rdfh_session(Session) :- 205 catch(http_session_id(Session), _, fail).
214rdfh_user(User) :- 215 rdfh_hook(user(User)), 216 !. 217rdfh_user(OpenId) :- 218 http_session_data(openid(OpenId)).
225rdfh_time(Seconds) :- 226 get_time(Now), 227 Seconds is round(Now). 228 229 230 /******************************* 231 * EXAMINE HISTORY * 232 *******************************/
238rdfh_triple_transaction(rdf(S,P,O), Transaction) :-
239 rdf(S,P,O,DB:Time),
240 After is Time - 1,
241 rdfh_db_transaction(DB, after(After), Transaction),
242 rdfh_transaction_member(assert(S,P,O,Time), Transaction).260rdfh_db_transaction(DB, true, Transaction) :- 261 !, 262 rdf_journal_file(DB, Journal), 263 journal_transaction(Journal, Transaction). 264rdfh_db_transaction(DB, id(Id), Transaction) :- 265 !, 266 must_be(atom, DB), 267 rdf_journal_file(DB, Journal), 268 open_journal(Journal, Fd), 269 call_cleanup((seek_journal(Fd, id(Id)), 270 read_transaction(Fd, Transaction)), 271 close(Fd)). 272rdfh_db_transaction(DB, Condition, Transaction) :- 273 !, 274 valid_condition(Condition), 275 rdf_journal_file(DB, Journal), 276 open_journal(Journal, Fd), 277 seek_journal(Fd, Condition), 278 stream_transaction(Fd, Transaction). 279 280valid_condition(Var) :- 281 var(Var), 282 !, 283 instantiation_error(Var). 284valid_condition(after(Time)) :- 285 !, 286 must_be(number, Time). 287valid_condition(Cond) :- 288 type_error(condition, Cond).
294open_journal(JournalFile, Fd) :-
295 open(JournalFile, read, Fd, [encoding(utf8)]).301journal_transaction(JournalFile, Transaction) :- 302 open_journal(JournalFile, Fd), 303 stream_transaction(Fd, Transaction). 304 305stream_transaction(JFD, Transaction) :- 306 call_cleanup(read_transaction(JFD, Transaction), close(JFD)). 307 308read_transaction(In, Transaction) :- 309 repeat, 310 read(In, T0), 311 ( T0 == end_of_file 312 -> !, fail 313 ; transaction(T0, In, T), % transaction/3 is not steadfast 314 T = Transaction 315 ). 316 317transaction(begin(Id, Nest, Time, Msg), In, 318 rdf_transaction(Id, Nest, Time, Msg, Actions, Others)) :- 319 !, 320 read(In, T2), 321 read_transaction_actions(T2, Id, In, Actions, Others). 322transaction(start(_), _, _) :- !, fail. % Open journal 323transaction(end(_), _, _) :- !, fail. % Close journal 324transaction(Action, _, Action). % Action outside transaction? 325 326read_transaction_actions(end(Id, _, Others), Id, _, [], Others) :- !. 327read_transaction_actions(end_of_file, _, _, [], []) :- !. % TBD: Incomplete transaction (error) 328read_transaction_actions(Action, Id, In, Actions, Others) :- 329 ignore_in_transaction(Action), 330 !, 331 read(In, T2), 332 read_transaction_actions(T2, Id, In, Actions, Others). 333read_transaction_actions(Action, Id, In, [Action|Actions], Others) :- 334 read(In, T2), 335 read_transaction_actions(T2, Id, In, Actions, Others). 336 337ignore_in_transaction(start(_)). 338ignore_in_transaction(end(_)). 339ignore_in_transaction(begin(_,_,_,_)). 340ignore_in_transaction(end(_,_,_)).
The implementation relies on the incrementing identifier numbers and time-stamps.
358seek_journal(Fd, Spec) :- 359 stream_property(Fd, file_name(File)), 360 size_file(File, Size), 361 Here is Size//2, 362 Last = last(-), 363 ( is_after_spec(Spec) 364 -> ( bsearch_journal(Fd, 0, Here, Size, Spec, Last) 365 -> true 366 ; arg(1, Last, StartOfTerm), 367 StartOfTerm \== (-), 368 seek(Fd, StartOfTerm, bof, _) 369 ) 370 ; bsearch_journal(Fd, 0, Here, Size, Spec, Last) 371 ). 372 373is_after_spec(after(_Time)).
379bsearch_journal(Fd, Start, Here, End, Spec, Last) :- 380 start_of_transaction(Fd, Here, StartOfTerm, Begin), 381 !, 382 compare_transaction(Spec, Begin, Diff), 383 ( Diff == (=) 384 -> seek(Fd, StartOfTerm, bof, _) 385 ; Diff == (<) 386 -> NewHere is Start+(Here-Start)//2, 387 NewHere < Here, 388 nb_setarg(1, Last, StartOfTerm), 389 bsearch_journal(Fd, Start, NewHere, Here, Spec, Last) 390 ; NewHere is StartOfTerm+(End-StartOfTerm)//2, 391 NewHere > StartOfTerm, 392 bsearch_journal(Fd, StartOfTerm, NewHere, End, Spec, Last) 393 ). 394bsearch_journal(Fd, Start, Here, _End, Spec, Last) :- 395 NewHere is Start+(Here-Start)//2, 396 NewHere < Here, 397 bsearch_journal(Fd, Start, NewHere, Here, Spec, Last). 398 399compare_transaction(id(Id), begin(Id2,_,_,_), Diff) :- 400 !, 401 compare(Diff, Id, Id2). 402compare_transaction(after(Time), begin(_,_,T,_), Diff) :- 403 !, 404 compare(Diff, Time, T).
411start_of_transaction(Fd, From, Start, Term) :- 412 seek(Fd, From, bof, _), 413 skip(Fd, 10), 414 repeat, 415 seek(Fd, 0, current, Start), 416 read(Fd, Term), 417 ( transaction_start(Term) 418 -> ! 419 ; Term == end_of_file 420 -> !, fail 421 ; fail 422 ). 423 424transaction_start(begin(_Id,_Nest,_Time,_Message)).
430rdfh_transaction_member(Action, Transaction) :-
431 rdf_transaction_actions(Transaction, Actions),
432 member(Action, Actions)
RDF Persistent store change history
This module deals with accessing the journal files of the RDF persistency layer to get insight in the provenance and history of the RDF database. It is designed for Wiki-like collaborative editing of an RDF graph. We make the following assumptions:
Users are identified using a URI, typically an OpenID (http://openid.net/) Triples created by a user are added to a named graph identified by the URI of the user. Changes are grouped using
rdf_transaction(Goal, log(Message, User))The number that is associated with the named graph of a triple (normally expressing the line number in the source) is used to store the time-stamp. Although this information is redundant (the time stamp is the same as for the transaction), it allows for binary search through the history file for the enclosing transaction.