/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2006-2020, University of Amsterdam
VU University Amsterdam
CWI, Amsterdam
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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*/
:- module(rdf_litindex,
[ rdf_set_literal_index_option/1, % +Options
rdf_tokenize_literal/2, % +Literal, -Tokens
rdf_find_literal/2, % +Spec, -Literal
rdf_find_literals/2, % +Spec, -ListOfLiterals
rdf_token_expansions/2, % +Spec, -Expansions
rdf_stopgap_token/1, % -Token
rdf_literal_index/2, % +Type, -Index
rdf_delete_literal_index/1 % +Type
]).
:- autoload(rdf_db,
[ rdf_keys_in_literal_map/3,
rdf_find_literal_map/3,
rdf_new_literal_map/1,
rdf_monitor/2,
rdf_current_literal/1,
rdf_reset_literal_map/1,
rdf_insert_literal_map/4,
rdf_delete_literal_map/2,
rdf/3,
rdf_delete_literal_map/3,
rdf_insert_literal_map/3,
rdf_statistics_literal_map/2
]).
:- autoload(library(apply),[maplist/3]).
:- use_module(library(debug),[debug/3]).
:- autoload(library(double_metaphone),[double_metaphone/2]).
:- autoload(library(error),
[instantiation_error/1,must_be/2,domain_error/2]).
:- autoload(library(lists),[member/2,flatten/2,append/3]).
:- autoload(library(porter_stem),[tokenize_atom/2]).
:- autoload(library(snowball),[snowball/3]).
/** <module> Search literals
This module finds literals of the RDF database based on words, stemming
and _sounds like_ (metaphone). The normal user-level predicate is
- rdf_find_literals/2
*/
:- dynamic
literal_map/2, % Type, -Map
map_building/2, % Type, -Queue
new_token/2, % Hook
setting/1,
stopgap/1.
:- volatile
literal_map/2.
:- multifile
tokenization/2, % +Literal, -Tokens
exclude_from_index/2. % +Which, +Token
setting(verbose(false)). % print progress messages
setting(index_threads(1)). % # threads for creating the index
setting(index(thread(1))). % Use a thread for incremental updates
setting(stopgap_threshold(50000)). % consider token a stopgap over N
%! rdf_set_literal_index_option(+Options:list)
%
% Set options for the literal package. Currently defined options
%
% * verbose(Bool)
% If =true=, print progress messages while building the
% index tables.
%
% * index_threads(+Count)
% Number of threads to use for initial indexing of
% literals
%
% * index(+How)
% How to deal with indexing new literals. How is one of
% =self= (execute in the same thread), thread(N) (execute
% in N concurrent threads) or =default= (depends on number
% of cores).
%
% * stopgap_threshold(+Count)
% Add a token to the dynamic stopgap set if it appears in
% more than Count literals. The default is 50,000.
rdf_set_literal_index_option([]) :- !.
rdf_set_literal_index_option([H|T]) :-
!,
set_option(H),
rdf_set_literal_index_option(T).
rdf_set_literal_index_option(Option) :-
set_option(Option).
set_option(Term) :-
check_option(Term),
functor(Term, Name, Arity),
functor(General, Name, Arity),
retractall(setting(General)),
assert(setting(Term)).
check_option(X) :-
var(X),
!,
instantiation_error(X).
check_option(verbose(X)) :-
!,
must_be(boolean, X).
check_option(index_threads(Count)) :-
!,
must_be(nonneg, Count).
check_option(stopgap_threshold(Count)) :-
!,
must_be(nonneg, Count).
check_option(index(How)) :-
!,
must_be(oneof([default,thread(_),self]), How).
check_option(Option) :-
domain_error(literal_option, Option).
/*******************************
* QUERY *
*******************************/
%! rdf_find_literal(+Spec, -Literal) is nondet.
%! rdf_find_literals(+Spec, -Literals) is det.
%
% Find literals in the RDF database matching Spec. Spec is defined
% as:
%
% ==
% Spec ::= and(Spec,Spec)
% Spec ::= or(Spec,Spec)
% Spec ::= not(Spec)
% Spec ::= sounds(Like)
% Spec ::= stem(Like) % same as stem(Like, en)
% Spec ::= stem(Like, Lang)
% Spec ::= prefix(Prefix)
% Spec ::= between(Low, High) % Numerical between
% Spec ::= ge(High) % Numerical greater-equal
% Spec ::= le(Low) % Numerical less-equal
% Spec ::= Token
% ==
%
% sounds(Like) and stem(Like) both map to a disjunction. First we
% compile the spec to normal form: a disjunction of conjunctions
% on elementary tokens. Then we execute all the conjunctions and
% generate the union using ordered-set algorithms.
%
% Stopgaps are ignored. If the final result is only a stopgap, the
% predicate fails.
%
% @tbd Exploit ordering of numbers and allow for > N, < N, etc.
rdf_find_literal(Spec, Literal) :-
rdf_find_literals(Spec, Literals),
member(Literal, Literals).
rdf_find_literals(Spec, Literals) :-
compile_spec(Spec, DNF),
DNF \== @(stopgap),
token_index(Map),
lookup(DNF, Map, _, SuperSet),
flatten(SuperSet, Set0),
sort(Set0, Literals).
%! rdf_token_expansions(+Spec, -Extensions)
%
% Determine which extensions of a token contribute to finding
% literals.
rdf_token_expansions(prefix(Prefix), [prefix(Prefix, Tokens)]) :-
token_index(Map),
rdf_keys_in_literal_map(Map, prefix(Prefix), Tokens).
rdf_token_expansions(sounds(Like), [sounds(Like, Tokens)]) :-
metaphone_index(Map),
rdf_find_literal_map(Map, [Like], Tokens).
rdf_token_expansions(stem(Like), [stem(Like, Tokens)]) :-
stem_index(Map),
rdf_find_literal_map(Map, [Like], Tokens).
rdf_token_expansions(Spec, Expansions) :-
compile_spec(Spec, DNF),
token_index(Map),
lookup(DNF, Map, SCS, _),
flatten(SCS, CS),
sort(CS, Expansions0),
join_expansions(Expansions0, Expansions).
join_expansions([], []).
join_expansions([H0|T0], [H|T]) :-
untag(H0, Tag, V0),
Tag =.. L0,
append(L0, [[V0|Values]], L1),
H =.. L1,
join_expansions_by_tag(T0, Tag, T1, Values),
join_expansions(T1, T).
join_expansions_by_tag([H|T0], Tag, T, [V0|VT]) :-
untag(H, Tag, V0),
!,
join_expansions_by_tag(T0, Tag, T, VT).
join_expansions_by_tag(L, _, L, []).
lookup(@(false), _, [], []) :- !.
lookup(or(H0,T0), Map, [CH|CT], [H|T]) :-
!,
lookup(H0, Map, CH, H),
lookup(T0, Map, CT, T).
lookup(H0, Map, [C], [H]) :-
lookup1(H0, Map, C, H).
lookup1(Conj, Map, Cond, Literals) :-
phrase(conj_to_list(Conj), List),
!,
rdf_find_literal_map(Map, List, Literals),
( Literals \== []
-> phrase(conj_to_cond(Conj), Cond)
; Cond = []
).
lookup1(_, _, _, []).
conj_to_list(and(A,B)) -->
!,
conj_to_list(A),
conj_to_list(B).
conj_to_list(@(false)) -->
!,
{fail}.
conj_to_list(Tagged) -->
{ untag(Tagged, L) },
!,
[L].
conj_to_list(L) -->
[L].
conj_to_cond(and(A,B)) -->
!,
conj_to_cond(A),
conj_to_cond(B).
conj_to_cond(Tagged) -->
{ untag(Tagged, _) },
!,
[ Tagged ].
conj_to_cond(_) -->
[].
%! compile_spec(+Spec, -Compiled)
%
% Compile a specification as above into disjunctive normal form
compile_spec(Spec, DNF) :-
expand_fuzzy(Spec, Spec2),
nnf(Spec2, NNF),
dnf(NNF, DNF).
expand_fuzzy(Var, _) :-
var(Var),
!,
throw(error(instantiation_error, _)).
expand_fuzzy(sounds(Like), Or) :-
!,
( atom(Like)
-> metaphone_index(Map),
double_metaphone(Like, Key),
rdf_find_literal_map(Map, [Key], Tokens),
list_to_or(Tokens, sounds(Like), Or)
; expand_fuzzy(Like, Or)
).
expand_fuzzy(stem(Like), Or) :-
!,
expand_fuzzy(stem(Like, en), Or).
expand_fuzzy(stem(Like, Lang), Or) :-
!,
( atom(Like)
-> stem_index(Map),
stem(Like, Lang, Key),
rdf_find_literal_map(Map, [Key], Tokens),
list_to_or(Tokens, stem(Like), Or)
; expand_fuzzy(Like, Or)
).
expand_fuzzy(prefix(Prefix), Or) :-
!,
( atom(Prefix)
-> token_index(Map),
rdf_keys_in_literal_map(Map, prefix(Prefix), Tokens),
list_to_or(Tokens, prefix(Prefix), Or)
; expand_fuzzy(Prefix, Or)
).
expand_fuzzy(case(String), Or) :-
!,
( atom(String)
-> token_index(Map),
rdf_keys_in_literal_map(Map, case(String), Tokens),
list_to_or(Tokens, case(String), Or)
; expand_fuzzy(String, Or)
).
expand_fuzzy(or(A0, B0), E) :-
!,
expand_fuzzy(A0, A),
expand_fuzzy(B0, B),
simplify(or(A,B), E).
expand_fuzzy(and(A0, B0), E) :-
!,
expand_fuzzy(A0, A),
expand_fuzzy(B0, B),
simplify(and(A,B), E).
expand_fuzzy(not(A0), not(A)) :-
!,
expand_fuzzy(A0, A).
expand_fuzzy(between(Low, High), Or) :-
!,
token_index(Map),
rdf_keys_in_literal_map(Map, between(Low, High), Tokens),
list_to_or(Tokens, between(Low, High), Or).
expand_fuzzy(le(High), Or) :-
!,
token_index(Map),
rdf_keys_in_literal_map(Map, le(High), Tokens),
list_to_or(Tokens, le(High), Or).
expand_fuzzy(ge(Low), Or) :-
!,
token_index(Map),
rdf_keys_in_literal_map(Map, ge(Low), Tokens),
list_to_or(Tokens, ge(Low), Or).
expand_fuzzy(Token, Result) :-
atomic(Token),
!,
( rdf_stopgap_token(Token)
-> Result = @(stopgap)
; Result = Token
).
expand_fuzzy(Token, _) :-
throw(error(type_error(Token, boolean_expression), _)).
simplify(Expr0, Expr) :-
simple(Expr0, Expr),
!.
simplify(Expr, Expr).
simple(and(@(false), _), @(false)).
simple(and(_, @(false)), @(false)).
simple(and(@(stopgap), Token), Token).
simple(and(Token, @(stopgap)), Token).
simple(or(@(false), X), X).
simple(or(X, @(false)), X).
simple(or(@(stopgap), Token), Token).
simple(or(Token, @(stopgap)), Token).
list_to_or([], _, @(false)) :- !.
list_to_or([X], How, One) :-
!,
tag(How, X, One).
list_to_or([H0|T0], How, or(H, T)) :-
tag(How, H0, H),
list_to_or(T0, How, T).
tag(sounds(X), Y, sounds(X,Y)).
tag(stem(X), Y, stem(X,Y)).
tag(prefix(X), Y, prefix(X,Y)).
tag(case(X), Y, case(X,Y)).
tag(between(L,H), Y, between(L,H,Y)).
tag(ge(L), Y, ge(L,Y)).
tag(le(H), Y, le(H,Y)).
untag(sounds(_,Y), Y).
untag(stem(_,Y), Y).
untag(prefix(_,Y), Y).
untag(case(_,Y), Y).
untag(between(_,_,Y), Y).
untag(le(_,Y), Y).
untag(ge(_,Y), Y).
untag(sounds(X,Y), sounds(X), Y).
untag(stem(X,Y), stem(X), Y).
untag(prefix(X,Y), prefix(X), Y).
untag(case(X,Y), case(X), Y).
untag(between(L,H,Y), between(L,H), Y).
untag(ge(L,Y), ge(L), Y).
untag(le(H,Y), le(H), Y).
%! nnf(+Formula, -NNF)
%
% Rewrite to Negative Normal Form, meaning negations only appear
% around literals.
nnf(not(not(A0)), A) :-
!,
nnf(A0, A).
nnf(not(and(A0,B0)), or(A,B)) :-
!,
nnf(not(A0), A),
nnf(not(B0), B).
nnf(not(or(A0,B0)), and(A,B)) :-
!,
nnf(not(A0), A),
nnf(not(B0), B).
nnf(A, A).
%! dnf(+NNF, -DNF)
%
% Convert a formula in NNF to Disjunctive Normal Form (DNF)
dnf(or(A0,B0), or(A, B)) :-
!,
dnf(A0, A),
dnf(B0, B).
dnf(and(A0,B0), DNF):-
!,
dnf(A0, A1),
dnf(B0, B1),
dnf1(and(A1,B1), DNF).
dnf(DNF, DNF).
dnf1(and(A0, or(B,C)), or(P,Q)) :-
!,
dnf1(and(A0,B), P),
dnf1(and(A0,C), Q).
dnf1(and(or(B,C), A0), or(P,Q)) :-
!,
dnf1(and(A0,B), P),
dnf1(and(A0,C), Q).
dnf1(DNF, DNF).
/*******************************
* TOKEN INDEX *
*******************************/
%! token_index(-Map)
%
% Get the index of tokens. If not present, create one from the
% current database. Once created, the map is kept up-to-date using
% a monitor hook.
token_index(Map) :-
literal_map(token, Map),
!,
wait_for_map(token).
token_index(Map) :-
rdf_new_literal_map(Map),
assert(literal_map(token, Map)),
register_token_updater,
message_queue_create(Queue),
assert(map_building(token, Queue)),
thread_create(make_literal_index(Queue), _,
[ alias('__rdf_tokenizer'),
detached(true)
]),
wait_for_map(token).
register_token_updater :-
Monitor = [ reset,
new_literal,
old_literal
],
( setting(index(default))
-> create_update_literal_thread(1),
rdf_monitor(thread_monitor_literal, Monitor)
; setting(index(thread(N)))
-> create_update_literal_thread(N),
rdf_monitor(thread_monitor_literal, Monitor)
; rdf_monitor(monitor_literal, Monitor)
).
make_literal_index(Queue) :-
call_cleanup(
make_literal_index,
( message_queue_destroy(Queue),
retractall(map_building(token, _)))).
%! make_literal_index
%
% Create the initial literal index.
make_literal_index :-
setting(index_threads(N)),
!,
threaded_literal_index(N),
verbose('~N', []).
make_literal_index :-
current_prolog_flag(cpu_count, X),
threaded_literal_index(X),
verbose('~N', []).
threaded_literal_index(N) :-
N > 1,
!,
message_queue_create(Q, [max_size(1000)]),
create_index_threads(N, Q, Ids),
forall(rdf_current_literal(Literal),
thread_send_message(Q, Literal)),
forall(between(1, N, _),
thread_send_message(Q, done(true))),
maplist(thread_join, Ids, _).
threaded_literal_index(_) :-
forall(rdf_current_literal(Literal),
register_literal(Literal)).
create_index_threads(N, Q, [Id|T]) :-
N > 0,
!,
thread_create(index_worker(Q), Id, []),
N2 is N - 1,
create_index_threads(N2, Q, T).
create_index_threads(_, _, []) :- !.
index_worker(Queue) :-
repeat,
thread_get_message(Queue, Msg),
work(Msg).
work(done(true)) :- !.
work(Literal) :-
register_literal(Literal),
fail.
%! clean_token_index
%
% Clean after a reset.
clean_token_index :-
forall(literal_map(_, Map),
rdf_reset_literal_map(Map)),
retractall(stopgap(_)).
%! rdf_delete_literal_index(+Type)
%
% Fully delete a literal index
rdf_delete_literal_index(Type) :-
must_be(atom, Type),
( retract(literal_map(Type, Map))
-> rdf_reset_literal_map(Map) % destroy is unsafe
).
/*******************************
* THREADED UPDATE *
*******************************/
%! create_update_literal_thread(+Threads)
%
% Setup literal monitoring using threads. While loading databases
% through rdf_attach_db/2 from rdf_persistency.pl, most of the
% time is spent updating the literal token database. While loading
% the RDF triples, most of the time is spend in updating the AVL
% tree holding the literals. Updating the token index hangs on
% updating the AVL trees holding the tokens. Both tasks however
% can run concurrently.
create_update_literal_thread(Threads) :-
message_queue_create(_,
[ alias(rdf_literal_monitor_queue),
max_size(50000)
]),
forall(between(1, Threads, _),
create_index_worker(initial)).
:- dynamic
index_worker_id/1,
extra_worker_count/1.
create_index_worker(Status) :-
( retract(index_worker_id(Id0))
-> true
; Id0 = 1
),
succ(Id0, Id1),
assertz(index_worker_id(Id1)),
atom_concat(rdf_literal_monitor_, Id0, Alias),
inc_extra_worker_count(Status),
thread_create(monitor_literals(Status), _,
[ alias(Alias)
]).
monitor_literals(initial) :-
set_prolog_flag(agc_margin, 0), % we don't create garbage
repeat,
thread_get_message(rdf_literal_monitor_queue, Literal),
register_literal(Literal),
fail.
monitor_literals(extra) :-
set_prolog_flag(agc_margin, 0),
repeat,
( thread_get_message(rdf_literal_monitor_queue, Literal,
[ timeout(1)
])
-> register_literal(Literal),
fail
; !
),
with_mutex(create_index_worker, dec_extra_worker_count),
thread_self(Me),
thread_detach(Me).
thread_monitor_literal(new_literal(Literal)) :-
!,
thread_send_message(rdf_literal_monitor_queue, Literal).
thread_monitor_literal(Action) :-
!,
monitor_literal(Action).
%! check_index_workers(+Queue, +Keys)
%
% Increase the number of workers indexing literals sent to Queue
% if the queue gets overfull.
check_index_workers(Alias, Keys) :-
max_extra_workers(Max),
Max > 0,
message_queue_property(Queue, alias(Alias)),
message_queue_property(Queue, size(Size)),
Size > 10000,
\+ ( extra_worker_count(Extra),
Extra >= Max
),
!,
debug(rdf_litindex,
'Creating extra literal indexer (Queue=~D, Keys=~D)',
[Size, Keys]),
with_mutex(create_index_worker, create_index_worker(extra)).
check_index_workers(_, _).
inc_extra_worker_count(extra) :-
!,
( retract(extra_worker_count(C0))
-> C is C0+1
; C = 1
),
asserta(extra_worker_count(C)).
inc_extra_worker_count(_).
dec_extra_worker_count :-
retract(extra_worker_count(C0)),
!,
C is C0-1,
asserta(extra_worker_count(C)).
dec_extra_worker_count.
max_extra_workers(Max) :-
current_prolog_flag(cpu_count, Count),
Max is Count//2.
/*******************************
* MONITORED UPDATE *
*******************************/
monitor_literal(new_literal(Literal)) :-
register_literal(Literal).
monitor_literal(old_literal(Literal)) :-
unregister_literal(Literal).
monitor_literal(transaction(begin, reset)) :-
rdf_monitor(monitor_literal, [-old_literal]),
clean_token_index.
monitor_literal(transaction(end, reset)) :-
rdf_monitor(monitor_literal, [+old_literal]).
%! register_literal(+Literal)
%
% Associate the tokens of a literal with the literal itself.
register_literal(Literal) :-
( rdf_tokenize_literal(Literal, Tokens0)
-> sort(Tokens0, Tokens),
text_of(Literal, Lang, Text),
literal_map(token, Map),
add_tokens(Tokens, Lang, Text, Map)
; true
).
add_tokens([], _, _, _).
add_tokens([H|T], Lang, Literal, Map) :-
rdf_insert_literal_map(Map, H, Literal, Keys),
( var(Keys)
-> ( rdf_keys_in_literal_map(Map, key(H), Count),
setting(stopgap_threshold(Threshold)),
Count > Threshold
-> assert(stopgap(H)),
rdf_delete_literal_map(Map, H)
; true
)
; forall(new_token(H, Lang), true),
( Keys mod 1000 =:= 0
-> progress(Map, 'Tokens'),
( Keys mod 10000 =:= 0
-> check_index_workers(rdf_literal_monitor_queue, Keys)
; true
)
; true
)
),
add_tokens(T, Lang, Literal, Map).
%! unregister_literal(+Literal)
%
% Literal is removed from the database. As we abstract from lang
% and type qualifiers we first have to check this is the last one
% that is destroyed.
unregister_literal(Literal) :-
text_of(Literal, _Lang, Text),
( rdf(_,_,literal(Text))
-> true % still something left
; rdf_tokenize_literal(Literal, Tokens0),
sort(Tokens0, Tokens),
literal_map(token, Map),
del_tokens(Tokens, Text, Map)
).
del_tokens([], _, _).
del_tokens([H|T], Literal, Map) :-
rdf_delete_literal_map(Map, H, Literal),
del_tokens(T, Literal, Map).
%! rdf_tokenize_literal(+Literal, -Tokens) is semidet.
%
% Tokenize a literal. We make this hookable as tokenization is
% generally domain dependent.
rdf_tokenize_literal(Literal, Tokens) :-
tokenization(Literal, Tokens),
!. % Hook
rdf_tokenize_literal(Literal, Tokens) :-
text_of(Literal, _Lang, Text),
atom(Text),
tokenize_atom(Text, Tokens0),
select_tokens(Tokens0, Tokens).
select_tokens([], []).
select_tokens([H|T0], T) :-
( exclude_from_index(token, H)
-> select_tokens(T0, T)
; number(H)
-> ( integer(H),
between(-1073741824, 1073741823, H)
-> T = [H|T1],
select_tokens(T0, T1)
; select_tokens(T0, T)
)
; atom_length(H, 1)
-> select_tokens(T0, T)
; default_stopgap(H)
-> select_tokens(T0, T)
; stopgap(H)
-> select_tokens(T0, T)
; T = [H|T1],
select_tokens(T0, T1)
).
%! rdf_stopgap_token(-Token) is nondet.
%
% True when Token is a stopgap token. Currently, this implies one
% of:
%
% - exclude_from_index(token, Token) is true
% - default_stopgap(Token) is true
% - Token is an atom of length 1
% - Token was added to the dynamic stopgap token set because
% it appeared in more than _stopgap_threshold_ literals.
rdf_stopgap_token(Token) :-
( var(Token)
-> rdf_stopgap_token2(Token)
; rdf_stopgap_token2(Token), !
).
rdf_stopgap_token2(Token) :-
exclude_from_index(token, Token).
rdf_stopgap_token2(Token) :-
default_stopgap(Token).
rdf_stopgap_token2(Token) :-
atom(Token),
atom_length(Token, 1).
rdf_stopgap_token2(Token) :-
stopgap(Token).
%! default_stopgap(?Token)
%
% Tokens we do not wish to index, as they create huge amounts of
% data with little or no value. Is there a more general way to
% describe this? Experience shows that simply word count is not a
% good criterion as it often rules out popular domain terms.
default_stopgap(and).
default_stopgap(an).
default_stopgap(or).
default_stopgap(of).
default_stopgap(on).
default_stopgap(in).
default_stopgap(this).
default_stopgap(the).
%! text_of(+LiteralArg, -Lang, -Text) is semidet.
%
% Get the textual or (integer) numerical information from a
% literal value. Lang is the language to use for stemming.
% Currently we use English for untyped plain literals or literals
% typed xsd:string. Formally, these should not be tokenized, but a
% lot of data out there does not tag strings with their language.
text_of(type(xsd:string, Text), en, Text) :- !.
text_of(type(_, Text), -, Text) :- !.
text_of(lang(Lang, Text), Lang, Text) :- !.
text_of(Text, en, Text) :- atom(Text), !.
text_of(Text, -, Text) :- integer(Text).
/*******************************
* STEM INDEX *
*******************************/
%! stem_index(-Map) is det.
%
% Get the stemming literal index. This index is created on demand.
% If some thread is creating the index, other threads wait for its
% completion.
stem_index(Map) :-
literal_map(stem, Map),
!,
wait_for_map(stem).
stem_index(Map) :-
rdf_new_literal_map(Map),
assert(literal_map(stem, Map)),
assert((new_token(Token, Lang) :- add_stem(Token, Lang, Map))),
message_queue_create(Queue),
assert(map_building(stem, Queue)),
thread_create(fill_stem_index(Map, Queue), _,
[ alias('__rdf_stemmer'),
detached(true)
]),
wait_for_map(stem).
wait_for_map(MapName) :-
( map_building(MapName, Queue)
-> catch(thread_get_message(Queue, _), _, true),
wait_for_map(MapName)
; true
).
fill_stem_index(StemMap, Queue) :-
call_cleanup(
forall(rdf_current_literal(Literal),
stem_literal_tokens(Literal, StemMap)),
( message_queue_destroy(Queue),
retractall(map_building(stem, _)))).
stem_literal_tokens(Literal, StemMap) :-
rdf_tokenize_literal(Literal, Tokens),
!,
sort(Tokens, Tokens1),
text_of(Literal, Lang, _Text),
insert_tokens_stem(Tokens1, Lang, StemMap).
stem_literal_tokens(_,_).
insert_tokens_stem([], _, _).
insert_tokens_stem([Token|T], Lang, Map) :-
( atom(Token)
-> ( stem(Token, Lang, Stem)
-> rdf_insert_literal_map(Map, Stem, Token, Keys),
( integer(Keys),
Keys mod 1000 =:= 0
-> progress(Map, 'Stem')
; true
)
; true
)
; true
),
insert_tokens_stem(T, Lang, Map).
add_stem(Token, Lang, Map) :-
stem(Lang, Token, Stem),
rdf_insert_literal_map(Map, Stem, Token, _).
stem(Token, LangSpec, Stem) :-
main_lang(LangSpec, Lang),
downcase_atom(Token, Lower),
catch(snowball(Lang, Lower, Stem), _, fail).
main_lang(LangSpec, Lang) :-
sub_atom(LangSpec, Before, _, _, -),
!,
sub_atom(LangSpec, 0, Before, _, Lang).
main_lang(LangSpec, Lang) :-
downcase_atom(LangSpec, Lang).
/*******************************
* METAPHONE INDEX *
*******************************/
metaphone_index(Map) :-
literal_map(metaphone, Map),
!,
wait_for_map(metaphone).
metaphone_index(Map) :-
rdf_new_literal_map(Map),
assert(literal_map(metaphone, Map)),
assert((new_token(Token, Lang) :- add_metaphone(Token, Lang, Map))),
message_queue_create(Queue),
assert(map_building(metaphone, Queue)),
thread_create(fill_metaphone_index(Map, Queue), _,
[ alias('__rdf_metaphone_indexer'),
detached(true)
]),
wait_for_map(metaphone).
fill_metaphone_index(MetaphoneMap, Queue) :-
call_cleanup(
fill_metaphone_index(MetaphoneMap),
( message_queue_destroy(Queue),
retractall(map_building(metaphone, _)))).
fill_metaphone_index(MetaphoneMap) :-
token_index(TokenMap),
rdf_keys_in_literal_map(TokenMap, all, Tokens),
metaphone(Tokens, MetaphoneMap).
metaphone([], _).
metaphone([Token|T], Map) :-
( atom(Token),
double_metaphone(Token, SoundEx)
-> rdf_insert_literal_map(Map, SoundEx, Token, Keys),
( integer(Keys),
Keys mod 1000 =:= 0
-> progress(Map, 'Metaphone')
; true
)
; true
),
metaphone(T, Map).
add_metaphone(Token, _Lang, Map) :-
atom(Token),
!,
double_metaphone(Token, SoundEx),
rdf_insert_literal_map(Map, SoundEx, Token).
add_metaphone(_, _, _).
%! rdf_literal_index(+Type, -Index) is det.
%
% True when Index is a literal map containing the index of Type.
% Type is one of:
%
% - token
% Tokens are basically words of literal values. See
% rdf_tokenize_literal/2. The `token` map maps tokens to full
% literal texts.
% - stem
% Index of stemmed tokens. If the language is available, the
% tokens are stemmed using the matching _snowball_ stemmer.
% The `stem` map maps stemmed to full tokens.
% - metaphone
% Phonetic index of tokens. The `metaphone` map maps phonetic
% keys to tokens.
rdf_literal_index(token, Map) :-
!,
token_index(Map).
rdf_literal_index(stem, Map) :-
!,
stem_index(Map).
rdf_literal_index(metaphone, Map) :-
!,
metaphone_index(Map).
rdf_literal_index(Type, _Map) :-
domain_error(literal_index, Type).
/*******************************
* UTIL *
*******************************/
verbose(Fmt, Args) :-
setting(verbose(true)),
!,
format(user_error, Fmt, Args).
verbose(_, _).
progress(Map, Which) :-
setting(verbose(true)),
!,
rdf_statistics_literal_map(Map, size(Keys, Values)),
format(user_error,
'\r~t~w: ~12|Keys: ~t~D~15+; Values: ~t~D~20+',
[Which, Keys, Values]).
progress(_,_).