1 | /**********************************************************************
|
---|
2 | *
|
---|
3 | * summarise.cpp --
|
---|
4 | * Copyright (C) 1999 The New Zealand Digital Library Project
|
---|
5 | *
|
---|
6 | * A component of the Greenstone digital library software
|
---|
7 | * from the New Zealand Digital Library Project at the
|
---|
8 | * University of Waikato, New Zealand.
|
---|
9 | *
|
---|
10 | * This program is free software; you can redistribute it and/or modify
|
---|
11 | * it under the terms of the GNU General Public License as published by
|
---|
12 | * the Free Software Foundation; either version 2 of the License, or
|
---|
13 | * (at your option) any later version.
|
---|
14 | *
|
---|
15 | * This program is distributed in the hope that it will be useful,
|
---|
16 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
|
---|
17 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
---|
18 | * GNU General Public License for more details.
|
---|
19 | *
|
---|
20 | * You should have received a copy of the GNU General Public License
|
---|
21 | * along with this program; if not, write to the Free Software
|
---|
22 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
---|
23 | *
|
---|
24 | *********************************************************************/
|
---|
25 |
|
---|
26 | /* The function 'summarise' produces, given a document text and a query,
|
---|
27 | * a (query-biased) summary. In the future, several types of summaries will
|
---|
28 | * be supported.
|
---|
29 | */
|
---|
30 |
|
---|
31 | #include "summarise.h"
|
---|
32 | #include "unitool.h"
|
---|
33 | #include <string.h>
|
---|
34 |
|
---|
35 |
|
---|
36 | /* **************** LOCAL PROTOTYPES **************** */
|
---|
37 |
|
---|
38 | text_t summarise_startend(text_t &htmlstr, int summaryLength);
|
---|
39 | text_t summarise_keywords(text_t &htmlstr, text_t &query, int summaryLength);
|
---|
40 |
|
---|
41 | text_t next_sentence(text_t::iterator& start, text_t::iterator& end);
|
---|
42 | text_t previous_sentence(text_t::iterator& start, text_t::iterator& end);
|
---|
43 | bool paragraph_tag(text_t::iterator start);
|
---|
44 |
|
---|
45 |
|
---|
46 | /****************************************************
|
---|
47 | NAME: summarise
|
---|
48 | DESC: produce a summary for a document
|
---|
49 | *****************************************************/
|
---|
50 |
|
---|
51 | text_t summarise(text_t &htmlstr, text_t &query, int summaryLength) {
|
---|
52 | // return summarise_startend(htmlstr,summaryLength);
|
---|
53 | return summarise_keywords(htmlstr,query,summaryLength);
|
---|
54 | }
|
---|
55 |
|
---|
56 |
|
---|
57 | /****************************************************
|
---|
58 | NAME: summarise_startend
|
---|
59 | DESC: return first and last sentences of a document
|
---|
60 | *****************************************************/
|
---|
61 |
|
---|
62 | text_t summarise_startend(text_t &htmlstr, int summaryLength) {
|
---|
63 | text_t::iterator str_start = htmlstr.begin(), str_end = htmlstr.end();
|
---|
64 | text_t answer;
|
---|
65 |
|
---|
66 | // add first sentences up to half the summary length
|
---|
67 |
|
---|
68 | text_t::iterator str_current = str_start;
|
---|
69 | while(str_current<str_end && answer.size()<(summaryLength/2)) {
|
---|
70 | text_t sentence = next_sentence(str_current,str_end);
|
---|
71 | answer.append(sentence);
|
---|
72 | }
|
---|
73 |
|
---|
74 | summaryLength -= answer.size(); // summary length left for last sentences
|
---|
75 | if(summaryLength<0)
|
---|
76 | summaryLength = 0;
|
---|
77 |
|
---|
78 | str_end = str_current;
|
---|
79 | str_current = htmlstr.end()-1;
|
---|
80 | text_t lastSentence;
|
---|
81 | while(str_current>str_end &&
|
---|
82 | lastSentence.size()<summaryLength) {
|
---|
83 | text_t sentence = previous_sentence(str_current,str_end);
|
---|
84 | lastSentence = sentence + lastSentence;
|
---|
85 | }
|
---|
86 |
|
---|
87 | answer += " ... ";
|
---|
88 | answer += lastSentence;
|
---|
89 |
|
---|
90 | return answer;
|
---|
91 | }
|
---|
92 |
|
---|
93 |
|
---|
94 | /****************************************************
|
---|
95 | NAME: summarise_keywords
|
---|
96 | DESC: build a summary with sentences containing keyword(s).
|
---|
97 | the sentences with most matching keywords are returned
|
---|
98 | first.
|
---|
99 | *****************************************************/
|
---|
100 |
|
---|
101 | text_t summarise_keywords(text_t &htmlstr, text_t &query, int summaryLength) {
|
---|
102 |
|
---|
103 | if ((query.size()==0) || (htmlstr.size()==0)) {
|
---|
104 | return "";
|
---|
105 | }
|
---|
106 |
|
---|
107 | text_tarray allterms, terms;
|
---|
108 | splitchar(query.begin(),query.end(),' ',allterms);
|
---|
109 |
|
---|
110 | // consider only non-empty terms
|
---|
111 | for(text_tarray::iterator term = allterms.begin();
|
---|
112 | term < allterms.end(); ++term) {
|
---|
113 | if(!(*term).empty())
|
---|
114 | terms.push_back(*term);
|
---|
115 | }
|
---|
116 |
|
---|
117 | if (terms.size()==0) {
|
---|
118 | return "";
|
---|
119 | }
|
---|
120 |
|
---|
121 | text_tarray::iterator terms_start = terms.begin(), terms_end = terms.end();
|
---|
122 |
|
---|
123 | //text_tarray::iterator terms_current = terms_start;
|
---|
124 | //strstr("merde",*terms_current);
|
---|
125 |
|
---|
126 | text_t::iterator str_start = htmlstr.begin(), str_end = htmlstr.end();
|
---|
127 |
|
---|
128 | vector<text_tarray> answers(terms.size());
|
---|
129 | // an array of array of sentences for the summary:
|
---|
130 | // answers[0] contains sentences with 1 keyword
|
---|
131 | // answers[1] contains sentences with 2 keywords, etc.
|
---|
132 | vector<int> answersSize(terms.size());
|
---|
133 | // answersSize[0] is the combined size of sentences with 1 keyword, etc.
|
---|
134 | for(vector<int>::iterator size = answersSize.begin();
|
---|
135 | size<answersSize.end(); ++size)
|
---|
136 | *size = 0; // initialise sentence size
|
---|
137 |
|
---|
138 | int totfound = 0;
|
---|
139 | text_t::iterator str_current = str_start;
|
---|
140 | while(str_current<str_end && answersSize[terms.size()-1]<summaryLength) {
|
---|
141 | // if the size of best sentences is greater than summary, that's enough!
|
---|
142 | text_t sentence = next_sentence(str_current,str_end);
|
---|
143 |
|
---|
144 | text_tarray::iterator terms_current = terms_start;
|
---|
145 | int nFound = 0;
|
---|
146 | while(terms_current!=terms_end) {
|
---|
147 | text_t::iterator word = findword(sentence.begin(),sentence.end(),
|
---|
148 | *terms_current);
|
---|
149 | if(word!=sentence.end())
|
---|
150 | { ++nFound; ++totfound; }
|
---|
151 | ++terms_current;
|
---|
152 | }
|
---|
153 |
|
---|
154 | if(nFound>0 && answersSize[nFound-1]<summaryLength) {
|
---|
155 | answers[nFound-1].push_back(sentence);
|
---|
156 | answersSize[nFound-1] += sentence.size();
|
---|
157 | }
|
---|
158 | }
|
---|
159 |
|
---|
160 | text_t answer;
|
---|
161 | for(vector<text_tarray>::iterator sentarray = answers.end()-1;
|
---|
162 | sentarray>=answers.begin(); --sentarray)
|
---|
163 | for(text_tarray::iterator sentence = (*sentarray).begin();
|
---|
164 | sentence < (*sentarray).end(); ++sentence) {
|
---|
165 | answer.append(*sentence);
|
---|
166 | if(answer.size()>=summaryLength)
|
---|
167 | return answer;
|
---|
168 | }
|
---|
169 |
|
---|
170 | if(!answer.empty())
|
---|
171 | return answer;
|
---|
172 |
|
---|
173 | return summarise_startend(htmlstr,summaryLength);
|
---|
174 | }
|
---|
175 |
|
---|
176 |
|
---|
177 | /* *********************** LOCAL FUNCTIONS ******************* */
|
---|
178 |
|
---|
179 | /* NAME: next_sentence
|
---|
180 | DESC: returns next sentence, text-only (ie. HTML markup is removed)
|
---|
181 | */
|
---|
182 |
|
---|
183 | text_t next_sentence(text_t::iterator& start, text_t::iterator& end) {
|
---|
184 | text_t sentence; // the sentence to be returned
|
---|
185 | bool foundPunctuation = false; // set to true by '.', '!' or '?'
|
---|
186 | while(start<end && !foundPunctuation) {
|
---|
187 | switch (*start) {
|
---|
188 | case '<': // skip over rest of html tag
|
---|
189 | if(paragraph_tag(start) && has_unicode_letdig(sentence))
|
---|
190 | foundPunctuation = true;
|
---|
191 | while ((start<end) && (*start!='>'))
|
---|
192 | ++start;
|
---|
193 | if(start<end) ++start;
|
---|
194 | break;
|
---|
195 | case '.':
|
---|
196 | case '!':
|
---|
197 | case '?':
|
---|
198 | sentence.push_back(*start);
|
---|
199 | ++start;
|
---|
200 | if(start>=end ||
|
---|
201 | (is_unicode_space(*start) && (*(start-2)<'A' || *(start-2)>'Z'))) {
|
---|
202 | foundPunctuation = true;
|
---|
203 | }
|
---|
204 | break;
|
---|
205 | default:
|
---|
206 | sentence.push_back(*start);
|
---|
207 | ++start;
|
---|
208 | break;
|
---|
209 | }
|
---|
210 | }
|
---|
211 | return sentence;
|
---|
212 | }
|
---|
213 |
|
---|
214 |
|
---|
215 | /* NAME: previous_sentence
|
---|
216 | DESC: returns previous sentence, text-only (ie. HTML markup is removed)
|
---|
217 | */
|
---|
218 |
|
---|
219 | text_t previous_sentence(text_t::iterator& start, text_t::iterator& end) {
|
---|
220 | text_t sentence; // the sentence to be returned
|
---|
221 | bool found1stPunctuation = false, // set to true by '.', '!' or '?'
|
---|
222 | // first punct. is included in results
|
---|
223 | found2ndPunctuation = false; // second punct. is stop condition,
|
---|
224 | // and is not included in results
|
---|
225 | while(start>end && !found2ndPunctuation) {
|
---|
226 | switch (*start) {
|
---|
227 | case '>': // skip over rest of html tag
|
---|
228 | while ((start>end) && (*start!='<')) // backtrack to beginning of tag
|
---|
229 | --start;
|
---|
230 | if(start>end) {
|
---|
231 | if(paragraph_tag(start) && has_unicode_letdig(sentence))
|
---|
232 | found2ndPunctuation = true;
|
---|
233 | --start;
|
---|
234 | }
|
---|
235 | break;
|
---|
236 | case '.':
|
---|
237 | case '!':
|
---|
238 | case '?':
|
---|
239 | if(!is_unicode_space(*(start+1)) ||
|
---|
240 | (start-1>end && *(start-1)>='A' && *(start-1)<='Z')) {
|
---|
241 | // if next character is not a blank, or preceding character is
|
---|
242 | // a capital letter, we guess it's an acronym (e.g. "U.S.A.")
|
---|
243 | sentence.text_as_usvector().insert(sentence.text_as_usvector().begin(),
|
---|
244 | start,start+1);
|
---|
245 | --start;
|
---|
246 | } else
|
---|
247 | if(has_unicode_letdig(sentence) || found1stPunctuation)
|
---|
248 | found2ndPunctuation = true;
|
---|
249 | else {
|
---|
250 | sentence.text_as_usvector().insert(
|
---|
251 | sentence.text_as_usvector().begin(),start,start+1);
|
---|
252 | --start;
|
---|
253 | found1stPunctuation = true;
|
---|
254 | }
|
---|
255 | break;
|
---|
256 | default:
|
---|
257 | sentence.text_as_usvector().insert(
|
---|
258 | sentence.text_as_usvector().begin(),start,start+1);
|
---|
259 | --start;
|
---|
260 | break;
|
---|
261 | }
|
---|
262 | }
|
---|
263 | return sentence;
|
---|
264 | }
|
---|
265 |
|
---|
266 |
|
---|
267 | // start is positioned on the '<'
|
---|
268 | bool paragraph_tag(text_t::iterator start) {
|
---|
269 | if(*start=='<') {
|
---|
270 | ++start;
|
---|
271 | if(*start=='p' || *start=='P') {
|
---|
272 | ++start;
|
---|
273 | if(is_unicode_space(*start) || *start=='>')
|
---|
274 | return true;
|
---|
275 | }
|
---|
276 | }
|
---|
277 | return false;
|
---|
278 | }
|
---|