Contents of /trunk/README

                             WAIT 1.8

                  Copyright (c) 1996-2000, Ulrich Pfeifer

------------------------------------------------------------------------
    This program is free software; you can redistribute it and/or
    modify it under the same terms than Perl itself.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
------------------------------------------------------------------------

News:

Locking
=======

WAIT now supports some basic locking.

Speed
=====

Searching large collections is now considerably faster:

        $table->search({attr  => 'text', 
                        cont  => $query, 
                        top   => 1, 
                        picky => 0});

Table indices may now be tuned to improve search performance.  The
index tuning can be switched on and off using $table->set(top=>1/0) to
allow for bulk inserts.

Documentation
=============

WAIT is still not documented really.  But Andreas König took the
trouble to comment the example scripts.  This will help you
implementing your own applications.  I added some tiny scripts to
index e.g. your .yow file or the fourtune databases.

SourceForge
===========

WAIT is registered on SourceForge now:

        http://wait.sourceforge.net/
        https://sourceforge.net/project/?group_id=4814

I will keep the CVS repository up to date.  If you have some spare
tuits, feel free to contribute.

Ulrich Pfeifer <upf@wait.de> 

------------------------------------------------------------------------
NAME
    WAIT - a rewrite of the freeWAIS-sf engine in Perl and XS

SYNOPSIS
    A Synopsis is not yet available.

Status of this document
    I started writing down some information about the implementation before
    I forget them in my spare time. The stuff is incomplete at least. Any
    additions, corrections, ... welcome.

PURPOSE
    As you might know, I developed and maintained freeWAIS-sf (with the help
    of many people in The Net). FreeWAIS-sf is based on freeWAIS maintained
    by the Clearing House for Network Information Retrieval (CNIDR) which in
    turn is based on wais-8-b5 implemented by Thinking Machine et al. During
    this long history - implementation started about 1989 - many people
    contributed to the distribution and added features not foreseen by the
    original design. While the system fulfills its task now, the code has
    reached a state where adding new features is nearly impossible and even
    fixing longstanding bugs and removing limitations has become a very time
    consuming task.

    Therefore I decided to pass the maintenance to WSC Inc. and built a new
    system from scratch. For obvious reasons I choosed Perl as
    implementation language.

DESCRIPTION
    The central idea of the system is to provide a framework and the
    building blocks for any indexing and search system the users might want
    to build. Obviously the framework limits the class of system which can
    be build.

           +------+     +-----+     +------+
       ==> |Access| ==> |Parse| ==> |      |
           +------+     +-----+     |      |
                           ||       |      |     +-----+
                           ||       |Filter| ==> |Index|
                           \/       |      |     +-----+
          +-------+     +-----+     |      |
       <= |Display| <== |Query| <-> |      |
          +-------+     +-----+     +------+

    A collection (aka table) is defined by the instances of the access and
    parse module together with the filter definitions. At query time in
    addition a query and a display module must be choosen.

  Access

    The access module defines which documents are members of a database.
    Usually an access module is a tied hash, whose keys are the Ids of the
    documents (did = document id) and whose values are the documents
    themselves. The indexing process loops over the keys using `FIRSTKEY'
    and `NEXTKEY'. Documents are retrieved with `FETCH'.

    By convention access modules should be members of the `WAIT::Document'
    hierarchy. Have a look at the `WAIT::Document::Split' module to get the
    idea.

  Parse

    The task of the parse module is to split the documents into logical
    parts via the `split' method. E.g. the `WAIT::Parse::Nroff' splits
    manuals piped through nroff(1) into the sections *name*, *synopsis*,
    *options*, *description*, *author*, *example*, *bugs*, *text*, *see*,
    and *environment*. Here is the implementation of `WAIT::Parse::Base'
    which handles documents with a pretty simple tagged format:

      AU: Pfeifer, U.; Fuhr, N.; Huynh, T.
      TI: Searching Structured Documents with the Enhanced Retrieval
          Functionality of freeWAIS-sf and SFgate
      ER: D. Kroemker
      BT: Computer Networks and ISDN Systems; Proceedings of the third
          International World-Wide Web Conference
      PN: Elsevier
      PA: Amsterdam - Lausanne - New York - Oxford - Shannon - Tokyo
      PP: 1027-1036
      PY: 1995

      sub split {                     # called as method
        my %result;
        my $fld;

        for (split /\n/, $_[1]) {
          if (s/^(\S+):\s*//) {
            $fld = lc $1;
          }
          $result{$fld} .= $_ if defined $fld;
        }
        return \%result;
      }

    Since the original document cannot be reconstructed from its attributes,
    we need a second method (*tag*) which marks the regions of the document
    with tags for the different attributes. This tagged form is used by the
    display module to hilight search terms in the documents. Besides the
    tags for the attributes, the method might assign the special tags `_b'
    and `_i' for indicating bold and italic regions.

      sub tag {
        my @result;
        my $tag;

        for (split /\n/, $_[1]) {
          next if /^\w\w:\s*$/;
          if (s/^(\S+)://) {
            push @result, {_b => 1}, "$1:";
            $tag = lc $1;
          }
          if (defined $tag) {
            push @result, {$tag => 1}, "$_\n";
          } else {
            push @result, {}, "$_\n";
          }
        }
        return @result;               # we don't go for speed
      }

    Obviously one could implement `split' via `tag'. The reason for having
    two functions is speed. We need to call `split' for each document when
    indexing a collection. Therefore speed is essential. On the other hand,
    `tag' is called in order to display a single document and may be a
    little slower. It may care about tagging bold and italic regions. See
    `WAIT::Parse::Nroff' how this might decrease performance.

  Filter definition

    From the Information Retrieval perspective, the hardest part of the
    system is the filter module. The database administrator defines for each
    attribute, how the contents should be processed before it is stored in
    the index. Usually the processing contains steps to restrict the
    character set, case transformation, splitting to words and transforming
    to word stems. In WAIT these steps are defined naturally as a pipeline
    of processing steps. The pipelines are made up by functions in the
    package WAIT::Filter which is pre-populated by the most common functions
    but may be extended any time.

    The equivalent for a typical freeWAIS-sf processing would be this
    pipeline:

            [ 'isotr', 'isolc', 'split2', 'stop', 'Stem']

    The function `isotr' replaces unknown characters by blanks. `isolc'
    transforms to lower case. `split2' splits into words and removes words
    shorter than two characters. `stop' removes the freeWAIS-sf stopwords
    and `Stem' applies the Porter algorithm for computing the stem of the
    words.

    The filter definition for a collection defines a set of pipelines for
    the attributes and modifies the pipelines which should be used for
    prefix and interval searches.

    Several complete working examples come with WAIT in the script
    directory. It is recommended to follow the pattern of the scripts
    smakewhatis and sman.

1	WAIT 1.8
2
3	Copyright (c) 1996-2000, Ulrich Pfeifer
4
5	------------------------------------------------------------------------
6	This program is free software; you can redistribute it and/or
7	modify it under the same terms than Perl itself.
8
9	This program is distributed in the hope that it will be useful,
10	but WITHOUT ANY WARRANTY; without even the implied warranty of
11	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
12	------------------------------------------------------------------------
13
14	News:
15
16	Locking
17	=======
18
19	WAIT now supports some basic locking.
20
21	Speed
22	=====
23
24	Searching large collections is now considerably faster:
25
26	$table->search({attr => 'text',
27	cont => $query,
28	top => 1,
29	picky => 0});
30
31	Table indices may now be tuned to improve search performance. The
32	index tuning can be switched on and off using $table->set(top=>1/0) to
33	allow for bulk inserts.
34
35	Documentation
36	=============
37
38	WAIT is still not documented really. But Andreas König took the
39	trouble to comment the example scripts. This will help you
40	implementing your own applications. I added some tiny scripts to
41	index e.g. your .yow file or the fourtune databases.
42
43	SourceForge
44	===========
45
46	WAIT is registered on SourceForge now:
47
48	http://wait.sourceforge.net/
49	https://sourceforge.net/project/?group_id=4814
50
51	I will keep the CVS repository up to date. If you have some spare
52	tuits, feel free to contribute.
53
54	Ulrich Pfeifer <upf@wait.de>
55
56	------------------------------------------------------------------------
57	NAME
58	WAIT - a rewrite of the freeWAIS-sf engine in Perl and XS
59
60	SYNOPSIS
61	A Synopsis is not yet available.
62
63	Status of this document
64	I started writing down some information about the implementation before
65	I forget them in my spare time. The stuff is incomplete at least. Any
66	additions, corrections, ... welcome.
67
68	PURPOSE
69	As you might know, I developed and maintained freeWAIS-sf (with the help
70	of many people in The Net). FreeWAIS-sf is based on freeWAIS maintained
71	by the Clearing House for Network Information Retrieval (CNIDR) which in
72	turn is based on wais-8-b5 implemented by Thinking Machine et al. During
73	this long history - implementation started about 1989 - many people
74	contributed to the distribution and added features not foreseen by the
75	original design. While the system fulfills its task now, the code has
76	reached a state where adding new features is nearly impossible and even
77	fixing longstanding bugs and removing limitations has become a very time
78	consuming task.
79
80	Therefore I decided to pass the maintenance to WSC Inc. and built a new
81	system from scratch. For obvious reasons I choosed Perl as
82	implementation language.
83
84	DESCRIPTION
85	The central idea of the system is to provide a framework and the
86	building blocks for any indexing and search system the users might want
87	to build. Obviously the framework limits the class of system which can
88	be build.
89
90	+------+ +-----+ +------+
91	==> \|Access\| ==> \|Parse\| ==> \| \|
92	+------+ +-----+ \| \|
93	\|\| \| \| +-----+
94	\|\| \|Filter\| ==> \|Index\|
95	\/ \| \| +-----+
96	+-------+ +-----+ \| \|
97	<= \|Display\| <== \|Query\| <-> \| \|
98	+-------+ +-----+ +------+
99
100	A collection (aka table) is defined by the instances of the access and
101	parse module together with the filter definitions. At query time in
102	addition a query and a display module must be choosen.
103
104	Access
105
106	The access module defines which documents are members of a database.
107	Usually an access module is a tied hash, whose keys are the Ids of the
108	documents (did = document id) and whose values are the documents
109	themselves. The indexing process loops over the keys using `FIRSTKEY'
110	and `NEXTKEY'. Documents are retrieved with `FETCH'.
111
112	By convention access modules should be members of the `WAIT::Document'
113	hierarchy. Have a look at the `WAIT::Document::Split' module to get the
114	idea.
115
116	Parse
117
118	The task of the parse module is to split the documents into logical
119	parts via the `split' method. E.g. the `WAIT::Parse::Nroff' splits
120	manuals piped through nroff(1) into the sections name, synopsis,
121	options, description, author, example, bugs, text, see,
122	and environment. Here is the implementation of `WAIT::Parse::Base'
123	which handles documents with a pretty simple tagged format:
124
125	AU: Pfeifer, U.; Fuhr, N.; Huynh, T.
126	TI: Searching Structured Documents with the Enhanced Retrieval
127	Functionality of freeWAIS-sf and SFgate
128	ER: D. Kroemker
129	BT: Computer Networks and ISDN Systems; Proceedings of the third
130	International World-Wide Web Conference
131	PN: Elsevier
132	PA: Amsterdam - Lausanne - New York - Oxford - Shannon - Tokyo
133	PP: 1027-1036
134	PY: 1995
135
136	sub split { # called as method
137	my %result;
138	my $fld;
139
140	for (split /\n/, $_[1]) {
141	if (s/^(\S+):\s*//) {
142	$fld = lc $1;
143	}
144	$result{$fld} .= $_ if defined $fld;
145	}
146	return \%result;
147	}
148
149	Since the original document cannot be reconstructed from its attributes,
150	we need a second method (tag) which marks the regions of the document
151	with tags for the different attributes. This tagged form is used by the
152	display module to hilight search terms in the documents. Besides the
153	tags for the attributes, the method might assign the special tags `_b'
154	and `_i' for indicating bold and italic regions.
155
156	sub tag {
157	my @result;
158	my $tag;
159
160	for (split /\n/, $_[1]) {
161	next if /^\w\w:\s*$/;
162	if (s/^(\S+)://) {
163	push @result, {_b => 1}, "$1:";
164	$tag = lc $1;
165	}
166	if (defined $tag) {
167	push @result, {$tag => 1}, "$_\n";
168	} else {
169	push @result, {}, "$_\n";
170	}
171	}
172	return @result; # we don't go for speed
173	}
174
175	Obviously one could implement `split' via `tag'. The reason for having
176	two functions is speed. We need to call `split' for each document when
177	indexing a collection. Therefore speed is essential. On the other hand,
178	`tag' is called in order to display a single document and may be a
179	little slower. It may care about tagging bold and italic regions. See
180	`WAIT::Parse::Nroff' how this might decrease performance.
181
182	Filter definition
183
184	From the Information Retrieval perspective, the hardest part of the
185	system is the filter module. The database administrator defines for each
186	attribute, how the contents should be processed before it is stored in
187	the index. Usually the processing contains steps to restrict the
188	character set, case transformation, splitting to words and transforming
189	to word stems. In WAIT these steps are defined naturally as a pipeline
190	of processing steps. The pipelines are made up by functions in the
191	package WAIT::Filter which is pre-populated by the most common functions
192	but may be extended any time.
193
194	The equivalent for a typical freeWAIS-sf processing would be this
195	pipeline:
196
197	[ 'isotr', 'isolc', 'split2', 'stop', 'Stem']
198
199	The function `isotr' replaces unknown characters by blanks. `isolc'
200	transforms to lower case. `split2' splits into words and removes words
201	shorter than two characters. `stop' removes the freeWAIS-sf stopwords
202	and `Stem' applies the Porter algorithm for computing the stem of the
203	words.
204
205	The filter definition for a collection defines a set of pipelines for
206	the attributes and modifies the pipelines which should be used for
207	prefix and interval searches.
208
209	Several complete working examples come with WAIT in the script
210	directory. It is recommended to follow the pattern of the scripts
211	smakewhatis and sman.
212