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Wissen Full-Text Search & Classification Engine

Project description

Changes

  • add learner.rbuild ()
  • Add Rocchino full-text classifier
  • Changed learner.build() and train() args

Introduce

Wissen Search & Classification Engine is a simple search engine mostly written in Python and C in year 2008.

At that time, I would like to study Lucene earlier version with Lupy and CLucene. And I also had maden my own search engine for excercise.

Its file format, numeric compressing algorithm, indexing process are quiet similar with Lucene.

But I got tired reverse engineering, so query and result-fetching parts was built from my imagination. As a result it’s entirely unorthodox and possibly very inefficient. Wissen’s searching mechanism is similar with DNA-RNA-Protein working model translated into ‘Index File-Temporary Small Replication Buffer-Qeury Result’.

  • Every searcher (Cell) has a single index file handlers group (DNA group in nuclear)
  • Thread has multiple small buffer (RNA) for replicating index as needed part
  • Query class (Ribosome) creates qeury result (Protein) by synthesising buffers’ inforamtion (RNAs)
  • Repeat from 2nd if expected more results

Installation

Wissen contains C extension, so need C compiler.

pip install wissen

Quick Start

All field text type should be str or utf-8 encoded bytes in Python 3.x, and unicode or utf-8 encoded string in Python 2.7. Otherwise encoding should be specified.

Indexing and Searching

Here’s an example indexing only one document.

import wissen

# indexing
analyzer = wissen.standard_analyzer (max_term = 3000)
col = wissen.collection ("./col", wissen.CREATE, analyzer)
indexer = col.get_indexer ()

song = "violin sonata in c k.301"
composer = u"wolfgang amadeus mozart"
birth = 1756
home = "50.665629/8.048906" # Lattitude / Longitude of Salzurg
genre = "01011111" # (rock serenade jazz piano symphony opera quartet sonata)

document = wissen.document ()

# object to return, any object serializable by pickle
document.set_content ([song, composer])

# text content to generating auto snippet by given query terms
document.set_auto_snippet (song)

# add searchable fields
document.add_field ("default", song, wissen.TEXT)
document.add_field ("composer", composer, wissen.TEXT)
document.add_field ("birth", birth, wissen.INT16)
document.add_field ("genre", genre, wissen.BIT8)
document.add_field ("home", home, wissen.COORD)

indexer.add_document (document)
indexer.close ()

# searching
analyzer = wissen.standard_analyzer (max_term = 8)
col = wissen.collection ("./col", wissen.READ, analyzer)
searcher = col.get_searcher ()
print searcher.query (u'violin', offset = 0, fetch = 2, sort = "tfidf", summary = 30)
searcher.close ()

Result will be like this:

{
 'code': 200,
 'time': 0,
 'total': 1
 'result': [
  [
   ['violin sonata in c k.301', 'wofgang amadeus mozart'], # content
   '<b>violin</b> sonata in c k.301', # auto snippet
   14, 0, 0, 0 # additional info
  ]
 ],
 'sorted': [None, 0],
 'regex': 'violin|violins',
}

Learning and Classification

Here’s an example guessing one of ‘play golf’, ‘go to bed’ by weather conditions.

import wissen

analyzer = wissen.standard_analyzer (max_term = 3000)

# learning

mdl = wissen.model ("./mdl", wissen.CREATE, analyzer)
learner = mdl.get_learner ()

document = wissen.labeled_document ("Play Golf", "cloudy windy warm")
learner.add_document (document)
document = wissen.labeled_document ("Play Golf", "windy sunny warm")
learner.add_document (document)
document = wissen.labeled_document ("Go To Bed", "cold rainy")
learner.add_document (document)
document = wissen.labeled_document ("Go To Bed", "windy rainy warm")
learner.add_document (document)
learner.close ()

mdl = wissen.model ("./mdl", wissen.MODIFY, analyzer)
learner = mdl.get_learner ()
learner.listbydf () # show all terms with DF (Document Frequency)
learner.close ()

mdl = wissen.model ("./mdl", wissen.MODIFY, analyzer)
learner = mdl.get_learner ()
learner.build (dfmin = 2) # build corpus DF >= 2
learner.close ()

mdl = wissen.model ("./mdl", wissen.MODIFY, analyzer)
learner = mdl.get_learner ()
learner.train (
  cl_for = wissen.ALL, # for which classifier
  selector = wissen.CHI2, # feature selecting method
  select = 0.99, # how many features?
  orderby = wissen.MAX, # feature ranking by what?
  dfmin = 2 # exclude DF < 2
)
learner.close ()


# gusessing

mdl = wissen.model ("./mdl", wissen.READ, analyzer)
classifier = mdl.get_classifier ()
print classifier.guess ("rainy cold")
print classifier.guess ("rainy cold", cl = wissen.FEATUREVOTE)
print classifier.guess ("rainy cold", cl = wissen.NAIVEBAYES)
print classifier.guess ("rainy cold", cl = wissen.TFIDF)
print classifier.guess ("rainy cold", cl = wissen.SIMILARITY)
classifier.close ()

Result will be like this:

{
  'code': 200,
  'total': 1,
  'time': 5,
  'result': [('Go To Bed', 1.0)],
  'classifier': 'meta'
}

Limitation

Before you test Wissen, you should know some limitation.

  • Wissen search cannot sort by string type field, but can by int/bit/coord types and TFIDF ranking.
  • Wissen classification doesn’t have purporse for accuracy but performance as realtime (means within 1 second) quessing. So I used relatvely simple and fast classification algorithms. If you need accuracy, it’s not fit to you.

Configue Wissen

When indexing/learing it’s not necessory to configure, but searching/guessing it should be configure. The reason why Wissen allocates memory per thread for searching and classifying on initializing.

wissen.configure (
  numthread,
  logger,
  io_buf_size = 4096,
  mem_limit = 256
)
  • numthread: number of threads which access to Wissen collections and models. if set to 8, you can open multiple collections (or models) and access with 8 threads. If 9th thread try to access to wissen, it will raise error
  • logger: see next chapter
  • io_buf_size = 4096: Bytes size of flash buffer for repliacting index files
  • mem_limit = 256: Memory limit per a thread, but it’s not absolute. It can be over during calculation if need, but when calcuation has been finished, would return memory ASAP.

Finally when your app is terminated, call shutdown.

wissen.shutdown ()

Logger

from wissen.lib import logger

logger.screen_logger ()

# it will create file '/var/log.wissen.log', and rotated by daily base
logger.rotate_logger ("/var/log", "wissen", "daily")

Standard Analyzer

Analyzer is needed by TEXT, TERM types.

Basic Usage is:

analyzer = wissen.standard_analyzer (
  max_term = 8,
  numthread = 1,
  ngram = True or False,
  stem_level = 0, 1 or 2 (2 is only applied to English Language),
  make_lower_case = True or False,
  stopwords_case_sensitive = True or False,
  ngram_no_space = True or False,
  strip_html = True or False,
  stopwords = [word,...]
)
  • stem_level: 0 and 1, especially ‘en’ language has level 2 for hard stemming
  • make_lower_case: make lower case for every text
  • stopwords_case_sensitive: it will work if make_lower_case is False
  • ngram_no_space: if False, ‘泣斬 馬謖’ will be tokenized to _泣, 泣斬, 斬_, _馬, 馬謖, 謖_. But if True, addtional bi-gram 斬馬 will be created between 斬_ and _馬.
  • strip_html
  • stopwords: Wissen has only English stopwords list, You can use change custom stopwords. Stopwords sould be unicode or utf8 encoded bytes

Wissen has some kind of stemmers and n-gram methods for international languages and can use them by this way:

analyzer = standard_analyzer (ngram = True, stem_level = 1)
col = wissen.collection ("./col", wissen.CREATE, analyzer)
indexer = col.get_indexer ()
document.add_field ("default", song, wissen.TEXT, lang = "en")

Implemented Stemmers

Except English stemmer, all stemmers can be obtained at IR Multilingual Resources at UniNE.

  • ar: Arabic
  • de: German
  • en: English
  • es: Spanish
  • fi: Finnish
  • fr: French
  • hu: Hungarian
  • it: Italian
  • pt: Portuguese
  • sv: Swedish

Bi-Gram Index

If ngram is set to True, these languages will be indexed with bi-gram.

  • cn: Chinese
  • ja: Japanese
  • ko: Korean

Also note that if word contains only alphabet, will be used English stemmer.

Tri-Gram Index

The other languages will be used English stemmer if all spell is Alphabet. And if ngram is set to True, will be indexed with tri-gram if word has multibytes.

Methods Spec

  • analyzer.index (document, lang)
  • analyzer.freq (document, lang)
  • analyzer.stem (document, lang)
  • analyzer.count_stopwords (document, lang)

Collection

Collection manages index files, segments and properties.

col = wissen.collection (
  indexdir = [dirs],
  mode = [ CREATE | READ | APEND ],
  analyzer = None,
  logger = None
)
  • indexdir: path or list of path for using multiple disks efficiently
  • mode
  • analyzer
  • logger: # if logger configured by wissen.configure, it’s not necessary

Collection has 2 major class: indexer and searcher.

Indexer

For searching documents, it’s necessary to indexing text to build Inverted Index for fast term query.

indexer = col.get_indexer (
  max_segments = int,
  force_merge = True or False,
  max_memory = 10000000 (10Mb),
  optimize = True or False
)
  • max_segments: maximum number of segments of index, if it’s over, segments will be merged. also note during indexing, segments will be created 3 times of max_segments and when called index.close (), automatically try to merge until segemtns is proper numbers
  • force_merge: When called index.close (), forcely try to merge to a single segment. But it’s failed if too big index - on 32bit OS > 2GB, 64bit > 10 GB
  • max_memory: if it’s over, created new segment on indexing
  • optimize: When called index.close (), segments will be merged by optimal number as possible

For add docuemtn to indexer, create document object:

document = wissen.document ()

Wissen handle 3 objects as completly different objects between no relationship

  • returning content
  • snippet generating field
  • searcherble fields

Returning Content

Wissen serialize returning contents by pickle, so you can set any objects pickle serializable.

document.set_content ({"userid": "hansroh", "preference": {"notification": "email", ...}})

or

document.set_content ([32768, "This is smaple ..."])

Snippet Generating Field

This field should be unicode/utf8 encoded bytes.

document.set_auto_snippet ("This is sample...")

Searchable Fields

document also recieve searchable fields:

document.add_field (name, value, ftype = wissen.TEXT, lang = "un", encoding = None)

document.add_field ("default", "violin sonata in c k.301", wissen.TEXT, "en")
document.add_field ("composer", "wolfgang amadeus mozart", wissen.TEXT, "en")
document.add_field ("lastname", "mozart", wissen.STRING)
document.add_field ("birth", 1756, wissen.INT16)
document.add_field ("genre", "01011111", wissen.BIT8)
document.add_field ("home", "50.665629/8.048906", wissen.COORD6)
  • name: if ‘default’, this field will be searched by simple string, or use ‘name:query_text’
  • value: unicode/utf8 encode text, or should give encoding arg.
  • ftype: see below
  • encoding: give like ‘iso8859-1’ if value is not unicode/utf8
  • lang: language code for standard_analyzer, “un” (unknown) is default

Avalible Field types are:

  • TEXT: analyzable full-text, result-not-sortable
  • TERM: analyzable full-text but position data will not be indexed as result can’t search phrase, result-not-sortable
  • STRING: exactly string match like nation codes, result-not-sortable
  • LIST: comma seperated STRING, result-not-sortable
  • COORDn, n=4,6,8 decimal precision: comma seperated string ‘latitude,longititude’, latitude and longititude sould be float type range -90 ~ 90, -180 ~ 180. n is precision of coordinates. n=4 is 10m radius precision, 6 is 1m and 8 is 10cm. result-sortable
  • BITn, n=8,16,24,32,40,48,56,64: bitwise operation, bit makred string required by n, result-sortable
  • INTn, n=8,16,24,32,40,48,56,64: range, int required, result-sortable

Repeat add_document as you need and close indexer.

for ...:
  document = wissen.document ()
  ...
  indexer.add_document (document)
  indexer.close ()

If searchers using this collection runs with another process or thread, searcher automatically reloaded within a few seconds for applying changed index.

Searcher

For running searcher, you should wissen.configure () first and creat searcher.

searcher = col.get_searcher (
  max_result = 2000,
  num_query_cache = 200
)
  • max_result: max returned number of searching results. default 2000, if set to 0, unlimited results
  • num_query_cache: default is 200, if over 200, removed by access time old

Query is simple:

searcher.query (
  qs,
  offset = 0,
  fetch = 10,
  sort = "tfidf",
  summary = 30,
  lang = "un"
)
  • qs: string (unicode) or utf8 encoded bytes. for detail query syntax, see below
  • offset: return start position of result records
  • fetch: number of records from offset
  • sort: “(+-)tfidf” or “(+-)field name”, field name should be int/bit type, and ‘-‘ means ascending. if sort is “”, records order is index time desc
  • summary: number of terms for snippet
  • lang: default is “un” (unknown)

For deleting indexed document:

searcher.delete (qs)

All documents will be deleted immediatly. And if searchers using this collection run with another process or thread, theses searchers automatically reloaded within a few seconds.

Finally, close searcher.

searcher.close ()

Query Syntax

  • violin composer:mozart birth:1700~1800

    search ‘violin’ in default field, ‘mozart’ in composer field and search range between 1700, 1800 in birth field

  • violin allcomposer:wolfgang mozart

    search ‘violin’ in default field and any terms after allcomposer will be searched in composer field

  • violin -sonata birth:~1800

    not contain sonata in default field

  • violin -composer:mozart

    not contain mozart in composer field

  • violin or piano genre:00001101/all

    matched all 5, 6 and 8th bits are 1. also /any or /none is available

  • violin or ((piano composer:mozart) genre:00001101/any)

    support unlimited priority ‘()’ and ‘or’ operators

  • (violin or ((allcomposer:mozart wolfgang) -amadeus)) sonata (genre:00001101/none home:50.6656,8.0489~10000)

    search home location coordinate (50.6656, 8.0489) within 10 Km

  • “violin sonata” genre:00001101/none home:50.6656/8.0489~10

    search exaclt phrase “violin sonata”

  • “violin^3 piano” -composer:”ludwig van beethoven”

    search loose phrase “violin sonata” within 3 terms

Model

Model manages index, train files, segments and properties.

mdl = wissen.model (
  indexdir = [dirs],
  mode = [ CREATE | READ | MODIFY | APPEND ],
  analyzer = None,
  logger = None
)

Learner

For building model, on Wissen, there’re 3 steps need.

  • Step I. Index documents to learn
  • Step II. Build Corpus
  • Step III. Selecting features and save trained model

Step I. Index documents

Learner use wissen.labeled_document, not wissen.document. And can additional searchable fields if you need. Label is name of category.

learner = mdl.get_learner ()
for label, document in trainset:

  labeled_document = wissen.labeled_document (label, document)
  # addtional searcherble fields if you need
  labeled_document.add_field (name, value, ftype = TEXT, lang = "un", encoding = None)
  learner.add_document (labeled_document)

learner.close ()

Step II. Building Corpus

Document Frequency (DF) is one of major factor of classifier. Low DF is important to searching but not to classifier. One of importance part of learning is selecting valuable terms, but so low DF terms is not very helpful for classifying new document because new document has also low probablity of appearance.

So for learnig/classification efficient, it’s useful to eliminate too low and too high DF terms. For example, Let’s assume you index 30,000 web pages for learing and there’re about 100,000 terms. If you build corpus with all terms, it takes so long time for learing. But if you remove DF < 10 and DF > 7000 terms, 75% - 80% of all terms will be removed.

# reopen model with MODIFY
mdl = wissen.model (indexdir, MODIFY)
learner = mdl.get_learner ()

# show terms order by DF for examin
learner.listbydf (dfmin = 10, dfmax = 7000)

# build corpus and save
learner.build (dfmin = 10, dfmax = 7000)

As a result, corpus built with about 25,000 terms. It will take time by number of terms.

Note that once call build(),

  • you cannot add additional training documents
  • you cannot run build () again

The reason why when low/high DF terms are eliminated by build(dfmin, dfmax), related index files will be also shrinked unrecoverably for performance. Then if these works are needed, you should do from step I again. But there’s another option: rbuild()

# reindexable & rebuiladble build corpus and save
learner.rbuild (dfmin = 10, dfmax = 7000)
learner.close ()

# reopen model APPEND mode
mdl = wissen.model (indexdir, MODIFY)
learner = mdl.get_learner ()
for ...:
  labeled_document = wissen.labeled_document (label, document)
  learner.add_document (labeled_document)

learner.rbuild (dfmin = 10, dfmax = 7000)
learner.train (...)

Reindexable & rebuiladble method rbuild() is very similar with build() but differences are these things:

  • It make SIMILARITY and ROCCHINO classifiers inefficient
  • You can add documents additionally with opening model with MODIFY (or APPEND) mode
  • And can rebuild corpus any time

So rbuild() is useful during classification testing/profiling phase or small size model. Also if you think your classifier has been trained optimally, you have option to call build () for classifying performance.

Step III. Feature Selecting and Saving Model

Features means most valuable terms to classify new documents. It is important understanding many/few features is not good for best result. It maybe most important to select good features for classification.

For example of my URL classification into 2 classes works show below results. Classifier is NAIVEBAYES, selector is GSS and min DF is 2. Train set is 20,000, test set is 2,000.

  • features 3,000 => 82.9% matched, 73 documents is unclassified
  • features 2,000 => 82.9% matched, 73 documents is unclassified
  • features 1,500 => 83.4% matched, 75 documents is unclassified
  • features 1,000 => 83.6% matched, 79 documents is unclassified
  • features 500 => 83.1% matched, 86 documents is unclassified
  • features 200 => 81.1% matched, 108 documents is unclassified
  • features 50 => 76.0% matched, 155 documents is unclassified
  • features 10 => 58.7% matched, 326 documents is unclassified

As results show us that over 2,000 snd under 1,000 features will be unchanged or degraded for classification quality. Also fewer features increase unclassified ratio.

mdl = wissen.model (indexdir, MODIFY)
learner = mdl.get_learner ()

learner.train (
  cl_for = [
    ALL (default) | NAIVEBAYES | FEATUREVOTE |
    TFIDF | SIMILARITY | ROCCHINO
  ],
  select = number of features if value is > 1 or ratio,
  selector = [
    CHI2 | GSS | DF | NGL | MI | TFIDF | IG | OR |
    OR4P | RS | LOR | COS | PPHI | YULE | RMI
  ],
  orderby = [SUM | MAX | AVG],
  dfmin = 0,
  dfmax = 0
)
learner.close ()
  • cl_for: train for which classifier, if not specified this features used default for every classifiers haven’t own feature set. So train () can be called repeatly for each classifiers
  • select: number of features if value is > 1 or ratio to all terms. Generally it might be not over 7,000 features for classifying web pages or news articles into 20 classes.
  • selector: mathemetical term scoring alorithm to selecting features considering relation between term and term / term and label. Also DF, and term frequency (TF) etc.
  • orderby: final scoring method. one of sum, max, average value
  • dfmin, dfmax: In spite of it had been already removed by build(), it can be also additional removed for optimal result for specific classifier

Finding Best Training Options

Generally, differnce attibutes of data set, it hard to say which options are best. It is stongly necessary number of times repeating process between train () and guess () for best result and that’s not easy process.

  • index ()
  • build or rbuid ()
  • train (initial options)
  • measure results with guess ()
  • if previously rbuild used, append additional documents, rbuild ()
  • train (another options)
  • measure results again with guess ()
  • find best optiaml training options with your data set

For getting result accuracy, your pre-requisite data should be splitted into train set for tran () and test set for guess () to measure precision and recall.

Feature Selecting Methods

  • CHI2 = Chi Square Statistic
  • GSS = GSS Coefficient
  • DF = Document Frequency
  • NGL = NGL
  • MI = Mutual Information
  • TFIDF = Term Frequecy - Inverted Document Frequency
  • IG = Information Gain
  • OR = Odds Ratio
  • OR4P = Kind of Odds Ratio(? can’t remember)
  • RS = Relevancy Score
  • LOR = Log Odds Ratio
  • COS = Cosine Similarity
  • PPHI = Pearson’s PHI
  • YULE = Yule
  • RMI = Residual Mutual Information

I personally prefer OR, IG and GSS selectors with MAX method.

Classifier

Finally,

classifier = mdl.get_classifier ()
classifier.quess (
  qs,
  lang = "un",
  cl = [META(Default) | NAIVEBAYES | FEATUREVOTE | ROCCHINO | TFIDF | SIMILARITY ],
  top = 0,
  cond = ""
)
classifier.close ()
  • qs: full text stream to classify
  • lang
  • cl: which classifer, META is default
  • top: how many high scored classified results, default is 0, means high scored result(s) only
  • cond: conditional document selecting query. Some classifier execute calculating with lots of documents like ROCCHINO and SIMILARITY, so it’s useful shrinking number of documents. This only work when you put additional searchable fields using labeled_document.add_field (…).

Implemented Classifiers

  • NAIVEBAYES: Naive Bayes Probablility
  • FEATUREVOTE: Feature Voting Classifier
  • ROCCHINO: Rocchino Classifier
  • TFIDF: Max TDIDF Score
  • SIMILARITY: Max Cosine Similarity
  • META: default guessing, merging and decide with multiple results guessed by NAIVEBAYES, FEATUREVOTE, ROCCHINO Classifiers

If you need speed most of all, NAIVEBAYES is a good choice. NAIVEBAYES is an old theory but it still works with very high performance at both speed and accuracy if given proper training set.

More detail for each classifier alorithm, googling please.

Optimizing Each Classifiers

For give some detail options to a classifier you can use setopt (classfier, option name = option value,…).

classifier = mdl.get_classifier ()
classifier.setopt (wissen.ROCCHINO, topdoc = 200)

SIMILARITY, ROCCHINO classifiers basically have to compare with entire indexed document documents, but Wissen can compare with selected documents by ‘topdoc’ option. These number of documents will be selected by high TFIDF score for classifying performance reason. Default topdoc value is 100. If you set to 0, Wissen will compare with all documents have one of features at least. But on my experience, there’s no critical difference except speed performance.

Also note that currently possible optimizing options is only ‘topdoc’.

Change Log

0.11 - fix HTML strip and segment merging etc.

0.10 - change version format, remove all str*_s ()

0.9.0.5 - fix long long int, bit type

0.9.0.3 - fix logger encoding

0.9.0.2 - fix snippet-making

0.9.0.1 - support Python 3.x

0.8.0.13 - change license from BSD to GPL V3

Copyright (c) 2015 by Hans Roh

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