KNOWLEDGE DISCOVERY FROM THE WEB
Maryam Hazman
Central Lab for Agricultural Expert Systems Agricultural Research Center, Ministry of Agriculture and Land Reclamation,
Giza, Egypt
Samhaa R. El-Beltagy
Computer Science Department, Faculty of Computers and Information, Cairo University, Giza, Egypt
Ahmed Rafea
Computer Science Department, American university, Cairo, Egypt
Salwa El-Gamal
Computer Science Department, Faculty of Computers and Information, Cairo University Giza, Egypt
Keywords: knowledge discovery, index
ing, web content mining.
Abstract: The World Wide Web is a rich resource of information and knowledge. Within this resource, finding
relev
ant answers to some given question is often a time consuming activity for a user. In the presented work
we construct a web mining technique that can extract information from the web and create knowledge from
it. The extracted knowledge can be used to respond more intelligently to user requests within the diagnosis
domain. Our system has three main phases namely: a categorization phase, an indexing phase, and search a
phase. The categorization phase is concerned with extracting important words/phrases from web pages then
generating the categories included in them. The indexing phase is concerned with indexing web page
sections. While the search phase interacts with the user in order to find relevant answers to their questions.
The system was tested using a training web pages set for the categorization phase. Work in the indexing and
search phase is still in going.
1 INTRODUCTION
The World Wide Web is a huge collection of texts,
which is constantly growing. This amount of text is
a valuable resource of information and knowledge.
Finding useful information in this resource is not an
easy task. People want to extract useful information
from these texts quickly and at a low cost (Loh et
al., 2000). They prefer reaching a certain paragraph,
which is of concern to them instead of reading an
entire document. In addition, when searching for an
item of interest using a traditional search engine,
numerous results are returned which requires the
user to manually try to filter through these results.
This places an overhead on the user in terms of item
and effort. Research in Web mining is moving the
World Wide Web towards a more useful
environment in which users can quickly and easily
find information they need (Scime, 2004).
This paper addresses the particular problem of
tryin
g to find a certain section that is of concern to a
user. The goal of the research described here is to
develop a Web mining system that can be used for
answering a user request within the diagnosis
domain. To perform this goal, the system
automatically discovers categories in a set of web
documents within some predefine domain. The
system then uses these categories to classify various
sections from other web pages within the same
domain. If a section belongs to a diagnosis category,
it will be indexed and stored in a database table.
When a user submits a query in the form of some
observations, the system will look for them in the
index table. The answer is provided in the form of a
disorder category with a link to its source section in
303
Hazman M., R. El-Beltagy S., Rafea A. and El-Gamal S. (2005).
KNOWLEDGE DISCOVERY FROM THE WEB.
In Proceedings of the Seventh International Conference on Enterprise Information Systems, pages 303-308
DOI: 10.5220/0002547103030308
Copyright
c
SciTePress
the web page. To achieve this goal, we build a
system with three main phases: a categorization
phase, an indexing phase, and a search phase. The
categorization phase extracts categories included in
a training web pages set and classifies these
categories. The indexing phase assigns a category
for each section in a web page section if possible
and indexes the diagnostic sections. The search
phase interacts with the user to search for relevant
answers to their question.
The rest of this paper is organized as follows:
section 2 presents related work. Section 3 describes
the architecture of the proposed system. Sections 4,
5, 6, 7, and 8 present the categories extraction
module, categories module and heuristic rules
component, the indexing module, repository
component and knowledge finder with the user
interface respectively. Finally section 9 provides the
conclusion for the presented research.
2 RELATED WORK
Zaiane defines Web mining as the extraction of
interesting and potentially useful patterns and
implicit information from artifacts or activities
related to the World Wide Web (Zaiane, 1999). Web
mining research is at the cross roads of research
from several research communities, such as
database, information retrieval, and Artificial
Intelligence, especially the sub-areas of machine
learning and natural language processing. However,
there is confusion when comparing efforts from
different points of view (Kosala and Blockeel,
2000). Today the most recognized categories of the
Web mining fall into three areas of interest based on
the type of Web data to be mined: web content
mining, web structure mining, and web usage
mining (Kosala and Blockeel, 2000), (Doherty,
2000), (Borges and Levene, 1999), (Madria et al.,
1999), (Pal et al., 2002). In practice, the three Web
mining tasks could be used in isolation or combined
in an application (Kosala and Blockeel, 2000). Web
structure mining is the process of inferring
knowledge from World Wide Web organization and
links between references and referents in the Web.
Web usage mining mines the secondary data derived
from the interactions of the users while interacting
with the web (Kosala and Blockeel, 2000). Web
content mining is concerned with the discovery of
new information and knowledge from web based
data, documents, and pages (Hsu, 2002). It is
mainly based on research in information retrieval
and text mining, such as information extraction, text
classification and clustering, and information
visualization. However, it also includes some new
applications, e.g., Web resource discovery (Chen
and Chau 2004). Our work on knowledge discovery
from Web is related to web content mining.
KPS is an information mining algorithm. It
employs keywords, patterns and/or samples to
extract information from semi-structured textual
Web pages to mine the desired information (Guan
and Wong, 1999). El-Beltagy et al. (2004) present a
model for information extraction and intelligent
search. It automates augmenting segments of
organizational documents that cover similar
concepts within a known domain with metadata. The
model uses dynamically acquired background
domain knowledge in order to construct the
documents categories. Liu et al. (2003) propose a set
of effective techniques to perform the task of mining
and organizing topic-specific knowledge on the
Web. They find and compile topic specific
knowledge (concepts and definitions) on the Web.
Loh et al. (2000) present an approach for knowledge
discovery in texts extracted from the web. Instead of
analyzing words or attribute values, the approach is
based on concepts, which are extracted from texts to
be used as characteristics in the mining process.
Statistical techniques are applied on concepts in
order to find interesting patterns in concept
distributions or associations. For identifying
concepts in texts, a categorization algorithm is used
associated to a previous classification task for
concept definitions (Loh et al., 2000). In (Xu et al.,
2003) a research support system framework for web
data mining is presented. This framework is
designed for identifying, extracting, filtering and
analyzing data from web resources. It combines web
retrieval and data mining techniques together to
provide an efficient infrastructure to support web
data mining for research (Xu et al., 2003).
3 ARCHITECTURE
Recall from section one above that our proposed
system operates in three phases: a categorization
phase, an indexing phase, and a search phase. Figure
1 depicts the architecture of the proposed system in
terms of the main components and their interactions.
The categorization phase is concerned with using the
structure of some input documents (training web
pages) in order to determine categories and sub
categories that will generalize across some given
domain. This phase includes the categories extractor,
categorizer, and heuristic rules applier components.
The categories extractor parses the training web
pages set content to extract important words/phrases
that represent categories included in it, and generates
their corresponding knowledge XML file. Then, the
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304
Categorization Phase
Categories Extraction
categorizer automatically generates the main
categories, subcategories, and sub-subcategories
from XML using a set of hypothesis rules. The
indexing phase includes the indexing component,
which is responsible for indexing web page sections.
The search phase looks for the user query in the
repository. It includes the knowledge finder and the
user interface. The three phases are linked together
through the repository component.
The following sections describe the goals and
functionally of the above components in more
details.
4 THE CATEGORY EXTRACTOR
The objective of this component is to extract
important words/phrases in a training web pages set.
Each set of words or phrases would then represent
the category of its section, where html heading tags
(e.g., <h1>,.,<h4>) are used to define their
importance. Relationships between categories and
subcategories can also be deduced using heading
information (e.g., <h2> tag is a child for <h1> tag).
The heading information represents the dependency
between the sections in a web page. For example
given a set of documents in the agricultural domain,
the Diseases section can be followed by detailed
sections about specific disease categories such as
Fungal disease, which in turn will be followed by
specific Fungal disease instances like Wilt Root Rot.
So "Diseases" is the main category, Fungal is its
subcategory, and Wilt Root Rot is a subcategory of
Fungal. In other word, "Diseases" is the parent of
Fungal disease, which is a parent of Wilt Root Rot.
Important words/phrases extracted must be
converted into a more structured representation that
can be used to classify the extracted categories. To
do that, the categories extractor parses the training
web pages set content and generates their
corresponding knowledge XML files. This
procedure is performed offline once, and should
only be repeated if the content of a Web page has a
new category missing in the categories databases.
Although some of the extracted important
words/phrases are marked as heading html tags, they
do not in fact represent actual categories. For this
reason, we have identified the following rules to
determine if an important phrase can be safely
ignored: -
Figure 1: The proposed system architecture.
Search Phase
Indexing Phase
Training Web
Pages Set
Repository
Categorizer
XML File
Heuristic Rules
Indexing
Knowledge
Finder
User Interface
User
Web Page
KNOWLEDGE DISCOVERY FROM THE WEB
305
<Root>
<Category>
<Name> Disease </Name>
<HeadingLevel> 1 </HeadingLevel>
</Category >
<Category >
<Name> Fungal </Name >
<HeadingLevel> 2 </HeadingLevel>
</Category >
<Category >
<Name> Wilt Root Rot </Name>
<HeadingLevel > 3 </HeadingLevel>
</Category >
<Category >
<Name> Nutrition Deficient </Name>
<HeadingLevel> 1 </HeadingLevel>
</Category >
<Category >
<Name> Nitrogen Deficient </Name>
<HeadingLevel> 1 </HeadingLevel>
</Category >
<Category >
<Name > Potassium Deficient </Name>
<HeadingLevel> 1 </HeadingLevel>
</Category >
</Root>
Figure 2: The structure of the generated XML file from the category extractor component
Contains the word introduction.
Contains the word return.
Contains the word note.
Contains the word advice.
Contains the word recommendation.
Contains the word guidance.
Contains the word warning.
Contains the publication data (date, author,
publisher).
Is too lengthy a phrase (we use 8 words as
the upper limit for a useful phrase).
Figure 2 represents an example of a XML file
structure generated from this component.
5 THE CATEGORIZER
COMPONENT
The objective of the categorizer is to automatically
generate the main categories, sub-categories, and
sub-subcategories. It parses all the XML nodes, and
for each node performs stopword removal and word
stemming, which are standard operations in
information retrieval. Stopwords are words that
occur frequently in documents and have little
informational meaning. The process of stemming
finds the root of a word by removing its suffix and
prefix. We are used the lexical analyser for inflected
Arabic words described in (Rafea and Shaalan,
1993) to get a word's stem.
After obtaining the list of stems for each
important phrase that represents a category, the
important phrase along with its stem list is stored in
the database. The relationship between any given
category and other categories (child, parent,
grandparent) is also stored. Following this step, we
apply our mining algorithm, which is basically a set
of heuristic rules in order to obtain a set of
categories and subcategories that we can later use.
These rules are as follows (written in first order
predicate logic): -
The main category is a category that has no
parent in all the training set pages or for
which the number of times it appears to
have no parent, exceeds the number of
times that it appears to have a parent.
Main Category(X) Æ Category(X)
¬∃Y parent(Y,X)
Main Category(X) Æ Category(X)
Count(parent(NoParent,X),N)
Count(parent(Y,X),M)
N >= M
A subcategory is a category that has a
parent in all training set pages or for which
the number of times it appears to have
parent, exceeds the number of times that it
appears to have no parent.
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SubCategory(X) Æ Category(X)
Y parent(Y,X)
SubCategory(X) Æ Category(X)
Count(parent(NoParent,X),N)
Count(parent(Y,X),M)
M > N
A sub-subcategory is a category that has a
grandparent in all the training set pages.
SubSubCategory (X) Æ Category(X)
Z grandparent(Z,X)
Two categories are the same if they have
the same stemmed word set.
SameCategory (X,Y) Æ Category(X)
Category(Y)
(list(X) = list(Y))
6 THE INDEXING COMPONENT
The main goal of the indexing component is to index
the diagnostic sections for web pages in some given
domain. The domain we have worked on is the
agricultural domain. The indexing component
assigns a category to each section in a web page if
possible. It extracts a section's important
words/phrases then removes the stopwords and gets
their stem for determining the corresponding
category in the database. If a category does not exist
in the repository database then the categorizer
component is called. The categorizer determines if
there is a need for adding this category in the
repository as a new category or not.
Our index is not like other search engine indexes;
its purpose is to answer a query about a problem in
the diagnostic domain. For example, a user can
submit a query in the form of observations about a
plant to the system and get the reasoning of it as an
answer to his/her query. To build such an index, we
need taxonomy and some meta knowledge. In our
implementation, we have defined a domain-specific
taxonomy for the agricultural diagnostic domain in a
database table. At the end of the indexing stage, each
web page is characterized by a set of categories,
which are part of it.
Initially the diagnostic categories were simply
categorized by a vector of stemmed words and a link
to the source section from which they were
extracted. However, this simple representation was
found to suffer from a major drawback as
relationships between words and concepts to which
they are associated was lacking. As a result,
submitting a query stating that "The color of leaves
is red, and fruits have spots" would match with a
category item which has the sentence "The fruits are
red. Also, the leaves are spotted", even though it is
in fact irrelevant to the submitted query.
To resolve this problem, we have extended the
diagnostic category representation such that each
word within the vector of stemmed words, was
associated with its related concept.
7 THE REPOSITORY
The purpose of the repository is to enable the system
to store the extracted knowledge for the purpose of
searching it. The repository contains the full
categories of every web page. Within the repository,
each page is divided into sections which are stored
along with their categories, and the vector
characteristic their content. For diagnostic section its
index is stored.
The following seven tables are used within the
repository:-
1. SecIndex: stores a section's important
stemmed words as a vector of words with
their semantic concept.
2. SectionId: stores information about each
section, such as its category, original URL,
title, crop name, ..etc.
3. MainCat: stores a list of main categories.
4. SubCat: stores sub categories, linked with
their main category using the mainCatId.
5. Cat: stores category items, linked with their
subcategory and main category using the
SubCatId and mainCatId.
6. CategoryT: stores important words/phrases
of a section, as well as its parent, and its
ancestor as a list of words. This table is
mined to classify categories.
7. IndexWord: keeps the domain specific
words needed for indexing a section.
8 KNOWLEDGE FINDER AND
THR USER INTERFACE
A user can submit a query to the system via the user
interface component, the user interface component
then sends the user query to the knowledge finder.
The knowledge finder parses the query performing
stopwords removal and word stemming on it. It then,
formulates and prepares an SQL query, which is sent
to the repository database in order to find sections
containing information relevant to the user query.
When the result is more than one section, the various
sections are checked. If these sections belong to the
same item category the category is returned to the
user. Otherwise, it is deduced that these sections
belong to different item categories, and further
questions are presented to the user in order to
KNOWLEDGE DISCOVERY FROM THE WEB
307
confirm one of them. If there is a picture associated
with any of these sections, it is displayed to get
further confirmation. If the data entered by the user
is still not enough to confirm or rule out a category,
suspected categories are presented to the user with
links to their original section as a reference to the
user.
9 CONCLUSION
The objective of our research is to help Web users to
quickly and easily find an answer to some given
diagnostic question they have from specific
section(s) in some given document set. To achieve
this goal, we have constructed a web mining
technique that can extract information from the web
and create knowledge from it. Our system has been
built in the agricultural domain to extract
information from its related web pages, and to index
the diagnostic sections in it. The constructed index is
used for finding relevant knowledge to answer a user
query.
Our system has three main phases: the
categorization phase, the indexing phase, and the
search phase. The categorization phase has been
tested on a training web pages set, which is a
collection of extension documents. It automatically
generated 100 main categories, 145 sub categories,
and 127 sub-subcategory items. These categories
are used by the indexing component to assign for
each section in an input web page, a category if
possible. The indexing and search phases are still
under construction. Also, there are still some
problems must need to be solved like inheritance
from more than one category, and synonymous
words used in different web pages content.
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