SOFTWARE TOOLS FOR NAVIGATION IN DOCUMENT

DATABASES

Development of Information Navigation Service Based on Classification Schemes

Pavel Shapkin

MEPhI, Kashirskoe Shosse, 31, Moscow, Russia

Alexander Shapkin

VINITI, Usievicha, 20, Moscow, Russia

Keywords: Classification schemes, classification scheme mapping, information search, XML web services, Semantic

Web.

Abstract: Internet allows accessing large document databases contained in different information centres across the

world. Each database has its own search engine which is based on an index or classification scheme. Prob-

lems occur when a user tries to search different databases at once: different databases use different classifi-

cation schemes. This article describes a classification scheme mapping service which is useful in integration

of different databases in one search engine.

1 INTRODUCTION

Many information centers in the world are process-

ing scientific information. As an example of these

centers we can consider CAS, BIOSYS, Medline,

ISI etc. In Russia the All-Russian Scientific and

Technical Information Institute of Russian Academy

of Sciences (VINITI) is such center. Each centre

contains large amount of scientific information in

form of document databases. Each centre creates an

index of the documents based on a classification

scheme, e. g. Universal Decimal Classification

(UDC) or Mathematics Subject Classification

(MSC). By means of this classification scheme users

can search documents in database (Batty, 1998;

Gilyarevsky, 1971). But if a search involves differ-

ent databases simultaneously, problems occur: dif-

ferent information centers use different classification

schemes.

Nevertheless problem of searching different da-

tabases at once becomes more and more actual be-

cause of expansion of Internet, which connects dif-

ferent information centers in one worldwide network

(Clarke, 2000). In order to give users an opportunity

to search different document databases at once we

need a public resource which can provide a service

for converting concepts from one classification

scheme to another. It is important that user has not to

be familiar with distinctions in indexing and subject

representation in different information centers.

It is sometimes difficult to define concordances

between different classification schemes. This work

must be conducted by experts. That's why mapping

service can be separated in form of an independent

resource and used as a component of meta-search

engine. This service has to be maintained by organi-

zation which keeps track on changes in classification

schemes and uses experts to define concordances.

Using a mapping service between different clas-

sification schemes user has to know only one classi-

fication scheme. An attempt of building such a ser-

vice is carried out in VINITI. VINITI uses different

classification schemes during the processing of in-

coming document flow. Thus a large amount of

knowledge about concordance of classifications is

accumulated. Furthermore, VINITI is a member of

UDC Consortium, and is responsible for maintaining

Russian version of this classification.

455

Shapkin P. and Shapkin A. (2007).

SOFTWARE TOOLS FOR NAVIGATION IN DOCUMENT DATABASES - Development of Information Navigation Service Based on Classiﬁcation

Schemes.

In Proceedings of the Third International Conference on Web Information Systems and Technologies - Web Interfaces and Applications, pages 455-458

DOI: 10.5220/0001285804550458

 SciTePress

2 STRUCTURE OF

CLASSIFICATION SCHEME

SYSTEM

System of Classification Schemes (SCS) includes

classifications that are used in processing of incom-

ing flow of heterogeneous scientific information.

System allows maintaining a set of classifications

which have complicated structure and also compar-

ing them.

Atomic elements of classifications are called ru-

brics. Classification is a hierarchical structure of

rubrics based on “parent-child” relation among ru-

brics. Each rubric has a code — unique identifier

within the bounds of a classification.

The “parent-child” relation is main but not

unique relation between rubrics. Often it is needed to

represent more complicated interrelations of con-

cepts which are beyond strict hierarchical scheme.

That’s why simple hierarchical model of classifica-

tion scheme gets extended in SCS through introduc-

tion of direct links and other concepts. Furthermore

SCS has means for classification scheme mapping.

Detailed description of these concepts is given be-

low.

2.1 Rubric Properties

Each rubric has some backbone properties and a set

of optional properties which can vary according to

the type of classification scheme.

Backbone properties are rubric code and code of

parent rubric. Within the bounds of one classifica-

tion scheme rubric codes are unique. Each rubric

must have one parent. The only exceptions are root

rubrics of classifications, which have no parents.

Other common property of rubrics is its title

which can be given in different forms: full or short

and on different languages.

Some classification schemes support descriptors

(or keywords): each rubric can be concerned with a

list of keywords. This approach simplifies search of

rubrics.

Each classification scheme changes in time due

to evolution of subject representation in concerned

domain. Formally these changes mean addition,

modification or removal of rubrics.

To maintain lifecycle of a rubric, special proper-

ties are introduced:

 date of creation;

 date of exclusion from classification scheme;

 current status, or lifecycle stage.

Besides the “parent-child” relation direct links

between rubrics within a classification scheme are

allowed. These links represent references like “see

also”, “reference from”, “instead of” etc.

2.2 Classification Scheme Mapping

Comparison of classification schemes allows build-

ing links between rubrics contained in different clas-

sification schemes, in other words, mappings be-

tween classification schemes.

Examine two classification schemes R and Q.

Each of them is a finite set of rubrics:

R = {r

, r

, … r

[R]

} where [R] is cardinality of R,

Q = {q

, q

, … q

[Q]

} where [Q] is cardinality

of Q.

Mapping of rubric r

(source rubric) from classi-

fication scheme R to classification scheme Q (target

scheme) is a set of pairs (o

, p

) where o

is an opera-

tor and p

is nonempty set of rubrics from Q. Opera-

tors define meaning of relation, e. g. “includes” or

“is equivalent to”.

Consider an abstract example of mapping a ru-

bric r

from R to Q, (operators are underlined):

includes q

and q

is included in q

, q

Thus mapping of entire classification scheme R

to classification scheme Q is defined as a set of

mappings of all its rubrics to Q:

R → Q = {r

→ Q where i=1, 2, … [R]}

As follows from the above, mapping has a direc-

tion — from source classification scheme to target

classification scheme and mapping is one-to-many

relation: it contains one source rubric and many tar-

get rubrics.

Initially mappings are created by experts. But

expert work is expensive whereas system contains

more than 20 classification schemes. Experts cannot

create mappings between every pair of classifica-

tions. That’s why some mappings are computed

automatically from expert mappings, these are in-

verse and transitive mappings.

Consider an expert mapping M of classification

scheme R to classification scheme Q. Inverse map-

ping for M is mapping of Q to R, computed from M.

That is if rubric r

is mapped to q

with operator op

in M, then is inverse mapping q

is mapped to r

with inverse operator. Each operator has correspond-

WEBIST 2007 - International Conference on Web Information Systems and Technologies

456

ing inverse operator, e. g. “is included in” is inverse

of “includes”, etc.

Transitive mapping is a union of a chain of ex-

pert mappings. Suppose there exist expert or inverse

mappings between schemes R and Q, and between Q

and P. Then a transitive mapping of R to P can be

computed from these two mappings. During compu-

tation of transitive mapping compositions of map-

ping operators are used. For example, if rubric r

equivalent to q

, and q

includes p

, then r

includes

. Thus, “includes” is composition of “is equivalent

to” and “includes”.

Introduction of transitive and inverse mapping

gives an opportunity to construct mapping between

virtually any pair of classification schemes with

minimal cost: experts need to build only the basic

mappings, all other mappings will be evaluated “on

the fly”.

2.3 Quantitative Characteristics of

Classification Scheme System

At present system contains 25 classification

schemes, such as Universal Decimal Classification

(UDC), International Patent Classification (IPC),

AMS Mathematics Subject Classification (MSC),

Library and Information Science Abstracts (LISA),

VINITI Classification Index and others. Rubrics

count in a scheme varies from 200 to 67000. Total

number of rubrics contained in system is about 1

million.

Main list of descriptors contains 436000 key-

words and phrases, number of keywords bound to a

rubric varies from 1 to 150.

Inner links between rubrics are used in 11 classi-

fication schemes; mean part of rubrics connected

with direct links amounts to 14% of total rubric

count in classification scheme.

There are 19 expert mappings between separate

classification schemes.

3 WEB SERVICE

IMPLEMENTATION

SCS has a web-interface, which is an ASP.NET-

based application (Payne, 2001); data is represented

in XML format (Bean, 2003). The main part the ap-

plication is a set of two web-services:

 metadata service;

 mapping service.

By means of the metadata service users can re-

ceive information about classification schemes

which are available in the system. One can get a list

of available schemes, lists of their properties and

information on available mappings.

Mapping service allows users to get mapping of

a rubric from one classification scheme to another.

Both services allow access using SOAP, HTTP

GET or HTTP POST protocols.

Because implementation is based on an XML

web-service, it can be accessed from any type of

applications, e. g. from client application written on

any programming language, from a web-site or even

from AJAX-based web page. XML data can be

transformed using XSL (Holzner, 2001).

Along with web-service a simple HTML inter-

face was created. It uses AJAX to utilize metadata

service in order to obtain information about avail-

able classification schemes and their mappings. User

can choose source and target classification scheme

from a list, enter code of source rubric and then re-

ceive the list of rubrics on which source rubric is

mapped. An experimental test page of the service is

located at “http://solar.viniti.ru:8080/MapService/

mapform.aspx”.

4 USING SERVICE IN

INFORMATION PORTAL

Let us examine an example of utilizing classification

scheme mapping service within an information por-

tal. Consider an internet resource containing a large

database of publications, e. g. of dissertations. Each

dissertation contains a Universal Decimal Classifica-

tion (UDC) index, which determines the area to

which this dissertation belongs. Suppose that portal

implements a new service that enables users to get a

list of patents whose area is close to the area of cho-

sen dissertation. Patents can be obtained from a pub-

licly available service like esp@cenet. The problem

is that patents are indexed with International Patent

Classification (IPC). That’s where the classification

scheme mapping service appears. To get a list of

patents it is needed first to send request containing

the UDC index of chosen dissertation to mapping

service. As a response portal system will receive a

list of IPC indexes related to this UDC index. Then

portal system can use this list in order to retrieve

required patents from patent database. Interaction

diagram for this example is shown on fig. 1

SOFTWARE TOOLS FOR NAVIGATION IN DOCUMENT DATABASES - Development of Information Navigation

Service Based on Classification Schemes

457

Figure 1: Classification scheme mapping service utiliza-

tion example.

5 SEMANTIC WEB

The main idea of Semantic Web is to make informa-

tion contained in web resources suitable not only for

use by people but also for processing by machines.

Instead of using HTML, which describes only the

representation of data, Semantic Web languages

allow to describe semantics of data explicitly.

One of Semantic Web principles is decentraliza-

tion of data and centralization of metadata. It means

that public metadata resources are needed. Classifi-

cation schemes are perfect examples of metadata,

thus service for accessing classification schemes and

their mappings can act as a metadata provider. In

order to integrate classification scheme service in

Semantic Web it may be necessary to bring XML

data representation format in correspondence with

standards of Semantic Web. It implies using lan-

guages like RDF (Resource Description Framework,

see W3C RDF Primer) and OWL (Ontology Web

Language, see W3C OWL Guide).

The aim of RDF is to standardize format of de-

scribing metadata used in web resources. Main con-

struction of RDF is triplet “object-attribute-value”. It

can be written as A(O, V) which means “object O

has an attribute A with value V”. Attributes are often

called properties or relations, and objects are also

called entities. Each element in the triplet can be

specified with its Uniform Resource Identifier (URI)

— global unique identifier. Triplets can be nested

and thus form a graph.

An example of graph describing a rubric from

VINITI Classification Index is shown on fig. 2. Enti-

ties are represented by ovals, values — by boxes and

relations are represented by arrows. Identifiers are

shown within the objects; types of objects are shown

near them. Entities’ and relations’ URIs are shown.

Use of URIs guarantees that, e. g. Child relation

will be recognized as the parent-child relation used

in VINITI Classification Index.

Figure 2: RDF representation graph for VINITI Classifica-

tion Index rubric.

6 CONCLUSION AND FURTHER

WORK

Classification scheme system can act as a source of

information about different classification schemes

for scientific information. Ability of mapping differ-

ent classification schemes allows to use this system

for purposes of integration document databases of

different information centers.

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