A COMPARATIVE STUDY OF THESAURI TOOLS

A Perspective from Integrability in Information Systems

Beatriz Pérez-León and M. Mercedes Martínez-González

Department of Computer Science, University of Valladolid, Campus ’Miguel Delibes’ s/n, Valladolid, Spain

Keywords:

Thesauri, Thesauri tools, Software integrability, SKOS, RDF, Semantic web.

Abstract:

The Semantic Web has brought a renewed interest in thesauri as support for semantic searches and other

added-value services. Tools that manage thesauri permit to create, edit, and query thesauri. But there is also

the possibility to import thesauri and to integrate thesauri. In fact, integrability at the information level has

also received an important push with the stabilisation of the SKOS standard as a W3C Recommendation. In

this paper several thesauri tools are evaluated and compared.

1 INTRODUCTION

Thesauri are conceptual tools that permit to organise

topics from a domain in a hierarchy of concepts and

subconcepts (topics and subtopics). This permits nav-

igation through topics and concept-based searches,

which are so valued in the Semantic Web context.

The W3C SKOS (Standard Knowledge Organi-

zation System) standard (Alistair Miles and Sean

Bechhofer, 2009) has stabilised very recently. But

even before its stabilisation, numerous initiatives have

been proposed to represent various thesauri with RD-

F/SKOS (Lacasta et al., 2007; Faro et al., 2008; Polo

et al., 2008). SKOS and RDF are the two Seman-

tic Web standards that will permit thesauri to get into

the integration arena, so important in web information

systems.

While traditionally thesauri were created manu-

ally or with text editors, new thesauri tools permit to

create, edit, or use (manage) thesauri. Previous re-

views of thesauri tools (Martinez and Leiva, 2001),

(Gilbert and Butler, 2003) focused on software fea-

tures, like creation and management of thesauri and

features related to software output (visualisation of

thesauri on the screen, printer, etc). In this paper we

review a set of thesauri tools, but we focus on com-

patibility with Semantic Web standards (RDF/SKOS)

and integrability or reusability of software. We deﬁne

a set of criteria for comparison, which include pur-

pose and functionality, interoperability and integra-

tion at the information level, and reusability of soft-

ware as components of third-party applications in in-

formation systems.

In this section we present a brief introduction to

the main characteristics of thesauri, and the crite-

ria used for evaluation (and comparison) of thesauri

tools. In section 2 we present the tools evaluated and

the results of the evaluation. Section 3 summarises the

conclusions obtained from the comparison of these

tools.

1.1 Thesauri

Thesauri are controlled vocabularies that collect and

organise terms from a domain. Terms are grouped

into concepts and relationships (equivalence, hier-

archical, associative) are established among them.

Notes are used to clarify their meaning.

The Equivalencerelationship divides terms in pre-

ferred, which will be used for the indexing and re-

trieving process, and non-preferred terms. The hier-

archy of concepts is indicated by Broader Term and

Narrower Term relationships. The Associative rela-

tionship is established between terms that are con-

ceptually related, but their relationships are neither

hierarchical nor equivalence relationships in nature.

These are referred to as Related Terms. Finally, Notes

serve to clarify the meaning and application of a term

in relation to other terms in the thesaurus. Notes

can be divided in scope notes, historical notes, editor

notes, usage note, etc.

203

Perez-LeÃ¸sn B. and Mercedes MartÃ nez-GonzÃ ˛alez M.

A COMPARATIVE STUDY OF THESAURI TOOLS - A Perspective from Integrability in Information Systems.

DOI: 10.5220/0002800502030206

In Proceedings of the 6th International Conference on Web Information Systems and Technology (WEBIST 2010), page

ISBN: 978-989-674-025-2

1.2 Methodology Applied

The methodology followed is inspired on the one pro-

posed by (Martinez and Leiva, 2001). It organises the

work in six steps:

1. Deﬁne criteria and tests

2. Search on the web for software of management of

thesauri that provide evaluation versions

3. Download the software

4. Read documentation

5. Perform the tests

6. Perform the analysis of results and draw conclu-

sions based upon the tests

1.3 Criteria for Evaluation

In this part we present the criteria used for the eval-

uation of the tools considered in section 2. Criteria

4 and 5 are related with compatibility with Semantic

Web (RDF/SKOS), integrability and extensibility of

software. The criteria for thesauri tools’ evaluation

are:

1. Purpose. Purpose for which the tool was created.

2. Functionalities. We have selected functionali-

ties considered relevant in some previous analysis

about what thesauri tools should offer (Severino,

2007). In this paper, because of space limits, we

will only consider the most relevant functionali-

ties: creating and editing thesauri, searches and

retrieval in thesauri, and navigation.

3. Thesauri Structures Supported. The the-

sauri structured considered in this study are:

terms (Preferred/descriptor, Non-preferred/non-

descriptor), equivalence, hierarchical, and asso-

ciative relationships. Notes (scope, historical, ed-

itor, ...) complete this list.

4. Formats Supported. The ability to import and/or

export thesauri represented with different formats

(including the Semantic Web SKOS standard) is

an important one for the aim of interoperability.

5. Provision of Software as Packages or Services.

Software integration is achieved by means of soft-

ware packages that can be used by other tools (.jar

packages for Java applications, widgets, services

that exchange XML messages, ...).

Except in the case of PoolParty. In this case we could

not have access to the software despite the fact that we regis-

tered for evaluation, and the tests were performed by check-

ing in its documentation if test operations were supported.

1.4 Tests Performed

The set of tests we have prepared to compare and

draw conclusions are:

• Test 1. To create a new Thesaurus from scratch.

• Test 2. To insert terms, relationships and notes.

• Test 3. To create a term which is at the same time

a narrower and broader term of other.

• Test 4. To search different terms.

• Test 5. To import a Thesaurus.

• Test 6. To export a Thesaurus.

Checking automatically thesaurus integrity is con-

sidered an important function of thesauri tools by ex-

perts in thesauri creation ((Sánchez, 2009), (Martinez

and Leiva, 2001)). For this reason, we included some

tests to check this capability (test 3).

2 EVALUATION OF THESAURI

TOOLS

2.1 ThManager

ThManager

is distributed under the terms of the

GNU Lesser General Public License as published by

the Free Software Foundation. It was ﬁrst released in

2007.

• Purpose. ThManager is a thesaurus editor tool

that facilitates the creation and management of

thesauri using the SKOS format.

• Functionalities. ThManager has two modes of op-

eration, the Thesaurus Viewer and the Thesaurus

Editor (which guides the user through the edition

process). Terms can be added in the thesaurus one

by one or imported from ﬁles in RDF/SKOS for-

mat.The main limitation of this editor is that in-

tegrity checks are not automatically done by the

tool, which means that it did not pass Test 3.

The Thesaurus viewer is used to navigate through

concepts. In this tool it is not possible to per-

form an advanced search as a combination of log-

ical operators (AND, OR, NOT). However, "Ex-

act match", "Starts with" and "Contains" searches

are provided. To encourage re-use of thesauri,

ThManager offers a metadata proﬁle (title, lan-

guage, etc) of its thesauri based on Dublin Core.

• Thesauri Structures Supported. ThManager sup-

ports the three most important relationships in a

http://thmanager.sourceforge.net

WEBIST 2010 - 6th International Conference on Web Information Systems and Technologies

204

thesauri, the equivalence, the hierarchical, and

the associative relationship. Regarding notes,

ThManager only supports scope notes.

• Formats Supported. ThManager supports RD-

F/SKOS as a format not only to import but also

to export data.

• Provision of Software as Packages or Services.

Although ThManager is supposed to use an API

to access the thesauri stored in its repository (La-

casta et al., 2007), it is distributed as an ’off-the-

self’ application, with which this API is not pro-

vided. As well, its interface is not included in

the documentation provided with the tool. So, we

could not access or know the methods that this

API offers.

2.2 TemaTres

TemaTres

is a web application to manage documen-

tation languages. In August 2009 the 1.032 version

was released.

• Purpose. TemaTres is oriented to the develop-

ment of hierarchical thesauri, on which several ed-

itors can be working at the same time.

• Functionalities. When creating a new term in

a thesaurus, TemaTres deﬁnes a workﬂow with

three states for a term, Candidate, Active and Re-

jected. These states deﬁne what actions can be

performed with the terms. Validation is left to the

user, as the tool does not automatically check the

coherence of the thesaurus.

TemaTres presents both a systematic and an al-

phabetical list of terms. It offers different op-

tions to perform searches: simple search, ex-

panded search through related or hierarchical

terms, search terms suggestion (Did you mean:...).

• Thesauri Structures Supported. The relationships

allowed are the equivalence, the hierarchical, and

the associative relationship. Other relationships

can be established between terms of different the-

sauri. Any term can be annotated with scope

notes, historical notes, bibliographic notes or pri-

vate notes.

• Formats Supported. In TemaTres there is no op-

tion to import a thesaurus from any format, but

any thesaurus in TemaTres can be exported to text

format, Dublin Core, SKOS-Core, Zthes, MADS,

TopicMap (XTM 1.0), SiteMap 0.8, RSS.

• Provision of Software as Packages or Services.

TemaTres provides web services since version

1.0.32.

http://tematres.r020.com.ar

2.3 Term Tree

Term Tree

was ﬁrst released in 1999.

• Purpose. TermTree is a specialised thesaurus soft-

ware for creating and maintaining complex the-

sauri and taxonomies.

• Functionalities. In this application, a thesaurus

can be created inserting terms one by one, or im-

porting terms from different ﬁle formats, such as

ASCII structured tag ﬁle or MultiTes database.

When creating a relationship between terms the

validity of the requested link is checked.

Term Tree offers a powerful tool for searching.

The user may choose to search terms, ﬁelds asso-

ciated with a term, search by relation, or search by

date ranges (creation and modiﬁed dates). Stan-

dard wild cards, "*" and "?" are supported.

• Thesauri Structures Supported. Term Tree sup-

ports the three most important relationships in a

thesauri: the equivalence, the hierarchical, and

the associative relationship. Regarding annota-

tion, Term Tree supports the scope note and usage

note.

• Formats Supported. A thesaurus can be exported

to several text formats, Microsoft Excel spread-

sheet, HTML, XML, and others. However, the

formats used in the import process are restricted

to Term Tree tagged, MultiTes database and Aka

database.

• Provision of Software as Packages or Services.

According to Term Tree documentation, there is

an API available for custom application devel-

opment. However this API is not distributed in

the demonstration kit or documented elsewhere,

which means that we could not have access to it.

2.4 PoolParty

PoolParty

is a thesaurus management system for the

semantic web. We selected it because it is the ﬁrst

tool in which software integration in third-party ap-

plications and Semantic Web goals are basic pillars

of its design.

• Purpose. PoolParty can be used to build and

maintain multilingual thesauri providing a simple

user interface.

• Functionalities. PoolParty is a web based appli-

cation. The interface of PoolParty displays the in-

formation in two areas: the Concept hierarchytree

http:/ /www.termtree.com.au

http://poolparty.punkt.at/

A COMPARATIVE STUDY OF THESAURI TOOLS - A Perspective from Integrability in Information Systems

205

and the Concept details view. A thesaurus in Pool-

Party can be created by manual editing. When

creating a term or setting relationships among

terms there are drag and drop and autocomplete

facilities to help the user. PoolParty has the abil-

ity of extracting words and phrases that charac-

terise a document automatically. The only type of

search referred in the manuals is search based on

suggestions.

• Thesauri Structures Supported. PoolParty sup-

ports the three most important relationships in a

thesauri, the equivalence, the hierarchical, and the

associative relationship. Regarding annotation,

PoolParty only supports the scope note. Pool-

Party is compliant with most of the elements of

the SKOS standard. To avoid building a thesauri

which violates SKOS, it provides quality queries

to check the thesaurus’ integrity.

• Formats Supported. PoolParty is able to import

existing SKOS thesauri, which meet certain pre-

requisites, and to export to different formats such

as RDF/XML, N-Triples, Turtle, N3, TriX and

TriG.

• Provision of Software as Packages or Services.

According to its documentation, PoolParty offers

Web Services to access data via SOAP and REST.

3 CONCLUSIONS

There are not many free thesauri tools available. We

evaluated four tools that can either be downloaded for

free, either offer an evaluation version for free. Basic

functionalities are supported in all the tools evaluated

in a similar manner. All the tools revised permit the

construction and management of thesauri. However,

validation is only provided in some of them (Term

Tree and PoolParty). There are also differences in

the provision of advanced search. All of them sup-

port basic thesauri structures, with some differences

on the range of notes supported.

Interoperability has received the main attention at

the information exchange level. Almost all the tools

studied support thesauri import/export by means of

plain text formats or standard formats. SKOS/RDF

Semantic Web standards are not yet supported in all

tools. We think that this will change in the future with

the spread of RDF/SKOS.

Despite some tools are supposed to be designed

in layers that include APIs for thesaurus management

(Lacasta et al., 2007), (Ferreyra, ) they do not provide

a public API or package that can be reused indepen-

dently. Thus, interoperability at this level seems to be

the weak aspect of free thesauri software.

ACKNOWLEDGEMENTS

This work was partially supported by the Conse-

jería de Educación de la JCyL research projects

VA010B06 and VA012B08.

REFERENCES

Alistair Miles and Sean Bechhofer (2009). SKOS

Simple Knowledge Organization System Refer-

ence. W3C Recommendation 18 August 2009.

http://www.w3.org/TR/2009/

PR-skos-reference-20090818/.

Faro, S., Francesconi, E., Marinai, E., and Sandrucci, V.

(2008). Eurovoc studies lot2 d2.3 -report on execu-

tion and results of the interoperability tests. Technical

Report 10118, Publications Ofﬁce of the EC, Institute

of Legal Information Theory and Techniques ITTIG.

Ferreyra, D. Tematres: software libre para gestión de

tesauros. URI: http://www.r020.com.ar/tematres/

index.html.

Gilbert, J. and Butler, M. (2003). Review of existing tools

for working with schemas, metadata, and thesauri.

Technical Report HPL-2003-218, Digital Media Sys-

tems Laboratory, HP Laboratories Bristol.

Lacasta, J., Nogueras, J., Lopez-Pellicer, F. J., Muro-

Medrano, P., and Zarazaga-Soria, F. (2007). Thman-

ager: An open source tool for creating and visualizing

skos. Information Technology and Libraries (ITAL),

26(3):39–51.

Martinez, G. M. and Leiva, I. G. (2001). Evaluacion de

softwares de gestion de tesauros. Ciencias de la In-

formación, pages 32(3), 3–23.

Polo, L., Alvarez, J. M., and Rubiera, E. (2008). Promoting

government controlled vocabularios for the semantic

web: the eurovoc thesaurus and the cpv product classi-

ﬁcation system. In ESWC 2008, 1-5 june 2008, Tener-

ife, Spain, volume 50212 of Lecture Notes in Com-

puter Science, pages 111–122. Springer.

Severino, F. (2007). What thesaurus to deﬁne eu/acp rela-

tions? European journal of developmental research,

n 2, pages 327–351.

Sánchez, J. P. (2009). Diseño de un sistema colabora-

tivo para la creación y gestión de tesauros en internet

basado en skos. Master’s thesis.

WEBIST 2010 - 6th International Conference on Web Information Systems and Technologies

206