PLATAL - A Tool for Web Hierarchies
               Extraction and Alignment

              Bernardo Severo1 , Cassia Trojahn2 , and Renata Vieira1
    1
        Pontifı́cia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil
                     2
                       Université Toulouse 2 & IRIT, Toulouse, France



         Abstract. This paper presents PLATAL, a modular and extensible tool
         for extraction of hierarchical structures from web pages which can be
         automatically aligned and also manually edited via a graphical interface.
         Evaluation of alignments can be carried out using standard measures.


1       Introduction

Web sites are rich sources of information for a range of applications. Tools for
automatically extracting structured content from these sources and for compar-
ing content across web sites are valuable resources. For helping in these tasks, we
propose PLATAL (Platform of Alignment), a modular and extensible tool that
provides an integrated environment for extraction of web hierarchies and align-
ment creation, edition and evaluation. The main motivation behind PLATAL
is to assist users in the complete alignment cycle of two web hierarchies. Dif-
ferently from other matching tools offering a visual environment, like OLA [1],
Prompt [3], Homer [5], Yam++ [2] and SOA-based tool [4], PLATAL offers novel
functionalities: the possibility of automatically extracting hierarchical structures
from the web together with a centralised visual tool for alignment manipulation.


2       PLATAL modules

PLATAL is a standalone tool composed of four modules: (1) hierarchy extrac-
tion module, which extracts fragments from HTML pages using XPath expres-
sions; (2) automatic alignment module, which implements a set of terminological
(prefix, suffix, edit-distance) and structural matching techniques (similarity of
parents and children entities) for generating equivalence correspondences; (3)
manual alignment module, which allows users to edit or create alignments; and
(4) evaluation module, which takes two alignments and computes precision, re-
call and F-measure measures. These modules operate independently of each other
and alternative implementations can be added instead. Figure 1 shows a screen-
shot of automatic alignment creation. After loading two hierarchies, each hierar-
chy will be displayed in the respective section. Then, users can select one or more
alignment processes and start them (‘Start Alignment Process’). If at least one
method founds one correspondence between two entities, the user can see it by
2        Bernardo Severo, Cassia Trojahn, and Renata Vieira

selecting the source or target entity in the hierarchies (field ‘Correspondences’).
Alignments can be exported in the Alignment format3 (‘Save’).




                   Fig. 1. Automatic Alignment Module screenshot.

3     Conclusions and future work
We have presented a visual tool for extraction, alignment and evaluation of
web hierarchies. To the best of our knowledge, there is no publicly available
environment integrating all these features together. As future work, we plan
to improve the visualisation of alignments, develop a web-based version, allow
parametrisation and customisation of alignment techniques through the user
interface, and add a multilingual ontology matching module.

References
1. J. Euzenat, D. Loup, M. Touzani, and P. Valtchev. Ontology Alignment with OLA.
   In 3rd EON Workshop, pages 59–68, 2004.
2. D. H. Ngo and Z. Bellahsene. YAM++ : (not) Yet Another Matcher for Ontology
   Matching Task. In BDA, France, 2012.
3. N. F. Noy and M. A. Musen. PROMPT: Algorithm and Tool for Automated On-
   tology Merging and Alignment. In 17h AAAI, pages 450–455, 2000.
4. K. W. Onn, V. Sabol, M. Granitzer, W. Kienreich, and D. Lukose. A visual soa-
   based ontology alignment tool. In OM, 2011.
5. O. Udrea, R. Miller, and L. Getoor. Homer: Ontology visualization and analysis.
   In Demo session ISWC, 2007.

3
    http://alignapi.gforge.inria.fr/format.html