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Publicações

Publicações por Gracinda Carvalho

2013

A scalable spam filtering architecture

Autores
Ferreira, N; Carvalho, G; Pereira, PR;

Publicação
IFIP Advances in Information and Communication Technology

Abstract
The proposed spam filtering architecture for MTA1 servers is a component based architecture that allows distributed processing and centralized knowledge. This architecture allows heterogeneous systems to coexist and benefit from a centralized knowledge source and filtering rules. MTA servers in the infrastructure contribute to a common knowledge, allowing for a more rational resource usage. The architecture is fully scalable, ranging from all-in-one system with minimal components instances, to multiple components instances distributed across multiple systems. Filtering rules can be implemented as independent modules that can be added, removed or modified without impact on MTA servers operation. A proof-of-concept solution was developed. Most of spam is filtered due to a grey-listing effect from the architecture itself. Using simple filters as Domain Name System black and white lists, and Sender Policy Framework validation, it is possible to guarantee a spam filtering effective, efficient and virtually without false positives. © IFIP International Federation for Information Processing 2013

2009

IdSay: Question Answering for Portuguese

Autores
Carvalho, G; de Matos, DM; Rocio, V;

Publicação
EVALUATING SYSTEMS FOR MULTILINGUAL AND MULTIMODAL INFORMATION ACCESS

Abstract
IdSay is an open domain Question Answering (QA) system for Portuguese. Its current version can be considered a baseline version, using mainly techniques from the area of Information Retrieval (IR). The only external information it uses besides the text. collections is lexical information for Portuguese. It was submitted to the monolingual Portuguese task of the QA track of the Cross-Language Evaluation Forum 2008 (QA@CLEF) for the first time, and it answered correctly to 65 of the 200 questions in the first answer, and to 85 answers considering the three answers that could be returned per question. Generally, the types of questions that are answered better by IdSay system are measure factoids, Count factoids and definitions, but there is still work to be done in these areas, as well as in the treatment of time. List questions, location and people/organization factoids are the types of question with more room for improvement.

2012

Searching a Mixed Corpus in the Light of the New Portuguese Orthographic Norm

Autores
Carvalho, G; Falé, I; de Matos, DM; Rocio, V;

Publicação
Computational Processing of the Portuguese Language - 10th International Conference, PROPOR 2012, Coimbra, Portugal, April 17-20, 2012. Proceedings

Abstract
A mixed corpus of Portuguese is one in which texts of different origins produce different spelling variants for the same word. A new norm, which will bring together the written texts produced both in Portugal and Brazil, giving then a more uniform orthography, has been effective since 2009, but what happens in the perspective of search, to corpora created before the norm came into practice, or within the transition period? Is the information they contain outdated and worthless? Do they need to be converted to the new norm? In the present work we analyse these questions. © 2012 Springer-Verlag.

2010

Improving IdSay: A Characterization of Strengths and Weaknesses in Question Answering Systems for Portuguese

Autores
Carvalho, G; de Matos, DM; Rocio, V;

Publicação
COMPUTATIONAL PROCESSING OF THE PORTUGUESE LANGUAGE, PROCEEDINGS

Abstract
IdSay is a Question Answering system for Portuguese that participated at QA@CLEF 2008 with a baseline version (IdSayBL). Despite the encouraging results, there was still much room for improvement. The participation of six systems in the Portuguese task, with very good results either individually or in an hypothetical combination run, provided a valuable source of information. We made an analysis of all the answers submitted by all systems to identify their strengths and weaknesses. We used the conclusions of that analysis to guide our improvements, keeping in mind the two key characteristics we want for the system: efficiency in terms of response time and robustness to treat different types of data. As a result, an improved version of IdSay was developed, including as the most important enhancement the introduction of semantic information. We obtained significantly better results, from an accuracy in the first answer of 32.5% in IdSayBL to 50.5% in IdSay, without degradation of response time.

2007

Document retrieval for question answering: a quantitative evaluation of text preprocessing

Autores
Carvalho, G; de Matos, DM; Rocio, V;

Publicação
Proceedings of the First Ph.D. Workshop in CIKM, PIKM 2007, Sixteenth ACM Conference on Information and Knowledge Management, CIKM 2007, Lisbon, Portugal, November 9, 2007

Abstract
Question Answering (QA) has been an area of interest for researchers, in part motivated by the international QA evaluation forums, namely the Text REtrieval Conference (TREC), and more recently, the Cross Language Evaluation Forum (CLEF) through QA@CLEF, that since 2004 includes the Portuguese language. In these forums, a collection of written documents is provided, as well as a set of questions, which are to be answered by the participating systems. Each system is evaluated by its capacity to answer the questions, as a whole, and there are relatively few results published that focus on the performance of its different components and their influence on the overall system performance. That is the case of the Information Retrieval (IR) component, which is broadly used in QA systems. Our work concentrates on the different options of preprocessing Portuguese text before feeding it to the IR component, evaluating their impact on the IR performance in the specific context of QA, so that we can make a sustained choice of which options to choose. From this work we conclude the clear advantage of the basic preprocessing techniques: case folding and removal of punctuation marks. For the other techniques considered, stop word removal enhanced the performance of the IR system but that was not the case as far as Stemming and Lemmatization are concerned. © 2007 ACM.