Shou Matsumoto

UnBBayes: Modeling Uncertainty for Plausible Reasoning in the Semantic Web

The same assumptions that were essential in the document web are still applied for the Semantic Web (SW). They are radical notions of information sharing, which include [Allemang & Hendler, 2008]: (i) the Anyone can say Anything about Any topic (AAA) slogan; (ii) the open world assumption, i.e. there might exist more information out there that we are not aware of, and (iii) nonunique naming, meaning that different people can assign different names to the same concept. However, the Semantic Web differs from its predecessors in the sense that it intends to provide an environment not only for allowing information sharing but also for making it possible to have the effect of knowledge synergy. Nevertheless, this can lead to a chaotic scenario with disagreements and conflicts. We call an environment characterized by the above assumptions a Radical Information Sharing (RIS) environment. The challenge facing SW architects is therefore to avoid the natural chaos to which RIS environments are prone, and move to a state characterized by information sharing, cooperation and collaboration. According to [Allemang & Hendler, 2008], one solution to this challenge lies in modeling. Modeling is a simplified abstraction of some real world phenomenon, which, amongst other things, allows the organizing of information for the community use. Modeling supports information sharing in three ways: it provides a means for human communication, it provides a way for explaining conclusions, and it provides the managing of different viewpoints. There is an immense variety of modeling approaches. In this chapter we will go over a few of these approaches, showing how they can be used and their main limitations related to achieving the full potential of the Semantic Web. First we will show how to apply Unified Modeling Language (UML) [Rumbaugh et al., 1998] and Entity/Relationship (ER) [Chen, 1976] diagrams for modeling. Then we will present Knowledge Representation and Reasoning (KR&R) [Brachman & Levesque, 2004] and describe how KR&R overcomes some of the limitations of UML and ER. Finally, we present Ontology and the Semantic Web [Berners-Lee, 1999] and discuss how it differs from and moves beyond the previous approaches.

Probabilistic ontology and knowledge fusion for procurement fraud detection in Brazil

To cope with societys demand for transparency and corruption prevention, the Brazilian Office of the Comptroller General (CGU) has carried out a number of actions, including: awareness campaigns aimed at the private sector; campaigns to educate the public; research initiatives; and regular inspections and audits of municipalities and states. Although CGU has collected information from hundreds of different sources - Revenue Agency, Federal Police, and others - the process of fusing all this data has not been efficient enough to meet the needs of CGUs decision makers. Therefore, it is natural to change the focus from data fusion to knowledge fusion. As a consequence, traditional syntactic methods must be augmented with techniques that represent and reason with the semantics of databases. However, commonly used approaches fail to deal with uncertainty, a dominant characteristic in corruption prevention. This paper presents the use of Probabilistic OWL (PR-OWL) to design and test a model that performs information fusion to detect possible frauds in procurements involving Federal money. To design this model, a recently developed tool for creating PR-OWL ontologies was used with support from PR-OWL specialists and careful guidance from a fraud detection specialist from CGU.

Message passing for Hybrid Bayesian Networks using Gaussian mixture reduction

Hybrid Bayesian Networks (HBNs), which contain both discrete and continuous variables, arise naturally in many application areas (e.g., artificial intelligence, data fusion, medical diagnosis, fraud detection, etc). This paper concerns inference in an important subclass of HBNs, the conditional Gaussian (CG) networks. Inference in CG networks can be NP-hard even for special-case structures, such as poly-trees, where inference in discrete Bayesian networks can be performed in polynomial time. This paper presents an extension to the Hybrid Message Passing inference algorithm for general CG networks (i.e., networks with loops and many discrete parents). The extended algorithm uses Gaussian mixture reduction to prevent an exponential increase in the number of Gaussian mixture components. Experimental results compare performance of the new algorithm with existing algorithms.