REPOSITÓRIO P.PORTO
Repositório Científico do Politécnico do Porto
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Proposal for the combination of ontology assemble and ontology mapping processes
Publication . Silva, Nuno; Santos, Jorge; Rocha, João; Ramos, Carlos; Vale, Zita
Ontology mapping is dependent on the matching algorithms, which in turn depends on the semantics of the ontologies. This proposal grounds on two distinct technologies: ontology mapping and ontology assemble. The ontology mapping system is a service-oriented system in which autonomous plug-able services capture and represent the ontology mapping domain’s expertise. Automatic ontology mapping systems perform poorly due to the lack of ontologies’ semantics to reason upon. The assemble process aims to integrate well-founded, proofed knowledge into the domain ontologies, providing extra semantics. Exploiting such semantics indistinct phases of the ontology mapping process, we envisage that such semantics would be very useful in the improvement of the automatic mapping results. Conversely, the ontology mapping experiences would provide feed-back to the assemble process, suggesting its improvement too. The cyclic improvement would run indefinitely. This paper suggests therefore the combination of efforts from both the assemble and mapping processes towards a better semantic relations and assembled ontologies.
Decision support for power system control centers – a model based reasoning component
Publication . Malheiro, Nuno; Vale, Zita; Ramos, Carlos; Cordeiro, Manuel; Marques, Albino; Couto, Vieira; Ramos, Carlos; Vale, Zita
The increasing demand on Power System Control Centers (PSCC) for optimization of the use of the Electrical Network
implies, as one of its key focuses, the fastest possible restoration of service. Human PSCC operators (PSCCO) control the Electrical Network aided by a distributed system of sensors and actuators, which produce temporal information about the networks’ state. These distributed systems are known as Supervisory Control and Data acquisition or SCADA systems. In incident situations, in which SCADA systems can produce huge amounts of information, PSCCOs can become very stressed and loose the necessary focus to perform an accurate diagnosis and hence proper power restoration.
Several approaches have been made to develop systems which can cope with the particularly hard features of this
problem in real-time. This paper presents a model based teasoning component which is integrated in a multicomponent system with the task of Electrical Network diagnosis and restoration. This particular component adds
adaptability to the system ensuring correct behaviour on any topological variation of the part of the electrical network in service or its protection schemes. The whole system
is fully functional and operating in the Portuguese Electrical Network Dispatch Center.
Hybrid methods for the maintenance scheduling of generating units problem
Publication . Gomes, Nuno; Cordeiro, Manuel; Vale, Zita; Ramos, Carlos; Ramos, Carlos; Vale, Zita
Real world search and optimization problems are usually characterized by having large search spaces, being difficult to model and being constantly changing. Constraint Logic Programming (CLP) has proved to be a good tool to model and solve this type of problems despite some efficiency problems. It seams that the problem is related to some lack of a “global perspective” of the constraints in the search process, One way of overcoming this problem is to hybridize Constraint Logic Programming with Linear Programming (LP) in order to enhance the solving process by finding feasible solutions early in the search by “global reasoning”. In this work we propose 4 hybrid methods for solving a Maintenance Scheduling of Generating Units problem. The main idea is to take the advantages of both CLP and LP avoiding their problems. Some initial tests show that for some conditions all the hybrid methods can perform better than CLP alone.
An architecture to integrate discovered knowledge in a rule based system
Publication . Oliveira, Paulo; Rodrigues, Maria de Fátima Coutinho; Ramos, Carlos; Vale, Zita
The techniques and tools of Knowledge Discovery in Databases seek to transform data into knowledge in an “intelligent” and semi-automatic way. One of the possible uses to this discovered knowledge consists in its integration or fusion with the knowledge that is in the knowledge base of an Expert System. It thus complements the knowledge . initially given by the expert, which is not always complete, or the most up-to-date. Using an alternative source it is possible to discover knowledge that is implicit in data, and then proceed with its fusion with the one already in the
knowledge base. However, this process can result in errors appearing (for example, inconsistencies) in the knowledge
base resulting from the fusion. Thus, one of the requirements to fulfil is the consistency and correction of this new knowledge base.
A generic and domain independent architecture that allows a rule based knowledge fusion, in the context above described is presented. Consistency and correction are guaranteed through the detection of errors, and by the adoption of an approach based in maximal consistent subsets of rules.
Service-oriented semi-automatic ontology bridging
Publication . Silva, Nuno; Rocha, João; Ramos, Carlos; Vale, Zita
With the advent of Semantic Web, knowledge-based interoperability faces a new technological shift, in which ontologies and semantic web technologies play a major role. Exploiting the explicit semantic description of the domain of discourse allows reasoning and automatically acquiring semantic relations between two different domains of discourses. Such semantic relations would be further applied in converting data or documents between such domains. This process is named Ontology Mapping. This paper proposes a semi-automatic bridging process, based in the idea that while automatic matching algorithms do not provide enough information to overcome semantic heterogeneity, they represent valuable sources of similarities measurements between ontologies’ entities, which can be combined into an overall similarity measure according to each service specific requirements.