A abordagem POESIA para a integração de dados e serviços na Web semantica

Orientador: Claudia Bauzer MedeirosTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: POESIA (Processes for Open-Ended Systems for lnformation Analysis), a abordagem proposta neste trabalho, visa a construção de processos complexos envolvendo integração e análise de dados de diversas fontes, particularmente em aplicações científicas. A abordagem é centrada em dois tipos de mecanismos da Web semântica: workflows científicos, para especificar e compor serviços Web; e ontologias de domínio, para viabilizar a interoperabilidade e o gerenciamento semânticos dos dados e processos. As principais contribuições desta tese são: (i) um arcabouço teórico para a descrição, localização e composição de dados e serviços na Web, com regras para verificar a consistência semântica de composições desses recursos; (ii) métodos baseados em ontologias de domínio para auxiliar a integração de dados e estimar a proveniência de dados em processos cooperativos na Web; (iii) implementação e validação parcial das propostas, em urna aplicação real no domínio de planejamento agrícola, analisando os benefícios e as limitações de eficiência e escalabilidade da tecnologia atual da Web semântica, face a grandes volumes de dadosAbstract: POESIA (Processes for Open-Ended Systems for Information Analysis), the approach proposed in this work, supports the construction of complex processes that involve the integration and analysis of data from several sources, particularly in scientific applications. This approach is centered in two types of semantic Web mechanisms: scientific workflows, to specify and compose Web services; and domain ontologies, to enable semantic interoperability and management of data and processes. The main contributions of this thesis are: (i) a theoretical framework to describe, discover and compose data and services on the Web, inc1uding mIes to check the semantic consistency of resource compositions; (ii) ontology-based methods to help data integration and estimate data provenance in cooperative processes on the Web; (iii) partial implementation and validation of the proposal, in a real application for the domain of agricultural planning, analyzing the benefits and scalability problems of the current semantic Web technology, when faced with large volumes of dataDoutoradoCiência da ComputaçãoDoutor em Ciência da Computaçã

Implementation of an object-oriented university database using VODAK/VML prototype-2/C++

Object-oriented database (OODB) technology has become very popular and successful in recent years. Currently, there are many commercial object-oriented database systems available that are used for developing large and complex real world applications. In addition, there are many research prototypes of object-oriented databases available. In a joint research project of the CIS Dept at NJIT and GMD-IPSI an object-oriented data model called the Dual Model was developed. Using this Dual Model a university environment database schema was designed. This univesity database schema was implemented using the VODAK/VML OODB prototype - 1. The university database was then reimplemented using the C++ programming language, without any underlying database. In this thesis we have implemented a Dual Model based version of the university database, using the VODAK/VML OODB prototype - 2. This prototype is the first implemented prototype, which separates the structural and semantic aspects of a class definition. It also uses C++ as implementation language, while the previous prototype was based on Smalltalk - 80. To interact with the database we have developed a university database browser using the X11/MOTIF toolkit and C++

System support for object replication in distributed systems

Distributed systems are composed of a collection of cooperating but failure prone system components. The number of components in such systems is often large and, despite low probabilities of any particular component failing, the likelihood that there will be at least a small number of failures within the system at a given time is high. Therefore, distributed systems must be able to withstand partial failures. By being resilient to partial failures, a distributed system becomes more able to offer a dependable service and therefore more useful. Replication is a well known technique used to mask partial failures and increase reliability in distributed computer systems. However, replication management requires sophisticated distributed control algorithms, and is therefore a labour intensive and error prone task. Furthermore, replication is in most cases employed due to applications' non-functional requirements for reliability, as dependability is generally an orthogonal issue to the problem domain of the application. If system level support for replication is provided, the application developer can devote more effort to application specific issues. Distributed systems are inherently more complex than centralised systems. Encapsulation and abstraction of components and services can be of paramount importance in managing their complexity. The use of object oriented techniques and languages, providing support for encapsulation and abstraction, has made development of distributed systems more manageable. In systems where applications are being developed using object-oriented techniques, system support mechanisms must recognise this, and provide support for the object-oriented approach. The architecture presented exploits object-oriented techniques to improve transparency and to reduce the application programmer involvement required to use the replication mechanisms. This dissertation describes an approach to implementing system support for object replication, which is distinct from other approaches such as replicated objects in that objects are not specially designed for replication. Additionally, object replication, in contrast to data replication, is a function-shipping approach and deals with the replication of both operations and data. Object replication is complicated by objects' encapsulation of local state and the arbitrary interaction patterns that may exist among objects. Although fully transparent object replication has not been achieved, my thesis is that partial system support for replication of program-level objects is practicable and assists the development of certain classes of reliable distributed applications. I demonstrate the usefulness of this approach by describing a prototype implementation and showing how it supports the development of an example toy application. To increase their flexibility, the system support mechanisms described are tailorable. The approach adopted in this work is to provide partial support for object replication, relying on some assistance from the application developer to supply application dependent functionality within particular collators for dealing with processing of results from object replicas. Care is taken to make the programming model as simple and concise as possible

Simplifying the use of event-based systems with context mediation and declarative descriptions

Current trends like the proliferation of sensors or the Internet of Things lead to Cyber-physical Systems (CPSs). In these systems many different components communicate by exchanging events. While events provide a convenient abstraction for handling the high load these systems generate, CPSs are very complex and require expert computer scientists to handle correctly. We realized that one of the primary reasons for this inherent complexity is that events do not carry context. We analyzed the context of events and realized that there are two dimensions: context about the data of an event and context about the event itself. Context about the data includes assumptions like systems of measurement units or the structure of the encoded information that are required to correctly understand the event. Context about the event itself is data that provides additional information to the information carried by the event. For example an event might carry positional data, the additional information could then be the room identifier belonging to this position. Context about the data helps bridge the heterogeneity that CPSs possess. Event producers and consumers may have different assumptions about the data and thus interpret events in different ways. To overcome this gap, we developed the ACTrESS middleware. ACTrESS provides a model to encode interpretation assumptions in an interpretation context. Clients can thus make their assumptions explicit and send them to the middleware, which is then able to mediate between different contexts by transforming events. Through analysis of the provided contexts, ACTrESS can generate transformers, which are dynamically loaded into the system. It does not need to rely on costly operations like reflection. To prove this, we conducted a performance study which shows that in a content-based publish/subscribe system, the overhead introduced by ACTrESS’ transformations is too small to be measurable. Because events do not carry contextual information, expert computer scientists are required to describe situations that are made up of multiple events. The fact that CPSs promise to transform our everyday life (e.g., smart homes) makes this problem even more severe in that most of the target users cannot use CPSs. In this thesis, we developed a declarative language to easily describe situations and a desired reaction. Furthermore, we provide a mechanism to translate this high-level description to executable code. The key idea is that events are contextualized, i.e. our middleware enriches the event with the missing contextual information based on the situation description. The enriched events are then correlated and combined automatically, to ultimately be able to decide if the described situation is fulfilled or not. By generating small computational units, we achieve good parallelization and are able to elegantly scale up and down, which makes our approach particularly suitable for modern cloud architectures. We conducted a usability analysis and performance study. The usability analysis shows that our approach significantly simplifies the definition of reactive behavior in CPS. The performance study shows that the achieved automatic distribution and parallelization incur a small performance cost compared to highly optimized systems like Esper

Impact of Mobility on Information Systems and Information System Design

The subject of this thesis is to analyse the impact of mobile hardware and software on information systems, to survey existing approaches for specifying mobile systems of computer science in general, and to provide suitable means for the formal design of information systems comprising such mobile units in particular. We consider a mobile unit to denote a mobile hardware or software entity, and a mobile system as a system comprising or being accessed by such mobile components. The various forms of mobile units occurring in computer science are explained and a taxonomy for them is developed, followed by a detailed discussion of their effects on computer and information systems. Several approaches for specifying mobile systems are presented and classified, with a particular emphasis on formal methods. As it turns out, these approaches do not allow to describe the set-up and release of communication links or to distinguish between the ever-mobile units of a compound system and those which provide the fixed subsystem as the context for the mobile entities, which are both important aspects to consider when developing information systems with mobile components. Therefore, corresponding constructs are then presented as an extension to the specification language Troll and its theoretical foundations, i.e. extended data signatures and the Module Distributed Temporal Logic Mdtl, both being interpreted over event structures. Finally, the application of the constructs is illustrated with the development of a system for accessing web services from mobile phones, which complements the ongoing example of information retrieval via mobile agents used to explain the constructs and concepts.Thema dieser Arbeit ist die Analyse der Auswirkungen von mobiler Hard- und Software auf Informationssysteme, die Untersuchung vorhandener Ansätze zur Spezifikation mobiler Systeme in der Informatik allgemein und für den formalen Entwurf von Informationssystemen mit mobilen Einheiten insbesondere. "Mobile Einheit" wird dabei als Oberbegriff für mobile Hardware- und Softwarekomponenten verwendet, und ein "mobiles System" ist ein System, das solche mobilen Komponenten beinhaltet oder auf das durch diese zugegriffen wird. Wir beschreiben die verschiedenen Formen, in denen mobile Einheiten in der Informatik auftreten, und entwickeln eine entsprechende Taxonomie, bevor wir deren Auswirkungen auf Computer- und Informationssysteme ausführlich diskutieren. Verschiedene Ansätze zur Spezifikation mobiler Systeme werden vorgestellt und eingeordnet, wobei das Augenmerk speziell auf formalen Methoden liegt. Es stellt sich heraus, dass es keiner dieser Ansätze ermöglicht, den Auf- und Abbau von Kommunikationsverbindungen zu beschreiben und zwischen den stets mobilen Einheiten und denjenigen zu unterscheiden, die das feste Teilsystem als Kontext für sie bilden. Beides sind aber wesentliche Aspekte, die in der Entwicklung von Informationssystemen mit mobilen Bestandteilen zu berücksichtigen sind. Daher stellen wir dann entsprechende Sprachkonstrukte als Erweiterung der Spezifikationssprache Troll inklusive der formalen Grundlagen vor. Diese Grundlagen beruhen auf erweiterten Datensignaturen und einer modularen verteilten temporalen Logik Mdtl, die beide über Ereignisstrukturen interpretiert werden. Schließlich wird die Verwendbarkeit der Sprachkonstrukte in der Entwicklung eines Systems zur Nutzung von Web-Diensten von Mobiltelefonen aus illustriert