1,300 research outputs found
Combining Relational Algebra, SQL, Constraint Modelling, and Local Search
The goal of this paper is to provide a strong integration between constraint
modelling and relational DBMSs. To this end we propose extensions of standard
query languages such as relational algebra and SQL, by adding constraint
modelling capabilities to them. In particular, we propose non-deterministic
extensions of both languages, which are specially suited for combinatorial
problems. Non-determinism is introduced by means of a guessing operator, which
declares a set of relations to have an arbitrary extension. This new operator
results in languages with higher expressive power, able to express all problems
in the complexity class NP. Some syntactical restrictions which make data
complexity polynomial are shown. The effectiveness of both extensions is
demonstrated by means of several examples. The current implementation, written
in Java using local search techniques, is described. To appear in Theory and
Practice of Logic Programming (TPLP)Comment: 30 pages, 5 figure
Temporal reasoning in a logic programming language with modularity
Actualmente os Sistemas de Informação Organizacionais (SIO) lidam cada vez mais com informação que tem dependências temporais. Neste trabalho concebemos um ambiente de trabalho para construir e manter SIO Temporais. Este ambiente assenta sobre um linguagem lógica denominada Temporal Contextua) Logic Programming que integra modularidade com raciocínio temporal fazendo com que a utilização de um módulo dependa do tempo do contexto. Esta linguagem é a evolução de uma outra, também introduzida nesta tese, que combina Contextua) Logic Programming com Temporal Annotated Constraint Logic Programming, na qual a modularidade e o tempo são características ortogonais. Ambas as linguagens são formalmente discutidas e exemplificadas.
As principais contribuições do trabalho descrito nesta tese incluem:
• Optimização de Contextua) Logic Programming (CxLP) através de interpretação abstracta.
• Sintaxe e semântica operacional para uma linguagem que combina de um modo independente as linguagens Temporal Annotated Constraint Logic Programming (TACLP) e CxLP. É apresentado um compilador para esta linguagem.
• Linguagem (sintaxe e semântica) que integra de um modo inovador modularidade (CxLP) com raciocínio temporal (TACLP). Nesta linguagem a utilização de um dado módulo está dependente do tempo do contexto. É descrito um interpretador e um compilador para esta linguagem.
• Ambiente de trabalho para construir e fazer a manutenção de SIO Temporais. Assenta sobre uma especificação revista da linguagem ISCO, adicionando classes e manipulação de dados temporais. É fornecido um compilador em que a linguagem resultante é a descrita no item anterior. ABSTRACT- Current Organisational Information Systems (OIS) deal with more and more Infor-mation that, is time dependent. In this work we provide a framework to construct and maintain Temporal OIS. This framework builds upon a logical language called Temporal Contextual. Logic Programming that deeply integrates modularity with tem-poral reasoning making the usage of a module time dependent. This language is an evolution of another one, also introduced in this thesis, that combines Contextual Logic Programming with Temporal Annotated Constraint Logic Programming where modularity and time are orthogonal features. Both languages are formally discussed and illustrated.
The main contributions of the work described in this thesis include:
• Optimisation of Contextual Logic Programming (CxLP) through abstract interpretation.
• Syntax and operational semantics for an independent combination of the temporal framework Temporal Annotated Constraint Logic Programming (TACLP) and CxLP. A compiler for this language is also provided.
• Language (syntax and semantics) that integrates in a innovative way modularity
(CxLP) with temporal reasoning (TACLP). In this language the usage of a given
module depends of the time of the context. An interpreter and a compiler for
this language are described.
• Framework to construct and maintain Temporal Organisational Information Systems. It builds upon a revised specification of the language ISCO, adding temporal classes and temporal data manipulation. A compiler targeting the language presented in the previous item is also given
A semantic and agent-based approach to support information retrieval, interoperability and multi-lateral viewpoints for heterogeneous environmental databases
PhDData stored in individual autonomous databases often needs to be combined and
interrelated. For example, in the Inland Water (IW) environment monitoring domain,
the spatial and temporal variation of measurements of different water quality indicators
stored in different databases are of interest. Data from multiple data sources is more
complex to combine when there is a lack of metadata in a computation forin and when
the syntax and semantics of the stored data models are heterogeneous. The main types
of information retrieval (IR) requirements are query transparency and data
harmonisation for data interoperability and support for multiple user views. A
combined Semantic Web based and Agent based distributed system framework has
been developed to support the above IR requirements. It has been implemented using
the Jena ontology and JADE agent toolkits. The semantic part supports the
interoperability of autonomous data sources by merging their intensional data, using a
Global-As-View or GAV approach, into a global semantic model, represented in
DAML+OIL and in OWL. This is used to mediate between different local database
views. The agent part provides the semantic services to import, align and parse
semantic metadata instances, to support data mediation and to reason about data
mappings during alignment. The framework has applied to support information
retrieval, interoperability and multi-lateral viewpoints for four European environmental
agency databases.
An extended GAV approach has been developed and applied to handle queries that can
be reformulated over multiple user views of the stored data. This allows users to
retrieve data in a conceptualisation that is better suited to them rather than to have to
understand the entire detailed global view conceptualisation. User viewpoints are
derived from the global ontology or existing viewpoints of it. This has the advantage
that it reduces the number of potential conceptualisations and their associated
mappings to be more computationally manageable. Whereas an ad hoc framework
based upon conventional distributed programming language and a rule framework
could be used to support user views and adaptation to user views, a more formal
framework has the benefit in that it can support reasoning about the consistency,
equivalence, containment and conflict resolution when traversing data models. A
preliminary formulation of the formal model has been undertaken and is based upon
extending a Datalog type algebra with hierarchical, attribute and instance value
operators. These operators can be applied to support compositional mapping and
consistency checking of data views. The multiple viewpoint system was implemented
as a Java-based application consisting of two sub-systems, one for viewpoint
adaptation and management, the other for query processing and query result
adjustment
Semantic definition of a subset of the structured query language (SQL)
Journal ArticleSQL is a relational database definition and manipulation language. Portions of the manipulation language are readily described in terms of relational algebra. The semantics of a subset of the SQL select statement is described. The select statement allows the user to query the database. The select statement is shown to be equivalent to a series of relational and set operations. The semantics are described in terms of abstract data types for relation schemes, tuples, and relations. Certain forms of the union or intersection of two select statements are shown to have equivalent single select statement forms
Techniques for improving efficiency and scalability for the integration of information retrieval and databases
PhDThis thesis is on the topic of integration of Information Retrieval (IR) and Databases (DB), with
particular focuses on improving efficiency and scalability of integrated IR and DB technology
(IR+DB). The main purpose of this study is to develop efficient and scalable techniques for
supporting integrated IR and DB technology, which is a popular approach today for handling
complex queries over text and structured data.
Our specific interest in this thesis is how to efficiently handle queries over large-scale text
and structured data. The work is based on a technology that integrates probability theory and
relational algebra, where retrievals for text and data are to be expressed in probabilistic logical
programs such as probabilistic relational algebra or probabilistic Datalog. To support efficient
processing of probabilistic logical programs, we proposed three optimization techniques
that focus on aspects covered logical and physical layers, which include: scoring-driven query
optimization using scoring expression, query processing with top-k incorporated pipeline, and
indexing with relational inverted index.
Specifically, scoring expressions are proposed for expressing the scoring or probabilistic semantics
of implied scoring functions of PRA expressions, so that efficient query execution plan
can be generated by rule-based scoring-driven optimizer. Secondly, to balance efficiency and
effectiveness so that to improve query response time, we studied methods for incorporating topk
algorithms into pipelined query execution engine for IR+DB systems. Thirdly, the proposed
relational inverted index integrates IR-style inverted index and DB-style tuple-based index, which
can be used to support efficient probability estimation and aggregation as well as conventional
relational operations.
Experiments were carried out to investigate the performances of proposed techniques. Experimental
results showed that the efficiency and scalability of an IR+DB prototype have been
improved, while the system can handle queries efficiently on considerable large data sets for a
number of IR tasks
Extending the relational model with constraint satisfaction
We propose a new approach to data driven constraint programming. By extending the relational model to handle constraints and variables as first class citizens, we are able to express first order logic SAT problems using an extended SQL which we refer to as SAT/SQL. With SAT/SQL, one can efficiently solve a wide range of practical constraint and optimization problems. SAT/SQL integrates both SAT solver and relational data processing to enable efficient and large scale data driven constraint programming.
Furthermore, our research presents two novel meta-programming operators: MINREPAIR and MIN-CONFLICT which are iterative debugging facilities for constraint programming with SAT/SQL
SDK development for bridging heterogeneous data sources through connect bridge platform
Nesta dissertação apresentou-se um SDK para a criação de conectores a integrar com o CB Server, que pretende: acelerar o desenvolvimento, garantir melhores práticas e simplificar as diversas atividades e tarefas no processo de desenvolvimento. O SDK fornece uma API pública e simples, suportada por um conjunto de ferramentas, que facilitam o processo de desenvolvimento, explorando as facilidades disponibilizadas através da API. Para analisar a exatidão, viabilidade, integridade e acessibilidade da solução apresentam-se dois exemplos e casos de estudo. Através dos casos de estudo foi possível identificar uma lista de problemas, de pontos sensíveis e melhorias na solução proposta. Para avaliar a usabilidade da API, uma metodologia baseada em vários métodos de avaliação de usabilidade foi estabelecida. O múltiplo caso de estudo funciona como o principal método de avaliação, combinando vários métodos de pesquisa. O caso de estudo consiste em três fases de avaliação: um workshop, uma avaliação heurística e uma análise subjetiva. O caso de estudo envolveu três engenheiros de software (incluindo programadores e avaliadores). A metodologia aplicada gerou resultados com base num método de inspeção, testes de utilizador e entrevistas. Identificou-se não só pontos sensíveis e falhas no código-fonte, mas também problemas estruturais, de documentação e em tempo de execução, bem como problemas relacionados com a experiência do utilizador. O contexto do estudo é apresentado de modo a tirar conclusões acerca dos resultados obtidos. O trabalho futuro incluirá o desenvolvimento de novas funcionalidades. Adicionalmente, pretende-se resolver problemas encontrados na metodologia aplicada para avaliar a usabilidade da API, nomeadamente problemas e falhas no código fonte (por exemplo, validações) e problemas estruturais.In this dissertation, we present an SDK for the creation of connectors to integrate with CB Server which accelerates deployment, ensures best practices and simplifies the various activities and tasks in the development process. The SDK provides a public and simple API leveraged by a set of tools around the API developed which facilitate the development process by exploiting the API facilities. To analyse the correctness, feasibility, completeness, and accessibility of our solution, we presented two examples and case studies. From the case studies, we derived a list of issues found in our solution and a set of proposals for improvement. To evaluate the usability of the API, a methodology based on several usability evaluation methods has been established. Multiple case study works as the main evaluation method, combining several research methods. The case study consists of three evaluation phases – a hands-on workshop, a heuristic evaluation and subjective analysis. The case study involved three computer science engineers (including novice and expert developers and evaluators). The applied methodology generated insights based on an inspection method, a user test, and interviews. We identify not only problems and flaws in the source code, but also runtime, structural and documentation problems, as well as problems related to user experience. To help us draw conclusion from the results, we point out the context of the study. Future work will include the development of new functionalities. Additionally, we aim to solve problems found in the applied methodology to evaluate the usability of the API, namely problems and flaws in the source code (e.g. validations) and structural problems
Database rules and time: some proposed extensions to the SQL standard
The subject of this thesis is the incorporation of temporal
semantics into database rules and how the resultant syntax
might be reconciled with the evolving SQL standard. In particular, it explores time-driven rules and the time-relationship between triggering events and associated actions.
A review of the key research results in the area of
database rules and the syntax developed for the major
prototype implementations is conducted, and a working
syntax , free of any limitations within the SQL standard,
developed. Next, an operational definition is evolved
through the application of this working syntax to two
sample domains rich in 'temporal rules'. In each case a
graphical representation of the domain is presented using
an adapted object-oriented modelling technique followed by
a mapping into the working temporal syntax.
Attention is then turned to the SQL-92 standard and its
future successor SQL3. An assessment is made of their
implications for the working syntax developed in the
earlier chapters - with particular reference to the
specification of time and the use of database triggers.
When an attempt was made to re-cast the working syntax into
SQL, a satisfactory mapping, which succeeded in preserving
the semantics of the original, could not be achieved.
Support for time-based triggers; cyclic operations;
delayed actions and rule lifetimes necessitated the
development of appropriate modifications to the basic SQL3
draft syntax. The proposed extensions capture all of the
semantics required for the specification of time-based
rules.
The example applications indicated that an extended SQLcompliant
language approach allied to a sound objectoriented
modelling formalism had a broad applicability.
Furthermore, it was apparent that the addition of a
temporal dimension to rule actions was a key enabling
factor in increasing their semantic power
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