Compiling XPath into a State-less Forward-only Subset

International audienceWe show how the context state of XPath, accessed through the position() and last() pseudo-functions, can be eliminated in most cases by translating references to the context state with an equivalent contextfree expression, and how this enables the use of context state in combination with a subsequent forward-only transformation, allowing for execution of (almost) full XPath on any of the emerging streaming subsets. Specifically we show how the normalization into a core language as proposed in the current W3C Last Call draft of the XPath/XQuery Formal Semantics can be extended such that the context state and reverse axes can be eliminated from the core XPath (and potentially XQuery) language

Rewriting Declarative Query Languages

Queries against databases are formulated in declarative languages. Examples are the relational query language SQL and XPath or XQuery for querying data stored in XML. Using a declarative query language, the querist does not need to know about or decide on anything about the actual strategy a system uses to answer the query. Instead, the system can freely choose among the algorithms it employs to answer a query. Predominantly, query processing in the relational context is accomplished using a relational algebra. To this end, the query is translated into a logical algebra. The algebra consists of logical operators which facilitate the application of various optimization techniques. For example, logical algebra expressions can be rewritten in order to yield more efficient expressions. In order to query XML data, XPath and XQuery have been developed. Both are declarative query languages and, hence, can benefit from powerful optimizations. For instance, they could be evaluated using an algebraic framework. However, in general, the existing approaches are not directly utilizable for XML query processing. This thesis has two goals. The first goal is to overcome the above-mentioned misfits of XML query processing, making it ready for industrial-strength settings. Specifically, we develop an algebraic framework that is designed for the efficient evaluation of XPath and XQuery. To this end, we define an order-aware logical algebra and a translation of XPath into this algebra. Furthermore, based on the resulting algebraic expressions, we present rewrites in order to speed up the execution of such queries. The second goal is to investigate rewriting techniques in the relational context. To this end, we present rewrites based on algebraic equivalences that unnest nested SQL queries with disjunctions. Specifically, we present equivalences for unnesting algebraic expressions with bypass operators to handle disjunctive linking and correlation. Our approach can be applied to quantified table subqueries as well as scalar subqueries. For all our results, we present experiments that demonstrate the effectiveness of the developed approaches

Metodologia para reengenharia de processos C2A e B2A

Os processes de interação do Cidadão ou Empresa com a Administração Pública (AP), normalmente designados por Consumer-la-Administration (C2A) e Business-to-Administration (BZA), de acordo com algumas entidades como a ANACOM (http://www.anacom.pt, 2004), têm ainda a sua origem, na maioria dos casos, numa ótica baseada na organização interna da administração, por oposição a uma ótica desejável baseada nos serviços tal como são vistos pelo Cidadão ou Empresa. Estes processos, que constituem casos concretos de workflow, ao nível a que se pretende desenvolver na dissertação proposta, são modeláveis com precisão, recorrendo a linguagens como o Unified Modeling Language (UML), através dos seus vários diagramas. É assim possível estabelecer um conjunto de regras, aplicáveis com sistemática, que permitam a reengenharia desses processos, no sentido de obter não só uma solução orientada para o Actor principal (Cidadão ou Empresa), mas também para a eficiente. É ainda possível, como se pretende demonstrar através desta dissertação, estabelecer métricas de eventuais ganhos nas versões redesenhadas e derivar, em termos gerais, arquiteturas distribuídas que suportem as soluções propostas. /ABSTRACT - Methodology for Reengineering of C2A and B2A Processes The processes of interaction between Citizens and Businesses with the Public Administration (PA), usually designated for Consumer-to-Administration (C2A) and Business-to-Administration (B2/1), according to some entity like as ANACOM (http://www.anacom.pt, 2004), still reflect, in the majority of cases, the internal organization and procedures of the various agencies involved, and not the desirable perspective of services as seen by the citizen or enterprise. These processes, that constitute specific cases of workflows within the scope of this dissertation, can be modeled' with precision using languages as UML, through several of its diagrams. It is therefore possible to establish a set of rules, systematically applicable, that can guide the reengineering of these processes, not only towards an Actor (Citizen or Business) oriented approach but also achieving higher efficiency. It is also possible, as intends to demonstrate in this master thesis, to establish metrics for the possible gains, in the redesigned' versions, and' to derive, in general terms, distributed architectures that support the proposed solutions

New Fundamental Technologies in Data Mining

The progress of data mining technology and large public popularity establish a need for a comprehensive text on the subject. The series of books entitled by "Data Mining" address the need by presenting in-depth description of novel mining algorithms and many useful applications. In addition to understanding each section deeply, the two books present useful hints and strategies to solving problems in the following chapters. The contributing authors have highlighted many future research directions that will foster multi-disciplinary collaborations and hence will lead to significant development in the field of data mining