Eliminating Recursion from Monadic Datalog Programs on Trees

We study the problem of eliminating recursion from monadic datalog programs on trees with an infinite set of labels. We show that the boundedness problem, i.e., determining whether a datalog program is equivalent to some nonrecursive one is undecidable but the decidability is regained if the descendant relation is disallowed. Under similar restrictions we obtain decidability of the problem of equivalence to a given nonrecursive program. We investigate the connection between these two problems in more detail

Kiel Declarative Programming Days 2013

This report contains the papers presented at the Kiel Declarative Programming Days 2013, held in Kiel (Germany) during September 11-13, 2013. The Kiel Declarative Programming Days 2013 unified the following events: * 20th International Conference on Applications of Declarative Programming and Knowledge Management (INAP 2013) * 22nd International Workshop on Functional and (Constraint) Logic Programming (WFLP 2013) * 27th Workshop on Logic Programming (WLP 2013) All these events are centered around declarative programming, an advanced paradigm for the modeling and solving of complex problems. These specification and implementation methods attracted increasing attention over the last decades, e.g., in the domains of databases and natural language processing, for modeling and processing combinatorial problems, and for high-level programming of complex, in particular, knowledge-based systems

Achieving tightness in dl-programs

Reviewed by Francisco MartinsIn the field of the combination between description logics and rule-based reasoning systems, dl- programs have proved to be a very successful mechanism. One of their recognized shortcomings, however, is their lack of full tightness: the language constructs that feed data from the logic program have a local effect, leaving the knowledge base essentially unchanged throughout. In this paper, we present a construction that we call lifting, which allows predicates to be fully shared between the two components of a dl-program in a systematic way, and show how lifting can be used to provide intuitive solutions to a number of everyday reasoning problems involving the verification of integrity constraints and the implementation of default rules. This construction preserves consistency of the underlying knowledge base and complexity of the overall system. Furthermore, the resulting semantics of default rules has a natural interpretation under the original Reiter semantics

Chase of datalog programs and its application to solve the functional dependencies implication problem

[Resumen]Esta tesis presenta resultados en dos áreas principales. Por un lado se presentan resultados en el área de optimización de consultas recursivas (programas datalog recursivos lineales) en sistemas de gestión de bases datos deductivas (o convencionales pero que cumplan las especificaciones de SQL99) y por otro se presentan resultados en la implicación de dependencias funcionales en el modelo de datos deductivo. Para la optimización de programas recursivos lineales la aproximación adoptada es la de la optimización semántica de consultas que consiste en la utilización de las restricciones, que cumplen las bases de datos sobre las que se ejecutan las consultas, para obtener un programa más eficiente de evaluar. En concreto, se presentan dos algoritmos para la optimización de programas de datolg recursivos lineales cuando la base de datos sobre la que se ejecutan las consultas cumple un conjunto de dependencias funcionales. El primero se denomina chase de programas datalog y el segundo se denomina cyclic chase de programas datalog. Ambos algortimos persiguen el mismo objetivo (pero siguiendo dos aproximaciones ligeramente distintas), esto es, a partir de un progrma datalog recursivo lineal P y un conjunto de dependencias funcionales F, los dos algoritmos obtienen un programa P' que es equivalente a P cuando ambos (P y P') son evaluados sobre bases de datos que cumplen las dependencias funcionales F. Los dos algoritmos se basan en la utilización del chase, un procedimiento que originalmente se desarrolló para comprobar si una descomposición (de una relación universal) en distintas relaciones tenía pérdida de información o no. Los dos algoritmos utilizan la idea básica del chase (la igualación de variables siguiendo las dependencias funcionales) para la igualación de variables dentro de los programas datalog

Super Logic Programs

The Autoepistemic Logic of Knowledge and Belief (AELB) is a powerful nonmonotic formalism introduced by Teodor Przymusinski in 1994. In this paper, we specialize it to a class of theories called `super logic programs'. We argue that these programs form a natural generalization of standard logic programs. In particular, they allow disjunctions and default negation of arbibrary positive objective formulas. Our main results are two new and powerful characterizations of the static semant ics of these programs, one syntactic, and one model-theoretic. The syntactic fixed point characterization is much simpler than the fixed point construction of the static semantics for arbitrary AELB theories. The model-theoretic characterization via Kripke models allows one to construct finite representations of the inherently infinite static expansions. Both characterizations can be used as the basis of algorithms for query answering under the static semantics. We describe a query-answering interpreter for super programs which we developed based on the model-theoretic characterization and which is available on the web.Comment: 47 pages, revised version of the paper submitted 10/200

A Formal Approach to Combining Prospective and Retrospective Security

The major goal of this dissertation is to enhance software security by provably correct enforcement of in-depth policies. In-depth security policies allude to heterogeneous specification of security strategies that are required to be followed before and after sensitive operations. Prospective security is the enforcement of security, or detection of security violations before the execution of sensitive operations, e.g., in authorization, authentication and information flow. Retrospective security refers to security checks after the execution of sensitive operations, which is accomplished through accountability and deterrence. Retrospective security frameworks are built upon auditing in order to provide sufficient evidence to hold users accountable for their actions and potentially support other remediation actions. Correctness and efficiency of audit logs play significant roles in reaching the accountability goals that are required by retrospective, and consequently, in-depth security policies. This dissertation addresses correct audit logging in a formal framework. Leveraging retrospective controls beside the existing prospective measures enhances security in numerous applications. This dissertation focuses on two major application spaces for in-depth enforcement. The first is to enhance prospective security through surveillance and accountability. For example, authorization mechanisms could be improved by guaranteed retrospective checks in environments where there is a high cost of access denial, e.g., healthcare systems. The second application space is the amelioration of potentially flawed prospective measures through retrospective checks. For instance, erroneous implementations of input sanitization methods expose vulnerabilities in taint analysis tools that enforce direct flow of data integrity policies. In this regard, we propose an in-depth enforcement framework to mitigate such problems. We also propose a general semantic notion of explicit flow of information integrity in a high-level language with sanitization. This dissertation studies the ways by which prospective and retrospective security could be enforced uniformly in a provably correct manner to handle security challenges in legacy systems. Provable correctness of our results relies on the formal Programming Languages-based approach that we have taken in order to provide software security assurance. Moreover, this dissertation includes the implementation of such in-depth enforcement mechanisms for a medical records web application

Compressing probabilistic Prolog programs

Peer reviewe