Jose Alferes | Universidade Nova de Lisboa (original) (raw)

Papers by Jose Alferes

In this work we present External Transaction Logic, a logic that extends Transaction logic with t... more In this work we present External Transaction Logic, a logic that extends Transaction logic with the ability to model and execute transactions requiring interactions with external entities, as e.g. external web-source, web-services or agents. Transactions are defined in a logic programming style by the composition of internal and external primitives. These primitives are incorporated in a quite general manner, as a parameter of the External Transaction Logic theory, allowing the specification of transactions integrating knowledge and actions from multiple sources and semantics. Since one has different control over internal and external domains, different transaction properties are ensured depending on where actions are executed. Namely, internal actions executed in a knowledge base that we fully control, follow the standard ACID model of transactions. Contrarily, transactional properties over actions executed externally need to be relaxed, as it is impossible to rollback actions exec...

In this paper we show how planning can be achieved by means of abduction, a form of non-monotonic... more In this paper we show how planning can be achieved by means of abduction, a form of non-monotonic reasoning, in the LUPS language. LUPS employs the recently introduced notion of Dynamic Logic Programming, whereby the knowledge representation rules, namely those representing actions, can dynamically change, crucial when agents are to be situated in evolving environments. By integrating into a single framework several recent developments in the logic programming and non-monotonic reasoning field of research, this work contributes to a better modeling and understanding of rational agents. At the same time, it enjoys the advantages of a declarative and implementable specification, shortening the usual gap between theory and practice often found in logical based approaches to agents. The system integrating Dynamic Logic Programming, LUPS and Abduction, in order to achieve this form of planning, has been implemented.

Deontic logic programming (DLP) is a framework combining deontic logic and non-monotonic logic pr... more Deontic logic programming (DLP) is a framework combining deontic logic and non-monotonic logic programming, and it is useful to represent and reason about normative systems. In this paper we propose an implementation for reasoning in DLP that combines, in a modular way, a reasoner for deontic logic with a reasoner for stable model semantics.

Intelligenza Artificiale, 2011

Logic programming has often been considered less than adequate for modelling the dynamics of know... more Logic programming has often been considered less than adequate for modelling the dynamics of knowledge changing over time. In this paper we describe a simple though quite powerful approach to modelling the updates of knowledge bases expressed by generalized logic programs, by means of a new language, hereby christened EVOLP (after EVOlving Logic Programs). The approach was first sparked by a critical analysis of previous efforts and results in this direction [1,2,7,11], and aims to provide a simpler, and at once more general, formulation of logic program updating, which runs closer to traditional logic programming (LP) doctrine. From the syntactical point of view, evolving programs are just generalized logic programs (i.e. normal LPs plus default negation also in rule heads), extended with (possibly nested) assertions, whether in heads or bodies of rules. From the semantics viewpoint, a model-theoretic characterization is offered of the possible evolutions of such programs. These evolutions arise both from self (or internal) updating, and from external updating too, originating in the environment. This formulation sets evolving programs on a firm basis in which to express, implement, and reason about dynamic knowledge bases, and opens up a number of interesting research topics that we brush on.

Lecture Notes in Computer Science, 2003

Lecture Notes in Computer Science, 2000

Logic Based Program Synthesis and Transformation, 2002

Lecture Notes in Computer Science, 2006

Lecture Notes in Computer Science

Journal of Applied Non-Classical Logics, 1995

According to the paradigm of Dynamic Logic Programming, knowledge is given by a set of theories (... more According to the paradigm of Dynamic Logic Programming, knowledge is given by a set of theories (encoded as logic programs) representing different states of the world. Different states may represent time (as in updates), specificity (as in taxonomies), strength of the updating instance (as in the legislative domain), hierarchical position of knowledge source (as in organizations), etc. The mutual relationships extant between different states are used to determine the semantics of the combined theory composed of all individual ...

International Logic Programming Symp, Nov 1, 1994

In this paper we define a sound and (theoretically) complete top-down derivation procedure for a ... more In this paper we define a sound and (theoretically) complete top-down derivation procedure for a well-founded semantics of logic programs extended with explicit negation (WFSX). By its nature, it is amenable to a simple interpreter implementation in Prolog, and readily allows pre-processing into Prolog, showing promise as an efficient basis for further development. The derivation method is directly inspired on the semantic AND-tree characterization of WFSX in our paper [2], but docs not require knowledge of it. In fact, that ...

Extensions of Logic Programming, 1993

The purpose of this work is to define a theorem prover that retains the procedural aspects of log... more The purpose of this work is to define a theorem prover that retains the procedural aspects of logic programing. The proof system we propose (SLWV-resolution. for Selected Linear Without contrapositive clause Variants)) is defined for a set of clauses in the implicational form (keeping to the form of logic programs). not requiring contrapositives, and has an execution method that respects the execution order of literals in a clause, preserving the procedural flavor of logic programming. SLWV-resolution can be seen as a combination of ...