Mauricio Varea

Efficient and flexible access control via logic program specialisation

We describe the use of a flexible meta-interpreter for performing access control checks on deductive databases. The meta-program is implemented in Prolog and takes as input a database and an access policy specification. We then proceed to specialise the meta-program for a given access policy and intensional database by using the logen partial evaluation system. In addition to describing the programs involved in our approach, we give a number of performance measures for our implementation of an access control checker, and we discuss the implications of using this approach for access control on deductive databases. In particular, we show that by using our approach we get flexible access control with virtually zero overhead.

Dual transitions petri net based modelling technique for embedded systems specification

This paper presents a new modelling technique capable of modelling both control and data information using a single unified approach. This is achieved by modifying the classical Petri Net structure, allowing it to have two types of transitions and arcs. As a consequence, loops and conditional operations within complex specifications are easily identified. The system dynamic behaviour is modelled using a new marking scheme of the net consisting of a new element called value for data representation in addition to classical tokens used for control purpose. Structural definitions, behavioural rules and graphical representation of the new modelling technique are given. One potential application of the proposed modelling technique is the internal representation of embedded systems specification. Two examples are included illustrating the applicability and efficiency of the proposed modelling technique.

Dual Flow Nets: Modeling the control/data-flow relation in embedded systems

This paper addresses the interrelation between control and data flow in embedded system models through a new design representation, called Dual Flow Net (DFN). A modeling formalism with a very close-fitting control and data flow is achieved by this representation, as a consequence of enhancing its underlying Petri net structure. The work presented in this paper does not only tackle the modeling side in embedded systems design, but also the validation of embedded system models through formal methods. Various introductory examples illustrate the applicability of the DFN principles, whereas the capability of the model to with complex designs is demonstrated through the design and verification of a real-life Ethernet coprocessor.

Efficient and flexible access control via Jones-optimal logic program specialisation

We describe the use of a flexible meta-interpreter for performing access control checks on deductive databases. The meta-program is implemented in Prolog and takes as input a database and an access policy specification. For processing access control requests we specialise the meta-program for a given access policy and database by using the logen partial evaluation system. The resulting specialised control checking program is dependent solely upon dynamic information that can only be known at the time of actual access request evaluation. In addition to describing our approach, we give a number of performance measures for our implementation of an access control checker. In particular, we show that by using our approach we get flexible access control with virtually no overhead, satisfying the Jones optimality criterion. The paper also shows how to satisfy the Jones optimality criterion more generally for interpreters written in the non-ground representation.

Symbolic model checking of dual transition Petri Nets

This paper describes the formal verification of the recently introduced Dual Transition Petri Net (DTPN) models, using model checking techniques. The methodology presented addresses the Symbolic model checking of embedded systems behavioural properties, expressed in either computation tree logics (CTL) or linear temporal logics (LTL). The embedded system specification is given in terms of DTPN models. where elements of the model are captured in a four-module library which implements the behaviour of the model. Key issues in the development of the methodology are the heterogeneity and the nondeterministic nature of the model. This is handled by introducing some modifications in both structure and behaviour of the model, thus reducing the points of nondeterminism. Several features of the methodology are discussed and two examples are given in order to show the validity of the model.

The Ecce and Logen partial evaluators and their web interfaces

We present ECCE and LOGEN, two partial evaluators for Prolog using the online and offline approach respectively. We briefly present the foundations of these tools and discuss various applications. We also present new implementations of these tools, carried out in Ciao Prolog. In addition to a command-line interface new user-friendly web interfaces were developed. These enable non-expert users to specialise logic programs using a web browser, without the need for a local installation.