Abstract
The ability to deal with partial knowledge is particularly important in a temporal domain. We describe a temporal language that accounts for incompletely specified temporal information about propositions. Temporal terms in the language denote time instants and inequality constraints are used to keep incomplete information about their order. The language is semantically based on the notion of maximal interval, the denotation of a proposition being a set of maximal intervals where it holds. The adequacy of maximal intervals for temporal knowledge representation has been justified elsewhere [5]. In a partial KB, abduction on the temporal order is generally needed to answer a query, and the answer is then conditional on the abduced facts. To comply with the intended semantics, an implicit form of temporal consistency has to be enforced, and this presents the main challenge to the design of the inference mechanism. We present here the syntax and declarative semantics of a propositional version of the language of maximal intervals and a first discussion of the problems in designing an inference system adequate to work with this temporal framework. Rather than presenting a complete solution, we discuss several a roaches.

Abstract
Important aspects of the implementation and calibration of a 3-D data acquisition system based on the ratio of two intensity images are described. These two images are obtained by illuminating the scene with a projector whose light is filtered, successively, by a graded and a constant neutral density filter. Calibration steps, involving the determination of camera and light projector geometric parameters and ratio calibration data, are analyzed. A new ratio calibration procedure is proposed. Results of two depth calculation methods are presented, and system accuracy is evaluated for several test scenes.

Abstract

Abstract
Andorra-I is an experimental parallel Prolog system that transparently exploits both dependent and-parallelism and or-parallelism. It constitutes the first implementation of the Basic Andorra model, a parallel execution model for logic programs in which determinate goals are executed before other goals. This model, besides combining two of the most important forms of implicit parallelism in logic programs, also provides a form of implicit coroutining. This means that Andorra-I not only supports standard Prolog but also provides the capabilities of flat committed-choice languages. In this paper, we discuss the preprocessor which enables Andorra-I to support full Prolog, including cut, commit, meta-predicates and side-effect predicates. The main functions of the preprocessor are to perform a mode analysis of the program by abstract interpretation, to use this information to recognize procedures containing pruning operators that are potentially ``noisy'', to protect calls to such ``sensitive'' predicates by restricting certain conjunctions to be executed sequentially, and finally to generate for each predicate a routine which will determine when calls to that predicate become executable through becoming clause determinate.

Abstract
Andorra-I is an experimental parallel Prolog system that transparently exploits both dependent and-parallelism and or-parallelism. It constitutes the first implementation of the Basic Andorra model, a parallel execution model for logic programs in which determinate goals are executed before other goals. This model, besides combining two of the most important forms of implicit parallelism in logic programs, also provides a form of implicit coroutining. This means that Andorra-I not only supports standard Prolog but also provides the capabilities of flat committed-choice languages. In this paper, we discuss the main issues involved in the implementation of the Andorra-I engine, covering both the sequential version which runs on uniprocessors and the parallel version which runs on shared-memory multiprocessors such as Sequent Symmetry. We then present performance data for our implementation. This data shows that Andorra-I, an interpreter, has a single-processor performance similar to the comparable sequential system, C-Prolog, while on multiple processors Andorra-I is able to obtain good speedups from both and-parallelism and or-parallelism. In suitable cases, the speedup obtained from exploiting both forms of parallelism combined is better than that obtainable from exploiting either kind alone.

Abstract
This work describes results comparing the influence of surface treatments (grinding, and immersion in 20% HNO3 solutions and distilled water) on (i) the corrosion resistance in 10% FeCl3 and 3.5% NaCl solutions, and (ii) the composition of passive films of AISI 304 stainless steel. Both immersion in HNO3 and in distilled water cause an increase in Cr concentration in the films. The acid treatment produces a more intense attack in 10% FeCl3 and increases the corrosion rate in 3.5% NaCl, whereas immersion in distilled water produces no changes in corrosion behaviour. It is argued that the improvement in pit initiation resistance often observed with stainless steel after a HNO3 treatment is essentially associated with removal of sulphide inclusions, and not with Cr enrichment in the film.