Abstract. We propose a modular, assertion-based system for verification and debugging of large logic programs, together with several interesting models for checking assertions statically in modular programs, each with different characteristics and representing different trade-offs. Our proposal is a modular and multivariant extension of our previously proposed abstract assertion checking model and we also report on its implementation in the CiaoPP system. In our approach, the specification of the program, given by a set of assertions, may be partial, instead of the complete specification required by traditional verification systems. Also, the system can deal with properties which cannot always be determined at compile-time. As a result, the proposed system needs to work with safe approximations: all assertions proved correct are guaranteed to be valid and all errors actual errors. The use of modular, context-sensitive static analyzers also allows us to introduce a new distinction between assertions checked in a particular context or checked in general. 1

Regular types are a powerful tool for computing very precise descriptive types for logic programs. However, in the context of real-life, modular Prolog programs, the accurate results obtained by regular types often come at the price of efficiency. In this paper we propose a combination of techniques aimed at improving analysis efficiency in this context. As a first technique we allow optionally reducing the accuracy of inferred types by using only the types defined by the user or present in the libraries. We claim that, for the purpose of verifying type signatures given in the form of assertions the precision obtained using this approach is sufficient, and show that analysis times can be reduced significantly. Our second technique is aimed at dealing with situations where we would like to limit the amount of reanalysis performed, especially for library modules. Borrowing some ideas from polymorphic type systems, we show how to solve the problem by admitting parameters in type specifications. This allows us to compose new call patterns with some precomputed analysis info without losing any information. We argue that together these two techniques contribute to the practical and scalable analysis and verification of types in Prolog programs.

presentada en la Facultad de Informática de la Universidad Politécnica de Madrid para la obtención del título de Doctor en Informática

Abstract. Termination analysis has received considerable attention, traditionally in the context of declarative programming and, recently, also for imperative and Object Oriented (OO) languages. In fact, there exist termination analyzers for OO which are capable of proving termination of medium size applications by means of global analysis, in the sense that all the code used by such applications has to be proved terminating. However, global analysis has important weaknesses, such as its high memory requirements and its lack of efficiency, since often some parts of the code have to be analyzed over and over again, libraries being a paramount example of this. In this work we present how to extend the termination analysis in the COSTA system in order to make it modular by allowing separate analysis of individual methods. The proposed approach has been implemented. We report on its application to the termination analysis of the core libraries of the phoneME project, a well-known open source implementation of Java Micro Edition (JavaME), a realistic but reduced version of Java to be run on mobile phones and PDAs. We argue that such experiments are relevant, since handling libraries is known to be one of the most relevant open problems in analysis and verification of real-life applications. Our experimental results show that our proposal dramatically reduces the amount of code which needs to be handled in each analysis and that this allows proving termination of a good number of methods for which global analysis is unfeasible. 1