Building validation tools for knowledge-based systems

The Expert Systems Validation Associate (EVA), a validation system under development at the Lockheed Artificial Intelligence Center for more than a year, provides a wide range of validation tools to check the correctness, consistency and completeness of a knowledge-based system. A declarative meta-language (higher-order language), is used to create a generic version of EVA to validate applications written in arbitrary expert system shells. The architecture and functionality of EVA are presented. The functionality includes Structure Check, Logic Check, Extended Structure Check (using semantic information), Extended Logic Check, Semantic Check, Omission Check, Rule Refinement, Control Check, Test Case Generation, Error Localization, and Behavior Verification

A Case-study for the Semantic Analysis of Sentences in Coq

This paper presents a case-study devoted to the formaliza-tion of sentence frames in the Coq system. Therefore, we instanciate these frames for performing a semantic analysis of simple sentences. In particular, we rely on a hierarchy of types for type-checking the conceptual well-formedness of sentences. To do so, we investigate how to exploit the particular features of the Coq type system in order to take advantage of this elegant unifying framework for encoding the syntax-semantics interface and then we show how to improve our approach for combining it with linguistic resources distributed

Visualization/animation of programs in Alma: obtaining different results

Alma, a system for program animation, receives as input a computer program and produces a sequence of visualizations that will describe its functionality. The system generates automatically program animations basing this process on the internal representation of those programs. The back-end of this system works over at? execution tree (DAST Decorated Abstract Syntax Tree), implementing the animation algorithm. This algorithm uses two bases of rules: visualizing rules (to associate graphical representation with program elements creating a visual description of the program state) and rewriting rules (to change the program state). In this paper the main goal will be to present the extensibility of the system in the sense of adding or modifying inputs and outputs. We also discuss the characteristics of Alma's architecture that make this possible.FC

CHR^vis: Syntax and Semantics

The work in the paper presents an animation extension (CHR^{vis}) to Constraint Handling Rules (CHR). Visualizations have always helped programmers understand data and debug programs. A picture is worth a thousand words. It can help identify where a problem is or show how something works. It can even illustrate a relation that was not clear otherwise. CHR^{vis} aims at embedding animation and visualization features into CHR programs. It thus enables users, while executing programs, to have such executions animated. The paper aims at providing the operational semantics for CHR^{vis}. The correctness of CHR^{vis} programs is also discussed

Extending and Relating Semantic Models of Compensating CSP

Business transactions involve multiple partners coordinating and interacting with each other. These transactions have hierarchies of activities which need to be orchestrated. Usual database approaches (e.g.,checkpoint, rollback) are not applicable to handle faults in a long running transaction due to interaction with multiple partners. The compensation mechanism handles faults that can arise in a long running transaction. Based on the framework of Hoare's CSP process algebra, Butler et al introduced Compensating CSP (cCSP), a language to model long-running transactions. The language introduces a method to declare a transaction as a process and it has constructs for orchestration of compensation. Butler et al also defines a trace semantics for cCSP. In this thesis, the semantic models of compensating CSP are extended by defining an operational semantics, describing how the state of a program changes during its execution. The semantics is encoded into Prolog to animate the specification. The semantic models are further extended to define the synchronisation of processes. The notion of partial behaviour is defined to model the behaviour of deadlock that arises during process synchronisation. A correspondence relationship is then defined between the semantic models and proved by using structural induction. Proving the correspondence means that any of the presentation can be accepted as a primary definition of the meaning of the language and each definition can be used correctly at different times, and for different purposes. The semantic models and their relationships are mechanised by using the theorem prover PVS. The semantic models are embedded in PVS by using Shallow embedding. The relationships between semantic models are proved by mutual structural induction. The mechanisation overcomes the problems in hand proofs and improves the scalability of the approach

An X-Windows Toolkit for knowledge acquisition and representation based on conceptual structures

This paper describes GET (Graph Editor and Tools), a tool based on Sowa's conceptual structures, which can be used for generic knowledge acquisition and representation. The system enabled the acquisition of semantic information (restrictions) for a lexicon used by a semantic interpreter for Portuguese sentences featuring some deduction capabilities. GET also enables the graphical representation of conceptual relations by incorporating an X-Windows based editor

Animation of Z Specifications By Translation to Prolog

Yazılım geliştirebilmenin formal metodları o yazılım tanımlamasının geçerliliğine bağlıdır. Böyle bir tanımlama genelde 'Z' gibi bir formal dilde ifade edilir. Ancak, geçerli olması için, 'Z' tanımlaması test edilmeli, bunu yapabilmek için de animasyon yapılabilecek ve icra edilebilecek bir forma transfer edilebilmelidir. 'Z' tanımlamalarının animasyonları için kullanılan dillerden birisi Prolog'dur. Bu makalede 'Z' şemalarını Prolog'a çeviren teknikler açıklanmaktadır.Aym zamanda bu tür bir çevirmenin eksikleri ve belirsizlikleri üzerinde durulacaktır.Formal methods of software development rely on the validation of the specification of the software. Such specification is normally expressed in a formal language such as Z. However, in order to be validated the Z specification must be tested, and to achieve this it has to be transformed into a form that can be executed or animated. Prolog was one of the languages used for animation of Z specifications. This paper explains the techniques used for translating Z schemas into Prolog predicates. It also examines some of this translation shortcomings and unreliable features