This is an introduction to the philosophy and use of OBJ, emphasizing its operational semantics, with aspects of its history and its logical semantics. Release 2 of OBJ3 is described in detail, with many examples. OBJ is a wide spectrum first-order functional language that is rigorously based on (order sorted) equational logic and parameterized programming, supporting a declarative style that facilitates verification and allows OBJ to be used as a theorem prover.

Issues of representation arise in natural language processing, user interface design, art, and indeed, communication with any medium. This paper addresses such issues using algebraic semiotics, which draws on algebraic speci cation to give (among other things) an algebraic theory of representation, and a generalization of blending in the sense of cognitive linguistics.

An approach to information visualization based on algebraic semiotics is introduced, and illustrated with examples. Semiotics is the general theory of signs, and algebraic semiotics is a new approach combining algebraic abstract data type theory with a grounding in social reality. The most important new ideas are to use semiotic spaces for systems of related signs, semiotic morphisms for representations of signs, and preservation orderings for the quality of representations.

This paper describes the Tatami project at UCSD, which is developing a system to support distributed cooperative software development over the web, and in particular, the validation of concurrent distributed software. The main components of our current prototype are a proof assistant, a generator for documentation websites, a database, an equational proof engine, and a communication protocol to support distributed cooperative work. We believe behavioral specification and verification are important for software development, and for this purpose we use first order hidden logic with equational atoms. The paper also briefly describes some novel user interface design methods that have been developed and applied in the project

recent advances in web technology, interface design, and specification. Our effort to improve the usability of such systems has led us into algebraic semiotics, while our effort to develop better formal methods for distributed concurrent systems has led us into hidden algebra and fuzzy logic. This paper discusses the Tatami system design, especially its software architecture, and its user interface principles. New work in the latter area includes an extension of algebraic semiotics to dynamic multimedia interfaces, and integrating Gibsonian affordances with algebraic semiotics. 1

Abstract: This paper proposes a new approach to style, arising from our work on computational media using structural blending, which enriches the conceptual blending of cognitive linguistics with structure building operations in order to encompass syntax and narrative as well as metaphor. We have implemented both conceptual and structural blending, and conducted initial experiments with poetry, including interactive multimedia poetry, although the approach generalizes to other media. The central idea is to analyze style in terms of blending principles, based on our finding that different principles from those of common sense blending are often needed for some contemporary poetic metaphors. 1

We present an algebraic framework for evidence exploration: the process of interpreting, manipulating, and navigating the proof structure or evidence produced by a model checker when attempting to verify a system specification for a temporal-logic property. Due to the sheer size of such evidence, single-step traversal is prohibitive and smarter exploration methods are required. Evidence exploration allows users to explore evidence through smaller, manageable views, which are definable in relational graph algebra, a natural extension of relational algebra to graph structures such as model-checking evidence. We illustrate the utility of our approach by applying the Evidence Explorer, our tool implementation of the evidence-exploration framework, to the Java meta-locking algorithm, a highly optimized technique deployed by the Java Virtual Machine to ensure mutually exclusive access to object monitor queues by threads.

The Tatami project is building a system to support software engineering over the internet, exploiting recent advances in web technology, interface design, and specification. Our effort to improve the usability of such systems led us into algebraic semiotics, while our effort to develop better formal methods for distributed concurrent systems led us into hidden algebra. We discuss the Tatami system design, especially user interface issues, and sketch an extension of algebraic semiotics for interface dynamics. 1 Introduction The Tatami project has pursued three main goals: 1. explore novel multimedia interface design principles, for easing the use of complex interactive systems; 2. build and use a generic distributed environment for cooperative work; and 3. verify distributed concurrent software. We discuss these goals in turn. The first is motivated by the difficulties many practicing engineers have with formal methods tools. We have taken theorem provers as a typically difficult c...

Abstract. We describe an environment that allows the users of the Theorema system to flexibly control aspects of computer-supported proof development. The environment supports the display and manipulation of proof trees and proof situations, logs the user activities (commands communicated with the system during the proving session), and presents (also unfinished) proofs in a human-oriented style. In particular, the user can navigate through the proof object, expand/remove proof branches, provide witness terms, develop several proofs concurrently, proceed step by step or automatically and so on. The environment enhances the effectiveness and flexibility of the reasoners of the Theorema system. 1

This position paper discusses various issues concerning requirements and design of proof assistant user interfaces (UIs). After a review of some of the difficulties faced by UI projects in academia, it presents a high-level description of proof assistant interaction. This is followed by an exposition of use cases and object identification. Several examples demonstrate the usefulness of these requirement elicitation techniques in the theorem proving domain. The second half of the paper begins with a consideration of the “principle of least effort ” for the design of theorem prover user interfaces. This is followed by a brief review of the “GUI versus text mode ” debate, proposals for better use of GUI facilities and a plea for better support of customisation. The paper ends with a discussion of architecture and system design issues. In particular, it argues for a platform architecture with an extensible set of components and the use of XML protocols for communication between UIs and proof assistant backends.