Simon J. Thompson

A Decision Procedure and Complete Axiomatization of Finite Interval Temporal Logic with Projection

This paper presents a complete axiomatization for propositional interval temporal logic (PITL) with projection. The axiomatization is based on a tableau decision procedure for the logic, which in turn is founded upon a normal form for PITL formulae. The construction of the axiomatization provides a general mechanism for generating axiomatizations thus: given a normal form for a new connective, axioms can be generated for the connective from the tableau construction using that normal form. The paper concludes with a discussion of aspects of compositionality for PITL with projection.

The Expressiveness of Spider Diagrams

Spider diagrams are a visual language for expressing logical statements. In this paper we identify a well-known fragment of first-order predicate logic that we call MFOL=, equivalent in expressive power to the spider diagram language. The language MFOL= is monadic and includes equality but has no constants or function symbols. To show this equivalence, in one direction, for each diagram we construct a sentence in MFOL= that expresses the same information. For the more challenging converse we prove that there exists a finite set of models for a sentence S that can be used to classify all the models for S. Using these classifying models we show that there is a diagram expressing the same information as S.

Clone detection and removal for Erlang/OTP within a refactoring environment

A well-known bad code smell in refactoring and software maintenance is duplicated code, or code clones. A code clone is a code fragment that is identical or similar to another. Unjustified code clones increase code size, make maintenance and comprehension more difficult, and also indicate design problems such as lack of encapsulation or abstraction. This paper proposes a token and AST based hybrid approach to automatically detecting code clones in Erlang/OTP programs, underlying a collection of refactorings to support user-controlled automatic clone removal, and examines their application in substantial case studies. Both the clone detector and the refactorings are integrated within Wrangler, the refactoring tool developed at Kent for Erlang/OTP.

The Haskell Refactorer, HaRe, and its API

We demonstrate the Haskell Refactorer, HaRe, both as an example of a fully-functional tool for a complete (functional) programming language, and to show the API which HaRe provides for building source-level program transformations for Haskell. We comment on the challenges presented by the construction of this and similar tools for language frameworks and processors.

Refactoring functional programs

Refactoring is the process of improving the design of existing programs without changing their functionality. These notes cover refactoring in functional languages, using Haskell as the medium, and introducing the HaRe tool for refactoring in Haskell.

Similar code detection and elimination for erlang programs

A well-known bad code smell in refactoring and software maintenance is duplicated code, that is the existence of code clones, which are code fragments that are identical or similar to one another. Unjustified code clones increase code size, make maintenance and comprehension more difficult, and also indicate design problems such as a lack of encapsulation or abstraction. This paper describes an approach to detecting ‘similar’ code based on the notion of anti-unification, or least-general common abstraction. This mechanism is used for detecting code clones in Erlang programs, and is supplemented by a collection of refactorings to support user-controlled automatic clone removal. The similar code detection algorithm and refactorings are integrated within Wrangler, a tool developed at the University of Kent for interactive refactoring of Erlang programs. We conclude with a report on case studies and comparisons with other tools.

Refactoring with wrangler, updated: data and process refactorings, and integration with eclipse

Wrangler is a refactoring tool for Erlang, implemented in Erlang. This paper reports the latest developments in Wrangler, which include improved user experience, the introduction of a number of data- and process-related refactorings, and also the implementation of an Eclipse plug-in which, together with Erlide, provides refactoring support for Erlang in Eclipse.

Behavioral reactivity and real time programming in XML: functional programming meets SMIL animation

XML and its associated languages are emerging as powerful authoring tools for multimedia and hypermedia web content. Furthermore intelligent presentation generation engines have begun to appear as have models and platforms for adaptive presentations. However XML-based models are limited by their lack of expressiveness in presentation and animation. As a result authors of dynamic adaptive web content must often use considerable amounts of script or code. The use of such script or code has two serious drawbacks. First such code undermines the declarative description possible in the original presentation language and second the scripting/coding approach does not readily lend itself to authoring by non programmers. In this paper we describe a set of XML language extensions inspired by features from the functional programming world which are designed to widen the class of reactive systems which could be described in languages such as SMIL. The described features extend the power of declarative modeling for the web by allowing the introduction of web media items which may dynamically react to continuously varying inputs both in a continuous way and by triggering discrete user-defined events. The two extensions described herein are discussed in the context of SMIL Animation and SVG but could be applied to many XML-based languages.

Specification and Prototyping of Structured Multimedia Documents using Interval Temporal Logic

This paper explores a formalism for describing a wide class of multimedia document constraints. We outline the requirements on temporal logic specification that arise from the multimedia documents application area. In particular, we highlight a canonical document example. Then we present the temporal logic formalism that we use. This formalism extends existing interval temporal logic with a number of new features: actions, framing of actions, past operators, a projection-like operator called filter and a new handling of interval length. A model theory and satisfaction relation are defined for the logic and a specification of the canonical example is presented.

The expressiveness of spider diagrams augmented with constants

Spider diagrams are a visual language for expressing logical statements. Spiders represent the existence of elements and contours denote sets. Several sound and complete spider diagram systems have been developed and it is known that the spider diagram language is equivalent in expressive power to monadic first order logic with equality. However, these sound and complete spider diagram systems do not contain syntactic elements analogous to constants in first order predicate logic. We extend the spider diagram language to include constant spiders which represent specific individuals and give formal semantics for the extended diagram language. We then prove that this extended system is equivalent in expressive power to the language of spider diagrams without constants