This paper describes the design and implementation of a unit and header inference system for spreadsheets. The system is based on a formal model of units that we have described in previous work. Since the unit inference depends on information about headers in a spreadsheet, a realistic unit inference system requires a method for automatically determining headers. The present paper describes (1) several spatial-analysis algorithms for header inference, (2) a framework that facilitates the integration of different algorithms, and (3) the implementation of the system. The combined header and unit inference system is fully integrated into Microsoft Excel and can be used to automatically identify various kinds of errors in spreadsheets. Test results show that the system works accurately and reliably. 1

We describe extensions to the Excel spreadsheet that integrate userdefined functions into the spreadsheet grid, rather than treating them as a "bolt-on". Our first objective was to bring the benefits of additional programming language features to a system that is often not recognised as a programming language. Second, in a project involving the evolution of a well-established language, compatibility with previous versions is a major issue, and maintaining this compatibility was our second objective. Third and most important, the commercial success of spreadsheets is largely due to the fact that many people find them more usable than programming languages for programming-like tasks. Thus, our third objective (with resulting constraints) was to maintain this usability advantage.

We introduce a visual specification language for spreadsheets that allows the definition of spreadsheet templates. A spreadsheet generator can automatically create Excel spreadsheets from these templates together with customized update operations. It can be shown that spreadsheets created in this way are free from a large class of errors, such as reference, omission, and type errors. We present a formal definition of the visual language for templates and describe the process of generating spreadsheets from templates. In addition, we present an editor for templates and analyze the editor using the Cognitive Dimensions framework. 1

We introduce “Facet-Streams”, a hybrid interactive surface for co-located collaborative product search on a tabletop. Facet-Streams combines techniques of information visualization with tangible and multi-touch interaction to materialize collaborative search on a tabletop. It harnesses the expressive power of facets and Boolean logic without exposing users to complex formal notations. Two user studies reveal how Facet-Streams unifies visual and tangible expressivity with simplicity in interaction, supports different strategies and collaboration styles, and turns product search into a fun and social experience.

Many of the difficulties users experience when working with interactive systems arise from misfits between the user’s conceptualisation of the domain and device with which they are working and the conceptualisation implemented within those systems. We report an analytical technique called CASSM (Concept-based Analysis for Surface and Structural Misfits) in which such misfits can be formally represented to assist in understanding, describing and reasoning about them. CASSM draws on the framework of Cognitive Dimensions (CDs) in which many types of misfit were classified and presented descriptively, with illustrative examples. CASSM allows precise definitions of many of the CDs, expressed in terms of entities, attributes, actions and relationships. These definitions have been implemented in Cassata, a tool for automated analysis of misfits, which we introduce and describe in some detail.

Abstract. Conceptual models communicate the important aspects of a problem domain to stakeholders. The models therefore should be accessible to users who need to interpret them. On the other hand, the quality of the produced models is highly dependent on the usability of the modelling method used. This paper presents a series of usability assessments conducted on a method that integrates the use of a semi-formal notation, namely the Unified Modelling Language (UML) and a formal notation, namely B. The assessments included a controlled experiment that evaluated the comprehensibility of the produced model and a survey that assessed the modelling process. The results suggest that the method is able to produce a comprehensible model. The method is accessible to users when the principles and roles of each notation are obvious and well understood, and when there is strong support from the environment. 1

Spreadsheets are widely used, and studies have shown that most end-user spreadsheets contain non-trivial errors. Most of the currently available tools that try to mitigate this problem require varying levels of user intervention. This paper presents a system, called UCheck, that detects errors in spreadsheets automatically. UCheck carries out automatic header and unit inference, and reports unit errors to the users. UCheck is based on two static analyses phases that infer header and unit information for all cells in a spreadsheet. We have tested UCheck on a wide variety of spreadsheets and found that it works accurately and reliably. The system was also used in a continuing education course for high school teachers, conducted through Oregon State University, aimed at making the participants aware of the need for quality control in the creation of spreadsheets.

Abstract — We have developed a web-based homework tutor for discrete mathematics that is a step of progress towards building an intelligent adaptive textbook. The student works on mathematical problems in a notation that is closely mapped to the notation the student would be expected to write on an exam paper. The tutor gives advice and feedback as the student is working, in a co-operative manner rather than submissionand-response. This feedback is linked into the topic structure of the intelligent book, allowing the student to query for content material relating to a piece of advice. More than one content item is available on any topic, allowing server rules to choose items the that are likely to be useful to the individual student, while still allowing the student to reject the tutor’s selection and choose a different content item.

The Intelligent Book project aims to improve online education by designing materials that can model the subject matter they teach, in the manner of a Reactive Learning Environment. In this paper, we investigate using an automated proof assistant, particularly Isabelle/HOL, as the model supporting first year undergraduate exercises in which students write proofs in number theory. Automated proof assistants are generally considered to be difficult for novices to learn. We examine whether, by providing a very specialised interface, it is possible to build something that is usable enough to be of educational value. To ensure students cannot “game the system ” the exercise avoids tactic-choosing interaction styles, but asks the student to write out the proof. Proofs are written using MathsTiles: composable tiles that resemble written mathematics. Unlike traditional syntax-directed editors, MathsTiles allow students to keep many answer fragments on the canvas at the same time, and do not constrain the order in which an answer is written. Also, the tile syntax does not need to match the underlying Isar syntax exactly, and different tiles can be used for different questions. The exercises take place within the context of an Intelligent Book. We performed a user study and qualitative analysis of the system. Some users were able to complete proofs with much less training than is usual for the automated proof assistant itself, but there remain significant usability issues to overcome.

Abstract approved: