We present a broad extension of the conventional formalism of state machines and state diagrams, that is relevant to the specification and design of complex discrete-event systems, such as multi-computer real-time systems, communication protocols and digital control units. Our diagrams, which we call statecharts, extend conventional state-transition diagrams with essentially three olements, dealing, respectively, with the notions of hierarchy, concurrency and communication. These transform the language of state diagrams into a highly structured' and economical description language. Statecharts are thus compact and expressive--small diagrams can express complex behavior--as well as compositional and modular. When coupled with the capabilities of computerized graphics, statecharts enable viewing the description at different levels of detail, and make even very large specifications manageable and comprehensible. In fact, we intend to demonstrate here that statecharts counter many of the objections raised against conventional state diagrams, and thus appear to render specification by diagrams an attractive and plausible approach. Statecharts can be used either as a stand-alone behavioral description or as part of a more general design methodology that deals also with the system's other aspects, such as functional decomposition and data-flow specification. We also discuss some practical experience that was gained over the last three years in applying the statechart formalism to the specification of a particularly complex system.

. Modern window-based user interfaces are actually a special kind of reactive system, and Petri nets may be fruitfully used to design such user - computer dialogues. This paper describes a software engineering tool aimed at supporting the use of high-level Petri nets for the specification, design and implementation of user interfaces in an event-driven interface system. We assess the rationale for the use of Petri nets in such a perspective. We then detail the object-oriented software architecture of the environment, and present an original algorithm for interpreting high-level Petri nets in an event-driven environment. Key-words : User Interface, Design, Computer tools for nets, High-level Petri nets. Contents 1. Introduction __________________________________________________________ 1 2. Event-driven programming ______________________________________________ 2 3. Architecture of interactive systems ________________________________________ 5 4. Designing event-driven interfaces wit...

Over the last few years, Model-Based User Interface Design has become an important tool for creating multi-device User Interfaces. By providing

Traditional system development methodologies have many shortcomings for highly interactive business applications; development phases can be poorly integrated and lack continuity; design is not grounded in task analysis. This paper presents five key activities that span several life cycle phases to address existing shortcomings. The activities form the methodological framework from which a specification framework can be derived. The methodological framework supports selection of design options, creating a design space for a specific class of problems. It lets user interface design be coupled to software engineering in a framework that supports effective decisions and actions. The five key activities support two transformations: the first from a methodological framework to a specification framework; the second from a specification framework to an implementation of an interactive application. Keywords Automatic generation, development methodology, dialogue, framework, guideline, interac...

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User Interface Management Systems have significantly reduced the effort required to build a user interface. However, current systems assume a set of standard "widgets" and make no provisions for defining new ones. This forces user interface designers to either do without or laboriously build new widgets with code. The Interface Object Graph is presented as a method for specifying and communicating the design of interaction objects or widgets. Two sample specifications are presented, one for a secure switch and the other for a two dimensional graphical browser. 1 INTRODUCTION Specification of user interfaces has been used to aid in the design of user-computer dialog and software. This work has led to the development of User Interface Management Systems or UIMSs. These systems significantly reduce the work required to design and specify a user-computer dialog. They also allow non-programmers to prototype and design complex user interfaces. However, current UIMSs assume that a set o...

Statecharts is a behavioural specification language for the specification of real-time event driven reactive systems. Recently, statecharts was related to a logical specification language, using which safety and liveness properties could be expressed# this language provides a compositional proof system for statecharts. However, the logical specification language is flat, with no facilities to account for the structure of statecharts; further, the primitives of this language are dependent on statecharts syntax, and cannot be related directly to the problem domain. This paper discusses a temporal logic-based specification language called FNLOG which addresses these problems.

It is usually very hard, both for designers and users, to reason reliably about user interfaces. This article shows that ‘push button ’ and ‘point and click ’ user interfaces are algebraic structures. Users effectively do algebra when they interact, and therefore we can be precise about some important design issues and issues of usability. Matrix algebra, in particular, is useful for explicit calculation and for proof of various user interface properties. With matrix algebra, we are able to undertake with ease unusally thorough reviews of real user interfaces: this article examines a mobile phone, a handheld calculator and a digital multimeter as case studies, and draws general conclusions about the approach and its relevance to design.

Employing diagrams in the UI causes problems that don't exist in so called Graphical User Interfaces. We are implementing a tool for generating editors for (a certain class of) diagrams from a specification. Diagram Editors are needed in really graphical UIs and interactive visual language environments. This paper addresses three aspects of the specification of diagram editors. After highlighting difficulties in user interaction with diagrams event automata are suggested as a model for specification of dialogs. Furthermore, it is discussed how objects selected by the user can automatically be assembled into semantically meaningful groups. These are needed for more complex editing operations. An easy and versatile way of specifying layout for diagram editors by constraints has been introduced in [1] and is generalized here. 1 Introduction So called Graphical User Interfaces (GUIs) are actually not graphical, but based on widgets. We share the opinion voiced in a recent CACM issue on GU...

Power has become a major concern for mobile computing systems such as laptops and handhelds, on which a significant fraction of software usage is interactive instead of computation-intensive. An analysis shows that over 90% of system energy and time is spent waiting for user input. Such idle periods provide vast opportunities for dynamic power management (DPM) and voltage scaling (DVS) techniques to reduce system energy. The user interface is in charge of system-user interaction. It often has a priori knowledge about how the user and system interact at a given moment. In this work, we propose to utilize such a priori knowledge and theories from the field of Psychology to predict user delays. We show that such delay predictions can be combined with DPM/DVS for aggressive power optimization. We verify the e#ectiveness of our methodologies using usage traces collected on a personal digital assistant (PDA) and a system power model based on accurate measurements. Experiments show that using predicted user delays for DPM/DVS achieves an average of 21.9% system energy reduction with little sacrifice in user productivity or satisfaction.