Consistent specification of interface suites in UML

The paper motivates and describes a model oriented approach for consistent specification of interface suites in UML. An interface suite is a coherent collection of interfaces defining interactions that transcend component boundaries. The specification of interface suites contains diagrammatic views and documentation, but it is extended with templates for structured specifications deriving from the ISpec approach. To guarantee that the specification views, documentation and templates are consistent, a specification model has been constructed. The model contains both structural and behavioural information, represented in the form of sequences of carefully designed tuples. The model provides the underlying structure for the tool supporting the design process. The tool directs the designer to specify all elements of the model in a consistent way. The specification is collected both by customized specification templates and by diagrams. The documentation and the diagram elements – both derived from the template information – are automatically generated. This prevents errors and provides specification consistency. Initial submission: 15 February 2002 / Revised submission: 20 September 2002 Published online: 2 December 2002 RID="*" ID="*"Supported by PROGRESS grant EES.5141 and ITEA DESS grant IT990211.     

Round-Trip Prototyping Based on Integrated Functional and User Interface Requirements Specifications

Requirements engineering in the new millennium is facing an increasing diversity of computerised devices comprising an increasing diversity of interaction styles for an increasing diversity of user groups. Thus the incorporation of user interface requirements into software requirements specifications becomes more and more mandatory. Validating these requirements specifications with hand-made, throw-away prototypes is not only expensive, but also bears the danger that validation results are not accurately fed back into the requirements specification. In this paper, we propose an enhancement of the requirements specification method SCORES for an explicit capturing of user interface requirements. The advantages of the approach are threefold. First, the user interface requirements specification is UML-compliant and integrated into the functional requirements specification. Second, prototypes for validation purposes can semi-automatically be generated. Third, the model-based generation of prototypes allows for ‘round-trip prototyping’ such that manual changes of the prototype during the validation process are automatically fed back into the requirements specification.     

Vacuity detection in temporal model checking

One of the advantages of temporal-logic model-checking tools is their ability to accompany a negative answer to the correctness query by a counterexample to the satisfaction of the specification in the system. On the other hand, when the answer to the correctness query is positive, most model-checking tools provide no witness for the satisfaction of the specification. In the last few years there has been growing awareness as to the importance of suspecting the system or the specification of containing an error also in the case model checking succeeds. The main justification of such suspects are possible errors in the modeling of the system or of the specification. Many such errors can be detected by further automatic reasoning about the system and the environment. In particular, Beer et al. described a method for the detection of vacuous satisfaction of temporal logic specifications and the generation of interesting witnesses for the satisfaction of specifications. For example, verifying a system with respect to the specification ϕ=AG(reqAFgrant) (“every request is eventually followed by a grant”), we say that ϕ is satisfied vacuously in systems in which requests are never sent. An interesting witness for the satisfaction of ϕ is then a computation that satisfies ϕ and contains a request. Beer et al. considered only specifications of a limited fragment of ACTL, and with a restricted interpretation of vacuity. In this paper we present a general method for detection of vacuity and generation of interesting witnesses for specifications in CTL^*. Our definition of vacuity is stronger, in the sense that we check whether all the subformulas of the specification affect its truth value in the system. In addition, we study the advantages and disadvantages of alternative definitions of vacuity, study the problem of generating linear witnesses and counterexamples for branching temporal logic specifications, and analyze the complexity of the problem. Published online: 22 January 2002     

Drag-and-drop multimedia: ¶an interface framework for digital libraries

In this paper, we describe a new interface for querying multimedia digital libraries and an interface building framework. The interface employs a drag-and-drop style of interaction and combines a structured natural-language style query specification with reusable multimedia objects. We call this interface DanDMM, short for “drag-and-drop multimedia”. DanDMM interfaces capture the syntax of the underlying query language, and dynamically reconfigure to reflect the contents of the data repository. A distinguishing feature of DanDMM is its ability to synthesize integrated interfaces that incorporate both example-based specification using multimedia objects, and traditional techniques including keyword, attribute, and free text-based search. We describe the DanDMM-builder, a framework for synthesizing DanDMM interfaces, and give several examples of interfaces that have been constructed using DanDMM-builder, including a remote-sensing library application and a video digital library. Received: 15 December 1997 / Revised: June 1999     

User Environments and Individuals: Experience with Adaptive Interface Agents

The traditional style of working with computers generally revolves around the computer being used as a tool, with individual users directly initiating operations and waiting for the results of them. A more recent paradigm of human-computer interaction, based on the indirect management of computing resources, is agent-based interaction. The idea of delegation plays a key part in this approach to computer-based work, which allows individuals to relinquish the routine, mechanistic parts of their everyday tasks, having them performed automatically instead. Adaptive interfaces combine elements of both these approaches, where the goal is to have the interface adapt to its users rather than the reverse. This paper addresses some of the issues arising from a practical software development process which aimed to support individuals using this style of interaction. This paper documents the development of a set of classes which implement an architecture for adaptive interfaces. These classes are intended to be used as part of larger user interface systems which are to exhibit adaptive behaviour. One approach to the implementation of an adaptive interface is to use a set of software “agents”– simple processes which effectively run “in the background”– to decompose the task of implementing the interface. These agents form part of a larger adaptive interface architecture, which in turn forms a component of the adaptive system.     

Human Factors in the Design of Supervisory Control Systems and Human–Machine Interfaces for Highly Automated Complex Systems

The design of control systems and human–machine interfaces in the field of complex and safety-critical environments remains today an open issue, in spite of the high technological evolution of the last decades. The increasing use of automation has improved efficiency, safety and ease of operations but, at the same time, it has complicated operators’ situation awareness and has changed the nature of their possible errors. The research activity described in this paper is an attempt to develop a methodological framework to support designers of control systems and human–machine interfaces. In particular, it focuses on the need for a deeply recursive approach related to the implementation of the systemic and human aspects of the design process of a human–machine system, intended as a Joint Cognitive System. A validating case study has been performed, based on the full application of the framework on the control of the turbine/alternator system of a thermoelectric power plant in northern Italy. Correspondence and offprint requests to: M. Piccini, Politecnico di Torino Dipartimento di Energetica, C.so Duca degli Abruzzi 24, 10129 Turin, Italy. Tel.: +39 011 564 4413; Fax: +39 011 564 4499; Email: mipiccin@polito.it     

Protocol synthesis and re-synthesis with optimal allocation of resources based on extended Petri nets

Protocol synthesis is used to derive a protocol specification, that is, the specification of a set of application components running in a distributed system of networked computers, from a specification of services (called the service specification) to be provided by the distributed application to its users. Protocol synthesis reduces design costs and errors by specifying the message exchanges between the application components, as defined by the protocol specification. In general, maintaining such a distributed application involves applying frequent minor modifications to the service specification due to changes in the user requirements. Deriving the protocol specification after each modification using the existing synthesis methods is considered expensive and time consuming. Moreover, we cannot identify what changes we should make to the protocol specification in correspondence to the changes in the service specification. In this paper, we present a new synthesis method to re-synthesize only those parts of the protocol specification that must be modified in order to satisfy the changes in the service specification. The method consists of a set of simple rules that are applied to the protocol specification written in an extended Petri net model. An application example is given along with some experimental results. Received: July 2001 / Accepted: July 2002 RID="*" ID="*" Supported by International Communications Foundation (ICF), Japan RID="**" ID="**" Supported by Communications and Information Technology Ontario (CITO) and Natural Sciences and Engineering Research Council (NSERC), Canada RID="*" ID="*" Supported by International Communications Foundation (ICF), Japan     

Effects of Airborne Data Link Communication on Demands, Workload and Situation Awareness

An airborne air-to-ground data link communication interface was evaluated in a multi-sector-planning scenario using an Airbus A 340 full flight simulator. In a close-to-reality experimental setting, eight professional crews performed a flight mission in a mixed voice/data link environment. Experimental factors were the medium (voice vs. data link), workload (low vs. high) and the role in the cockpit (pilot flying vs. pilot non-flying). Data link communication and the usability of the newly developed communication interface were rated positively by the pilots, but there is a clear preference for using a data link only in the phase of cruise. Cognitive demands were determined for selected sections of en-route flight. Demands are affected mainly by increased communication needs. In the pilots’ view, although a data link has no effect on safety or the possibilities of intervention, it causes more problems. The subjective workload, as measured with the NASA Task Load Index, increased moderately under data link conditions. A data link has no general effect on pilots’ situation awareness although flight plan negotiations with a data link cause a distraction of attention from monitoring tasks. The use of a data link has an impact on air-to-ground as well as intra-crew communication. Under data link conditions the pilot non-flying plays a more active role in the cockpit. Before introducing data link communication, several aspects of crew resource management have to be reconsidered. Correspondence and offprint requests to: T. Müller, Technical University of Berlin, Institute of Psychology and Ergonomics, Department of Human–Machine Systems, Jebensstrasse 1, 10623 Berlin, Germany.     

What are a Location’s “File” and “Edit” Menus?

The promise of mobile devices lies not in their capacity to duplicate the capabilities of desktop machines, but rather in their promise of enabling location-specific tasks. One of the challenges that must be addressed if they are to be used in this way is how intuitive interfaces for mobile devices can be designed that enable access to location-specific services usable across locations. We are developing a prototype mobile valet application that presents location-specific services organised around the tasks associated with a location. The basic elements of the interface exploits commonalties in the way we address tasks at various locations just as the familiar “file” and “edit” menus in various software applications exploit regularities in software tasks.     

Display Design of Process Systems Based on Functional Modelling

The prevalent way to present information in industrial computer displays is by using piping and instrumentation diagrams. Such interfaces have sometimes resulted in difficulties for operators because they are not sufficient to fulfil their needs. A systematic way that supports interface design therefore has to be considered. In the new design framework, two questions must be answered. Firstly, a modelling method is required to describe a process system. Such a modelling method can define the information content that must be displayed in interfaces. Secondly, how to communicate this information to operators efficiently must be considered. This will provide a basis for determining the visual forms that the information should take. This study discusses interface design of human–machine systems from these two points of view. Based on other scholars’ work, a comprehensive set of functional primitives is summarised as a basis to build a functional model of process systems. A library of geometrical presentations for these primitives is then developed. To support effective interface design, the concept of ‘functional macro’ is introduced and a way to map functional model to interface display is illustrated by applying several principles. To make our ideas clear, a central heating system is taken as an example and its functional model is constructed. Based on the functional model, the information to be displayed is determined. Several functional macros are then found in the model and their corresponding displays are constructed. Finally, by using the library of geometrical presentations for functional primitives and functional macros, the display hierarchy of the central heating system is developed. Reusability of functional primitives makes it possible to use the methodology to support interface design of different process systems.     

Higher-level techniques for hardware description and synthesis

The FLaSH (Functional Languages for Synthesising Hardware) system allows a designer to map a high-level functional language, SAFL, and its more expressive extension, SAFL+, into hardware. The system has two phases: first we perform architectural exploration by applying a series of semantics-preserving transformations to SAFL specifications; then the resulting specification is compiled into hardware in a resource-aware manner – that is, we map separate functions to separate hardware functional units (functions which are called multiple times become shared functional units). This article introduces the SAFL language and shows how program transformations on it can explore area-time trade-offs. We then show how the FLaSH compiler compiles SAFL to synchronous hardware and how SAFL transformations can also express hardware/software co-design. As a case study we demonstrate how SAFL transformations allow us to refine a simple specification of a MIPS-style processor into pipelined and superscalar implementations. The superset language SAFL+ (adding process calculi features but retaining many of the design aims) is then described and given semantics both as hardware and as a programming language. Published online: 17 December 2002     

A Method for Extracting and Stating Software Requirements that a User Interface Prototype Contains

User interface and requirements prototyping is a requirements elicitation technique. A user interface and requirements prototype is built during the requirements engineering phase of a software system development. Along with the user interface prototype are produced various documents such as the system requirement specification. When a prototype and other documents exist, they may not describe the same functionality, particularly because there may be behaviour of the prototype, artefacts of prototyping, that may not be intended. The problem is that in later development stages, when there is a prototype and other documents, it is often difficult to reconcile the difference between the prototype and the other documents. This paper presents an approach for avoiding this difficulty. It demonstrates the approach by showing its application to parts of a real software development.     

Exploring agent support at the user interface in e-commerce applications

In this paper, we present some of the results from our ongoing research work in the area of ‘agent support’ for electronic commerce, particularly at the user interface level. Our goal is to provide intelligent agents to assist both the consumers and the vendors in an electronic shopping environment. Users with a wide variety of different needs are expected to use the electronic shopping application and their expectations about the interface could vary a lot. Traditional studies of user interface technology have shown the existence of a ‘gap’ between what the user interface actually lets the users do and the users’ expectations. Agent technology, in the form of personalized user interface agents, can help to narrow this gap. Such agents can be used to give a personalized service to the user by knowing the user’s preferences. By doing so, they can assist in the various stages of the users’ shopping process, provide tailored product recommendations by filtering information on behalf of their users and reduce the information overload. From a vendor’s perspective, a software sales agent could be used for price negotiation with the consumer. Such agents would give the flexibility offered by negotiation without the burden of having to provide human presence to an online store to handle such negotiations. Published online: 25 July 2001     

The Human Communication Space: Towards I-centric Communications

In the last few years, a variety of concepts for service integration and corresponding systems have been developed. On the one hand, they aim for the interworking and integration of classical telecommunications and data communications services. On the other, they are focusing on universal service access from a variety of end-user systems. Many of the technical problems, resulting from the service integration, and service personalisation have been solved during the last years. However, all these systems are driven by the concept of providing several technologies to users by keeping the peculiarity of each service.  Looking at humans’ communication behaviour and their communication space, it is obvious that human beings interact habitually in a set of contexts with their environment. The individual information preferences and needs, persons to interact with, and the set of devices controlled by each individual define their personal communication space. Following this view, a new approach is to build communication systems not on the basis of specific technologies, but on the analysis of the individual communication spaces. The result is a communication system adapted to the demands of each individual (I-centric). The communication system will act on behalf of users’ demands, reflecting recent actions to enable profiling and self-adaptation to contexts and situations.  In this paper, we introduce I-centric Communications, an approach to design communication systems that adapt themselves to the individual communication space and individual environment and situation. In this context “I” means I, or individual, “Centric” means adaptable to I requirements and a certain user environment.     

Forming telecommunications software specifications from a service-driven model using enhanced software tools

Increasing diversity and sophistication among telecommunications customers has led to pressure on the telecommunications industry to give customer groups the capability to customize aspects of offered telecommunications services for their own particular needs. To offer such user-customizable services correctly, quickly, and cheaply, the telecommunications industry needs adequate techniques for transforming user requirements into software specifications and for realizing these software specifications with application code. In today's environment, several well-known software development life cycle processes exist for realizing software specifications; however, analogous techniques for transforming user requirements into explicit software specifications do not. This paper proposes a technique for transforming user requirements and then demonstrates its use on a sample telecommunications application. The technique creates a simulation environment that lets simulation users describe their application requirements and then determine the appropriate software specifications needed. The technique builds on aspects of a service-driven specification model and simulation software tools published earlier. Because the simulation environment derives from user requirements and produces software specifications, the proposed technique could represent the first phase of a service-driven software development life cycle process, eventually evolving from the nonservice-driven “requirements analysis” phase commonly used in practice today.     

Mechanized result verification: an industrial application

We present part of an industrial project where mechanized theorem proving is used for the validation of a translator which generates safety critical software. In this project, the mechanized proof is decomposed in two parts: one is done “online”, at each run of the translator, by a custom prover which checks automatically that the result of each translation meets some verification conditions; the other is done “offline”, once for all, interactively with a general purpose prover; the offline proof shows that the verification conditions checked by the online prover are sufficient to guarantee the correctness of each translation. The provably correct verification conditions can thus be seen as specifications for the online prover. This approach is called mechanized result verification. This paper describes the project requirements and explains the motivations to formal validation by mechanized result verification, provides an overview of the formalization of the specifications for the online prover and discusses in detail some issues we have addressed in the mechanized offline proof.     

A graphical user interface for Boolean query specification

Online information repositories commonly provide keyword search facilities through textual query languages based on Boolean logic. However, there is evidence to suggest that the syntactic demands of such languages can lead to user errors and adversely affect the time that it takes users to form queries. Users also face difficulties because of the conflict in semantics between AND and OR when used in Boolean logic and English language. Analysis of usage logs for the New Zealand Digital Library (NZDL) show that few Boolean queries contain more than three terms, use of the intersection operator dominates and that query refinement is common. We suggest that graphical query languages, in particular Venn-like diagrams, can alleviate the problems that users experience when forming Boolean expressions with textual languages. A study of the utility of Venn diagrams for query specification indicates that with little or no training users can interpret and form Venn-like diagrams in a consistent manner which accurately correspond to Boolean expressions. We describe VQuery, a Venn-diagram based user interface to the New Zealand Digital Library (NZDL). In a study which compared VQuery with a standard textual Boolean interface, users took significantly longer to form queries and produced more erroneous queries when using VQuery. We discuss the implications of these results and suggest directions for future work. Received: 15 December 1997 / Revised: June 1999     

Making Workflow Change Acceptable

Virtual professional communities are supported by network information systems composed from standard Internet tools. To satisfy the interests of all community members, a user-driven approach to requirements engineering is proposed that produces not only meaningful but also acceptable specifications. This approach is especially suited for workflow systems that support partially structured, evolving work processes. To ensure the acceptability, social norms must guide the specification process. The RENISYS specification method is introduced, which facilitates this process using composition norms as formal representations of social norms. Conceptual graph theory is used to represent four categories of knowledge definitions: type definitions, state definitions, action norms and composition norms. It is shown how the composition norms guide the legitimate user-driven specification process by analysing a case on the development of an electronic law journal.     

User interface specification with sequence diagrams: an application to the AIRBUS A380 Datalink system

The development of user interfaces for safety critical systems is driven by requirements specifications. Because user interface specifications are typically embedded within complex systems requirements specifications, they can be intractable to manage. Proprietary requirements specification tools do not support the user interface designer in modelling and specifying the user interface. In this paper, a new way of working with embedded user interface specifications is proposed, exploiting sequence diagrams with a hypertext structure for representing and retrieving use cases. This new tool concept is assessed through an application to the requirements specification for the Airbus A380 air traffic control Datalink system; engineers involved in the development of the Airbus cockpit used a prototype of the tool concept to resolve a set of user interface design anomalies in the requirements specification. The results of the study are positive and indicate the user interface to requirements specification tools which user interface designers themselves need.     

Deriving Goals from a Use-Case Based Requirements Specification

Use cases and scenarios have emerged as prominent analysis tools during requirements engineering activities due to both their richness and informality. In some instances, for example when a project’s budget or schedule time is reduced at short notice, practitioners have been known to adopt a collection of use cases as a suitable substitute for a requirements specification. Given the challenges inherent in managing large collections of scenarios, this shortcut is cause for concern and deserves focused attention. We describe our experiences during a goal-driven requirements analysis effort for an electronic commerce application. In particular, we identify the specific risks incurred, focusing more on the challenges imposed due to traceability, inconsistent use of terminology, incompleteness and consistency, rather than on traditional software project management risks. We conclude by discussing the impact of the lessons learned for requirements engineering in the context of building quality systems during goal and scenario analysis.