It is important to provide a recovery operation for applications with a graphical user interface. A restricted linear undo mechanism can conveniently be implemented using object-oriented techniques. Although linear undo provides an arbitrarily long history, it is not possible to undo isolated commands from the history without undoing all following commands. Various undo models have been proposed to overcome this limitation, but they all ignore the problem that in graphical user interfaces a previous user action might not have a sensible interpretation in another state. The selective undo mechanism introduced here can undo isolated commands by copying them into the current state if that is meaningful. Furthermore, the semantics of selective undo are argued to be more natural for the user because the mechanism only looks at the command to undo and the current state and does not depend on the history in between. The user interface for selective undo can also be implemented generically. S...

The interaction history of a document can be modelled as a tree of command objects. This model not only supports recovery (undo/redo), but is also suitable for cooperation between distributed users working on a common document. Various coupling modes can be supported. Switching between modes is supported by regarding different versions of a document as different branches of the history. Branches can then be merged using a selective redo mechanism. Synchronous cooperation is supported by replicating the document state and exchanging command objects. Optimistic concurrency control can be applied, because conflicting actions can later be undone automatically.

Frameworks are an object-oriented reuse technique that are widely used in industry but not discussed much by the software engineering research community. They are a way of reusing design that is part of the reason that some object-oriented developers are so productive. This paper compares and contrasts frameworks with other reuse techniques, and describes how to use them, how to evaluate them, and how to develop them. It describe the tradeoffs involved in using frameworks, including the costs and pitfalls, and when frameworks are appropriate.

In this paper, we show how elaborate support for framework-based software evolution can be provided based on explicit documentation of the hot spots of object-oriented application frameworks. Such support includes high-level transformations that guide a developer when instantiating applications from a framework by propagating the necessary changes, as well as application upgrading facilities based on these transformations. The approach relies on active declarative documentation of the design and evolution of the framework's hot spots, by means of metapatterns and their associated transformations.

this paper we demonstrate the use of Hy+ for evaluating software metrics, verifying constraints, and identifying design patterns. Software metrics can be used to find components with low reusability or components that are hard to understand. Checking the source code against constraints can help bring design flaws to light, eliminate sources of errors, and guarantee consistent style. Identifying design patterns in a software system can reveal design decisions and help in understanding the code. We conclude that the flexibility achieved by using a general purpose system like Hy+ give this approach advantages over special purpose reverse-engineering tools, although specialized tools will have better performance and more knowledge of specific software engineering tasks. Combining the advantages of the two approaches is an interesting challenge. - 1 -

The empirical study described in this paper addresses software reading for construction: how application developers obtain an understanding of a software artifact for use in new system development. This study focuses on the processes that developers would engage in when learning and using object-oriented frameworks. We analyzed 15 student software development projects using both qualitative and quantitative methods to gain insight into what processes occurred during framework usage. The contribution of the study is not to test predefined hypotheses but to generate well-supported hypotheses for further investigation. The main hypotheses we produce are that example-based techniques are well suited to use by beginning learners while hierarchy-based techniques are not because of a larger learning curve. Other more specific hypotheses are proposed and discussed.

To supply the financial engineering community with adequate and timely software support we advocate a reusability oriented approach to software development. The ap proach focuses on frameworks and reusable building blocks. This paper presents a domain specific framework for a calculation engine to be used in financial trading software. It is as such an example of using frameworks outside their typical domain of graphical user interfaces.

Providing the financial engineering community with adequate software tools presents several challenges to application developers. Experience shows that reusability-oriented software development as supported by object technology has the potential to meet these challenges. To back the argument, a project of building a pilot implementation of a swap valuation system using a comprehensive class library including an application framework is reported. As a novelty the project emphasized the use of so-called design patterns. The project experience suggests that the use of design patterns significantly eases the application of a large class library and facilitates the reuse of design.

The design of complex multimedia documents presents new challenges to authoring systems, because spatial and temporal features should be visualized and made accessible in an intuitive and direct-manipulative way. In this study, multimedia presentations are considered as hierarchical compositions of time objects that define serial or parallel synchronization of the inserted media objects. Media composition hierarchies support automatic temporal layout mechanisms. They are integrated into an object-oriented application framework called MET++. It provides direct manipulation interaction on temporal structures in a composition view that displays temporal and compositional relations, allows time transformations on composites, supports the definition of time-dynamic behavior of media objects through time functions, and has a flexible graphical layout in order to visualize context information. Keywords: multimedia composition, audio, 3D graphics, time synchronization, animation, user interfac...

This paper defines the relevant terms by relating them to the already wellestablished terms of object technology. In particular, the focus lies on a discussion of the deficiencies of the objectoriented paradigm and how componentware might solve these shortcomings. Furthermore, the role of objectoriented frameworks as underlying technology of plug & play software is illustrated. Finally, the paper tries t o answer the question of whether some enhancements of the object-oriented paradigm indeed represent the dawn of a new era of software development.