This paper focuses on the version models underlying both commercial systems and research prototypes. It provides an overview and classification of different versioning paradigms. Furthermore, it defines and relates fundamental concepts such as revisions, variants, configurations, and changes. In particular, we focus on intensional versioning, i.e., construction of versions based on configuration rules. Finally,we provide an overview of systems whichhave had significant impact on the development of the SCM discipline, and classify them according to a detailed taxonomy

This paper presents an overview of the Cedar programming environment, focusing on its overall structure-that is, the major components of Cedar and the way they are organized. Cedar supports the development of programs written in a single programming language, also called Cedar. Its primary purpose is to increase the productivity of programmers whose activities include experimental pro-gramming and the development of prototype software systems for a high-performance personal computer. The paper emphasizes the extent to which the Cedar language, with run-time support, has influenced the organization, flexibility, usefulness, and stability of the Cedar environment. It high-lights the novel system features of Cedar, including automatic storage management of dynamically allocated typed values, a run-time type system that provides run-time access to Cedar data type definitions and allows interpretive manipulation of typed values, and a powerful deuice-independent imaging model that supports the user interface facilities. Using these discussions to set the context, the paper addresses the language and system features and the methodologies used to facilitate the integration of Cedar applications. A comparison of Cedar with other programming environments further identifies areas where Cedar excels and areas where work remains to be done.

We describe a view-management component for interactive 3D user interfaces. By view management, we mean maintaining visual constraints on the projections of objects on the view plane, such as locating related objects near each other, or preventing objects from occluding each other. Our view-management component accomplishes this by modifying selected object properties, including position, size, and transparency, which are tagged to indicate their constraints. For example, some objects may have geometric properties that are determined entirely by a physical simulation and which cannot be modified, while other objects may be annotations whose position and size are flexible. We introduce algorithms that use upright rectangular extents to represent on the view plane a dynamic and efficient approximation of the occupied space containing the projections of visible portions of 3D objects, as well as the unoccupied space in which objects can be placed to

We present a general approach to the dynamic representation of 2D space that is well suited for userinterface layout. We partition space into two distinct categories: full and empty. The user can explicitly specify a set of possibly overlapping upright rectangles that represent the objects of interest. These full-space rectangles are processed by the system to create a representation of the remaining empty space. This representation makes it easy for users to develop customized spatial allocation strategies that avoid overlapping the full-space rectangles. We describe the representation; provide efficient incremental algorithms for adding and deleting full-space rectangles, and for querying the empty-space representation; and show several allocation strategies that the representation makes possible. We present two testbed applications that incorporate an implementation of the algorithm; one shows the utility of our representation for window management tasks; the other applies it to the layout of components in a 3D user interface, based on the upright 2D bounding boxes of their projections.

this paper. APPENDIX All measurements in Figures 4, 5, and 6 are in user mode CPU microseconds on a SPARCstation 2 running running SunOS 4.1.2. We used version 4.1 of the package in Reference 1. The machine had enough memory (64 MB) that paging was not an issue. All programs were compiled with gcc and statically linked. Garbage collection times are included. The tests were run for enough iterations in the same heap to force several collections

Most windowing systems follow the independent overlapping windows approach, which emerged as an answer to the needs of the 80s' applications and technology. Advances in computers, display technology, and the applications demand more functionalityfrom windowmanagement systems. Based on these changes and the problems of current windowing approaches, we have updated the requirements for multiwindow systems to guide new methods of window management. We propose elastic windows with improved spatial layout and rapid multi-window operations. Multi-window operations are achieved by issuing operations on window groups hierarchically organized in a space-filling tiled layout. Sophisticated multi-window operations and spatial layout dynamics helps users to handle fast task-switching and to structure their work environment to their rapidly changing needs. We claim that these multi-window operations and the improved spatial layout decrease the cognitive load on users. Users found our prototype syst...

SMILE is a multi-user software engineering environment that behaves as an intelligent assistant. SMILE presents a `fileless environment', derives and transforms data to shelter users from entering redundant information, automatically invokes programming tools, and actively participates in the software development and maintenance process. Unlike other intelligent assistants, SMILE is not a rule-based environment: its knowledge of software objects and the programming process is hardcoded into the environment. We describe SMILE's functionality and explain how we achieved this functionality without reliance on artificial intelligence technology. The development and maintenance of SMILE is supported in part by the United States Army, Software Technology Development Division of CECOM COMM/ADP, Fort Monmouth, NJ and in part by ZTI-SOF of Siemens AG, Munich, Germany. This paper was written while Dr. Kaiser was a Visiting Computer Scientist at the Software Engineering Institute, Carnegie-Mello...

Sam is an interactive multi-file text editor intended for bitmap displays. A textual command language supplements the mouse-driven, cut-and-paste interface to make complex or repetitive editing tasks easy to specify. The language is characterized by the composition of regular expressions to describe the structure of the text being modified. The treatment of files as a database, with changes logged as atomic transactions, guides the implementation and makes a general ‘undo’ mechanism straightforward. Sam is implemented as two processes connected by a low-bandwidth stream, one process handling the display and the other the editing algorithms. Therefore it can run with the display process in a bitmap terminal and the editor on a local host, with both processes on a bitmap-equipped host, or with the display process in the terminal and the editor in a remote host. By suppressing the display process, it can even run without a bitmap terminal.

Software is multidimensional but the tools that support it are not. The lack of tool support causes the software artifacts representing different dimensions to evolve independently and inconsistently. In order to support the evolution of multidimensional software, an environment must ensure that the different dimensions evolve concurrently. This can be accomplished through an integration framework that maintains consistency of the different dimensions as they evolve. We have build a prototype of such a mechanism by setting up and maintaining constraints among artifacts representing the different software dimensions. This paper describes that prototype and our experiences with it to date. 1

Powerful editing systems for developing complex software documents are difficult to engineer. Besides requiring efficient incremental algorithms and complex data structures, such editors must integrate smoothly with the other tools in the environment, maintain a sharable database of information concerning the documents being edited, accommodate flexible editing styles, provide a consistent, coherent, and empowering user interface, and support individual variations and project-wide configurations. Pan is a language-based editing and browsing system that exhibits these characteristics. This paper surveys the design and engineering of Pan, paying particular attention to a number of issues that pervade the system: incremental checking and analysis, information retention in the presence of change, tolerance for errors and anomalies, and extension facilities.