Current configuration management systems promote workspaces that isolate developers from each other. This isolation is both good and bad. It is good, because developers make their changes without any interference from changes made concurrently by other developers. It is bad, because not knowing which artifacts are changing in parallel regularly leads to problems when changes are promoted from workspaces into a central configuration management repository. Overcoming the bad isolation, while retaining the good isolation, is a matter of raising awareness among developers, an issue traditionally ignored by the discipline of configuration management. To fill this void, we have developed Palantr, a novel workspace awareness tool that complements existing configuration management systems by providing developers with insight into other workspaces. In particular, the tool informs a developer of which other developers change which other artifacts, calculates a simple measure of severity of those changes, and graphically displays the information in a configurable and generally non-obtrusive manner. To illustrate the use of Palantr, we demonstrate how it integrates with two representative configuration management systems.

Merging and splitting source code entities is a common activity during the lifespan of a software system; as developers rethink the essential structure of a system or plan for a new evolutionary direction, so must they be able to reorganize the design artifacts at various abstraction levels as seems appropriate. However, while the raw effects of such changes may be plainly evident in the new artifacts, the original context of the design changes is often lost. That is, it may be obvious which characters of which files have changed, but it may not be obvious where or why moving, renaming, merging, and/or splitting of design elements has occurred. In this paper, we discuss how we have extended origin analysis [1], [2] to aid in the detection of merging and splitting of files and functions in procedural code; in particular, we show how reasoning about how call relationships have changed can aid a developer in locating where merges and splits have occurred, thereby helping to recover some information about the context of the design change. We also describe a case study of these techniques (as implemented in the Beagle tool) using the PostgreSQL database system as the subject.

During software evolution, information about changes between different versions of a program is useful for a number of software engineering tasks. For many of these tasks, a purely syntactic differencing may not provide enough information for the task to be performed effectively. This problem is especially relevant in the case of object-oriented software, for which a syntactic change can have subtle and unforeseen effects. In this paper, we present a technique for comparing object-oriented programs that identifies both differences and correspondences between two versions of a program. The technique is based on a representation that handles object-oriented features and, thus, can capture the behavior of object-oriented programs. We also present JDIFF, a tool that implements the technique for Java programs, and empirical results that show the efficiency and effectiveness of the technique on a real program. 1.

Superimposition is a composition technique that has been applied successfully in many areas of software development. Although superimposition is a general-purpose concept, it has been (re)invented and implemented individually for various kinds of software artifacts. We unify languages and tools that rely on superimposition by using the language-independent model of feature structure trees (FSTs). On the basis of the FST model, we propose a general approach to the composition of software artifacts written in different languages, Furthermore, we offer a supporting framework and tool chain, called FEATUREHOUSE. We use attribute grammars to automate the integration of additional languages, in particular, we have integrated Java, C#, C, Haskell, JavaCC, and XML. Several case studies demonstrate the practicality and scalability of our approach and reveal insights into the properties a language must have in order to be ready for superimposition. 1.

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 describes an automated tool called Dex (Difference extractor) for analyzing syntactic and semantic changes in large C-language code bases. It is applied to patches obtained from a source code repository, each of which comprises the code changes made to accomplish a particular task. Dex produces summary statistics characterizing these changes for all of the patches that are analyzed. Dex applies a graph differencing algorithm to abstract semantic graphs (ASGs) representing each version. The differences are then analyzed to identify higher-level program changes. We describe the design of Dex, its potential applications, and the results of applying it to analyze bug fixes from the Apache and GCC projects. The results include detailed information about the nature and frequency of missing condition defects in these projects. 1.

Previous taxonomies of software evolution have focused on the purpose of the change (i.e., the why) rather than the underlying mechanisms. This paper proposes a taxonomy of software evolution based on the characterizing mechanisms of change and the factors that influence these mechanisms. The taxonomy is organized into the following logical groupings: temporal properties, objects of change, system properties, and change support. The ultimate goal

Three-way merging is a technique that may be employed for reintegrating changes to a document in cases where multiple independently modified copies have been made. While tools for three-way merge of ASCII text files exist in the form of the ubiquitous di# and patch tools, these are of limited applicability to XML documents.

Software evolution research is limited by the amount of information available to researchers: Current version control tools do not store all the information generated by developers. They do not record every intermediate version of the system issued, but only snapshots taken when a developer commits source code into the repository. Additionally, most software evolution analysis tools are not a part of the day-to-day programming activities, because analysis tools are resource intensive and not integrated in development environments. We propose to model development information as change operations that we retrieve directly from the programming environment the developers are using, while they are effecting changes to the system. This accurate and incremental information opens new ways for both developers and researchers to explore and evolve complex systems.

www.iam.unibe.ch/∼scg Abstract. Real world software systems change continuously to meet new demands. Most programming languages and development environments, however, are more concerned with limiting the effects of change rather than enabling and exploiting change. Various techniques and technologies to exploit change have been developed over the years, but there exists no common support for these approaches. We propose Changeboxes as a general-purpose mechanism for encapsulating change as a firstclass entity in a running software system. Changeboxes support multiple, concurrent and possibly inconsistent views of software artifacts within the same running system. Since Changeboxes are first-class, they can be manipulated to control the scope of change in a running system. Furthermore, Changeboxes capture the semantics of change. Changeboxes can be used, for example, to encapsulate refactorings, or to replay or analyze the history of changes. In this paper we introduce Changeboxes by means of a prototype implementation. We illustrate the benefits that Changeboxes offer for evolving software systems, and we present the results of a preliminary performance evaluation that assesses the costs associated with Changeboxes while suggesting possible strategies for improvement. 1