We present a new approach to the control of versions of software and other hierarchically structured entities. Any part of a system, from the smallest component to a complete system, may exist in different versions. The set of all possible versions under the refinement relation forms a partial order (in fact, a lattice). The fact that version V approximates version V in this order means that V is relevant to V in this sense: when constructing version V of a system, we can sometimes use version V of a component if nothing more appropriate is available. More precisely, a particular version of an entire system is formed by combining the most relevant existing versions of the various components of the system. We call this the variant structure principle; it makes precise the idea that components of a given version of the system can be inherited by more refined versions of the system.

The areas of application of hypermedia technology, combined with the capabilities that hypermedia provides for manipulating structure, create an environment in which version control is very important. A hypermedia version control framework has been designed to specifically address the version control problem in open hypermedia environments. One of the primary distinctions of the framework is the partitioning of hypermedia version control functionality into intrinsic and application-specific categories. The version control framework has been used as a model for the design of version control services for a hyperbase management system that provides complete version support for both data and structural entities. In addition to serving as a version control model for open hypermedia environments, the framework offers a clarifying and unifying context in which to examine the issues of version control in hypermedia.

The paper introduces a version management model which exploits knowledge about the contents of documents. This is in contrast to most existing models which basically consider versioned objects as flat (attributed) files. The benefits of the approach are illustrated by describing some sample operations which are not possible with a conventional model. The paper then discusses a feasible implementation of the model on top of an existing object-oriented data base management system. Finally, it discusses related work and indicates how a sophisticated configuration management system is being built on top of the version management system.

The Software Environments Project at the Software Engineering Institute has found considerable progress concerning support for software configuration management (CM) in environments and tools. This paper's intent is to highlight a spectrum of features provided by existing CM systems. The spectrum shows features as being extensions or generalizations of other features and these extensions represent the progress. As part of presenting the features, the scope of issues concerning users of CM systems is discussed. No single CM system provides all the functionality required by the different kinds of users of CM systems. Rather,

This paper describes the main components of the environment and outlines how they support maintenance of large software systems. CAPITL was designed with four principles in mind.

The UNIX filesystem supports a fixed set of attributes for filesystem objects, stored in inodes and directory entries. The (path-)name attribute is the sole means to identify and access a filesystem object. This turns out to be a rather severe limitation for certain complex applications such as large scale software development, where software objects typically evolve in a considerable number of versions. An approach to improve the situation is introduced by the attribute filesystem (AFS), the system described in this paper. The AFS combines the notion of immutable objects (versions) with the possibility to attach any number of user-definable attributes to any attributed software object (ASO). AFS objects can be identified by specifying any set of attribute value(s) as retrieve pattern. The name of an AFS object is treated as just another attribute. The AFS is equipped with a proper retrieve interface that allows non-unique identification of sets of objects and provides operations on th...

this document must be referred to ESD/AVS. Software Engineering Institute Carnegie Mellon University Pittsburgh, Pennsylvania 15213 1. Introduction

Software manufacture is the process of building or re-building a large software system from myriad components. The UNIX make program is the most well-known software manufacture tool. Make and similar systems have sev eral deficiencies when used for complex multi-language, multi-subsystem programs; this work addresses those problems related to abstraction mechanisms. Particular problem areas discussed include specifying indirect and derived dependencies, manufacture subprocesses, and handling systems composed of independently-developed subsystems.

Softwaremanufacture is the process of building or re-building a large software system from myriad components. The UNIX make program is the most well-known software manufacture tool. One deficiencyof make and similar systems is that theymanage only a single dependencyrelation. This paper shows howtosolveseveral software manufacture problems by generalizing such tools to support additional relations and relational expressions. Keywords and phrases: relational algebra, configuration management, software manufacture, programming environments, abstraction, make program, Computing Reviews categories: D.2.6 (Software Engineering: Programming Environments) . D.2.9 (Software Engineering: Management - Software Configuration Management) . General Terms: Design Relations Page i Table of Contents 1Introduction ............................................................................................................ 1 1.1 Context and Background .................................................

Software Configuration Management (SCM) is an important discipline in professional software development and maintenance. The importance of SCM has increased as programs have become larger, more long lasting, and more mission and life critical. This article discusses the evolution