Composing Software from Multiple Concerns: A Model and Composition Anomalies

Constructing software from components is considered to be a key requirement for managing the complexity of software. Separation of concerns makes only sense if the realizations of these concerns can be composed together effectively into a working program. Various publications have shown that composability of software is far from trivial and fails when components express complex behavior such as constraints, synchronization and history-sensitiveness. We believe that to address the composability problems, we need to understand and define the situations where composition fails. To this aim, in this paper we (a) introduce a general model of multi-dimensional concern composition, and (b) define so-called composition anomalies

An Analysis of Composability and Composition Anomalies

The separation of concerns principle aims at decomposing a given design problem into concerns that are mapped to multiple independent software modules. The application of this principle eases the composition of the concerns and as such supports composability. Unfortunately, a clean separation (and composition of concerns) at the design level does not always imply the composability of the concerns at the implementation level. The composability might be reduced due to limitations of the implementation abstractions and composition mechanisms. The paper introduces the notion of composition anomaly to describe a general set of unexpected composition problems that arise when mapping design concerns to implementation concerns. To distinguish composition anomalies from other composition problems the requirements for composability at the design level is provided. The ideas are illustrated for a distributed newsgroup system

A programming-language extension for distributed real-time systems

In this paper we propose a method for extending programming languages that enables the specification of timing properties of systems. The way time is treated is not language specific and the extension can therefore be included in many existing programming languages. The presented method includes a view on the system development process. An essential feature is that it enables the construction of (hard) real-time programs that may be proven correct independently of the properties of the machines that are used for their execution. It therefore provides a similar abstraction from the execution platform as is normal for non-real-time languages. The aim of this paper is to illustrate the method and demonstrate its applicability to actual real-time problems. To this end we define a simple programming language that includes the timing extension. We present a formal semantics for a characteristic part of the language constructs and apply formal methods to prove the correctness of a small example program. We consider in detail a larger example, namely the mine-pump problem known from the literature. We construct a real-time program for this problem and describe various ways to map the program to an implementation for different platforms

Models for composing software : an analysis of software composition and objects

In this report, we investigate component-based software construction with a focus on composition. In particular we try to analyze the requirements and issues for components and software composition. As a means to understand this research area, we introduce a canonical model for representing software. This model is used to analyze the object-oriented model of software composition

Composing Synchronization and Real-Time Constraints

There have been a number of publications illustrating the successes of object-oriented techniques in creating highly reusable software systems. Several concurrent languages have been proposed for specifying reusable synchronization specifications. Recently, a number of real-time object-oriented languages have been introduced for building object-oriented programs with real-time behavior. Composing and reusing object-oriented programs with both synchronization and real-time constraints has not been addressed adequately, although most real-time systems are concurrent. This paper analyzes the origins of the problems in composing and reusing synchronization and realtime specifications, first as separate concerns, and later as composed behavior. To overcome the so-called inheritance anomaly problems, this paper proposes modular and composable synchronization and real-time specification extensions to the object-oriented model. The applicability of the proposed mechanisms is illustrated through a number of examples

Abstract Composing Synchronization and Real-Time Constraints

There have been a number of publications illustrating the successes of object-oriented techniques in creating highly reusable software systems. Several concurrent languages have been proposed for specifying reusable synchronization specifications. Recently, a number of real-time object-oriented languages have been introduced for building object-oriented programs with real-time behavior. Composing and reusing object-oriented programs with both synchronization and real-time constraints has not been addressed adequately, although most real-time systems are concurrent. This paper analyzes the origins of the problems in composing and reusing synchronization and real-time specifications, first as separate concerns, and later as composed behavior. To overcome the so-called inheritance anomaly problems, this paper proposes modular and composable synchronization and real-time specification extensions to the object-oriented model. The applicability of the proposed mechanisms is illustrated through a number of examples. page 1 1

ARTICLE NO. 0088 Composing Synchronization and Real-Time Constraints

There have been a number of publications illustrating the successes of object-oriented techniques in creating highly reusable software systems. Several concurrent languages have been proposed for specifying reusable synchronization specifications. Recently, a number of real-time object-oriented languages have been introduced for building object-oriented programs with real-time behavior. Composing and reusing object-oriented programs with both synchronization and real-time constraints has not been addressed adequately, although most real-time systems are concurrent. This paper analyzes the origins of the problems in composing and reusing synchronization and realtime specifications, first as separate concerns, and later as composed behavior. To overcome the so-called inheritance anomaly problems, this paper proposes modular and composable synchronization and real-time specification extensions to the object-oriented model. The applicability of the proposed mechanisms is illustrated through a number of examples. © 1996 Academic Press, Inc. 1