Architectural Bleuprints - the 4+1 View Model of Software Architecture
Paper published in IEEE Software 12 (6) November 1995, pp. 42-50
Architectural Blueprints—The “4+1” View Model of Software Architecture
Philippe Kruchten Rational Software Corp.
Abstract This article presents a model for describing the architecture of software-intensive systems, based on the use of multiple, concurrent views. This use of multiple views allows to address separately the concerns of the various ‘stakeholders’ of the architecture: end-user, developers, systems engineers, project managers, etc., and to handle separately the functional and non functional requirements. Each of the five views is described, together with a notation to capture it. The views are designed using an architecture-centered, scenariodriven, iterative development process. Keywords: software architecture, view, object-oriented design, software development process
Introduction
We all have seen many books and articles where one diagram attempts to capture the gist of the architecture of a system. But looking carefully at the set of boxes and arrows shown on these diagrams, it becomes clear that their authors have struggled hard to represent more on one blueprint than it can actually express. Are the boxes representing running programs? Or chunks of source code? Or physical computers? Or merely logical groupings of functionality? Are the arrows representing compilation dependencies? Or control flows? Or data flows? Usually it is a bit of everything. Does an architecture need a single architectural style? Sometimes the architecture of the software suffers scars from a system design that went too far into prematurely partitioning the software, or from an over-emphasis on one aspect of software development: data engineering, or run-time efficiency, or development strategy and team organization. Often also the architecture does not address the concerns of all its “customers” (or “stakeholders” as they are called at USC). This problem has been noted by several authors: Garlan &
Architectural Blueprints—The “4+1” View Model of Software Architecture
Philippe Kruchten Rational Software Corp.
Abstract This article presents a model for describing the architecture of software-intensive systems, based on the use of multiple, concurrent views. This use of multiple views allows to address separately the concerns of the various ‘stakeholders’ of the architecture: end-user, developers, systems engineers, project managers, etc., and to handle separately the functional and non functional requirements. Each of the five views is described, together with a notation to capture it. The views are designed using an architecture-centered, scenariodriven, iterative development process. Keywords: software architecture, view, object-oriented design, software development process
Introduction
We all have seen many books and articles where one diagram attempts to capture the gist of the architecture of a system. But looking carefully at the set of boxes and arrows shown on these diagrams, it becomes clear that their authors have struggled hard to represent more on one blueprint than it can actually express. Are the boxes representing running programs? Or chunks of source code? Or physical computers? Or merely logical groupings of functionality? Are the arrows representing compilation dependencies? Or control flows? Or data flows? Usually it is a bit of everything. Does an architecture need a single architectural style? Sometimes the architecture of the software suffers scars from a system design that went too far into prematurely partitioning the software, or from an over-emphasis on one aspect of software development: data engineering, or run-time efficiency, or development strategy and team organization. Often also the architecture does not address the concerns of all its “customers” (or “stakeholders” as they are called at USC). This problem has been noted by several authors: Garlan &
References: 1. 2. 3. 4. 5. 6. 7. 8. D. Garlan & M. Shaw, “An Introduction to Software Architecture,” Advances in Software Engineering and Knowledge Engineering, Vol. 1, World Scientific Publishing Co. (1993). D. E. Perry & A. L. Wolf, “Foundations for the Study of Software Architecture,” ACM Software Engineering Notes, 17, 4, October 1992, 40-52. Ph. Kruchten & Ch. Thompson, “An Object-Oriented, Distributed Architecture for Large Scale Ada Systems,” Proceedings of the TRI-Ada ’94 Conference, Baltimore, November 6-11, 1994, ACM, p.262-271. G. Booch: Object-Oriented Analysis and Design with Applications, 2nd. edition, Benjamin-Cummings Pub. Co., Redwood City, California, 1993, 589p. K. P. Birman, and R. Van Renesse, Reliable Distributed Computing with the Isis Toolkit, IEEE Computer Society Press, Los Alamitos CA, 1994. K. Rubin & A. Goldberg, “Object Behavior Analysis,” CACM, 35, 9 (Sept. 1992) 48-62 B. I. Witt, F. T. Baker and E. W. Merritt, Software Architecture and Design—Principles, Models, and Methods, Van Nostrand Reinhold, New-York (1994) 324p. D. Garlan (ed.), Proceedings of the First Internal Workshop on Architectures for Software Systems, CMU-CS-TR-95-151, CMU, Pittsburgh, 1995. 15