OO SYSTEMS DEVELOPMENT

B

Y

B

RIAN

HENDERSON-SELLERS

METHOD ENGINEERING FOR

OO SYSTEMS DEVELOPMENT or the past 15 years, many proposed OO methodologies have sought to deliver full life-cycle support for systems development using OO tools. Many are highly prescriptive, that is, the methodology elements are highly interconnected. This inherent complexity makes it difficult for a methodology to be adapted to project-specific circumstances, especially (and usually) when project managers and developers are advised by the methodology’s creator that they must use all or none of the components of the methodology. Indeed, even with the advent of agile methodologies, frequently touted by their developers as offering more people-focus and flexibility, proponents often say an agile methodology like extreme programming (XP) must be followed in its entirety and that XP without, say, pair programming is not XP.

F

This metamodelbased framework helps distill the key ingredients in software engineering processes in ways that facilitate method engineering, along with process understanding.

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less popular alternative is provided by way of the theory of method engineering, which subsumes process engineering and product engineering. While discussed in the academic literature and implicit in ISO standards like 12207, it does not seem to be widely acknowledged or practiced by software engineers. Method engineering offers flexibility but is often viewed (unfairly) as also having a costly overhead (in terms of time, money, and people). Method engineering contrasts with the use of out-of-the-box methodologies presented as ready for immediate use. The cost and effort to the organization are often totally ignored when such a prepackaged methodology is used and found to be an inappropriate description of the system-user company’s business processes. Here, I explore (both theoretically and practically) the rationale behind a method-engineering approach, as well as its potential adoption by systems development teams.

A

Stages provide macro organization to the

Essential Process Components

Guidelines

Producers

perform

Work Units

help to

produce

create evaluate iterate maintain

Work Products are documented using

Languages

construction guidelines—both found in OPF.

Figure 1. The five major metaclasses in OPF [4].

OPEN Process Framework Method Engineering As noted earlier, I bias my discussion of how to A methodology (or method) includes both process apply method engineering toward the more novel aspects and work-product descriptions. Considering and interesting aspects of process engineering. The not only the methodology per se but the components definition of “process” should include not only that go together to form it, we can use the ideas of descriptions of phases, activities, tasks, and techmethod engineering to construct a full methodology niques but issues associated with human resources, from the elements, also known as method fragments. technology, and the life-cycle model to be used. In Typically, method fragments are stored in a reposi- contrast, the capability assessment and standards tory underpinned by a metamodel. Situational (or communities tend to use the term “process” at a situated) method engineering is defined as the cre- smaller scale, more like “activity” in OPF and “disciation of a method(ology) specifically attuned to the pline” in the Object Management Group’s Software project at hand [1, 2, 11]. I refer to both kinds of method engiFramework/metamodel Repository of process components neering—situational and nonsituational—under the generic label of method engineering. Concept A Methodological approaches Example 1 Example 2 Concept B of Concept A of Concept .A. . .. . . compatible with the theory of Example 1 Example 2 Concept C of Concept B of Concept .B. . .. . . method engineering include Role 1 Example 1 Example 2 Process Instance Evolution (PIE) of Concept C of Concept .C . . .. . . Role 2 [3], the ISO/IEC 12207 standard Example 1 Example 2 Role 1 Role 1 . . . .. . . [10], and, in the OO arena, the Example 1 Example 2 Role 2 Object-oriented Process, EnviRole 2 . . . .. . . ronment, and Notation (OPEN) framework and the OPEN Process Framework (OPF) [4]. an instance Engineering Figure 2. ofCreating However, these approaches tend to focus on the Process a process from its (SPEM). process-engineering elements of method engineering Metamodel metamodel [4]. and assume that the product side is addressed through Defining process as the modeling languages like UML. While ISO 12207 transformation of input to output (as in and OPF have many similarities in scope and granu- ISO/IEC12207 [10]), the notions of process and larity, the ISO model lacks a metamodel and adequate process improvement in many ISO standards and 74

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Software Process Improvement (SPI) contexts underline the granularity of interest often referred to as method fragment, method chunk (such as [11]), or process component (such as [4]). Here, I investigate how process engineering can be accomplished in the context of OPF. An important part of OPF is its comprehensive library of process components used in a variety of software projects and that cover changes in technology. OPF includes five major classes of these components (see Figure 1), all defined in the metamodel: Work Product. “A Work Product is anything of value produced during the development process” [4]. Work Products are the result of Producers (people) executing Work Units and are used either as input to other Work Units or delivered to clients. They also include externally supplied (such as by users) preexisting artifacts used as inputs to Work Units. Producer. “A Producer is responsible for creating, evaluating, iterating, and maintaining Work Products” [4]. Work Unit. A Work Unit is a functionally cohesive operation performed by a Producer. The three major classes of Work Unit are Activity, Task, and Technique. Language. A Language is used to document a Work Product. Stage. A Stage is an identified and managed duration within the process or a point in time at which some achievement is recognized.

THE PROCESS IS CREATED BY MEMBERS OF THE ORGANIZATION ITSELF, THUS GIVING THEM OWNERSHIP OF THE RESULTING OPEN PROCESS.

The OPF repository (see Figure 2) contains a range of predefined instances for each class and subclass in the metamodel; for example, there are about 30 predefined instances of Activity, 160 instances of Task, 200 instances of Techniques, and 76 instances of Role. In addition, users can add extra components from their own best practice. Typically, someone in the development organization, in the role of process engineer or method engineer, selects appropriate process/methodology components from the repository and combines them to form an actual process within the methodology (see Figure 3). This procedure is often called process construction and may (in one step) create a project-specific process directly or a two-step process to construct first an organizational standard process and then a project-specific process. Construction decisions need to account for myriad variables pertinent to the development organization. Variables include, but are not restricted to, Capability Maturity Model level of COMMUNICATIONS OF THE ACM October 2003/Vol. 46, No. 10

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Task

1

Code Construct the object model Develop and implement resource allocation plan develop iteration plan develop timebox plan set up metrics collection program specify quality goals Evaluate quality Identify CIRTs (Class, Instance, Role, orType) Map roles onto classes Test Write manuals and other documentation key 1. Project planning 2. Modeling and implementation: OO analysis, design, programming 3. Verification and validation

2

Activity 3 4 5

x x x x x x x

x

x x

x x

x x(OOP) x x

4. User review 5. Consolidation 6. Evaluation

Table 1. Task/Activity matrix example appropriate for a small process in which the requirements are set [7].

maturity, available skills, available tools, quality desired, time scales, degree of ceremony, and number of people on the development team. While most process construction today is carried out by a specialist (the process/method engineer), emerging embryonic software tools assist this engineer in doing it effectively and efficiently. Other ideas proposed in the academic literature not yet fully utilized include the Method Engineering Process Model of [11] and the method assembly rule set (specified using a formal language) of [1]. Each process component should be optimal, say, the best set of Work Units, Activities, Tasks, and Techniques. OPEN recommends construction of a number of matrices linking, for example, Activities with Tasks and Tasks with Techniques. The possibility values in these matrices indicate the likelihood of the effectiveness of each individual pair [8]. These values should be tailored to a specific organization or a specific project. While five levels—mandatory, recommended, optional, discouraged, forbidden—are recommended in published texts, I personally encourage individual organizations to use the matrices for process construction at the project level, perhaps using only two (use/do not use) or three (use/do not use/optional) values. Table 1 outlines typical Task/Activity pairs for a hypothetical process to build a small piece of software when the requirements are fixed. I have identified eight appropriate Tasks for the six selected Activities. To fulfill these Tasks, a number of Techniques must be identified by the process engineer. In all, 25 are selected (in this example), as shown in Table 2. Finally, some 2. Technique/Task time sequencing is added by Tablematrix for the same using the Stage class of the example as in Table 1 [7]. 76


metamodel, as in Figure 1. The synergy between the stage view and the process elements results in an overall OPEN x process that may be oriented toward a particular organization or project or, more broadly, a specific domain (such as Web applications, business reengineering, or real-time software) (see the sidebar “Examples of Method/Process x Engineering” for application domains). Once developers determine which process they’ll use, this process is enacted on a real project (includx ing a method/process instance, as shown in Figure 3) through the allocation of resources, including roles played by personnel and time scheduling, as well as money and hardware. The method/process engineering approach has many advantages over an out-of-the-box approach. The process is created by members of the organization itself, thus giving them ownership of the resulting OPEN process; everyone has bought into it because they have had the opportunity to contribute to its formation. Along with local ownership, there is also global support because the framework and the repository from which the process was constructed are identical to the ones used by many other organizations worldwide. One can thus readily participate in user group meetings and forums. In addition, there’s a good chance that 6

Task Techniques Abstract class identification Abstraction utilization Class internal design Class naming Collaborations analysis Complexity measurement Contract specification Coupling measurement CRC card modeling Generalization and inheritance identification Implementation of services Implementation of structure Inspections Interaction modeling Package and subsystem testing Prototyping Relationship modeling Responsibility identification Role modeling Service identification State modeling Textual analysis Timeboxing Unit testing Walkthroughs key 1. Code 2. Construct the object model 3. Develop and implement resource allocation plan 4. Evaluate quality

1

x

2 x x x x x

3 4

5

6 7

x x x

x

x

x x

x x

x x

x x

x x

x

x x x x x x x x x x

x

x

x x

x x x 5. Identify CIRTs 6. Map roles onto classes 7. Test

x x

OPEN Process Framework Method/Process Metamodel

instance of

Methodology (Including Process)

instance of

Process Components are instances of

Repository of Predefined Method/ Process Components Construction Guidelines

Step 1. Method/ Process Engineer selects Method/Process Components and constructs Methodology

uses

Step 2. Project Manager

creates Method/Process Instance by allocating specific resources

Method/Process Instance

new hires will have the necessary skills gained from a worldwide community standard rather than from some idiosyncratic inhouse approach. Finally, since many such process instances can be created from a common framework, process engineers can create a family of processes for various industrial demands, including, for example, safety-critical software, background financial processing, and real-time stock market modeling. c Figure 3. Creating a project-specific process/method from the OPEN Process Framework.

THERE’S A GOOD CHANCE THAT NEW HIRES WILL HAVE THE NECESSARY SKILLS GAINED FROM A WORLDWIDE COMMUNITY STANDARD RATHER THAN FROM SOME IDIOSYNCRATIC IN-HOUSE APPROACH.

References 1. Brinkkemper, S. Method engineering: Engineering of information systems development methods and tools. Inf. Software Technol. 38. 4 (Apr. 1996), 275–280. 2. Brinkkemper, S., Saeki, M., and Harmsen, F. Assembly techniques for method engineering. In Proceedings of the Conference on Advanced Information Systems Engineering (Pisa, Italy, June 8–12). Springer Verlag, Berlin, 1998, 381–400. 3. Cunin, P.-Y., Greenwood, R., Francou, L., Robertson, I., and Warboys, B. The PIE Methodology: Concept and application. In Proceedings of the 8th European Workshop on Software Process Technology (Witten, Germany, June 19–21). Springer-Verlag, Berlin, 2001, 3–26. 4. Firesmith, D. and Henderson-Sellers, B. The OPEN Process Framework. An Introduction. Addison-Wesley, Harlow, Herts, U.K., 2002. 5. Haire, B., Lowe, D., and Henderson-Sellers, B. Supporting Web development in the OPEN process: Additional roles and techniques. In Object-Oriented Information Systems, LNCS 2425, Z. Bellahsene, D. Patel, and C. Rolland, Eds. Springer-Verlag, Berlin, 2002, 82–94. 6. Henderson-Sellers, B. Agile or rigorous OO methodologies: Getting the best of both worlds. Cutter IT J. 15, 1 (Jan. 2002), 25–33. 7. Henderson-Sellers, B. Process metamodelling and process construction: Examples using the OPEN Process Framework (OPF). Annals Software Engin. 14 (Dec. 2002), 341–362. 8. Henderson-Sellers, B., Haire, B., and Lowe, D. Using OPEN’s deontic matrices for e-business. In Engineering Information Systems in the Internet Context, C. Rolland, S. Brinkkemper, and M. Saeki, Eds. Kluwer Academic Publishers, Boston, 2002, 9–30. 9. Henderson-Sellers, B. and Serour, M. Creating a process for transitioning to object technology. In Proceedings of the 7th Asia-Pacific Software Engineering Conference (Singapore, Dec. 5–8). IEEE Computer Society Press, Los Alamitos, CA, 2000, 436–440. 10. International Standards Organization. Information Technology: Software Life-cycle Processes (ISO/IEC12207). Geneva, Switzerland, 1995.

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11. Ralyté, J. Requirements definition for the situational method engineering. In Engineering Information Systems in the Internet Context, C. Rolland, S. Brinkkemper, and M. Saeki, Eds. Kluwer Academic Publishers, Boston, 2002, 127–152. 12. Serour, M., Henderson-Sellers, B., Hughes, J., Winder, D., and Chow, L. Organizational transition to object technology: Theory and practice. In Object-Oriented Information Systems, LNCS 2425, Z. Bellahsene, D. Patel, and C. Rolland, Eds. Springer-Verlag, Berlin, 2002, 229–241.

Brian Henderson-Sellers ([email protected]) is a professor of information systems and Director of the Centre for Object Technology Applications and Research in the Faculty of Information Technology at the University of Technology, Sydney, Australia. © 2003 ACM 0002-0782/03/1000 $5.00

Examples of Method/Process Engineering

T

he following illustrative examples of method/process engineering are outlined in terms of process instances of OPEN, including an application in Web development, what a process for inserting a process into an organization might look like, an agile application, and how that application can be used with agents. Web development. How is Web development different from traditional software development? Differences include shorter time scales, a much tighter link between business models and the software architecture, and greater importance on the content management aspects of Web sites for evaluating an application’s business success. Each of these factors has a potential effect on the development process and hence on the form taken by an OPEN instance through the method/processing engineering approach described here. How Web OPEN was created is described in a number of articles, including [5, 8]. The new tasks and techniques introduced in this Web-focused project are summarized in the table here. Organizational transition. This process is an interesting use of OPF. Rather than choosing instances of Work Units from the repository for creating a software-development process, a process is created by the process engineer to support an organization’s transition from one culture to another—in this case, from non-OO to OO/CBD (component-based development). The process thus constructed [9] can be used to migrate an orgaNew activity • Web site management nization from a non-process-focused environment to one in which the OO/CBD culture is inculcated and the OPEN process (an instance New tasks • Design content management strategy tailored for software development this time) is used. The experience • Create content (on Web site) of one organization—a legal publisher—in adopting OPEN was docu• Undertake content management • Build white site/wireframe prototype mented in [12]. • Design Web site standards • Design Web site architecture Agile processes. To construct an agile instantiation of OPF, one • Create navigation map for Web site might identify, say, four major activities: coding, designing, review• Define acceptance criteria for Web site • Define Web site testing strategy ing, and testing. The associated tasks and techniques discovered are • Undertake testing of Web site usually determined more informally, in contrast to the formal matrix New techniques template approach outlined in this article. These tasks include, for • Web metrics example, those recommended in XP (such as pair programming, the • Web template • Branding planning game, system metaphors, and refactoring)—all elements I “borrowed” from XP for inclusion in the more recent versions of the New roles • Web designer (HTML/page construction) OPF. The current OPF repository thus readily supports agile or light• Graphic designer (visuals) • Prototype developer weight process construction [6]. In this newer, agile environment, process engineers might also New Work Units useful in Web wish to augment these OPF process components with new ones of development projects [7]. their own design or choosing. Agent-oriented methodologies. While I focus here on the OO software development environment, a natural extension—in the form of agent-oriented methodologies—is beginning to emerge into the mainstream of computing. As part of this emergence, we have created an initial version of OPEN to specifically support agent-oriented software systems development. In doing so, 13 new tasks and 10 new techniques were identified as needing to be added to the OPF repository. They focus on supporting the internal architecture of agents, including deliberative and reactive reasoning and architectural models, including Beliefs, Desire, Intentions, without having to change the metamodel. Work is ongoing in the Agent OPEN project based at the Centre for Object Technology Applications and Research. c

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