Deploy Along The Grain

Alias: DeployPeopleAlongTheGrainOfTheDomain, One Person / Many Hats

One person, many hats.

... in the past, the roles of analysis, design and implementation have been split among different people.

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Some of the most powerful design insights come late in the design cycle, particularly during the phase we affectionately call "maintenance." But traditional staffing profiles deploy the most skilled designers at the front-end of the life cycle, leaving the later phases to "maintenance engineers."

Valuable architectural insight tends to emerge late in the life cycle, as a result of having addressed requirements from concrete, successive problems drawn from a given domain. It is then that a system can be refactored to consolidate design insight and polish reusable artifacts. (More can be said about this, but that's another tale.)

Such insight can best be harvested if people are deployed along the grain of the domain, and a given individual has responsibility for a well-defined part of it. Organizational categories like Analyst, Designer, Coder, Maintainer, and Reuse Expert can cut across the grain, and greatly increase organizational communication overhead and inertia. However, when responsibility for all these functions for a given part of the system is vested in a single person, the communication overhead for redesign with that part of the system can be largely intracranial. This is a one person/many hats strategy. A single individual can cope far more quickly with on-going bi-directional tensions between top-down elegance and bottom-up detail than can a functionally partitioned organization. Such a person can develop a more comprehensive sense of the possibilities that the design space allows, and exploit these to develop more genuinely durable artifacts.

A reusable API or object-oriented framework is, in many respects, a domain-specific language. Given this, Wirth's classic admonition that language design is better done by a single guiding intelligence, rather than by a committee, applies. (See the Pascal quote in ArchitectControlsProduct.)

Small teams deployed along the grain should be able to glean similar benefits. Team members would be responsible for distinct parts of their team's domain. Metafunctions like pure management and documentation might be factored and assigned to additional individuals. Interpersonal communication would primarily be concerned with interface negotiation, and not become mired with approving changes to internals.

The key here is committing talented designers to a part of the system, and keeping them there until late in the life cycle, when hindsight is available from addressing a range of design issues.

There is some commonality between this and Alexander's Architect/Builder notions as well, as in ArchitectAlsoImplements. This sort of personnel deployment strategy is a de facto favorite in academic environments and in some small organizations, both of which often exhibit marked productivity advantages over traditional industrial organizations. If an organization really wants to get truly reusable software, it will have to be willing to budget time and talent in such a way as to exploit the insights that lead to it at the point in the life cycle where they become available. But reuse isn't something that can itself easily be factored into its own department. The people who build and maintain something in the first place have the best, most intimate knowledge of how to generalize it.

There is certain amount of Alexandrian wiggle room with regard to the question of how one knows where the grain is, especially at the onset of a project. Often its something people settle into.

Therefore:

Deploy people along the grain of the domain. That is to say, give them dedicated, long term responsibility for a manageable piece of the system, thereby enabling them to exploit opportunities to consolidate and improve the reusability of their parts of the system as experience accrues.

Frequently, there will be significant degree of self-selection at work when this patterns is employed, a variation on SelfSelectingTeam. Managers should keep a watchful eye open for the emergence of new roles, as people elect to spontaneously fill them.

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This pattern plays out in specializations such as OwnerPerDeliverable and more specifically CodeOwnership. It should be contrasted with the approach suggested by Extreme Programming [BibRef-Beck1999] advocates, though the effective divisions of labor may not be as different as a simple-minded comparison might suggest.

This pattern is constrained by the forces of ConwaysLaw; or perhaps it is the embodiment of it. You also need to take people's skills into account, as stated in SkillMix [BibRef-Cockburn1996] or as in SubsystemBySkill.

This pattern originally appeared as Brian Foote's DeployPeopleAlongTheGrainOfTheDomain at PLoP 2000. The material was drawn largely intact from a discussion of Reuse Teams that took place in early December of 1993 in either comp.objector on an early incarnation of the patterns mailing list.