Preamble
All too often choosing a development method is seen as a matter of faith, to be enforced uniformly whatever the problems at hand.
As it happens, this dogmatic approach is not limited to procedural methodologies but also affect some agile factions supposedly immunized against such rigid stances.
A more pragmatic approach should use simple and robust principles to pick and apply methods depending on development problems.
Iterative vs Phased Development
Beyond the variety of methodological dogmas and tools, there are only two basic development patterns, each with its own merits.
Iterative developments are characterized by the same activity (or a group of activities) carried out repetitively by the same organizational unit sharing responsibility, until some exit condition (simple or combined) verified.
Phased developments are characterized by sequencing constraints between differentiated activities that may or may not be carried out by the same organizational units. It must be stressed that phased development models cannot be reduced to fixed-phase processes (e.g waterfall); as a corollary, they can deal with all kinds of dependencies (organizational, functional, technical, …) and be neutral with regard to implementations (procedural or declarative).
A straightforward decision-tree can so be built, with options set by ownership and dependencies:
Shared Ownership: Agile Schemes
A project’s ownership is determined by the organizational entities that are to validate the requirements (stakeholders), and accept the products (users).
Iterative approaches, epitomized by the agile development model, is to be the default option for projects set under the authority of single organizational units, ensuring shared ownership and responsibility by business analysts and software engineers.
Projects set from a business perspective are rooted in business processes, usually through users’ stories or use cases. They are meant to be managed under the shared responsibility of business analysts and software engineers, and carried out independently of changes in architecture capabilities (a,b).
Projects set from a system perspective potentially affect architectures capabilities. They are meant to be managed under the responsibility of systems architects and carried out independently of business applications (d,b,c).
Transparency and traceability between the two perspectives would be significantly enhanced through the use of normalized capabilities, e.g from the Zachman’s framework:
- Who: enterprise roles, system users, platform entry points.
- What: business objects, symbolic representations, objects implementation.
- How: business logic, system applications, software components.
- When: processes synchronization, communication architecture, communication mechanisms.
- Where: business sites, systems locations, platform resources.
It must be noted that as far as architecture and business driven cycles don’t have to be synchronized (principle of continuous delivery), the agile development model can be applied uniformly; otherwise phased schemes must be introduced.
Cross Dependencies: Phased Schemes
Cross dependencies mean that, at some point during project life-cycle, decision-making may involve organizational entities from outside the team. Two mechanisms have traditionally been used to cope with the coordination across projects:
- Fixed phases processes (e.g Analysis/Design/Implementation) have shown serious shortcomings, as illustrated by notorious waterfall.
- Milestones improve on fixed schemes by using check-points on development flows instead of predefined activities. Yet, their benefits remain limited if development flows are still defined with regard to the same top-down and one-fits-all activities.
Model based systems engineering (MBSE) offers a way out of the dilemma by defining flows directly from artifacts. Taking OMG’s model driven architecture (MDA) as example:
- Computation Independent Models (CIMs) describe business objects and activities independently of supporting systems.
- Platform Independent Models (PIMs) describe systems functionalities independently of platforms technologies.
- Platform Specific Models (PSMs) describe systems components as implemented by specific technologies.
Projects can then be easily profiled with regard to footprints, dependencies, and iteration patterns (domain, service, platform, or architecture, …).
That understanding puts the light on the complementarity of agile and phased solutions, often known as scaled agile.
Further Reading
- Thread
- How To Pick Development Models
- Products, Projects, Processes
- System Engineering
- Projects as non-zero sum games
- Projects Have to Liaise
- Phased Yet Lean Processes
- Milestones
- Work Units
- Models in Driving Seats
- Iterative Processes
- Development Patterns & Strategies
- Spaces, Paths, Paces (Part 1)
- Spaces, Paths, Paces (Part 2)