What Makes a Good Architecture?
There is no architecture that is inherently good or bad.
An architecture is more or less suitable depending on its stated purpose and goals.
For example, a distributed 3-tier client-server architecture may be suitable for an enterprise finance management system but may not be suitable for an avionics application.
Architecture can be evaluated, but the evaluation must be done in the context of specific goals.
Rules of Thumb
Rules of thumb are principles that can be broadly applied when designing an architecture.
- They are not intended to be strictly accurate or reliable for every situation.
- Failure to apply a rule of thumb does not necessarily mean that the architecture is flawed.
Rules of thumb can be categorized into:
- Process recommendations
- Structural (product) recommendations
Process Recommendations
- The architecture team should have the functional requirements and a prioritized list of quality attributes that the system must satisfy.
- The architecture should be actively reviewed with the involvement of system stakeholders.
- The architecture should be analyzed using relevant quantitative measures, such as maximum throughput.
- The architecture should be formally evaluated for quality attributes before changes become difficult.
- The architecture should support incremental implementation through a skeletal system.
Structural Recommendations
- The architecture should have well-defined modules based on information hiding and separation of concerns.
- Each module should have a well-defined interface so development teams can work independently.
- Modules that produce data should be separated from modules that consume data to improve modifiability and support staged upgrades.
- The architecture should avoid depending on a particular version of a product or tool.
- If such dependency exists, changing to another product should be easy and inexpensive.
