Separation of Concerns

Last modified 05 Mar 2021 18:03 +01:00

The system is designed with many requirements in mind, some of them slightly conflicting:

  • We need user interface that quickly adapts to the needs of specific customer. The user interface should support all the nuances of business logic (e.g. specific edit forms).

  • We need custom business logic that will quickly adapt to customer’s business processes and identity management logic. E.g. we need special-purpose services used by custom applications

  • We need stable model that will enforce the rules of the system, such as consistency of data mappings and access control policies (RBAC).

  • We need re-usable provisioning connectors that will connect to the external systems (as source, target or both). We do not want to adapt these modules to specific business logic and we want them to be developed independently from the rest of the system.

  • We want object repository that can store data in a variety of storage systems. We want a data model that is reasonably stable, as we want other models to take advantage of that.

Therefore we design the system in a form of layers, subsystems and components. The layers depend on the lower layers, but we expect that each layer will be developed with a different dynamics and will address a different concern.

Subsystems Responsibility Dynamics Description

User Interface

Presentation Logic

Changing quickly, easy to change

Interaction with system administrator, support for engineers configuring the system, services to end users.

Custom Business Logic

Unexpected functionality

Moderate changes, easy to adapt

Special-purpose services, custom logic.

IDM Model

Identity management and governance logic, policy enforcement

Slow to change, open-closed principle

Enforcement of a policy structure and data consistency. Some form of automation (e.g. roles), but quite rigid to change outside of the constraints of the model.


Integration Logic

Moderate changes, quickly connecting new systems

Connectors to manage users/groups on target systems, connectors to pull source information. Need to add and replace connectors quickly, sharing connectors with other systems


Data Storage

Very stable but moderately easy to extend

Storing data of the basic data model and also other (unexpected) data. Basic data model must be very stable (other layers depend on it), but it should be easy to extend.