TBDP provides a solution for graceful & gradual transitions. Transitions can be enterprise level: system exits & entries; or at micro level when a component/process exits or a new one (probably a replacement) makes an entry. TBDP can be a architecture level pattern or can be a inter/intra component level design pattern.
TBDP virtually does not exist in the software world / academia. This is one of the main reasons why so many legacy systems are running with numerous wrappers, increasing complexity & cost of running systems. Absence of TBDP reflects absence of concern to long term requirements like managing obsolescence or gracefully retiring enterprise class systems.
Transition Bridge software implemented using TBDP can manage gradual migrations of enterprise systems. TBDP can help avoiding nightmares of a big bang migration or worse, postponing migration of a legacy system, forever.
TBDP is composed of following construct elements:
- Responsibility (service) Registry: Functional responsibilities are registered into this registry with the system Id responsible to fulfill this responsibility. This responsibility can be enterprise wide or can be limited to a set of users/departments/offices. This responsibility gradually widens for the new system being implemented and gradually diminishes for the old system being retired.
- OTN and NTO maps: Old to New and New to Old mappings are just code, ID, keys mapping between the old and new systems. Examples are mapping of product codes, account numbers etc.
- Responsibility Orchestrator: This is the main engine of the TBDP. For a given service, this engine routes a service / transaction request to either the old system, to the new system or to both of them in a particular order, depending on the configuration for the service in the Responsibility Registry. Depending on the source of the request the orchestrator can apply OTN or NTO mappings to the codes, IDs or Keys in the service request, using the OTN and NTO maps. It is also responsible for inter system recon and maintenance of any Inter System Account required during migration.
- Service Request Proxy: Services affected by migration have to be routed to the Service Request Proxy provided by the TBDP. This proxy receives a service request, logs the same and forwards the same to the Responsibility Orchestrator to fulfil the request.
Patterns can provide SOP driven bot workers to implement complex Responsibility Orchestrations in complex migrations using the TBDP.
It is surprising that providing for exit is not addressed by architects or designers of enterprise class systems. Lessons learnt from the last 40 to 50 years, must be used to bring these provisions into every enterprise class system.
