Chapter 5: Loose coupling and Federation
Loose Coupling
- Old applications were tightly coupled and were executed and maintained as huge chunk of code, which is hard to maintain and change.
- Loosely coupled applications are independent of each other in terms of execution, so can be replaced without affecting others.
- Such loosely coupled applications can be tightly coupled by themselves, that tight coupling is among the subcomponents it has.
- Other advantages can be
o Create new applications easily by assembling such discrete services/applications
o Create secured business applications quickly, as security can be another independent service itself which can be hooked with other services.
o Isolate problems easily, to locate failures, easy to test.
o Such services can be reused and can be sold separately to other applications
Licensing
- Licensing has been changed to one perpetual license to subscription based, for services used. SOA services can be licensed in similar fashion. Different applications/domains have different ways to do it.
- How licensing and charging such services be different? Like some financial services can be charged per transaction.
Federation
- It’s about governing policies,
- Services has some set of policies which are used application / companywide (imagine federal government) and these policies can have local flavour per each department, which is more domain specific for the environment in which those services will operate (imagine state government).
- So Federation is used to solve integration issues. In other words changing global policies to suit local needs, so that integration can be easy.
SOA and Federation
- Federation is implemented using SOA registries, where application-wide or global policies are in SOA registry, which is treated as parent registry by other domain specific registries.
- Every domain (or department) will have its individual registry which inherits from global policies and also includes domain specific policy.
- Security can be one of the global policies.
- Domain is defined by SOA registry and SOA broker. And other SOA components can be shared across domains.
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