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Planning and Implementing SOA
The capacity planning exercise will show where there is a need to apply optimisation. The minimum
optimisation to meet targets is a more appropriate target than reducing the run-time overhead to the
absolute minimum. The first targets for optimisation should be the situation where a number of small, lowlevel
services are aggregated to create a widely-used service, and where there is little or no requirement for
direct use of the low-level services. In this instance, direct native calls to the low-level services can be made
with little adverse impact. In fact, this interchange could bypass the ESB entirely, with the high-level service
making direct RPC calls to the required applications.
The important step in this optimisation is that the original logical model should be retained, and the nature
of the optimisation, together with the reasons for the decision to optimise should be recorded. The Chief
Architect should review all such cases to ensure the best compromise has been reached.
Other optimisation considerations include:
Ensuring that encryption is truly necessary, and only applying encryption to the sensitive portions of a
large message.
Consider breaking multi-function services down into several simpler single-function services (as the
simpler service will have simpler and smaller message requirements).
Consider using alternative messaging protocols to HTTP for inside-the-firewall deployment.
Consider the use of Binary XML or compression to reduce the size of XML messages.
Consider physically relocating services to minimise network overheads.
Whatever trade-offs are made for the sake of performance, it is important that it is not treated as a one-person
decision that is the responsibility of a technical architect. The impact on agility and the ability to meet the
forward plans of the business must be considered, alongside each compromise of the ideal architecture.
SERVICE-ORIENTED DEVELOPMENT
CATALYST
A key challenge to organisations when getting to grips with SOA is in the development area. It is no longer
about application development, it is about service development, yet understanding the impact on the
development function can be complex.
SUMMARY
There is a SOA lifecycle in the same way as there is an application development lifecycle.
Planning the infrastructure for SOA will require careful thought.
Services within a SOA may be combined in unforeseen ways.
SOA and Agile can be complementary.
ANALYSIS
There is a SOA lifecycle in the same way as there is an application
development lifecycle.
Development pressures in the past have always meant that applications are developed with little thought
for reuse, change, or integration. This mindset will need to change in a SOA environment. However, it is
clear that there is a lifecycle for SOA just as there is for earlier types of application development.
December 2006 Section 1: SOA Deployment 27