Service Oriented Architecture suggestions

Question

For personal and university research reasons I am thinking of building a simple CRM using a service oriented architecture. Its meaning is just to explain the architecture itself

Answer 1

I would define SaaS as a Business model rather than an architecture; however like all business domain requirements it will influence systems architecture but it, itself is not. What you have defined is essential a Service Oriented Architecture.

Your statement "independent and the ability to combine them to offer new services" is the essential non-functional design requirement that suggests SOA.

Good implementation for SOA is about having well defined and flexible interfaces, with very clear delineation of responsibilities. However it is difficult subject to be prescriptive about. The proof is in the eating; does it provide that flexible reuse. My suggestion is spend time reading SOA design pattern resources, and understand the defining characteristics with regard to the appropriate context for use. Then apply the Single Responsibility principle appropriate level of abstraction. c.f. (Domain) Space Based Architecture is kind of SOA meta-pattern.

In regard to Authorisation, I recommend following the service approach, use a distribute directory services system like open LDAP, and note that is entirely reasonable for service provides and users to have their own credentials and you can use Public-Private keys for signing messages.

The main suggestion is study and learn from experience of others:

• http://www.soapatterns.org/
• http://martinfowler.com/eaaCatalog/

Answer 2

SOA doesn't forces to use XML.

Currently web technologies dominate, and define future. So we in my company selected JSON RESTful services as foundation. And SOA as principles.

There is no sense to suggest languages, because the purpose of SOA and good implementation is - to enable any language or framework to be used

(FYI we use Java with Spring MVC-based web-services, Node.js, PHP)