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Anyone who has not been submersed in the entire development life-cycle of a large scale e-commerce solution could be forgiven for not realising that the Web sites front end E-commerce system represents less than half of the development effort in putting together a complete E-commerce system.
Leaving aside the great marketing software companies do to us and our eagerness to implement E-commerce solutions the facts are that existing retailers and wholesalers already have pre-existing backend systems such as accounting, stock control and shipping that any new serious, public facing front end system must tie into.
Just to keep things clear shipping in this case does not refer to shipping the goods to the Web site customer; it refers to movement of materials and supplies involved with the production or manufacture of the goods the enterprise sells.
It is the need for existing systems to “talk-to-each-other”, to be able to exchange data, information and records to keep the whole business running is underlying driving force. There are many perspectives and definitions surrounding these needs, the most useful way of understanding all of these complexities is to describe them as the messaging that needs to take place within the supply chain.
In practice SOA is implemented with industry standard protocols such as XML, it’s important to note that these protocols do change, after all XML is extensible and that means it will change as a result of revision.
Whilst all systems should be designed to be low maintenance, there is some benefit here in thinking about the publication delivery and consumption of any particular service.
When designing an ERP system using SOA there are a number of key principals to bear in mind; the delivery will change and must be able to change as technologies change.
It is details of the architecture that will change, the design principals will not change. This means the publication and consumption of any service which will continue to use the same architecture, the same design principle and as such can be considered as unchanging.
That design principle is the interface, it is the term used to formalise the details interaction between that which is offered (to be consumed) and that which does the consuming. It is like a contract between two parties, except here it is two parts of a multi-part system.