Learning outcomes

Executing application service-oriented integration

This form of integration has become important over the last two years since the increased availability of web service software and a gradual maturing of the web service standards.

A web service is an interface to an application that employs standard Internet technologies to invoke a particular service. Usually the Internet technology used is the HTTP protocol. As an example of this consider the suppliers who take part in the bulk buying system detailed in the previous section. If they wish to expose the functions of their site using a web service then typical services that might be exposed would be:

• QueryStockLevel item. This would return with the number in stock of the item designated by item.
  
• QuotePrice item quantity. This would return with a quote for the cost of selling quantity of item.
  
• MakeOrder item quantity. This would place an order for quantity of item. The service would return with confirmation that the order had been placed or that it was not possible to satisfy it.

Application service-oriented integration is not new. Companies in the past have placed APIs over their applications that can either be called remotely by other components of the integrated system or have placed simple message processing code on top of the application. This code would read a message, decode it and then invoke the service required. However, now that web services are beginning to become popular this form of message-oriented service should be very popular in the near future.

A web service can emerge in a number of ways:

• A set of services can be mounted on top of an existing application.
  
• A set of services can be created from new using a technology such as .Net from Microsoft.
  
• An application service provider might provide web services as part of the application functionality that it provides. For example an application service provider that provides functionality for manufacturing enterprises may provide services that carry out tasks such as raw material ordering, batch production scheduling and completion notification.

The developer of an integrated system which uses a service oriented approach could, indeed, approach the development of this system by mapping business processes. The major difference, then, between this approach and the business process approach lies in the fact that the main focus in the implementation would be the identification of services that map onto components of the business processes.