Chapter 6 

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Application integration involves integrating new applications with existing or

legacy applications. Since an enterprise's business relies on the continuity of its

existing applications, it is important to integrate the new applications with

minimal disruptions. Integrating with home grown legacy applications presents a

bigger challenge, since these systems have no vendor provided or off the shelf

adapter layers. Not only do you have to write the adapter layers yourself, these

home grown applications may be more idiosyncratic, with an architecture that is

more opaque and difficult to understand.

Business process integration involves integrating an enterprise's existing

systems to support a set of business processes. A 

business process

 is a series of

(often asynchronous) steps that together complete a business task or function. For

example, the adventure builder enterprise has a business process for fulfilling pur 

chase orders submitted to its order processing center. The order fulfillment busi 

ness process includes such steps as validating a customer's credit card,

communicating with various suppliers to fill different parts of an order, and noti 

fying the customer of the order status at various stages of processing. 

Integration is often accomplished by exchanging documents, which more and

more are XML documents, among business processes according to defined busi 

ness rules. The different processes transform the documents by applying their

individual business rules, and then they route the documents to other processes.

Good examples are business processes that do such things as handle purchase

orders and invoices, or incorporate supplier catalogs. Each such business process

runs a workflow that interacts with other entities, either internal or external. 

6.1.2 Example Integration Scenarios

Examining some typical scenarios helps to bring these integration requirements into

better perspective. We use the scenarios present in our adventure builder enterprise

example for illustration. One common integration scenario is that of the adventure

builder enterprise, which may want to make its inventory available online to expand

its customer reach. The enterprise may have existing applications and databases 

for example, catalog and inventory databases, along with order processing and cus 

tomer relationship management (CRM) systems for its business. These systems

and databases need to be enhanced to accommodate the e store. 

Adventure builder enterprise purchases and customizes the CRM package, but

its order processing system may be homegrown. As much as possible, the enter 

prise wants to reduce software duplication and keep its infrastructure costs to a

minimum. To that end, it may want to use these same systems to handle the e store