Process of Creating Integration Objects

Creating Integration Objects Using the EAI Siebel Wizard Business Service
(Optional) Configuring the integration object (see Guidelines for Configuring Integration Objects)
Validating Integration Objects
Compiling your changes into the SRF file
Testing Integration Objects
(Optional) Deploying Integration Objects to the Run-Time Database

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You can add extension columns to existing base tables. Adding an extension column avoids additional joins to extension tables for storing custom attributes. You can add extension columns to any of the following table types:

Data tables
Intersection tables
Interface tables
Standard extension tables
Custom extension tables
Extension (Siebel)

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This video gives you an idea related to Web Service in General, which is necessary to know to design Siebel Integration using Web Services
- what a Web Service is called,
- what are its various components,
- how it has been standaradised,
- what is a WSDL, PORT, Binding, Service End Point
and lot other answers related to Web Services in Generic.