An Application Services Interface (ASI) is a release-independent interface published by Siebel Systems that allows you to integrate Siebel applications with external applications.
ASIs are published in a standard metadata format, such as Extensible Markup Language Document Type Definitions (XML DTD) and Web Services Descriptive Language/XML Schemas (WSDL/XSD) and are built using the ASI Framework.
There are two types of ASIs :
1. Inbound ASI is used to accept data into Siebel applications from an external system using Siebel workflows, Siebel Business Services, and Siebel Data Synchronization services through the Siebel Object Manager.
2. An Outbound ASI is used to send data out based on a UI event or a trigger in your Siebel workflow.