SOAP (Simple Object Access Protocol) is a network protocol used to exchange messages in XML format between systems. The messages are transported via HTTP or HTTPS.
The VertiGIS Integrator has a predefined default SOAP interface where the incoming messages are received and processed (inbound). This interface has several functions to access the geodatabase.

Check out SOAP Interface for more information.

Outbound messages can be sent to an external SOAP interface (outbound).
The parameterization of the SOAP interface can be carried out by adapting the XSLT transformations.

For more information check out UT XML and VertiGIS Integrator XSL API chapters.