The main job of the SIS is to evaluate compositions, to control invoking services.

Composition components specify which services to invoke, when. They may include conditional logic, to invoke different services depending on parameters in the request, or the outcome of earlier services in the composition.

What’s in a composition?

A composition contains the following information:

  • an optional description

  • references to any macros the composition requires

  • a script that specifies the services to invoke

  • optional interceptors that can modify signaling parameters in service input or output messages

  • configuration options that can modify SIS behaviour when the composition runs.

Warning Care should be taken to make sure compositions invoke services in a sensible order. For example, services that perform some form of authorization would typically run before the others.
Tip Management operations on the SIS define the services that compositions can use.
See the SIS Administration Guide for more information.

Below is a sample composition, and a description of schema syntax.

Sample composition

The example below shows a simple composition that invokes two services. Its main elements are: composition-name/vendor/version, which defines this composition’s component identity; service-ref, which declares the services that this composition requires; and script, which specifies how to invoke those services.

VIA Diagram Script

When the SIS evaluates this composition, it will:

  • invoke the VPN service

  • wait for the outcome

  • then invoke the Prepay service.

Composition schema syntax

The base XML schema sis-composition-1.8.xsd defines the basic structure of a composition. SIS variants extend this base schema with protocol-specific properties.

IN compositions

Compositions for IN protocols may use the XML schema in-sis-composition-1.8.xsd to extend the generic schema for SIS compositions. IN compositions use the following corresponding schema namespaces:

<composition xmlns=""
    xsi:schemaLocation=" in-sis-composition-1.8.xsd

SIP compositions

Compositions for SIP may use the XML schema sip-sis-composition-1.8.xsd to extend the generic schema for SIS compositions. SIP compositions use the following corresponding schema namespaces:

<composition xmlns=""
      xsi:schemaLocation=" sip-sis-composition-1.8.xsd
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