SigMa has several built-in variables and arrays, each representing a data element concerning the session and its messages. The most important ones are the %HEADERS[] and %SDP[] arrays that are used to retrieve the headers and SDP elements for a given message. The built-in variables and arrays also have a built-in hierarchy to represent the various elements within headers and SDP specification.

This section shows the lists of built-in variables and arrays, with their valid forms, descriptions, and illustrations.