Action dictionaries contain strings to be tested against a specified delta stream and an action to be executed if the string is found. An action can consist of any arbitrary Delta language statements. Set dictionaries contain strings with no actions. The Delta program can test whether a string in a particular stream is in a set, and act accordingly. New acronyms can be handled simply by adding them to this set dictionary.
Set dictionaries are useful as well for expressing exceptions to particular rules.
In addition, procedures written in C can be called directly from Delta programs. 5.2 DeltaTools Delta programs can be monitored and controlled with DeltaTools, the interactive development environment included in debugging versions of Delta programs. DeltaTools includes commands for executing, tracing, and setting breakpoints in Delta programs at the Delta source code level, displaying and manipulating the delta, generating synthesizer values and synthesizing from a delta, and directing input and output. For example, rule developers can instruct the system to pause each time the delta or a particular stream in the delta changes. A particularly useful feature of DeltaTools is its interactive delta manipulation commands.