Interface Configuration File

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15 May 2015

The interface configuration file tells the PLEXIL Executive how to route commands, lookups, and planner updates to the appropriate interface adapters and exec listeners.

Interface Configuration Format

The interface configuration file is an XML file supplied to the PLEXIL Executive that describes all adapters and listeners available to the Executive, and (optionally) the mapping between command and lookup names, and the adapters which implement those commands and lookups.

This file always has the Interfaces element as its root. The Interfaces element body may contain any of these optional elements:

  • Adapter - describes an interface adapter, an object that implements commands, lookups, and/or planner updates;
  • Listener - describes an exec listener, an object that reports on node state transitions in the plan, and other execution events.

Adapter and Listener elements may appear in any order, any number of times, inside the Interfaces element. In general, at least one Adapter should be supplied for any plan that interacts with its environment in any way.

The outline of a typical interface configuration file is:

<Interfaces>
 <Adapter AdapterType="adapter_type" ... more attributes as required ... >
  ... configuration data for adapter_type as required ...
 </Adapter>
 ... more Adapter elements ...
 <Listener ListenerType="listener_type" ... more attributes as required ... >
  <Filter FilterType="filter_type" ... more attributes as required ... >
   ... configuration data for filter_type as required ...
  </Filter>
  ... configuration data for listener_type as required ...
 </Listener>
 ... more Listener elements ...
</Interfaces>

Adapter Format

An Adapter element specifies what kind of adapter will be constructed. There is one required attribute, AdapterType. Adapter elements may also take the following optional attribute:

  • LibPath - names the shared library file containing the adapter implementation. The library file name defaults to libAdapterType.so on Linux and libAdapterType.dylib on Mac OS X.

All Adapter elements may contain one or more of the following optional elements, which specify how the Executive may use them:

  • DefaultAdapter - signifies that this adapter should be used for all interfaces not registered to another adapter.
  • DefaultCommandAdapter - signifies that this adapter should be used for all commands not registered to another adapter.
  • DefaultLookupAdapter - signifies that this adapter should be used for all lookups not registered to another adapter.
  • PlannerUpdate - signifies that this adapter should be used for planner updates.
  • CommandNames - contains a comma-separated list of specific command names for which this adapter will be used.
  • LookupNames - contains a comma-separated list of specific state names for which this adapter will be used. Optionally takes an attribute:
    • TelemetryOnly - boolean-valued attribute (default false). If true, LookupNow will take its value for these states from the most recently received value, instead of attempting a live query.

Note that some adapter types automatically register themselves for the appropriate functions.

Adapter elements may also contain additional attributes and elements as required by the particular type of adapter.

Note: If a command or lookup is executed for which no adapter is assigned, the Executive will halt with a run-time exception.

Listener Format

The Listener element has one required attribute, ListenerType. This specifies what kind of exec listener will be constructed. Listener elements may contain the following optional elements:

  • Filter - specifies an event filter for the listener. This element has one required attribute, FilterType.
  • LibPath - names the shared library file containing the listener implementation. The library file name defaults to libListenerType.so on Linux and libListenerType.dylib on Mac OS X.

Listener and Filter elements may contain additional attributes and elements, as required by the particular listener or filter type.

Example

Here is an example of a simple interface configuration file. Several others can be found in the examples directory of the PLEXIL distribution.

<Interfaces>
 <Adapter AdapterType="Dummy">
  <DefaultAdapter />
 </Adapter>
 <Adapter AdapterType="OSNativeTime" />
 <Listener ListenerType="LuvListener" />
 <Listener ListenerType="PlanDebugListener" />
</Interfaces>

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