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Tracing and Debugging: trace/visualdebug


There are two options for tracing and debugging:


Tracing the Evaluation: trace
In order to trace the evaluation process, simply add "trace" to a ObjectLogic query:

@{q1, options[trace]} ?- ?X:?Y.

The tracing feature is described in more detail in Tracing the evaluation process.

Debugging the Evaluation with the Graphical Debugger: visualdebug
NOTE: This debugging tool is not officially supported. It has a couple of limitations which need to be considered carefully before using the tool:

If you use "visualdebug" a GUI opens at the server side. This means that if you do not have access to the server then you basically have to restart OntoBroker before continuing.
The debugger is deeply integrated in the OntoBroker inference kernel. It is possible that the debugger will crash the OntoBroker server while or after debugging.

To keep a long story short: Never use this tool on a production server!!

In order to debug the evaluation process, simply add "visualdebug" to the ObjectLogic query:

@{q1, options[visualdebug]} ?- ?X:?Y.

The visual debugger is an advanced debugging tool which shows

The rule graph
The selected rules
The output of the different program re writers
A graphical display of the compiled operatornet
A step-by-step debugger which shows the data flow in the operatornet

We currently do not have a detailed documentation on this debugger as this tool is used primary by the internal OntoBroker research and development team.

NOTE 1: If access control is enabled (i.e. the configuration parameter Security.AccessControl is set to on), you need the special permission "ob:reasoner:debug" to use this query option.

NOTE 2: The visual debugger option is not available if you are using the collaboration server. It will be silently ignored.