Python implementation

The following figure provides some details about classes and interfaces of the implementation.

Base module implementation

Each component in the Base module has been implemented by means of generic class or interface that will specialize in the following packages.

In particular, the Handler class collects InputProgram and OptionDescriptor objects communicated by the user.

For what the asynchronous mode is concerned, the class Service depends from the interface CallBack, since once the reasoning service has terminated, the result of the computation is returned back via a class CallBack.

Platforms module implementation

In order to support a new platform, the Handler and Service components must be adapted.

For the desktop platform we developed a DesktopHandler and a DesktopService, which generalizes the usage of a solver on the desktop platform, allowing both synchronous and asynchronous execution modes.

Languages module implementation

This module includes specific classes for the management of input and output to ASP, Datalog and PDDL solvers.

The Mapper component of the Languages module is implemented via a Mapper class, that allows to translate input and output into Python objects. Such translations are guided by ANTLR4 library and Predicate abstract class, also present in the module.

To make possible translate facts into strings and vice versa, the classes that want to represent a predicate, must extend the abstract class Predicate, and must be implemented by including the following code:

  • predicateName=”string_name” : must be entered as a class field and must contain the predicate name (in the ASP/Datalog case) or the action name (in the PDDL case) to map;
  • [(“class_field_name_1”, int), (“class_field_name_2”), …] : Is a list that must be passed to super in the constructor, and must contain so many tuples how many are the class field, containing the field name, sorted by the position of the terms they represent, and optionally the keyword int if the field represents an integer.

Thanks to the structure of the Predicate class, this information is passed to the Mapper class, to correctly perform the translation mechanism.

If the classes intended for the translation are not constructed correctly in this way, an exception is raised.

In addition to the Mapper, this module features three sub-modules which are more strictly related to ASP, Datalog and PDDL.

Specialization module implementation

The classes DLVAnswerSets, DLV2AnswerSets, ClingoAnswerSets, DLVHEXAnswerSets implement specific extensions of the AnswerSets class, the SPDPlan class extends Plan, while IDLVMinimalModels extends MinimalModels . These classes are in charge of manipulating the output of the respective solvers (e.g. IDLV).

Moreover, this module can contain classes extending OptionDescriptor to implement specific options of the solver at hand.

Class Diagram

A complete UML Class Diagram is available here.

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