PLEXIL5

The Plan Execution Interchange Language (PLEXIL) is an open source synchronous language developed by NASA for commanding and monitoring autonomous systems. PLEXIL Formal Interactive Verification Environment (PLEXIL5) is a tool that implements a formal executable semantics of PLEXIL. PLEXIL5 provides a graphical interface that enable access to formal verification techniques such as model-checking, symbolic execution, theorem proving, and static analysis of plans. The graphical environment supports formula editing and visualization of counterexamples, interactive simulation of plans at different granularity levels, and random initialization of external environment variables.

PLEXIL’s operational semantics has been formally specified and key meta-theoretical properties of the language, such as determinism and compositionality, have been formally verified in the Prototype Verification System (PVS). This formalization yields a formal executable semantics of the language that serves as an efficient formal interpreter and reference implementation of PLEXIL. This formal semantics is at the core of the verification capabilities of PLEXIL5. The formal analysis capabilities offered by PLEXIL5 are based on PLEXIL’s rewriting logic semantics written in the Maude system and verified in PVS.

The graphical user interface has been developed in Java using the model-view-controller pattern. The object oriented model represents the hierarchical structure of plans, their execution behavior, and the external environment. The view consists of several classes that present the user with views of the tree-like-structure of plans. The controller consists of a custom controller-facade class and listener classes using and extending the Java framework. PLEXIL5 supports a number of input formats defining plans. For this purpose, the tool links a series of parsers and translators that internally

1. generate the format supported by the rewriting logic semantics of the language implemented in Maude and

2. construct an object oriented plan model from Maude’s output.

Java and Maude communicate as processes at the operating system’s level with help of the Java/Maude Integration API, developed as part of the PLEXIL5 framework.

Current Release

PLEXIL5 v0.0 (May-31-2018)

Requirements

• Apache Ant

• Maude Interpreter Binaries. Copy maude.linux64, maude.linux, maude.intelDarwin to plexilite folder.

Compiling and running

In build directory:

$ ant run

License

The code in this repository is released under NASA's Open Source Agreement. See the directory LICENSES; see also the copyright notice at the end of this file.

Authors

• César A. Muñoz ([email protected]), NASA Langley Research Center, USA.
• Hector Cadavid, Escuela Colombiana de Ingeniería, Colombia.
• Camilo Rocha, Pontificia Universidad Javeriana de Cali, Colombia.
• Marco Feliú, National Institute of Aerospace, USA.

Copyright Notice

Copyright 2016 United States Government as represented by the Administrator of the National Aeronautics and Space Administration. All Rights Reserved.

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