This software translates MAPGEN(Europa and APGEN) domains to ASPEN, and the resulting domain can be used to perform planning for the Mars Exploration Rover (MER). In other words, this is a conversion of two distinct planning languages (both declarative and procedural) to a third (declarative) planning language in order to solve the problem of faithful translation from mixeddomain representations into the ASPEN Modeling Language.
The MAPGEN planning system is an example of a hybrid procedural/ declarative system where the advantages of each are leveraged to produce an effective planner/scheduler for MER tactical planning. The adaptation of the same domain to an entirely declarative planning system (ASPEN) was investigated, and, with some translation, much of the procedural knowledge encoding is amenable to declarative knowledge encoding.
The approach was to compose translators from the core languages used for adapting MAGPEN, which consists of Europa and APGEN. Europa is a constraint-based planner/scheduler where domains are encoded using a declarative model. APGEN is also constraint-based, in that it tracks constraints on resources and states and other variables. Domains are encoded in both constraints and code snippets that execute according to a forward sweep through the plan. Europa and APGEN communicate to each other using proxy activities in APGEN that represent constraints and/or tokens in Europa. The composition of a translator from Europa to ASPEN was fairly straightforward, as ASPEN is also a declarative planning system, and the specific uses of Europa for the MER domain matched ASPEN’s native encoding fairly closely.
On the other hand, translating from APGEN to ASPEN was considerably more involved. On the surface, the types of activities and resources one encodes in APGEN appear to match one-to-one to the activities, state variables, and resources in ASPEN. But, when looking into the definitions of how resources are profiled and activities are expanded, one sees code snippets that access various information available during planning for the moment in time being planned to decide at the time what the appropriate profile or expansion is. APGEN is actually a forward (in time) sweeping discrete event simulator, where the model is composed of code snippets that are artfully interleaved by the engine to produce a plan/schedule. To solve this problem, representative code is simulated as a declarative series of task expansions.
Predominantly, three types of procedural models were translated: loops, if-statements, and code blocks. Loops and if-statements were handled using controlled task expansion, and code blocks were handled using constraint networks that maintained the generation of results based on what the order of execution would be for a procedural representation.
One advantage with respect to performance for MAPGEN is the use of APGEN’s GUI. This GUI is written in C++ and Motif, and performs very well for large plans.
This work was done by Gregg R. Rabideau, Russell L. Knight, Matthew Lenda, and Pierre F. Maldague of Caltech for NASA’s Jet Propulsion Laboratory.
The software used in this innovation is available for commercial licensing. Please contact Dan Broderick at
This Brief includes a Technical Support Package (TSP).
Translating MAPGEN to ASPEN for MER
(reference NPO-48597) is currently available for download from the TSP library.
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Overview
The document titled "Translating MAPGEN to ASPEN for MER" is a technical support package from NASA's Jet Propulsion Laboratory (JPL) that discusses the adaptation of the MAPGEN planning system for the Mars Exploration Rover (MER) mission into the ASPEN planning system. MAPGEN is a hybrid procedural/declarative system that effectively combines the strengths of both approaches for tactical planning in rover operations.
The document outlines the challenges and methodologies involved in translating MAPGEN, which consists of two core components: Europa and APGEN. Europa is a constraint-based planner that uses a declarative model, while APGEN operates as a forward-sweeping discrete event simulator that encodes activities and resources through code snippets. The translation process to ASPEN, which is also a declarative planning system, was relatively straightforward for the Europa component due to the compatibility of their encoding methods.
However, translating APGEN to ASPEN proved to be more complex. The document explains that while the activities and resources in APGEN seem to align with those in ASPEN, the underlying definitions and execution mechanisms differ significantly. APGEN's procedural elements, such as loops and if-statements, required careful handling through controlled task expansion and constraint networks to maintain the integrity of the planning process.
The document highlights the performance advantages of MAPGEN, particularly its graphical user interface (GUI) written in C++ and Motif, which performs well with large plans compared to ASPEN's Java-based GUI, which tends to slow down under similar conditions.
The research presented in the document demonstrates the successful application of the translation process over five operational days, where input from MAPGEN was used to generate plans in ASPEN, allowing for a comparative analysis of the two systems' effectiveness.
Overall, the document serves as a technical overview of the methodologies employed in translating a complex planning system for space missions, showcasing the innovative approaches taken by JPL researchers to enhance the capabilities of rover operations through advanced planning and scheduling techniques. It emphasizes the potential for broader applications of these technologies in aerospace and other fields.
