Temporal Reasoning in Nested Temporal Networks with Alternatives

Barták, Roman; Čepek, Ondřej; Hejna, Martin

doi:10.1007/978-3-540-89812-2_2

Cited by 8 publications

(8 citation statements)

References 6 publications

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“…ex i × ex j × s j ≥ ex i × ex j × e i + d i (x), as in [6]. The resulting propagation is however usually weak: this is quite expected since no specific constraint structure is assumed for the ex i variables.…”

Section: Temporal Reasoning With Alternative Resources and Activitiesmentioning

confidence: 93%

“…Stronger propagation can be obtained for nested alternative blocks [6,12], for alternative groups of time-interval variables [57] and for alternative resources: the basic technique used to perform filtering is the same in all cases and is described here in the context of alternative resources. In detail, let a i be an activity requiring ρ units of one resource out of a set R of m alternative resources, propagation can be performed as if a i was split into m alternative activities a 0 i , .…”

Section: Temporal Reasoning With Alternative Resources and Activitiesmentioning

confidence: 99%

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Optimal methods for resource allocation and scheduling: a cross-disciplinary survey

Lombardi

Milano

2012

Constraints

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Classical scheduling formulations typically assume static resource requirements and focus on deciding when to start the problem activities, so as to optimize some performance metric. In many practical cases, however, the decision maker has the ability to choose the resource assignment as well as the starting times: this is a far-from-trivial task, with deep implications on the quality of the final schedule. Joint resource assignment and scheduling problems are incredibly challenging from a computational perspective. They have been subject of active research in Constraint Programming (CP) and in Operations Research (OR) for a few decades, with quite difference techniques. Both the approaches report individual successes, but they overall perform equally well or (from a different perspective) equally poorly. In particular, despite the well known effectiveness of global constraints for scheduling, comparable results for joint filtering of assignment and scheduling variables have not yet been achieved. Recently, hybrid approaches have been applied to this class of problems: most of them work by splitting the overall problem into an assignment and a scheduling subparts; those are solved in an iterative and interactive fashion with a mix of CP and OR techniques, often reporting impressive speed-ups compared to pure CP and OR methods. Motivated by the success of hybrid algorithms on resource assignment and scheduling, we provide a cross-disciplinary survey on such problems, including CP, OR and hybrid approaches. The main effort is to identify key modeling and solution techniques: they may then be applied in the construction of new hybrid algorithms, or they may provide ideas for novel filtering methods (possibly based on decomposition, or on alternative representations of the domain store). In detail, we take a constraint-based perspective and, according to the equation CP = model + propagation + search, we give an overview of state-of-art models, propagation/bounding techniques and search strategies.

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Section: Temporal Reasoning With Alternative Resources and Activitiesmentioning

confidence: 93%

Section: Temporal Reasoning With Alternative Resources and Activitiesmentioning

confidence: 99%

Optimal methods for resource allocation and scheduling: a cross-disciplinary survey

Lombardi

Milano

2012

Constraints

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show abstract

“…The idea of alternative behaviors has also been investigated in (off-line) scheduling, where the notion of Temporal Network with Alternatives has been introduced (Barták et al, 2008). It is quite evident however that, as anticipated in the introduction, the concept of execution modality is inspired to an (online) action centered approach (Brenner and Nebel, 2009), rather than on a constraints/scheduling based one (Cesta and Fratini, 2009).…”

Section: Modeling Rover's Actionsmentioning

confidence: 99%

Robust Execution of Rover Plans via Action Modalities Reconfiguration

Scala

Micalizio

Torasso

2014

Proceedings of the 6th International Conference on Agents and Artificial Intelligence

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Robust execution of exploration mission plans has to deal with limited computational power on-board a planetary rover, and with limited rover's autonomy. In most cases, these limitations practically prevent the rover to synthesize a new mission plan when some unexpected contingency arises. The paper shows that when such deviations refers to anomalies on the consumption of resources, robust execution can be achieved efficiently through an action reconfiguration approach instead of a replanning from scratch. Building up on an extended action model representation, the paper proposes an effective continual planner-ReCon-that, exploiting a general purpose CSP solver, is able to (i) detect violations of mission resource constraints, and (ii) find (if any) a new configuration of actions.

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“…The idea of alternative behaviors has also been investigated in (off-line) scheduling, where the notion of Temporal Network with Alternatives has been introduced [1]. It is quite evident however that, as anticipated in the introduction, the concept of execution modality is inspired to an (on-line) action centered approach [4], rather than on a constraints/scheduling based one [6].…”

Section: Modeling Rover's Actionsmentioning

confidence: 99%

“…Off-line approaches, such as [3,8], avoid replanning by anticipating, at planning time, the possible contingencies. The result of such a planning phase is a contingent plan that encodes choices between functionally equivalent sub-plans 1 . At execution time, the plan executor is able to select a contingent plan according to the current contextual conditions.…”

Section: Introductionmentioning

confidence: 99%

ReCon: An Online Task ReConfiguration Approach for Robust Plan Execution

Scala

Micalizio

Torasso

2015

Lecture Notes in Computer Science

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The paper presents an approach for the robust plan execution in presence of consumable and continuous resources. Plan execution is a critical activity since a number of unexpected situations could prevent the feasibility of tasks to be accomplished; however, many robotic scenarios (e.g. in space exploration) disallow robotic systems to perform significant deviations from the original plan formulation. In order to both (i) preserve the "stability" of the current plan and (ii) provide the system with a reasonable level of autonomy in handling unexpected situations, an innovative approach based on task reconfiguration is presented. Exploiting an enriched action formulation grounding on the notion of execution modalities, ReCon replaces the replanning mechanism with a novel reconfiguration mechanism, handled by means of a CSP solver. The paper studies the system for a typical planetary rover mission and provides a rich experimental analysis showing that, when the anomalies refer to unexpected resources consumption, the reconfiguration is not only more efficient but also more effective than a plan adaptation mechanism. The experiments are performed by evaluating the recovery performances depending on constraints on computational costs.

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Temporal Reasoning in Nested Temporal Networks with Alternatives

Cited by 8 publications

References 6 publications

Optimal methods for resource allocation and scheduling: a cross-disciplinary survey

Optimal methods for resource allocation and scheduling: a cross-disciplinary survey

Robust Execution of Rover Plans via Action Modalities Reconfiguration

ReCon: An Online Task ReConfiguration Approach for Robust Plan Execution

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