Policy-based Coordination in PAGODA: A Case Study

Abstract

PAGODA (Policy And GOal Based Distributed Autonomy) is a modular architecture for specifying and prototyping autonomous systems. A PAGODA node (agent) interacts with its environment by sensing and affecting, driven by goals to achieve and constrained by policies. A PAGODA system is a collection of PAGODA nodes cooperating to achieve some mutual goal. This paper describes a specification of PAGODA using the Russian Dolls model of policy-based coordination. In PAGODA there are two forms of coordination: local and global. Local coordination is used to compose the components of a PAGODA node. The local coordinator is concerned with ensuring component level synchronization constraints, cross component message ordering constraints, routing of notifications, and interaction with the external world. The global coordinator is concerned with dissemination of information, negotiation of responsibilities, and synchronization of activities. Requirements for a PAGODA node coordinator are given and an example set of policies is specified. Principles for showing that the policies satisfy the requirements are discussed as a first step toward a logic of policy-based coordination. Development of a distributed coordinator is the subject of ongoing work. Some challenges and possible solutions are discussed.

Modelling and Analyzing Adaptive Self-assembly Strategies with Maude

“…[22,3]). Among those, the PAGODA project [22] is the closest in spirit and shape. Our work is original in its clear and neat representation and role of control data in the architecture, and in the fact this is, as far as we know, the first analysis of self-assembly strategies based on statistical model checking.…”

“…[13]), with a particular focus on adaptive systems (e.g. [22,3]). Among those, the PAGODA project [22] is the closest in spirit and shape.…”

“…Note that, while the tower of reflection relies on a white-box adaptation, the russian dolls approach can deal equally well with black-box components, because wrapped configurations can be managed by message passing. The RRD model has been further exploited for modeling policy-based coordination [21] and for the design of PAGODA, a modular architecture for specifying autonomous systems [22]. The case study presented in the next sections will conform to this model.…”

A White Box Perspective on Behavioural Adaptation

“…Note that, while the tower of reflection relies on a white-box architecture, the Russian Dolls approach can deal equally well with black-box components, because wrapped configurations can be managed by message passing. RRD has been further exploited for modeling policy-based coordination [73], for the design of PAGODA, a modular architecture for specifying autonomous systems [74], in the composite actors used in [32], and, by ourselves, in the design and analysis of self-assembly strategies for robot swarms [21].…”

“…Building upon the authors experience in the development of the PAGODA framework [74] (cf. Section 4.2), PobSAM combines the actor model of coordination [2] with process algebra machinery and shares the white-box spirit of separating application and adaptation concerns.…”