Isolation Modeling and Analysis Based on Mobility

Abstract

In a mobile system, mobility refers to a change in position of a mobile object with respect to time and its reference point, whereas isolation means the isolation relationship between mobile objects under some scheduling policies. Inspired by event-based formal models and the ambient calculus, we first propose the two types of special events, entering and exiting an ambient, as movement events to model and analyze mobility. Based on mobility, we then introduce the notion of the isolation of mobile objects for ambients. To ensure the isolation, a priority policy needs to be used to schedule the movement of mobile objects. However, traditional scheduling policies focus on task scheduling and depend on the strong hypothesis: The scheduled tasks are independent—that is, the scheduled tasks do not affect each other. In a practical mobile system, mobile objects and ambients interact with each other. It is difficult to separate a mobile system into independent tasks. We finally present an automatic approach for generating a priority scheduling policy without considering the preceding assumption. The approach can guarantee the isolation of the mobile objects for ambients in a mobile system. Experiments demonstrate these results.

Analyzing Isolation in Mobile Systems

“…As mentioned before, these existing work always investigates the scheduling problems based on traditional task scheduling, and the efforts hardly reason about scheduling. Based on more fine-grained event scheduling, Jiang et al [16] attempt to model and analyze isolation from the perspective of mobility, which is the most related to this work. However, their work focuses on fixed priority event scheduling and gener-ates a priority scheduling sequence by computing an execution sequence of a system, which do not consider event scheduling with a loop.…”

“…The generated scheduling sequence may contain a loop. Thus this work is actually an extension of [16] aiming to solve the safety isolation problems in complex mobile systems, which is original and different from all these related work.…”

“…In this section, a fine-grained event-based formal model called dependency structure [18], [17], [16] is briefly introduced as a system model for modeling Compared with these existing intersection control approaches, our work offers a totally different solution based on formal methods, which provides a solid theoretic foundation and supports analyzing and reasoning at a higher abstract level. Moreover, our approach can be more general and less dependent on communication, which can be widely applied for nearly any sort of complicated driving contexts that may be encountered in the real world.…”

“…In this section, a fine-grained event-based formal model called dependency structure [18], [17], [16] is briefly introduced as a system model for modeling Figure 1 A running example with four vehicles crossing one intersection (from the literature [7]). complex mobile systems.…”

“…According to the definition, all possible states of a dependency structure can be computed one by one. For a more detailed explanation of dependency structure, please refer to the literatures [18], [17], [16], [11].…”