8043922
Intensionality of modal logic for Robust Ambient Calculus
Abstract Computation with mobility becomes a novel distributed computation paradigm with the development of network technology. The calculus of Mobile Ambient is a widely studied formal mechanism for describing both mobile computing and mobile computation. To improve this process calculus, Robust Mobile Ambient is introduced by providing co-actions. This paper deals with the modal logic for finite fragment of this calculus without communication primitives. In details, we compare standard behavioral equivalence with the equivalence induced by the logic (=L) and with the structural congruence. As a result, we prove the intensionality of the logic and at the same time, an axiomatization for = L is given. The authors thank the three referees for many constructive suggestions and comments.
17905406
On the Markovian Randomized Strategy of Controller for Markov Decision Processes
This paper focuses on the so called controller synthesis problem, which addresses the question of how to limit the internal behavior of a given system implementation to meet its specification, regardless of the behavior enforced by the environment. We consider this problem in the probabilistic setting, where the underlying model has both probabilism and nondeterminism and the nondeterministic choices in some states are assumed to be controllable while the others are under the control of an unpredictable environment. As for the specification, it is defined by probabilistic computation tree logic. We show that under the restriction that the controller exploits only Markovian randomized strategy, the existence of such a controller is decidable, which is done by a reduction to the decidability of first-order theory for reals. This also gives rise to an algorithm which can synthesize the controller if it does exist.
5876317
Framework of performance evaluation for mobile process based on mobile ambient
Formal methodology for distributed and concurrent system, especially computation system with mobility, is increasingly important both in the theory and the practice. Based on the calculus of mobile ambient (MA), a widely studied formal mechanism for mobile computation, this paper focuses on the quantitative analysis of mobile computation system and provides a framework of performance evaluation for it. In details, this paper introduces an enhanced labelled transition system as the system model, and assigns rate to each label through so-called cost function. Based on it, the labelled transition system can be mapped to continuous time Markov chains and thus performance evaluation can be carried out by standard numerical techniques and tools. In some sense the main work of this paper can be regarded as integrating behavior and performance analysis in a compositional formal framework, which provides some basis of unified formal methodology for the development of mobile system.
8665982
Structure analysis for dynamic software architecture based on spatial logic
The requirement for modifying system structure during system execution is specified by dynamic software architectures. The system architecture style should remain one style or transform within a scope so that some constraints need to be imposed on during the system execution. Our work expands such an idea along two directions in the setting of formalism. The first direction is to model the system by a graph-based calculus stressing the structure. The other direction lies in that we tailor spatial logic to be a suitable logic as the system specification for structure. The model and specification are basis for the model checking algorithm that is to verify whether the system evolution satisfies some structure constraints. We invite a master-slave architecture style as a running example from the beginning and throughout the paper to demonstrate our approach. Such work can be seen as the basis of the structure analysis for architectures.
17432425
Structure analysis for dynamic software architecture
The open and dynamic Internet environment greatly urges software entities that are distributed on different locations to coordinate with each other to accomplish a computing task. Software architecture is applied to abstract the software entities to be components and the coordination between them to be connectors and then a model is extracted as the architecture on which the design, analysis and verification are based. Currently, the notion of dynamic software architectures that can modify their architecture and enact modifications during the system execution has become one of the most active research areas. In this paper, we focus on the dynamic evolution of system structure other than coordination mechanisms (e.g. communication protocols). It is widely recognized that some restrictions should be imposed on the system evolution to ensure that the system structure may remain one style or transform within a scope. These conditions, to a large extent, make the system execute under control as expected.
15877902
Tree logic with recursion and model checking algorithm
Semi-structured data plays an increasingly important role in the exchange of information between globally distributed applications, which invokes renewed interests in typed programming languages that can manipulate tree-like data structures. Tree logic, inherited from ambient logic, is introduced as the formal foundation of related programming language and type systems. In this paper, we introduce recursion into such logic system, which can describe the tree data more clearly and concisely. By making a distinction between proposition and predicate, a concise semantics interpretation for our modal logic is given. We also develop a model checking algorithm for the logic without . operator. The correctness of the algorithm is shown. Such work can be seen as the basis of the semi-structured data processing language and more flexible type system.
2051959
Performance Evaluation of Forwarding Strategies for Location Management in Mobile Networks
This paper presents a methodology for evaluating the performance of forwarding strategies for location management in a personal communication services (PCS) mobile network. A forwarding strategy in the PCS network can be implemented by two mechanisms: a forwarding operation which follows a chain of databases to locate a mobile user and a resetting operation which updates the databases in the chain so that the current location of a mobile user can be known directly without having to follow a chain of databases. In this paper, we consider the PCS network as a server whose function is to provide services to the mobile user for ‘updating the location of the user as the user moves across a database boundary’ and ‘locating the mobile user’. We use a Markov chain to describe the behavior of the mobile user and analyze the best time when forwarding and resetting should be performed in order to optimize the service rate of the PCS network. We demonstrate the applicability of our approach with hexagonal and mesh coverage models for the PCS network and provide a physical interpretation of the result.
11068219
An approximation algorithm for haplotype inference by maximum parsimony
This paper studies haplotype inference by maximum parsimony using population data. We define the optimal haplotype inference (OHI) problem as given a set of genotypes and a set of related haplotypes, find a minimum subset of haplotypes that can resolve all the genotypes. We prove that OHI is NP-hard and can be formulated as an integer quadratic programming (IQP) problem. To solve the IQP problem, we propose an iterative semi-definite programming based approximation algorithm, (called SDPHapInfer). We show that this algorithm finds a solution within a factor of O(logn) of the optimal solution, where n is the number of genotypes. This algorithm has been implemented and tested on a variety of simulated and biological data. In comparison with three other methods: HAPAR, HAPLOTYPER, and PHASE, the experimental results indicate that SDPHapInfer and HAPLOTYPER have similar error rates. In addition, the results generated by PHASE have lower error rates on some data but higher error rates on others. The error rates of HAPAR are higher than the others on biological data. In terms of efficiency, SDPHapInfer, HAPLOTYPER, and PHASE output a solution in a stable and consistent way, and they run much faster than HAPAR when the number of genotypes becomes large.
17694458
Optimal broadcasting on incomplete star graph interconnection networks
Broadcasting is an important collective communication operation in many applications which use parallel computing. In this paper, we focus on designing broadcasting algorithms for general incomplete star graphs. We propose two optimal one-to-all broadcasting algorithms for incomplete star graphs with a single-port communication model. An incomplete star graph with N nodes, where (n - 1)! < N < n!, is a subgraph of an n-dimensional star graph. The first scheme is single-message one-to-all broadcasting that takes O(nlogn) steps. The second one is multi-message one-to-all broadcasting that takes O(nlogn + m) steps.
206854715
Task Migration in 2D Wormhole-Routed Mesh Multicomputers
In this paper, two simple task migration schemes are first proposed for 2D mesh, multicomputers with supporting X-Y wormhole routing in the one-port communication model. We next propose a hybrid task migration scheme which attempts to minimize the total transmission latency. Finally, we compare all of our proposed task migration schemes using performance analysis.
295636
Agent-Based Forwarding Strategies for Reducing Location Management Cost in Mobile Networks
An important issue in location management for dealing with user mobility in wireless networks is to reduce the cost associated with location updates and searches. The former operation occurs when a mobile user moves to a new location registration area and the network is being informed of the mobile user's current location; the latter operation occurs when there is a call for the mobile user and the network must deliver the call to the mobile user. In this paper, we propose and analyze a class of new agent-based forwarding schemes with the objective to reduce the location management cost in mobile wireless networks. We develop analytical models to compare the performance of the proposed schemes with existing location management schemes to demonstrate their feasibility and also to reveal conditions under which our proposed schemes are superior to existing ones. Our proposed schemes are particularly suitable for mobile networks with switches which can cover a large number of location registration areas.