Mobile UNITY: Reasoning and Specification in Mobile Computing

Mobile computing represents a major point of departure from the traditional distributed computing paradigm. The potentially very large number of independent computing units, a decoupled computing style, frequent disconnections, continuous position changes, and the location-dependent nature of the behavior and communication patterns present designers with unprecedented challenges in the areas of modularity and dependability. So far, the literature on mobile computing is dominated by concerns having to do with the development of protocols and services. This paper complements this perspective by considering the nature of the underlying formal models that will enable us to specify and reason about such computations. The basic research goal is to characterize fundamental issues facing mobile computing. We want to achieve this in a manner analogous to the way concepts such as shared variables and message passing help us understand distributed computing. The pragmatic objective is to develop techniques that facilitate the verification and design of dependable mobile systems. Towards this goal we employ the methods of UNITY. To focus on what is essential we center our study on ad-hoc networks whose singular nature is bound to reveal the ultimate impact of movement on the way one computes and communicates in a mobile environment. To understand interactions we start with the UNITY concepts of union and superposition and consider direct generalization to transient interactions. The motivation behind the transient nature of the interactinos comes from the fact that components can communicate with each other only when they are within a certain range. The notation we employ is a highly-modular extension of the UNITY programming notation. Reasoning about mobile computation relies on extensions to the UNITY proof logic

Mobile UNITY Coordination Constructs Applied to Packet Forwarding for Mobile Hosts

With recent advances in wireless communication technology, mobile computing is an increasingly important area of research. A mobile system is one where independently executing components may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. Mobile UNITY is a language and logic for specifying and reasoning about mobile systems, the components of which must operate in a highly decoupled way. In this paper it is argued that Mobile UNITY contributes to the modular development of system specifications because of the declarative fashion in which coordination among components is specified. The packet forwarding mechanism at the core of the Mobile IP protocol for routing to mobile hosts is taken as an example. A Mobile UNITY specification of packet forwarding and the mobile system in which it must operate is developed. Mobile hosts are the components that can disconnect from one location in the network and reconnect to another at any point during system execution. Finally, the role of formal program verification in the development of protocols like Mobile IP is discussed

Mobile UNITY: A Language and Logic for Concurrent Mobile Systems

Traditionally, a distributed system has been viewed as a collection of fixed computational elements connected by a static network. Prompted by recent advances in wireless communications rechnology, the emerging field of mobile computing is challenging these assumptions by providing mobile hosts with connectivity that may change over time, raising the possibility that hosts may be called upon to operate while only weakly connected to or while completely disconnected from other hosts. We define a concurrent mobile system as one where independently executing coponents may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. Note that this definition is general enough to encompass a system of mobile hosts moving in physical space as well as a system of migrating software agents implemented on a set of possibly non-mobile hosts. In this paper, we present Mobile UNITY, which is a notation for expressing such systems and a logic for reasoning about their temporal properties. Based on the UNITY language of Chandy and Misra, our goal is to find a minimalist model of mobile computation that will allow us to express mobile components in a modular fashion and to reason formally about the possible behaviors of a system composed from mobile components. We also show how the model can contribute to our understanding of mobility by exploring new abstractions for loosely coupled communication and coordination among components

Reasoning about Program Interactions in the Presence of Mobility

Mobile computing is emerging as an important new paradigm which has the potential to reshape our thinking about distributed computation. Mobility has far-reaching implications on what designers and users can assume about communication patterns, resource availability, and applciation behaviors as components move from one location to another while joining or leaving groups of other components in their vicinity. New distributed algorithms are likely to be required as the nature of applications shifts with the emergence of this new kind of computing environment. Formal methods have an important role to play in the midst of these developments both in terms of helping the research community better understand fundamental issues germane to mobile computing and by providing pratical solutions to difficult design problems

Assertional Reasoning about Pairwise Transient Interactions in Mobile Computing

Mobile computing represents a major point of departure from the traditional distributed computing paradigm. The potentially very large number of independent computing units, a decoupled computing style, frequent disconnections, continuous position changes, and the location-dependent nature of the behavior and communication patterns of the individual components present designers with unprecedented challenges in the areas of modularity and dependability. This paper describes two ideas regarding a modular approach to specifying and reasoning about mobile computing. The novelty of our approach rests with the notion of allowing transient interactions among programs which mobe in space. In this paper we restrict our concert to pariwise interactions involving variable sharing and action asynchronization. The motivation behind the transient nature of the interactions comes from the fact that components can communicate with each other only when they are within a certain range. The notation we propose is meant to simplify the writing of mobile applciaitons and is a direct extension of that used in UNITY. Reasoning about mobile bomputations relies on the UNITY proof logic

Unique transcriptomic landscapes identified in idiopathic spontaneous and infection related preterm births compared to normal term births.

Preterm birth (PTB) is leading contributor to infant death in the United States and globally, yet the underlying mechanistic causes are not well understood. Histopathological studies of preterm birth suggest advanced villous maturity may have a role in idiopathic spontaneous preterm birth (isPTB). To better understand pathological and molecular basis of isPTB, we compared placental villous transcriptomes from carefully phenotyped cohorts of PTB due to infection or isPTB between 28-36 weeks gestation and healthy term placentas. Transcriptomic analyses revealed a unique expression signature for isPTB distinct from the age-matched controls that were delivered prematurely due to infection. This signature included the upregulation of three IGF binding proteins (IGFBP1, IGFBP2, and IGFBP6), supporting a role for aberrant IGF signaling in isPTB. However, within the isPTB expression signature, we detected secondary signature of inflammatory markers including TNC, C3, CFH, and C1R, which have been associated with placental maturity. In contrast, the expression signature of the gestational age-matched infected samples included upregulation of proliferative genes along with cell cycling and mitosis pathways. Together, these data suggest an isPTB molecular signature of placental hypermaturity, likely contributing to the premature activation of inflammatory pathways associated with birth and providing a molecular basis for idiopathic spontaneous birth

Expressing Code Mobility in Mobile UNITY

Advancements in network technology have led to the emergence of new computing paradigms that challenge established programming practices by employing weak forms of consistency and dynamic forms of binding. Code mobility, for instance, allows for invocation-time binding between a code fragment and the location where it executes. Similarly, mobile computing allows hosts (and the software they execute) to alter their physical location. Despite apparent similarities, the two paradigms are distinct in their treatment of location and movement. This paper seeks to uncover a common foundation for the two paradigms by exploring the manner in which stereotypical forms of code mobility can be expressed in a programming notation developed for mobile computing. Several solutions to a distributed simulation problem are used to illustrate the modeling strategy for programs that employ code mobility