Generic Ada code in the NASA space station command, control and communications environment

The results of efforts to apply powerful Ada constructs to the formatted message handling process are described. The goal of these efforts was to extend the state-of-technology in message handling while at the same time producing production-quality, reusable code. The first effort was initiated in September, 1984 and delivered in April, 1985. That product, the Generic Message Handling Facility, met initial goals, was reused, and is available in the Ada Repository on ARPANET. However, it became apparent during its development that the initial approach to building a message handler template was not optimal. As a result of this initial effort, several alternate approaches were identified, and research is now on-going to identify an improved product. The ultimate goal is to be able to instantly build a message handling system for any message format given a specification of that message format. The problem lies in how to specify the message format, and one that is done, how to use that information to build the message handler. Message handling systems and message types are described. The initial efforts, its results and its shortcomings are detailed. The approach now being taken to build a system which will be significantly easier to implement, and once implemented, easier to use, is described. Finally, conclusions are offered

A Linear Specification Language for Petri Nets

This paper defines a category GNet with object set all Petri nets. A morphism in GNet from a net N to a net N' gives a precise way of simulating every evolution of N by an evolution of N'. We exhibit a morphism from a simple message handler to one with error-correction, showing that the more refined message handler can simulate any behaviour of its simple counterpart. The existence of such a morphism proves the correctness of the refinement

Using SMS text messaging for teaching and data collection in the behavioral sciences

Recent interest in university teaching has focused on interactivity in lectures and practical classes, and teachers in several fields have set up systems in which students can interact with the lecturer using mobile-phone-based SMS text messaging. This approach has particular potential in psychology, where students could use SMS messaging as a way of responding in simple psychology experiments or demonstrations. We describe a simple architecture for an SMS-based responding, using an SMS-to-HTTP message relay service, and a PHP/MySQL input-output handler. We describe briefly two experiments we have run using the system. The first experiment examined anchoring effects in an SMS-based auction. The second experiment examined delay discounting, with participants indicating their intertemporal preferences using SMS. Finally, we evaluate the feedback we obtained from students about the practical and conceptual issues surrounding text-message-based responding

INTRANET BASE-SMART AGENT ALERT SYSTEM USING EMAIL AND SHORT MESSAGE SERVICE (SMS) BROADCAST

The internet has changed the face of communication and enables more people to reach more other people than ever before. In this work, we employ the robustness of the internet by developing a smart agent alert system that delivers spy information instantly. The short message service (SMS) and Email capabilities were maximized to achieve this, seven model blocks were used: SMS model, Email model, the administrator console, the mail checker, web handler, the web interface and database model. SMS model is responsible for routing the SMS, it connect with the short message service centre (SMSC). When the system sends a text message to a user, the phone actually sends the message to the SMSC, which stores the message and then delivers it when the recipient is on the network. Email model is responsible for sending the message to the user; it connects to the mail checker to report back to the system where the mail is delivered to the user. The administrator console is an administration tool that enables Email and SMS Alert (EMSA) System administrators to administer the EMSA system components. As an integral part of the EMSA System, the console works as an independent process. It enables EMSA system administrators to manage actions related to user and changing data, activation and deactivation of the EMSA system, and controlling the web handler and mail checker. KEYWORDS: Alert system, Smart Agent, Short message service (SMS)

Kompics: a message-passing component model for building distributed systems

The Kompics component model and programming framework was designedto simplify the development of increasingly complex distributed systems. Systems built with Kompics leverage multi-core machines out of the box and they can be dynamically reconfigured to support hot software upgrades. A simulation framework enables deterministic debugging and reproducible performance evaluation of unmodified Kompics distributed systems. We describe the component model and show how to program and compose event-based distributed systems. We present the architectural patterns and abstractions that Kompics facilitates and we highlight a case study of a complex distributed middleware that we have built with Kompics. We show how our approach enables systematic development and evaluation of large-scale and dynamic distributed systems

Monotonic Prefix Consistency in Distributed Systems

We study the issue of data consistency in distributed systems. Specifically, we consider a distributed system that replicates its data at multiple sites, which is prone to partitions, and which is assumed to be available (in the sense that queries are always eventually answered). In such a setting, strong consistency, where all replicas of the system apply synchronously every operation, is not possible to implement. However, many weaker consistency criteria that allow a greater number of behaviors than strong consistency, are implementable in available distributed systems. We focus on determining the strongest consistency criterion that can be implemented in a convergent and available distributed system that tolerates partitions. We focus on objects where the set of operations can be split into updates and queries. We show that no criterion stronger than Monotonic Prefix Consistency (MPC) can be implemented.Comment: Submitted pape

Security architectures in mobile integrated pay-TV

This paper presents the design and describes the advantage of the state-of-the-art Mobile Integrated Conditional Access System (MICAS) concerning interoperability, personalisation, security and operational costs in Pay-TV systems. The Message Handling Subsystem is proposed and outlined together with ‘Follow-Me’ service, which proposed herewith to extend mobility and personalisation concepts on Pay-TV service

Web Services: A Process Algebra Approach

It is now well-admitted that formal methods are helpful for many issues raised in the Web service area. In this paper we present a framework for the design and verification of WSs using process algebras and their tools. We define a two-way mapping between abstract specifications written using these calculi and executable Web services written in BPEL4WS. Several choices are available: design and correct errors in BPEL4WS, using process algebra verification tools, or design and correct in process algebra and automatically obtaining the corresponding BPEL4WS code. The approaches can be combined. Process algebra are not useful only for temporal logic verification: we remark the use of simulation/bisimulation both for verification and for the hierarchical refinement design method. It is worth noting that our approach allows the use of any process algebra depending on the needs of the user at different levels (expressiveness, existence of reasoning tools, user expertise)

An Object-Oriented Language-Database Integration Model: The Composition-Filters Approach

This paper introduces a new model, based on so-called object-composition filters, that uniformly integrates database-like features into an object-oriented language. The focus is on providing persistent dynamic data structures, data sharing, transactions, multiple views and associative access, integrated with the object-oriented paradigm. The main contribution is that the database-like features are part of this new object-oriented model, and therefore, are uniformly integrated with object-oriented features such as data abstraction, encapsulation, message passing and inheritance. This approach eliminates the problems associated with existing systems such as lack of reusability and extensibility for database operations, the violation of encapsulation, the need to define specific types such as sets, and the incapability to support multiple views. The model is illustrated through the object-oriented language Sina