Reactive programming has recently gained popularity as a paradigm that is well-suited for developing event-driven and interactive applications. It facilitates the development of such applications by providing abstractions to express time-varying values and automatically managing dependencies between such values. A number of approaches have been recently proposed embedded in various languages such as Haskell, Scheme, JavaScript, Java, .NET, etc. This survey describes and provides a taxonomy of existing reactive programming approaches along six axes: representation of time-varying values, evaluation model, lifting operations, multidirectionality, glitch avoidance, and support for distribution. From this taxonomy, we observe that there are still open challenges in the field of reactive programming. For instance, multidirectionality is supported only by a small number of languages, which do not automatically track dependencies between time-varying values. Similarly, glitch avoidance, which is subtle in reactive programs, cannot be ensured in distributed reactive programs using the current techniques. INTRODUCTIONToday's applications are increasingly becoming highly interactive, driven by all sorts of events originating from within the applications and their outside environment. Such event-driven applications maintain continuous interaction with their environment, processing events and performing corresponding tasks such as updating the application state and displaying data [Pucella 1998]. The most interactive part of such appli- Author's addresses: Software Languages Lab, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Brussels, Belgium; email: ebainomu@vub.ac.be Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies show this notice on the first page or initial screen of a display along with the full citation. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works requires prior specific permission and/or a fee. Permissions may be requested from Publications Dept., ACM, Inc., 2 Penn Plaza, Suite 701, New York, NY 10121-0701 USA, fax +1 (212) 869-0481, or permissions@acm.org. cations is usually the GUI, which typically needs to react to and coordinate multiple events (e.g., mouse clicks, keyboard button presses, multi-touch gestures, etc.).These applications are difficult to program using conventional sequential programming approaches, because it is impossible to predict or control the order of arrival of external events and as such control jumps around event handlers as the outside environment changes unexpectedly (inverted control, i.e., the control flow of a program is driven by external events and not by an order specified by the programmer). Moreo...

A new field in distributed computing, called Ambient Intelligence, has emerged as a consequence of the increasing availability of wireless devices and the mobile networks they induce. Developing software for mobile networks is extremely hard in conventional programming languages because the network is dynamically demarcated. This leads us to postulate a suite of characteristics of future Ambient-Oriented Programming languages. A simple reflective programming language, called AmbientTalk, that meets the characteristics is presented. It is validated by implementing a collection of high level language features that are used in the implementation of an ambient messenger application .

In this paper, we describe AmbientTalk: a domainspecific language for orchestrating service discovery and composition in mobile ad hoc networks. AmbientTalk is a distributed object-oriented programming language whose actor-based, eventdriven concurrency model makes it highly suitable for composing service objects across a mobile network. The language is a so-called ambient-oriented programming language which treats network partitions as a normal mode of operation. We describe AmbientTalk's object model, concurrency model and distributed communication model in detail. We also highlight the major influences from other languages and middleware that have shaped AmbientTalk's design.

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Abstract. Coordination languages for ad hoc networks with a fluid topology do not offer adequate support to detect and deal with device disconnection. Such a disconnection is particularly relevant if the device provided context information rather than emitting messages, as such context information then becomes invalid. This paper proposes the Fact Space Model which establishes a logic coordination language on top of Lime's federated tuple space. In the model, the federated space offers applications a consistent view of their environment over which they can reason using logic rules. These rules encode which conclusions may be drawn from the presence of particular facts, and are similarly used to ensure the consistency of these conclusions when devices go out of range. By allowing applications to add application-specific hooks to these rules, the application programmer is offered a general-purpose mechanism to respond to the discovery and disconnection of devices.