Ambient-Oriented Programming in AmbientTalk

Abstract

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 .

Parallel actor monitors: Disentangling task-level parallelism from data partitioning in the actor model

“…Since then it has been one of the main rules in stateful actor languages such as Erlang [6], Akka and Scala [7], Kilim [8], ProActive [9], E [10], Salsa [11] and AmbientTalk [12]. In all these languages execution of parallel messages within a single actor is disallowed by construction, e.g.…”

“…For instance, AmbientTalk [12] supports symbiosis with Java [14], which can be used to take advantage of multi-threading as provided by the Java language. However, such a backdoor reintroduces the traditional concurrency problems and forces the programmer to think in two different paradigms (actor model and thread based model).…”

“…AmbientTalk [12] is an actor language with an event loop concurrency model adopted from E [10]. In this model, actors are represented as containers of regular objects encapsulating a single thread of execution (an event loop) which perpetually take a message from their message queue and invoke the corresponding method of the object denoted as the receiver of the message.…”

Exception Handling and Asynchronous Active Objects: Issues and Proposal

“…... ( 4) ( 5) public void handle (GlobalNetworkException exc) ( 6) // handler associated to the Broker asynchronous active object ( 7) { ... } (10) (11) class PollProviders implements Service (12) { (13) ... (14) public void body () (15) { ... } (16) public void handle (BadParameterException exc) (17) // handler associated to the PollProviders service (18) { signal (new NoAirportInDestinationException (...); } (19) public void handle (NoProviderException exc) (20) // handler associated to the PollProviders service (21) { ... } (22) } (23) (24) class ContactParties implements Service (25) { (26) public void body () (27) { (28) ... (29) sendMessage (new RequestMessage (aClient, (30) "ContactSelectedProvider") (31) { (32) public void handle (OffLineException exc) (33) // handler associated to a request (34) { (35) wait(120); (36) retry(); (37) } (38) }); (39) ... gether to the achievement of a global task. In the example, such a handler should be de ned somewhere at the level of the requesting Broker object it should be invoked whenever one or more travel providers signal an exception, and it should be able to access the Broker context.…”

Multi-threaded Active Objects

“…Active objects, on the other hand, return futures [6] as placeholders for the result, allowing the invoker to continue its execution. Futures can be created and accessed either explicitly, like in Creol [7] and JCoBox [8], or implicitly as in ASP [3] (Asynchronous Sequential Processes) and AmbientTalk [9]. A key benefit of the implicit creation is that no distinction is made between synchronous (i.e., local) and asynchronous (i.e., remote) operations in the program.…”