Differences

This shows you the differences between two versions of the page.

--- at:tutorial:distribution [2007/04/26 20:07] – elisag
+++ at:tutorial:distribution [2007/04/26 20:16] – elisag
@@ Line 1: / Line 1: @@
+<note>
+This tutorial is under heavy construction!
+</note>
 ====== Distributed Programming ======
-This section discusses how AmbientTalk virtual machines can discover and communicate with each other over the network.
+This tutorial chapter discusses how AmbientTalk virtual machines can discover and communicate with each other over the network.
-The integration of distribution was one of the main concerns in the design of AmbientTalk programming model. More specifically, as a distributed programming languages that adheres to the Ambient-Oriented Programming paradigm, AmbientTalk incorporates partial failures and discovery lookup facilities at the heart of its distributed programming model. Rather than creating stubs and skeletons to manage remote communications, AmbientTalk integrates them transparently to the developer thanks to its concurrency model based on actors and far references. Far references are in fact a vital feature of the distributed model of AmbientTalk that allows the language to be able to handle the so-called volatile connections featured in mobile ad hoc networks.  This section mainly explains the language abstractions to export and discover other remote objects, and handle partial failures. But first, let us start simply by showing how to enable the network functionality.
+The integration of distribution was one of the main concerns in the design of AmbientTalk programming model. More specifically, as a distributed programming languages that adheres to the Ambient-Oriented Programming paradigm, AmbientTalk incorporates partial failures and discovery lookup facilities at the heart of its distributed programming model. Rather than creating stubs and skeletons to manage remote communications, AmbientTalk integrates them transparently to the developer thanks to its concurrency model based on actors and far references. Far references are in fact a vital feature of the distributed model of AmbientTalk that allows the language to be able to handle the so-called volatile connections featured in mobile ad hoc networks.  This chapter mainly explains the language abstractions to export and discover other remote objects, and handle partial failures. But first, let us start simply by showing how to enable the network functionality.
 ===== Starting the Network.. =====
@@ Line 51: / Line 54: @@
 The code block to execute when the service type becomes available is parameterized with the actual remote reference to the discovered service object. In the example above, ''messenger'' is a remote reference to the remote object exporting the ''InstantMessenger'' service type. Imagine the interaction between the instant messenger applications executing the above code of two persons, e.g. Bart and Lisa. When the instant messenger of Bart and the instant messenger of Lisa come into one another's communication range, Bart will discover Lisa and Lisa will discover Bart via the ''InstantMessenger'' service type. Then, both will interchange their names and store it in their ''buddyList''.
 <note>
-We are using a future to get the return value of the ''getName'' asynchrnonus message invocation. For further details about futures and the ''when:becomes:'' language construct, we refer the reader to the previous chapter on the concurrency model of AmbientTalk.
+We are using a future to get the return value of the ''getName'' asynchrnonus message invocation. For further details about futures and the ''when:becomes:'' language construct, we refer the reader to the previous chapter on the [[actors|concurrency model of AmbientTalk]].
 </note>
@@ Line 61: / Line 64: @@
 ===== Partial Failure Handling =====
-Let us consider again the example instant messenger application described in previous subsection to further explain the semantics of AmbientTalk's remote object references and how they deal with transient disconnections. When an object discovers a service type, the ''when'' observers are triggered receiving as parameter a remote far reference to the remote object discovered. As explained in previous sections, far references operates asynchronously. When a client object sends a message via a remote reference, the message is buffered in the remote far reference and the client does not even wait for the message to be delivered. This is crucial in distributed computing in order to prevent race conditions. The parameter passing in the context of distribution works similar to the inter-actor message sending semantics:
+Let us consider again the example instant messenger application described in previous section to further explain the semantics of AmbientTalk's remote object references and how they deal with transient disconnections.
+When an object discovers a service type, the ''when'' observers are triggered receiving as parameter a remote far reference to the remote object discovered. As explained in previous sections, far references operates asynchronously. When a client object sends a message via a remote reference, the message is buffered in the remote far reference and the client does not even wait for the message to be delivered. This is crucial in distributed computing in order to prevent race conditions. The parameter passing in the context of distribution works similar to the inter-actor message sending semantics:
   - Objects are always passed by far reference, except for isolate objects which are passed by copy.
   - Native data types are always passed by copy.
 When a remote far reference receives a messages, it flushes the message to the remote object providing that it is connected. If the remote far reference is disconnected, messages are accumulate in its inbox in order to be transmitted once the reference becomes reconnected at a later point in time once the network connection is restored.