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in Sect. 3 the translation of the Jason constructs, the Jason reasoning cycle,the process orchestration of eJason, and the current limitations of the approachare explained. Some early benchmarks results for the eJason prototype are reportedin Sect. 4. Finally, a summary of our conclusions and items for futurework appear in Sect. 5.2 ErlangErlang [3, 10] is a functional concurrent programming language created by Ericssonin the 1980s. The chief strength of the language is that it provides excellentsupport for concurrency, distribution and fault tolerance on top of a dynamicallytyped and strictly evaluated functional programming language. It enablesprogrammers to write robust and clean code for modern multiprocessor and distributedsystems. In this section we briefly describe the key aspects of Erlang.2.1 Functional ErlangIn Erlang basic values are: integers, floats, atoms (starting with a lowercaseletter), bit strings, binaries, and funs (to create anonymous functions), and processidentifiers (pids). The compound values are lists and tuples. Erlang syntaxincludes a record construct which provides syntactic sugar for accessing the elementsof a tuple by name, instead of by position. Functions are first class citizensin Erlang. For example, consider the declaration of the function factorial thatcalculates the factorial of a number.factorial(0) -> 1;factorial(N) when N > 0 -> N * factorial(N - 1).As in Prolog, variable identifiers (N) start with a capital letter, and atoms(factorial) with a lowercase letter. Like Prolog, Erlang permits only singleassignment to variables.As virtually all functional programming languages, Erlang supports higherorder functions.2.2 Concurrent and Distributed ErlangAn Erlang system (see Fig. 1) is a collection of Erlang nodes. An Erlang node (orErlang Run-time System) is a collection of processes, with a unique node name.Communication is asynchronous and point-to-point, with one process sending amessage to a second process identified by its pid. Messages sent to a process areput in its message queue, also referred to as a mailbox. Informally, a mailbox isa sequence of values ordered by their arrival time. Mailboxes can in theory storeany number of messages. Although mailboxes are ordered, language constructspermit retrieving messages from the process mailbox in arbitrary order.As an alternative to addressing a process using its pid, there is a facility forassociating a symbolic name with a pid. The name, which must be an atom,9
Node 1registryNode 2registryProc BProc CmailboxProc AprocessdictionaryFig. 1. An Erlang multi-node systemis automatically unregistered when the associated process terminates. Messagepassing between processes in different nodes is transparent when pids are used,i.e., there is no syntactical difference between sending a message to a process inthe same node, or to a remote node. However, the node must be specified whensending messages using registered names, as the pid registry is local to a node.A unique feature of Erlang that greatly facilitates building fault-tolerantsystems is that processes can be “linked together” in order to detect and recoverfrom abnormal process termination. If a process P 1 is linked to another processP 2 , and P 2 terminates with a fault, process P 1 is automatically informed of thefailure of P 2 . It is possible to create links to processes at remote nodes.As an integral part of Erlang, the OTP library provides a number of veryfrequently used design patterns (behaviours in Erlang terminology) for implementingrobust distributed and concurrent systems. The most important OTPdesign patterns are generic servers that implement client/server architectures,and supervisors, to build robust systems. Other OTP design patterns implement,for instance, a publish-subscribe mechanism, and a finite state machine.3 Implementing Jason in ErlangThis section describes the implementation of a subset of Jason in Erlang.3.1 A simple running example in JasonTo illustrate the implementation of Jason in Erlang, we use the example in Fig. 2,which illustrates the main syntactical elements of the Jason language.This somewhat artificially programmed agent is a counter, which prints amessage when finished. The initial beliefs of the agent are (a), representing that10
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EnvironmentHardwareLocal SoftwareC+
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a cognitive layer can connect as a
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can reliably be differentiated and
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4 ExperimentTo evaluate the feasibi
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learn or gain knowledge from experi
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A Programming Framework for Multi-A
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exchange and storage of tuples (key
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Although some success [13] [14] hav
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as well as important non-functional
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component plans have been instantia
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A in the example) can evaluate all
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1. robot-1 issues a Localization(ro
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ACKNOWLEDGMENTThis work has been su
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The code was analysed both objectiv
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a conversation is following. Additi
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the context of a communication-heav
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Table 1. Core Agent ProtocolsAgent
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statistically significant using an
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to the conversation and has a perfo
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principal reasons. Firstly, it is a
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2. Muldoon, C., O’Hare, G.M.P., C
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In the following section we will at
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DevelopmentProductionHuman Readabil
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will then evaluate this new format
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encoder, it is first checked if the
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nents themselves. However, since th
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optimized for this format feature s
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Java serialization and Jadex Binary
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10. P. Hoffman and F. Yergeau, “U
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Caching the results of previous que
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querying an agent’s beliefs and g
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or relative performance of each pla
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were run for 1.5 minutes; 1.5 minut
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Size N K n p c qry U c upd Update c
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epresentation. The cache simply act
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6 ConclusionWe presented an abstrac
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Typing Multi-Agent Programs in simp
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1 // agent ag02 iterations (" zero
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3.1 simpAL OverviewThe main inspira
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3.2 Typing Agents with Tasks and Ro
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Defining Agent Scripts in simpAL (F
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that sends a message to the receive
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* error: wrong type for the param v
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Given an organization model, it is
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Learning to Improve Agent Behaviour
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2.1 Agent Programming LanguagesAgen
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choosing actions is to find a good
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1 init module {2 knowledge{3 block(
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of a module. For example, to change
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if bel(on(X,Y), clear(X)), a-goal(c
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mance. Figure 2d shows the same A f
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the current percepts of the agent.
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Author IndexAbdel-Naby, S., 69Alelc
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