User Guide - Department of Information and Computing Sciences
Contents
1. PROGRAM envAgent BELIEFBASE bombAt X Y X Y11T bombAt X Y X1 Y1 T bombAt X Y T GOALBASE PLANBASE Java BlockWorld enter 4 1 1 L start 1 gt PG RULES PR RULES start Y lt TRUE Java BlockWorld senseBombs BOMBS IF bombAt 5 Y BOMBS THEN Java BlockWorld east L Java BlockWorld pickup L Java BlockWorld west L Java BlockWorld west L Java BlockWorld drop L Java BlockWorld east L F Java BlockWorld south L start Y 1 Figure 19 External Actions in BlockWorld environment Load the 3APL agent envAgent from the examples directory Load a block world configuration through the Load from File button under the World menu of the block world environment and select the blockworld world from the examples directory see Figure 20 Execute the 3APL agent and observe the behavior of the agent The blue circle around the agent in the environment indicates the range of its sense actions i e which blocks of the environment the agent can perceive if it performs a senseBombs action The sense range can be modified by the Sense Range button of the block world environment The list of all actions that the 3APL agents can perform in this block world is as follows void enter X Y C Create a agent representation in the environment at position X Y The time out of this action is indicated by C milliseconds or 1 for infinite ti2. PG RULES PR RULES prloop lt listi L loop L loop L lt L SKIP loop L lt L HIT Add H loop T whileloop lt TRUE WHILE listi L AND NOT empty L DO Extract L Figure 16 List manipulations in 3APL by PR rules or while goal single exclamation mark allows the matched goal in the goal base to contain additional subgoals Execution blocks if a match cannot be found 5 3 Communicating Agents In multi agent systems individual agents must be able to do two things they must be able to find other agents that offer some service and they must be able to communicate with one another To this end the 3APL multi agent platform supports a service directory and communication facilities Both of these facilities are implemented as functionalities of AMS 5 3 1 Agent Communication Messages from one agent to another agent are delivered by the underlying transport layer as shown in 17 The messages themselves have a specific structure which is compliant with the FIPA standards for agent communication 6 The following fields are necessary elements of a message e Receiver String identity of the receiving agent e Performative String communicative act type inform request e Content WFF formula that expresses the content of the message Messages can be sent by the dedicated 3APL capabilities Send Receiver Performative Content 14 5 3 Communicating Agents 5 GETTING STA
3. dest Dest Goto Room Movebox Room Dest if box Dest then Transported PR RULES Figure 11 A simple 3APL program example belief base This contains the information of the agent including its general information about the world as well as specific information about its environment Beliefs are stored as Prolog clauses For example pos room1 can be used to indicate that the agent believes its current position is room1 The belief base can be extended with a Prolog program using the LOAD option see section 5 1 4 below 5 1 Loading and Executing a Simple Agent 5 GETTING STARTED capabilities These are mental actions that an agent can perform The execution of a mental action updates the agent s belief base Capabilities are of the form Pre Capability t Post A mental action can be executed if the belief base entails the beliefs corresponding to their pre conditions Like in Prolog the NOT operator in pre and post conditions is interpreted as negation as failure The execution of the mental actions implies that the belief base will entail the beliefs that correspond to their post conditions after the execution For example the mental action Goto R can be executed if the agent is at a position pos P After the execution of the mental action the position of the agent is not pos p anymore but pos R goal base This contains a set of goals separated by a comma A goal denotes a state that the agent wants to ach
4. editor is opened displaying the contents of the agent program The user 4 3 Sniffer 4 USER INTERFACE Terence toa Figure 5 The Agent properties panel Meaning Execute the selected agent Execute the selected agent for one deliberation cycle Stop the execution of the selected agent Edit the 3APL program of the selected agent Recompile the program of the selected agent MA OF Fs Remove the selected agent from the platform Figure 6 Agent status icons can now change the program The changes can then be saved and applied if the 3APL program is parsed correctly otherwise a parse errors is generated If the user wants to reset the configuration of the agent i e its initial bases are set as specified by the agent program the user can select the recompile button which is the fifth button Finally the sixth button closes the selected agent and removes it from the platform Similar buttons on the top of the window have similar meaning for multi agent cases see section 5 3 4 3 Sniffer One of the tools which can be activated to observe the communication between agents is the Sniffer tool It can be executed by clicking the Sniffer icon located at the top of the main window This tool produces an output like displayed in figure 7 This tool is used to visualize the conversations betwe
5. of the selected template program with the exception of the first instruction which is program NAM E instruction This has been filled with the name of the agent the user has given in the agent name field Users can add their own templates In order for this to work the template program must be placed in the templates directory A copy of the template will be created The name of the new agent is taken from the Agent name field as shown above in figure 10 This name will replace every occurrence of 1 in the program This means that a template must have a first sentence such as program 1 5 Getting Started In this section we show by examples how the 3APL platform can be used In particular we discuss simple examples of 3APL programs to show the meaning of the control buttons manipulations of the agent s belief base goal base and plan base Also we discuss an example of a multi agent system where the use of communication action Send the way to request services of other agents through the AMS Agent Management System agent and the use of a so called project file are explained Finally we discuss how a shared environment for 3APL agents can be implemented using external Java programs The 3APL agents can then execute actions including sensing actions in the shared environment It should be noted that we do not present the formal syntax and semantics of the 3APL pro gramming language in this user guide In fact we assume that the reader
6. the platform the agent should be added to reset moved to initial position or removed from the blockworld environment respectively The effects of the mentioned events on the platform are realized by the platform through invocation of one of the methods in the Plugin interface createlnstance resetInstance and removelnstance 6 1 2 Details of Plugin factory public interface Plugin 4 public List getMethods public String toString public String getDescription public Instance createInstance String agentName public void resetInstance Instance i public void removeInstance Instance i List getMethods This method is called by the platform at startup to get the methods this plugin provides It must return a Collection containing Method objects String toString This method must return the name of the Plugin String getDescription This method must return the description of the Plugin Instance createInstance String agentName This method is called by the platform every time an agent is added It must create a new Instance object That object refers belongs to the agent identified by the argument agentName Note that this name is unique void resetInstance Instance i Called by the platform when the agent this instance refers to is reset that is the user pressed the recompile agent button void removelnstance Instance i Called by the platform when the agent this instance refers to is about to be removed fro
7. 2 Service Directory Facilitator In general a directory facilitator provides yellow page services to agents on a platform It maintains a searchable list of services of agents which have been registered Agents can search the directory to find another agent that offers a service A full directory facilitator has not yet been implemented in the 3APL platform However agents can use the agent management system to simulate the functionality of a directory facilitator To register a service an agent can send an inform message to the AMS of which the content is a simple expression of the from description Service that describes the service to be announced To unregister the same procedure is used with NOT added before the description To request a list of agents that provide a particular service an agent can send a query message to the AMS with a service description in the content Suppose we have an agent seller that wishes to announce to the AMS that it can sell computers This agent will execute the communication action Send ams inform description sellcomp When the agent seller has no more computers to sell it can notify the AMS by the action 15 5 3 Communicating Agents 5 GETTING STARTED PROGRAM harry BELIEFBASE me harry you sally GOALBASE hello PLANBASE PG RULES hello lt lt PR RULES you You AND NOT sent You inform hello You Send You inform hello You me Me AND rec
8. 21 6 22 SourcecOde i544 HAKA MA aaa GG dd 21 4 USER INTERFACE 1 3APL Platform The 3APL platform is an experimental tool designed to support the development implementation and execution of 3APL agents 2 It provides a graphical interface through which a user can develop and execute 3APL agents using several facilities such as a syntax colored editor and several debugging tools The platform allows communication among agents The platform can run on several machines connected in a network such that agents hosted on 3APL platforms can communicate with each other More detailed information on the 3APL platform can be found in 5 2 Software Requirements 3APL platform has been tested on Windows 98 Windows NT and Windows XP as well as Linux and Unix Solaris 3APL is written in Java 2 JDK1 5 0 06 and makes use of the Prolog engine of JIProlog which is also written in java The 3APL package consists of a jar file that contains all the class files needed as well as some examples of 3APL programs The package needs approximately 850 KB 3 Installation In order to install 3APL Platform you need to follow the next procedure e Download the 3ap1 zip file from the following URL http www cs uu nl 3ap1 download html e Extract the contents of the ZIP file into a directory The content consists of a 3ap1 jar file and a directory called example This directory contains a number of examples that will be discussed and explained in sec
9. 3APL Platform User Guide Mehdi Dastani 16th November 2006 CONTENTS CONTENTS Contents 1 3APL Platform 3 2 Software Requirements 3 3 Installation 3 4 User Interface 3 4 1 Messages window iag apa dd te ee a a aaa Geo 5 4 2 Agent properties s m ienaa ee eA a ee a 5 ALS Qn A eer ses deg SE ee Be aa a Es Sg ee ee Eh ee GNG 6 4 4 Message sender iosian e ee aa 7 4 5 Template agents cp MAGA e a a BSA a aa BS 8 5 Getting Started 8 5 1 Loading and Executing a Simple Agent o a 9 Dll Programm Structure ss sa aa rs de die es a a a a NG LUNA ala 9 541 22 Lo dins a Programas 5 5 54 ii NT a a asta age Ge Shae ess A GG 10 dol 3 Executing Program 4 ici aa be n ee y AAA 11 5 1 4 External Prolog Files 2 0 0 o eee ee eee eee 11 5 1 5 List Manipulation in 3APL e 13 5 2 Goal Dynamics usa a daa la a daa SOS NA a NG 13 5 3 Communicating Agents cao o 14 5 3 1 Agent Communication 14 5 3 2 Service Directory Facilitator oo o en 15 5 4 Shared Environment and External Actions 0a 17 6 Plugin Developers Guide 19 6 1 Anatomy Of a plugin a Ki AA Ba a BR ABA tt NGA hh DBA 19 ES E A ayy fu Re E halang 20 6 1 2 Details of Plugin factory omar a KG 20 6 1 3 Details of Instance product o o e e 20 6 1 4 Details of Methods s oarda ts BRA HAL AA td sh 21 6 2 Example pl Bin ria A A Re A 21 6 2 1 Description 4 pas da Ka ala Se an DUA de te es da
10. RTED Agent Platform Agent 3 Management Di recor Facilitator System Message Transport System Figure 17 Multi agent platform architecture Agents can receive a message in their belief base at each moment in time When an agent sends a message to a second agent then the belief base of the sender is updated with the formula sent Receiver Performative Content and the belief base of the receiver is updated with the formula received Sender Performative Content An example of two agents capable of saying hello to each other is shown in figure 18 These agents are called harry and sally Now load both 3APL programs harry and sally from the examples directory If you run them they will start by saying hello and respond to each other s hello with a thanks The process of the message passing can be followed by two tools provided in the platform i e the Communication panel tool as shown in figure 4 and the Sniffer tool as shown in figure 7 To see the content of a message you can double click the message labels In the previous example the agents Harry and Sally were loaded separately In order not to load all agents one by one for the next time they are needed one can save a set of agents as a project such that they i e the project can be loaded simultaneously next time A number of agents that are loaded on the platform can be saved as a project by the command Save Project or Save Project As under the File menu 5 3
11. ad practice to store dynamic beliefs as part of an external Prolog file 5 1 5 List Manipulation in 3APL The 3APL language does not provide common data structures like arrays or records Instead of records 3APL uses Prolog facts which represent data in the belief base of the agent For example an address can be stored as follows address john_baley 15 oxford_road islington uk Instead of arrays or vectors 3APL uses Prolog lists By definition a list is either an empty list or a complex list such as HIT H1 H2 T and H1 T1 H2 T2 In general you cannot access the elements of a list directly Instead you have to decompose it step by step There are many possible ways to do this for example through PR rules or while construct as shown in Figure 16 The use of PR rules to access the elements of a list employs two PR rules one that recognizes the empty list and one that reduces the list To use while goals for repetition we must somehow store the progress of the loop in the belief base of the agent In this example this is achieved by deleting elements from the belief base If none are left the loop is done In order to run this example load the 3APL program list 3apl from the examples directory and execute it Observe the changes in the belief base and plan base 5 2 Goal Dynamics There are five actions in 3APL operating on the goal base These actions are designed to add and remove goals to from the goal base and te
12. al Prolog files can be loaded into the 3APL belief base by means of the LOAD command at the beginning of a 3APL program In this way the belief base of an agent is extended with the clauses defined in that file These additional clauses will be used to execute test actions and to check the pre conditions of mental actions the guards of the rules or the conditions of while loops and if then else statements Since we use JIProlog 8 a prolog engine written in JAVA the standard JIProlog predicates and commands are also directly available in 3APL see JIProlog 11 5 1 Loading and Executing a Simple Agent 5 GETTING STARTED user manual 8 for more details In order to implement a 3APL agent which employs an external Prolog file load in the 3APL platform the file arithmetics 3apl from the examples directory This program is illustrated in Figure 14 Execute this 3APL program and observe that the agent has an initial plan which is a sequence of three abstract plans These abstract plans are subsequently refined by applying the corresponding PR rules As you can see after the application of the first PR rule the plan is refined and executed The test action times X Y Z is then executed which provides substitu tions for the variables X Y and Z Note that the predicate times X Y Z is defined in the external file cal p1 which is loaded by the LOAD statement In this Prolog file which is also included in the examples directory two other pred
13. an agent may contain the description of the agent if the agent has reported its description to the AMS when it is executed The agent can report its descriptions to AMS by sending an inform message to it For instance a seller agent may inform the AMS 4 1 Messages window 4 USER INTERFACE that he is a seller by performing the following communication action in the next sections we will explain agent communication in more details Send ams inform description seller The last icon in Figure 3 can only appear if the 3APL program of the agent is saved after a modification through which a syntax error is created Note that the agent has already been loaded on the platform see section 4 2 for modifying 3APL programs on the platform The fact that the agent was loaded already implies that the program was correctly complied before modification An erroneous agent program cannot be loaded on the 3APL platform The System Messages tab will display the error message This tab is generally used to display information about the platform 4 1 Messages window If an agent sends a message to another agent or to the AMS the message will be displayed in the Communication tab If the message is addressed to an agent which is also located on the platform no HAP Home Agent Platform is displayed The HAP is shown on the Communication tab whenever an agent receives a message from an agent on another platform e g seller 10 0 0 12 The System Messages ta
14. arguments exists the platform will give a Function not found exception ListPar execute Instance instance ListPar params Called by the platform to execute this method The arguments passed are in params documentation for the ListPar type can be found in the platform Javadoc generated documentation 6 2 Example plugin In this section the use of the plugin system is illustrated by an example The implementation is best understood by examining the source code see section 6 2 2 6 2 1 Description The example is a simple window plugin It allows each agent to open at maximum one window write text to it and close it again Additionally we want to hide the window if the agent is reset or removed We need three methods e windowOpen If hidden show the window e windowClose If shown close the window e windowWriteLn String line Write a single text line to the window Apart from printing Hello World this plugin can actually be somewhat usefull for debugging 6 2 2 Sourcecode package windowplugin import Javax swing import Java awt BorderLayout import Java util import ics TripleApl x RRR RR kk k k k Plugin aokk k kk kk public class WindowPlugin 21 6 2 Example plugin 6 PLUGIN DEVELOPERS GUIDE implements Plugin Vector _methods new Vector public WindowPlugin _methods add new WindowMethod_writeLn return a Collection of Method objects this plugin provides pub
15. b is shown in figure 4 3APL Platform Unnamed Project loj x File Edit Project Tools Help 5 a e Sse a gt 7 0 Communication system Messages Agent properties Source lihanks sally sally harry inform thanks harry Figure 4 The Communication tab of the 3APL platform 4 2 Agent properties The user can select an agent by clicking on the agent s name in the visual tree The Agent properties tab shows the current belief base goal base plan base capabilities goal planning rules and plan revision rules of the agent If the agent is running the inference log is filled with the reasoning steps The reasoning step includes selection and applications of rules and selection and execution of plans These steps form the so called agent s deliberation cycle 3 The Agent properties tab is shown in figure 5 On the left side of this panel the control buttons for the selected agent are located The functionalities of the control buttons are listed in figure 6 If the user selects the first button the agent s deliberation process commences The second button is the same as the first except that the deliberation process commences only for one deliberation cycle The user can select the third button to halt the deliberation process at any time Editing 3APL programs on the platform can be done by selecting the fourth button A syntax highlighting text
16. derLayout CENTER by default show agent show write line to window public void writeLn String line 4 System out println Window writeLn called add text newline character _textArea append line n if the window is hidden show it show get this instance s agent name public String toString return _agentName oR Method kkkkkkkkkkkk class WindowMethod window0pen implements Method Vector _arguments new Vector public List getArguments no arguments return _arguments public String getName 4 return windowOpen public String getDescription return If hidden show the window 23 6 2 Example plugin 6 PLUGIN DEVELOPERS GUIDE public ListPar execute Instance instance ListPar arg 4 WindowInstance instance show no return value return null oR OR RRR Method kkkkkkkkkkk class WindowMethod_windowClose implements Method Vector _arguments new Vector public List getArguments no arguments return arguments public String getName return windowClose public String getDescription return If shown close the window public ListPar execute Instance instance ListPar arg 4 WindowInstance instance hide no return value return null Pec RK Method xkkkkkkkkkkkk class WindowMethod_writeLn implements Method Vector _arguments new Vector public WindowMeth
17. eived You inform hello Me AND NOT sent You inform thanks You Send You inform thanks You PROGRAM sally BELIEFBASE me sally you harry GOALBASE hello PLANBASE PG RULES hello lt lt PR RULES you You AND NOT sent You inform hello You Send You inform hello You me Me AND received You inform hello Me AND NOT sent You inform thanks You Send You inform thanks You Figure 18 Communicating agents in 3APL 16 5 4 Shared Environment and External Actions 5 GETTING STARTED Send ams inform NOT description sellcomp On the other hand an agent that wants to buy computers and is therefore looking for a computer seller can use a message like Send ams query description sellcomp If the AMS finds agents with the required description it returns a message with a list of agent names in its content In the example this will be a list consisting of one element seller So the sender of the query will get the following fact in its belief base received ams reply name seller If the AMS cannot find an agent with the required description it will return the empty list 5 4 Shared Environment and External Actions As explained 3APL agents can either perform mental actions to update their beliefs or perform communication actions to communicate with other agents In addition to mental and communi cation actions 3APL agents can perform external actio
18. el There is also a small possibility that the 3APL program cannot be parsed without specific syntax error messages being provided In that case you must carefully recheck the syntax of your program 5 1 3 Executing a Program If the program cleaning 3ap1 is loaded successfully you can execute it by pressing the run button gt on the left hand side of the Agent properties panel Similar buttons on the top of the window have similar meaning for multi agent cases see section 5 3 You will now see various things moving It is best to focus on the plan base Press the M button to stop the program running The button will execute only one deliberation cycle at a time After execution you can trace the execution by means of the Inference Log window at the bottom part of the Agent properties panel After a PG rule is selected the body of the rule is added to the plan base After that the first basic action is executed This process of selection and execution continues until all plans have been executed and no rules are applicable anymore If you want to run the program again you will have to reset the belief base goal base and the plan base To reset use the lt button You can edit the program by clicking the yellow button After editing the command Save and recompile in the edit window will reset and reload the program The button can be used to remove a program from the Agent properties panel 5 1 4 External Prolog Files Extern
19. en the agents on the platform On the left side of the sniffer window the loaded agents as well as the AMS are shown Every message produces an arrow with its origin starting at the position of the sender and its head ending at the receiver of the message A performative speech acts such as inform and request 6 is displayed on every arrow If a user double clicks this performative the content of the message appears in an additional message box as illustrated in figure 8 This message box displays the contents of the message We have chosen this form to avoid clutter on the sniffer output window 4 4 Message sender 4 USER INTERFACE EN 3 ol x ang al 1 a iter al I a ter al i po te kara E aller L pi 1 fepi TITE y Freel Homer repi jec tomera Y T fer istomer2 Pa T epi mel T ke Pa Figure 7 An example output of the Sniffer tool x Pan O ForSale computer 500 Figure 8 An example output of the message box 4 4 Message sender Another platform tool available to the user is the custom message sender Using this tool the user can send a message to an agent loaded on the platform The custom message sender tool is illustrated in figure 9 101 xi MessagelD h 2 Se
20. gramming Multi agent Systems Languages frameworks techniques and tools ProMAS03 Mehdi Dastani Jurgen Dix Amal El Fallah Seghrouchni eds LNAI 3067 Springer Berlin 2004 Mehdi Dastani and Frank de Boer and Frank Dignum and John Jules Meyer Programming Agent Deliberation An Approach Illustrated Using the 3APL Language Proceedings of The Second Conference on Autonomous Agents and Multi agent Systems AAMAS 03 Melbourne Australia 2003 25 REFERENCES REFERENCES 4 Mehdi Dastani and Jeroen van der Ham and Frank Dignum Communication for Goal Directed Agents In Communication in Multi agent Systems Agent Communication Languages and Conversation Policies Marc Philippe Huget ed 239 252 LNCS 2003 5 Eric ten Hoeve 3APL Platform Master thesis computer science Utrecht University 2003 http www cs uu nl 3ap1 thesis tenhoeve EricTenHoeve pdf 6 FIPA FIPA ACL Message Structure Specification Foundation for Intelligent Physical Agents XC00061 2001 7 FIPA FIPA Contract Net Interaction Protocol Specification Foundation for Intelligent Phys ical Agents SC00029H 2002 8 Ugo Chirico Java Internet Prolog http www ugosweb com jiprolog index shtml 26
21. icates are defined as well plus and min see figure 15 PROGRAM externalProlog LOAD cal pl CAPABILITIES TRUE Multiplies X Y Z multiplies X Y Z TRUE Addition X Y Z addition X Y Z TRUE Subtraction X Y Z substraction X Y Z BELIEFBASE numi 10 num2 43 GOALBASE PLANBASE multiply addQ subtract PG RULES PR RULES multiply lt numi X AND num2 Y times X Y Z Multiplies X Y Z add lt numi X AND num2 Y plus X Y Z Addition X Y Z F subtract lt numi X AND num2 Y min X Y Z Subtraction X Y Z Figure 14 Arithmetic 3APL program using external Prolog file Although the Prolog clauses from an external file are part of the belief base they are not shown explicitly in the belief base window of the Agent properties panel The reason for this is method ological External Prolog file will typically contain utilities like general rules for some problem 12 5 2 Goal Dynamics 5 GETTING STARTED plus A B C C is A B min A B C C is A B times A B C C is A B Figure 15 Prolog file cal p1 domain We expect that these Prolog clauses remain unchanged during execution The Agent properties panel is meant to trace changes to the belief base for debugging purposes Therefore we decided not to clutter the belief base window with external Prolog clauses which are not meant to change For this reason we consider it b
22. ieve For example clean transport indicates two goals clean and transport The first goal indicates that the agent wants to clean the rooms and the second goal indicates that the agent wants to transport boxes to their destinations These are just two examples of basic goals also called atomic goals Complex goals can be formed by conjunction of atomic goals plan base The plan base contains a list of plans that the agents wants to perform Agents can start with an initial set of plans but new plans can also be generated during agent executions These plans are generated to achieve the agent s goals In this example the initial plan base is empty pg rule base This rule base contains a list of planning rules called PG rules each indicates which plan should be generated to achieve a goal Each pg rule is of the form Head Guard Body If the head of the rule matches an agent s goal and the belief base of the agent entails the guard of the rule then the body of the rule which is a plan will be added to the plan base In the PG rules of Figure 11 the accolades and are used to indicate the body of the rule 5 1 2 Loading a Program Use the menu item Open File to load a 3APL file see Figure 12 Choose and load the file cleaning 3ap1 from the example directory There are three possibilities after loading a 3APL 2 3APL Platform Un File Edit Project Toc New Close Open Project Open File Sa
23. is familiar with the 3APL programming language and its formal semantics A detailed presentation of the 3APL pro gramming language and its semantics can be read in 1 More information on 3APL programming language can be found in 2 4 5 1 Loading and Executing a Simple Agent 5 GETTING STARTED 5 1 Loading and Executing a Simple Agent In this section we explain how to write a simple 3APL program 5 1 1 Program Structure An example of a simple 3APL program is shown in figure 11 As you can see this program consists of five fields i e PROGRAM CAPABILITIES BELIEFBASE GOALBASE PLANBASE PG RULES and PR RULES These words are 3APL dedicated instructions The basic action names start with capital letters goals and beliefs are prolog like terms and punctation are used in specific way The BNF specification of 3APL programming language can be found at 3APL webpage http ww cs uu n1 3ap1 bnf html PROGRAM cleaning CAPABILITIES pos P Goto R NOT pos P pos R pos P AND dirty R Vacuum R NOT dirty R pos P1 AND box P1 Movebox P1 P2 4 NOT pos P1 NOT box P1 pos P2 box P2 TRUE IsClean clean TRUE Transported transport BELIEFBASE dirty room1 dest room1 box room2 pos room3 GOALBASE clean transport PLANBASE PG RULES clean lt dirty Room Goto Room Vacuum Room if not dirty R then IsClean transport lt box Room AND
24. lic List getMethods 4 return _methods return the name of the Plugin public String toString return WindowPlugin return the description of the Plugin public String getDescription Y return A Window where agents can write text to Create a new Instance the instance refers belongs to a specific agent identified by that agents name public Instance createInstance String agentName return new WindowInstance agentName Called by the interpreter when the agent this instance refers to is reset public void resetInstance Instance agent WindowInstance agent hide Called by the interpreter when the agent this instance refers to is about to be remove from the platform public void removeInstance Instance agent WindowInstance agent dispose oR ORR Instance RRR class WindowInstance extends JFrame implements Instance widget to write text into JTextArea _textArea new JTextArea 22 6 2 Example plugin 6 PLUGIN DEVELOPERS GUIDE string reference to unique agent name String _agentName public WindowInstance String agentName set the window title and size super Agent agentName setSize 200 200 store agent name _agentName agentName add textarea wrapped in scrollpane to center getContentPane setLayout new BorderLayout getContentPane add new JScrollPane _textArea Bor
25. m the platform The instance must take care that all listeners etc are removed so that it can be garbage collected 6 1 3 Details of Instance product public interface Instance public String toString String toString This method should return the agent s name this instance refers to 20 6 2 Example plugin 6 PLUGIN DEVELOPERS GUIDE 6 1 4 Details of Method public interface Method 4 public String getName public String getDescription public List getArguments public ListPar execute Instance instance ListPar params String getName Get the function name The returned function name is assumed to be unique across all methods listed by Plugin getMethods This method is used by the platform in order to form an appropriate Java call For example the name sense from plugin Blockworld would map to a 3APL Java call like this Java Blockworld sense argl arg2 argN RETURN_VALUE String getDescription Get function description This is used to display additional help information to the user in the 3APL platform interface List getArguments Returns a collection of strings describing the arguments that should be passed to this method The number of strings in this list is important as it is used to match the function calls based on their footprint e g two string will only match a 3APL Java call with two arguments If less or more arguments are given and no other method with the given number of
26. me boolean north Move agent on block north boolean east Move agent on block east boolean south Move agent on block south boolean west Move agent on block west boolean pickup O Attempt to take bomb at agents current location boolean drop Attempt to drop bomb at agents current location ListPar senseTrap Sense the position of the bomb trap ListPar sensePosition Sense the position of the agent 18 6 PLUGIN DEVELOPERS GUIDE Jox World Properties env bomb i0 Figure 20 Block World Window ListPar senseBombs Sense for bombs in the visible area ListPar senseStones Sense for stones in the visible area ListPar senseAgents sense for agents in visible area 6 Plugin Developers Guide The motivation for introducing Plugins to the 3APL platform is to extend the capabilities of the agents running on the platform with Java programs external shared environment The Plugin is a systematic way to achieve this goal by using it as an interface between the 3APL platform and Java programs In particular the Plugin facilitates the interaction between individual agents running on the platform and the Java programs These interactions include method calls from agents to Java programs and event notification from the platform GUI The implementation documentation of a plugin example i e blockworld plugin can be found at http www cs uu nl 3ap1 docs blockworld
27. nder setier2 v Receiver eustomer2 y Performative inform Content fione SEND CANCEL Figure 9 The message sender tool with example data entered All message parameters must be filled in by the user i e the sender and the receiver of the message which can be selected from a list of agents currently on the platform the performative of the message and the content of the message which is a belief formula When the user press on the SEND button a confirmation dialog will be displayed if the message is successfully sent The user can then send other messages or use the CANCEL button to close this tool Whether a message sent to the agent will actually be handled depends on several factors The most important one is if the agent is running If it is not then the message is stored in its message buffer until the agent becomes active again 4 5 Template agents 5 GETTING STARTED 4 5 Template agents If the user selects Add New Agent in the Project menu a window is shown which is illustrated in figure 10 Cancel Figure 10 The Add New Agent dialog The list shown in the Templates window is taken from the templates directory The templates are 3APL programs which implement agents with some common abilities for example seller or customer If the user has given a name for the new agent and has selected a template the agent will be added to the platform with the chosen name The agent program is a copy
28. ns with respect to an environment The environment of 3APL agents is assumed to be implemented as a Java program In particular the actions that can be performed in this environment are determined by the methods of the Java program i e the methods specify the effect of those actions in that environment and the state of the environment is represented by the data structures of the Java program i e either public or private The external actions that can be performed by 3APL agents have the following general form Java CLASSNAME METHOD LIST where CLASSN AME is the name of the Java Class that implements the environment METHOD is the actual action to be performed in the environment and LIST is a list of returned values It is important to note that METHOD is a parameterized method of the java class CLASSNAME and that LIST is a list of values returned by the METHOD An example of an external action is as follows Java BlockW orld east L where the external action east is performed in the environment BlockWorld The effect of this action is that the positions of the agent in the block world environment is shifted one slot to the right In order to illustrate the use of 3APL external actions consider the 3APL agent envAgent 3apl shown in figure 19 This agent performs external actions in the BlockWorld environment This environment is the first window that pops up when the 3APL platform is started see section 6 for more de
29. od_writeLn _arguments add The line to write public List getArguments return _arguments public String getName 4 return writeLn 24 REFERENCES REFERENCES public String getDescription return Write a single line to the text window public ListPar execute Instance instance ListPar arg final String string arg get 0 toString WindowInstance instance writeLn string no return value return null pe ROR Method kkkkkkkkkkk class WindowMethod_ readLn implements Method Vector _arguments new Vector public List getArguments no arguments return arguments public String getName return readLn public String getDescription return Read text from the text window public ListPar execute Instance instance ListPar arg final String text WindowInstance instance readLn final ListPar p new ListPar p add new ConstSymPar text return p References 1 2 3 M Dastani M B van Riemsdijk and J J Ch Meyer Programming multi agent systems in 3APL In R H Bordini M Dastani J Dix and A El Fallah Seghrouchni editors Multi Agent Programming Languages Platforms and Applications Springer Berlin 2005 Mehdi Dastani Birna van Riemsdijk Frank Dignum John Jules Meyer A Programming Lan guage for Cognitive Agents Goal Directed 3APL Proceedings of the First Workshop on Pro
30. refman index html 6 1 Anatomy of a plugin Plugins are Java methods grouped together under a single name the plugin name These methods are callable from the 3apl agent The agent can pass arguments to these functions and they in turn can return values To create a plugin you need to implement three interfaces 1 ics TripleApl Plugin factory class 2 ics TripleApl Instance product class 3 ics TripleApl Method plugin method function 19 6 1 Anatomy of a plugin 6 PLUGIN DEVELOPERS GUIDE 6 1 1 Overview At startup the platform loads all Plugin implementing classes from the plugins directory It then queries the found plugin classes for their external functionalities Java methods they provide to individual agents This is done by the platform through invocation of the method getMethods of the Plugin interface The idea behind the plugin is to systematize the relation between agent platform and external functionalities that can be used by the agents In particular the external functionalities should be linked to the individual agents running on the platform such that the effect of any change on individual agents create reset or remove on the platform can be realized on and passed to the corresponding external functionalities For example consider a blockworld as an external functionality in which the agents running on the platform can be present and move around In such a case if the user create reset or remove an agent on
31. st if the goal base entails a goal The syntax of these actios are follows goalaction AdoptGoal goal DropGoal goal y DropAllGoals goal goal goal IP AdoptGoal takes as an argument a grounded goal and adds that goal to the end of the goal base Execution blocks if not all variables in the goal argument have been substituted DropGoal takes as an argument a goal which may contain free variables The first goal in the goal base which is equivalent with the goal argument is then removed Execution blocks if such a goal cannot be found DropAllGoals also takes as an argument a goal which may contain free variables All goals in the goal base that entail the goal argument are removed from the goal base If no goal argument is given to DropAllGoals the entire goal base is emptied DropAllGoals never blocks The exclamation marks are used to test the goal base just as the question mark is used to test the belief base The variables contained in the test goal are bounded by the terms in the first matching goal in the goal base A double exclamation mark forces an exact match whereas a 13 5 3 Communicating Agents 5 GETTING STARTED PROGRAM list CAPABILITIES list1 HITI Extract HITI NOT list1 HIT list1 T TRUE Add H elem H BELIEFBASE listi john mary sue ellen bill empty GOALBASE PLANBASE prloop whileloop
32. tails on how the environment part of the platform works The initial plan of this agent is to enter the block world followed by the abstract plan start The entering part of the plan can be achieved by performing the external action enter 4 1 1 which has the effect that the agent enters the block world at position 4 1 The last parameter of the enter action is to indicate the time out of the action The value 1 indicates that the time out for the action is infinite a positive integer would indicate the time out in milliseconds see the specification of the environment actions under the Library item of the Tools menu of the 3APL platform The start abstract plan can be achieved by sensing at each row of the block world for bombs starting from the the first row If there is a bomb on its right block then the bomb will be moved to its left block The sensing action is accomplished by the senseBombs action resulting in the list of perceivable bombs The list is then examined to find out if there is a bomb on the right block This is done through the Prolog clause called bombAt pl If there a bomb on its right block then a sequence of external actions are performed in order to go to the bomb pick it up going twice to the left side dropping the goal there and going back to the original position The agent then moves to the next row and starts the process of moving bombs again 17 5 4 Shared Environment and External Actions 5 GETTING STARTED
33. tion 5 of this user guide e To start the 3APL platform on Windows double click the file 3ap1 jar or alternatively type java jar 3apl jar in a Command Prompt window at the 3apl directory e To start the 3APL platform in Mac OS X double click the file 3ap1 jar e To start the 3APL platform in Unix or Linux type java jar 3apl jar to a prompt in the 3apl directory The implementation documentation of the 3APL platform can be found at http ww cs uu n1 3ap1 docs aplp refman index html 4 User Interface When the 3APL platform is started the user is presented with the window shown in figure 1 The user should select whether the application is intended to act as a server or as a client The server option must be selected the first time the 3APL platform is run If the user selects the server option the application starts a new instance of the name server which is a part of the JAS library The client option can be selected only if the 3APL platform is running as a server already When the user selects the client option the IP of the server with which the client platform should connect must be filled in Once the choice has been made the application continues and the user is presented with two windows The first appearing window with the name blockworld is a shared environment in which agents can perform actions This window will be discussed in details in section 5 The second window is the 3APL platform main window shown in fig
34. ure 2 4 USER INTERFACE 4 3APL Platform Config loj xj Server C Cient P BS a E OK Cancel Figure 1 The startup dialog 3APL Platform Unnamed Project loj x File Edt Project Tools Help Communication System Messages Agent properties Source APL Platform version 3 0 initialised IAMS initialised Figure 2 The main window Left of the main window is a visual tree which represents the agents hosted on this platform The leaves of the tree show the names of the agents that are running on the platform The Agent Management System AMS which is responsible for registration of the hosted agents on the platform is also listed However AMS is not a real agent i e it cannot be controlled or inspected by the user Initially there are no agents on the platform except the AMS On the righthand side of the name of an agent is an icon displaying the status of this agent The possible status of an agent and their representing icons are illustrated in figure 3 Icon Meaning 3AP1 program is compiled successfully and the agent is ready Agent s deliberation process is started Agent s deliberation process is stopped Agent s deliberation process is ended fi a ii 3APL program cannot be compiled because a syntax error has occurred Figure 3 Status icons of agents An icon displaying the status of
35. ve Project Save Project As Close Project Exit Figure 12 Loading a 3APL program program 10 5 1 Loading and Executing a Simple Agent 5 GETTING STARTED 3APL Platform Unnamed Project loj x File Edt Project Tools Help 15 D 9 S a gt gt 7 14 EJ ams Communication System Messages Agent properties Source boiefbase Flenbase d Goalbase P dirty room1 E lempty lclean P fuest room1 transport SS pox room2 z lay law law Capabiltiesbase PR Rules PG Rules pos P Goto R NA lempry Clean lt dirty 4 NOT pos P AND pos R Room Goto Bo Room Vacuum Ro pos P AND dirty R lom IF NOT dirt Vacuum R NOT d Y R THEN IsClea irty R In 3 pos P1 AND box P1 transport lt 1 Movebox P1 P2 pox Room AND de NOT pos P1 AND N st Dest Go OT box P1 AND pos to Room Movebo IP2 AND box P2 lx Room Dest IF TRUE IsClean cl box Dest THEN eanit El Irransvortedi1 12 ar Inference Log Figure 13 Agent Properties Panel program If the program can be parsed successfully you will see the Agent properties panel as in figure 13 Now you can edit the program or execute it directly However if there is a syntax error in the program the program will not load Error messages appear in the System Messages pan
Download Pdf Manuals
Related Search