CASA: HOW TO
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1. catch ParseException e return new PerformDescriptor new Status 1 Malformed content field content Expected a legal run time command PerformDescriptor ret new PerformDescriptor try BufferedAgentUI ui new BufferedAgentUI Status execResult abclEval content null ui send back FAILURE SUCCESS or PROPOSE depending on a status value of lt 0 O or gt 0 if execResult getStatusValue lt 0 FAILURE return ret put ML PERFORMATIVE ML FAILURE ret put ML CONTENT CASAUtil serialize content execResult ui result ret put ML LANGUAGE casa else successful PROPOSE return ret put ML PERFORMATIVE ML PROPOSE ret put ML CONTENT CASAUtil serialize content execResult ui result ret put ML LANGUAGE casa catch Throwable e ret new PerformDescriptor 4 println error Failed to execute command from agent gt message getParameter ML SENDER content e ret put ML PERFORMATIVE ML FAILURE ret put ML CONTENT CASAUtil serialize ret ret put ML LANGUAGE casa return ret 2For example the server may want to specify a decision process agree or refuse to do the task February 4 2015 Knowledge Science Group University of Calgary 6 of 15 f CASA HOW TO 3 MESSAGE HANDLING Fundamentally this method receives the actual request message object as a parameter attempts to execute the lisp code in the content2. CASA HOW TO Rob Kremer Department of Computer Science University of Calgary 2500 University Dr Calgary Alberta Canada T2N 1N4 Email kremer cpsc ucalgary ca February 4 2015 Abstract CASA Collaborative Agent Systems Architecture is a framework for writing collaborative agents CASA aims to support many different agent conversational paradigms such as social commitment BDI Belief Desire Intention and ad hoc models and to support various standards such as the FIPA standard But CASA also aims to avoid forcing the programmer to commit to any particular paradigm This paper summarizes the structure of agents as well as the basic processing tasks of agents at runtime Contents il INESIS dad RA a Pa a e wee eS 3 2 e IA 3 21 Rin an ABEL c ch cle A ao a e ey 3 2 2 Wito a Danc Agnes lt a uc ee we a eee FPR ee A ee 3 2 3 Deferring execution of code until later o oo aa ea ee 3 3 Wenst e Handie ou a a a e te a e ae ks Se a oaa a 5 3 1 Handle an incoming message a 5 de Handle a new type of request ee 5 3 3 Deferring processing a callback from an incoming message ooo aa 10 3 4 Ignore an incoming request and not reply o o o e 10 3 5 Send a message to another agent dia ti kaor e e a ae Pea 10 4 Making an agent and it s attributes persistent o oo a e a e 11 5 Cooperation Domains esse eg at ee a e a ee ls le g a Ae a 12 5 1 Send a request through a coopera
3. s thread or the thread of the caller of the agent s constructor If you need to execute code during the agent s idle time the time when the agent isn t handling incoming messages etc you need only override the agent s doIdle method COverride protected boolean doldle 4 boolean superRet super doldle boolean ret code return superRet ret Don t forget to call the super version of the method You should return true iff either the super implementation returns true or your code does something You should avoid doing anything too lengthy during the idle call and return control to the outer processing loop within a second or two You may need to divide up your work do some of it now return and carry on next time the doIde method is called Warning doIdle is called whenever an agent becomes idle ie many times so any code here will be run many times You have to be smart about having the code run selectively 2 3 Deferring execution of code until later There are situations where you want to execute code later or the current threat is not the agent s nor mal thread eg the AWT thread and the code must be executed in the agent s main thread To do February 4 2015 Knowledge Science Group University of Calgary 3 of 15 fas CASA HOW TO 2 BASICS Method Thread Description Constructor caller creator Be sure to call the parent constructor first in the constructor
4. to stuff the request in into a proxy message before sending it The form of CooperationDomain constructCDProxy shown here will construct a broadcast message signified by a for the final receiver You can exercise more control over the destination address by using the two additional polymorphic forms of CooperationDomain constructCDProxy MLMessage msg MLMessage getNewMLMessage setParameters new String ML PERFORMATIVE ML REQUEST ML ACT myAct ML CONTENT myContent ML REPLY_WITH A UNIQUE STRING lt this is important the system won t match the reply with the request without it Since we re going through a CD we have 3 options for how we want the the server to reply we can ask it to reply directly to us reply indirectly through the CD or indirectly through the CD but also let everyone else hear switch replyMethod case direct have the server reply directly to me bypassing the CD explicitly set the REPLY_TO to be direct msg setParameter ML REPLY_TO getURL toStringO break case publicThruCD have the server reply through the CD in directed mode everyone hears cd setDataValue directed null This tells the CD to use directed mode break case thruCD have the server reply through the CD in whisper mode by default this is the default behaviour so no need to do anything special break MLMessage proxy CooperationDomain constructCDProxyMessage msg getURL
5. Since the agent isn t initialized at all here there is not likely much you d want to do in the constructor initializeConstructor AbstractProcess Qualifiers caller creator called just before the message loop begins the agent is not fully initialized at this point it s not yet regis tered with the LAC You can override this method to deal with qualifiers specific to your agent See link casa AbstractProcess initializeRun Qualifiers and the top level documentation of link casa AbstractProcess for more detail initializeThread agent override this but be sure to call the super method to deal with an initialization but the agent is not yet registered with the LAC and will not yet have recovered any of it s persistent data if it is a persistent agent initializeA fterRegistration agent called just after the agent is registered with the LAC the agent is now fully initialized pendingFinishRun agent called when an exit has been called while the agent is still running Called only once finishRun agent called after the message loop has exited when the agent has just stopped running Called only once Execute code during idle time Table 1 default February 4 2015 Knowledge Science Group University of Calgary 4 of 15 f CASA HOW TO 3 MESSAGE HANDLING this just wrap the code in a Runnable object and call the method AbstractPr
6. cd sendMessage proxy There s not a lot of difference between an ordinary consider and one recieving a broadcaste but the difference is important This example is for a shortcutting server Most of the code here is directly from the template for a shortcutting request server see above but also the code in red is used to ensure that the client is forced to February 4 2015 Knowledge Science Group University of Calgary 12 of 15 f CASA HOW TO 5 COOPERATION DOMAINS reply back through through the CD You need not have the client reply through the CD and have the client reply directly back if you want You could also force the client to reply back in directed mode everyone can hear by adding a line sender setDataValue directed null and adding the sender in ML RECEIVER in the return PerformDescriptor as we did in the previous section public PerformDescriptor consider_myAct MLMessage msg URLDescriptor sender null try sender new URLDescriptor msg getParameter ML SENDER catch URLDescriptorException e e printStackTrace PerformDescriptor ret new PerformDescriptor ret put ML PERFORMATIVE ML SUCCESS shortcutting ret put ML ACT msg getAct push ML DISCHARGE toString if we received this msg through a CD we want to force the client to reply to us through the CD too if msg getParameter ML CD nul1 URLDescriptor replyto getURL replyto pushV
7. wishes to acknowledge the Canadian National Science and Engineering Research Council NSERC for financial support of the research February 4 2015 Knowledge Science Group University of Calgary 15 of 15
8. AbstractInternalFrame override makeMenuBar protected JMenuBar makeMenuBar 4 JMenuBar menuBar super makeMenuBar manipulate menuBar here public void putTab String title Component component Add a new tab a new title and component to the tab pane of the interface February 4 2015 Knowledge Science Group University of Calgary 14 of 15 f CASA HOW TO 6 INTERFACES public Component getTab String name Returns the component associated with the tab with the named label If no such label is found returns null public void removeTab Component component Remove the tab with the specified component from the tab pane of the interface public void removeTab String name Remove the tab with the specified label from tab pane of the interface public boolean setSelectedTab String name Sets the tab with the specified name as the new currently selected tab 6 4 Add a new interface to an agent The type of the interface is dictated by whether or not a graphic environment is present So there are two different methods you might override Code in TransientAgent will decide which to call Both return an instance of casa ui AgentUI or null if no interface is desired Note that these methods will only be called if a specific interface isn t specified on the command line TransientAgent makeDefaultTextInterface String String TransientAgent makeDefaultGUIInterface String String Acknowledgments The author
9. HOW TO 3 MESSAGE HANDLING not understood discharge action exception handler name received unexpected not understood discha timeout discharge action exception handler name received unexpected timeout discharge nopropose transformation optional negotiation the action to send a propose discharge message containing the result of performing the perform actio amp aux ask name concatenate string name ask offer name concatenate string name offer approver name concatenate string name approver For the client side defun request client will be named the act request client the act result action when the server responds with propose discharge this executed in the context of tha amp key request performative request request act the act base name request client name concatenate string the act base name for the ask client conversation setting this gives the agent a chance to AGREE or REFUSE a proposal from from the server default r propose decision performdescriptor 0 performative refuse the action to perform when we receive a AGREE reply to our REQUEST agree action the action to perform when we receive a REFUSE reply to our REQUEST refuse action exception handler name received unexpected refuse the action to perform when we receive a NOT_UNDERSTOOD reply to our REQUEST not understood action exception handler name receiv
10. TO 6 INTERFACES 6 Interfaces 6 1 Add a runtime command to an agent The runtime language of CASA is Lisp so to add a runtime command you define a new Lisp command which can easily be done in Java For details see the CASA User Manual Section 11 3 6 2 Add a menu or menu item to an agent s default graphical interface Subclass the appropriate subclass of AbstractInternalFrame override makeMenuBar protected JMenuBar makeMenuBar JMenuBar menuBar super makeMenuBar manipulate menuBar here There are several helpful mentors in the AbstractInternalFrame class that help with manipulating the menus and menu items public void insertMenuBar JMenu menu int location Inserts a new menu in the agent menu bar at the specified location The remaining items are moved over one public void insertMenuBarAfter JMenu menu String name Inserts a new menu in the agent menu bar after the named menu label public void insertMenuBarBefore JMenu menu String name Inserts a new menu in the agent menu bar before the named menu label public void replaceMenuBar JMenu menu Replace the menu with the same name If the name doesn t exist the new menu is added at the end public JMenu getMenuBarMenu String name Returns the menu with the label name You can then modify it as appropriate and reinsert it using replaceMenuBar 6 3 Add a tab pane to an agent s default graphical interface Subclass the appropriate subclass of
11. ed unexpected not understood timeout action exception handler name received unexpected timeout for the discharge client conversation failure action exception handler name received unexpected failure timeout discharge action exception handler name received unexpected timeout discharge nopropose transformation optional negotiation the action to send a propose discharge message containing the result of performing the perform actio aux ask name concatenate string name ask offer name concatenate string name offer approver name concatenate string name approver February 4 2015 Knowledge Science Group University of Calgary 9 of 15 f CASA HOW TO 3 MESSAGE HANDLING Creates a Conversation for a client side request supporting 1 an outgoing REQUEST while in state not started gt started and incoming messages AGREE REFUSE or not understood when in state started gt terminated or 2 an incoming PROPOSE while in state not started gt started and an outgoing AGREE or REFUSE when in state started gt terminated 3 3 Deferring processing a callback from an incoming message Assuming you re using callbacks in a conversation to handle messages you will occasionally run into the situation where you have to wait for something else to happen eg a user making a decision in a dialog box a conversation with another agent to terminate etc The easiest
12. escriptors StatusObject lt MLMessage gt This methods sends the message and waits for a response message that matches any one of the messageDescrip tors and returns that message If none of the messageDescriptors are matched within timeout milliseconds of the current time the method returns a negative status and a null in place of the MLMessage If you omit the MessageEventDescriptors altogether they will default to those appropriate for a request agree refuse not understood and failure February 4 2015 Knowledge Science Group University of Calgary 10 of 15 f CASA HOW TO 4 MAKING AN AGENT AND IT S ATTRIBUTES PERSISTENT To send a message to another agent using Lisp use the agent send command together with the the agent message command For example agent send agent message query ref nil anotherAgent language FIPA SL content any x agent name x A specialization of agent send is agent tell receiver command which is the equivalent of agent send agent message request execute receiver content command 4 Making an agent and it s attributes persistent An agent is persistent if it inherits from the Agent class and sets the attribute persistent to true which can be done either in the agent code or via the command line The agent stores the information in a file according the the LAC s setup All you have to do to make at attribute persistent is to mark it s declaration with the Persistent an
13. gTag warning println warning TransientAgent release_execute got bad status in message n message toString true notifyObservers ML EVENT_POST_STRING n html lt font color red gt lt b gt Failed command result from message getFromString htm1 lt b gt n stat February 4 2015 Knowledge Science Group University of Calgary 7 of 15 f CASA HOW TO 3 MESSAGE HANDLING n text html lt font gt n n return new PerformDescriptor catch Throwable e PerformDescriptor ret new PerformDescriptor new Status 747 println error TransientAgent release_execute cannot unmarshal problem from CONTENT field n content n expecting a tuple originalCommand String status Status textOutput String problem e ret put ML LANGUAGE text return ret The client receives the propose discharge message from the server as it s parameter parses out the reply returns a PerformDescriptor specifying the acceptability or otherwise of the result which would release the server of the social commitment to perform the task or not respectively Notice that in the case of success the client need not write anything into the PerformDescriptor but just leaves it as default which the system automatically takes as success and replies affirmatively The client could have returned null with the same affect Likewise the failure conditions also min
14. iaAtEnd sender can use sender or cd hopefully they re the same ret put ML REPLY_TO replyto toString TODO compute the result and put it in the CONTENT of the return message ret put ML CONTENT myContent return ret The client code for release_myAct should be similar code to the coloured code above in order to properly direct any replies The same applies to any code that leads to the generation of messages 5 2 Paying attention to or ignoring messages arriving from CDs not addressed to you Messages sent through a CD in directed mode so everyone in the CD can hear will arrive in every mem ber agent s message inbox even though they are not addressed to that agent By default CASA will merely dropped these messages since they are not addressed to you But you can change that be calling setObserveMes sages true which will allow processing of the incoming messages and call handler methods consider_ type methods in your agent The methods called are similar to the normal ones but with _evesdrop appended to them Eg instead of conclude_act MLMessage it s conclude_act_evesdrop MLMessage If the appropri ate evesdrop method isn t found Transient Agent evesdrop MLMessage will be called which does nothing be return DROP_ACTION your agent can override this to exhibit whatever behaviour you d like February 4 2015 Knowledge Science Group University of Calgary 13 of 15 f CASA HOW
15. imize the information packed into the PerformDescriptor as a negative status integer indicates to the system that a refuse propose discharge should be returned If you need more detailed control over the various actions at parts of the conversation the server function is defined as follows defun request server will be named the act request server the act result action when the server responds with propose discharge this executed in the context of tha key base name request server name concatenate string the act base name the actual request like performative override only to change the performative request performative request setting this gives the agent a chance to AGREE of REFUSE request decision performdescriptor O performative agree the action to perform when we receive a AGREE reply to our PROPOSE agree action the action to perform when we receive a REFUSE reply to our PROPOSE refuse action exception handler name received unexpected refuse the action to perform when we receive a NOT_UNDERSTOOD reply to our PROPOSE not understood action exception handler name received unexpected not understood timeout action exception handler name received unexpected timeout agree discharge action refuse discharge action exception handler name received unexpected refuse discharge February 4 2015 Knowledge Science Group University of Calgary 8 of 15 f CASA
16. nd back the result In this case TransientAgent is both the client and server of this conversation type so it defines in its casa TransientAgent init lisp file the following request server execute jcall jmethod agent get class name perform_execute agent event get msg casa MLMessage request client execute call method agent get class name release_execute agent event get msg casa MLMessage lThis file needs to be placed in any one of the places defined in the CASA User Manual Appendix A February 4 2015 Knowledge Science Group University of Calgary 5 of 15 f CASA HOW TO 3 MESSAGE HANDLING These functions are called with minimum arguments that only define the name of the act of the request message and task to be done when the server provides the server or the client handles the answer back respectively In both cases these are handled by Java method calls If desired you can specify further detail using various optional keyword parameters The server specifies it s method for actually doing the service public PerformDescriptor perform_execute MLMessage message String content message getParameter ML CONTENT if the content is quoted strip the quotes while content null amp amp content length gt 0 amp amp content charAt 0 gt amp amp content charAt content length 1 4 try content CASAUtil fromQuotedString content
17. notation For example a simple persistent boolean attribute to be stored in the properties under myFlag Persistent boolean myFlag a persistent object that will be stored in the properties under options x and options y because it has at least one Persistent attribute itself public class Options Persistent int x 4 Persistent double y 7 5 Persistent Options options a persistent object that will be stored in the properties under stuff in the standard CASA serial format because none of it s properties are marked Persistent Note that the class Stuff MUST have a toString method and a corresponding constructor that takes a single string public class Stuff int x 4 double y 7 5 public Stuff public Stuff String persistData 1 COverride public toString February 4 2015 Knowledge Science Group University of Calgary 11 of 15 f CASA HOW TO 5 COOPERATION DOMAINS OPersistent Stuff stuff new Stuff 5 Cooperation Domains 5 1 Send a request through a cooperation domain This section gives an example of how to carry on a request conversation between two or more agents who are members of a cooperation domain using the CD as an intermediary for the conversation To send create and send the initial request message This is done by constructing a typical request message and then using CooperationDomain constructCDProxy
18. ocess defer Runnable or AbstractProcess defer Runnable long where the first parameter is a Runnable object typically an anonymous class type and the second parameter is represents the minimum delay time in milliseconds For example the following code embedded in an agent will print Hello world to standard out one second or more after it is executed in the thread of the agent Runnable runnable new Runnable public void run printin Hello world H defer runnable 1000 3 Message Handling 3 1 Handle an incoming message If you really need to handle a message directly you can override TransientAgent handleMessage MLMessage but this is not recommended If you do it be sure to call the superclass s version if you don t handle the message 3 2 Handle a new type of request There is social commitment request conversation skeleton defined as a Lisp function Therefore to instantiate a new type of request you need only to execute that function and define at least the handler for the servicing or the request in the serving agent and a handler for dealing with the result in the client agent The best place to do this in your lt angent name or agent type name gt init lisp file which while be executed whenever your agent starts up see CASA User Manual Section 4 2 For example the TransientAgent class defines an execute request that requests another agent to execute some Lisp command on its behalf and se
19. of the message and then only needs to return a PerformDescriptor which not much more than a simple dictionary with the non default keys filled in which the system will use to construct a reply to the message The reply includes the result of the Lisp execution in the content field The client s code which is called upon receiving the reply is similar public PerformDescriptor release_execute MLMessage message String lang message getParameter ML LANGUAGE String performative message getParameter ML PERFORMATIVE String content message getParameter ML CONTENT String problem array try Object o CASAUtil unserializeArray content Object objects Object o problem originalCommand String String originalCommand String objects 0 problem Status object Status stat Status objects 1 problem text String String text String objects 2 problem object from Status Object object stat instanceof StatusObject lt gt StatusObject lt gt stat getObject null boolean html commandInterpreter getStyle RTCommandInterpreter STYLE_HTML boolean html false if stat null amp amp stat getStatusValue gt 0 notifyObservers ML EVENT_POST_STRING n html lt font color blue gt lt b gt Command result from tmessage getFromString htm1 lt b gt n stat n text html lt font gt n n else if isLoggin
20. tion domain 0000008 12 6 2 Paying attention to or ignoring messages arriving from CDs not addressed to you 13 6 Interfaces c cdi wae tw ewe eee SLA Dee bbe ee ee Re ha 13 6 1 Add a runtime command to an aged 13 6 2 Add a menu or menu item to an agent s default graphical interface 14 6 3 Add a tab pane to an agent s default graphical interface o 14 6 4 Add a new interface to an agent ee 15 f CASA HOW TO 1 INTRODUCTION 1 Introduction This document shows how to do various tasks in CASA 2 Basics 2 1 Run an agent Agents are usually started from the command line using the main method of the casa CASACommandLine class or the CASA class The syntax is explained in the CASACommandLine class documentation or if you run casa through CASACommandLine main with the qualifier help Note that a LAC agent should normally be running before you run any other CASA agent See the CASA User Manual Appendix E 2 2 Write a basic agent All you need to do to implement an agent is write your class extending casa Agent Make sure you override Agent s constructor with the lines public myAgent Qualifiers quals throws IPSocketException super quals You can then extend the agent as appropriate There are methods that you can override during an agents start up They all have different uses and you should be mindful of whether the method is executing in the agent
21. way to handle this is to just let your callback be called and in it s body check on the event you are waiting on If it s happened proceed but it it hasn t yet happened just return the value of DEFER_ACTION a constant defined in TransientAgent Since all callbacks return a PerformDescriptor your return call will be new PerformDescriptor new Status DEFER_ACTION This return will cause the system to call your callback again at a later time You can repeat returning DEFER_ACTION as many times as you want 3 4 Ignore an incoming request and not reply From a method answering called in response to determine a reply message in a request conversation you can just not reply by returning new PerformDescriptor new Status DROP_ACTION In the social commitment communication paradigm this will discard the associated commitment to reply only if the originating request was a broadcasted message MLMessage isBroadcaste 3 5 Send a message to another agent Call one of the following methods AbstractProcess sendMessage MLMessage Status TransientAgent sendMessage String String URLDescriptor String Status The second one calls the first but constructions a message for you out of the parameters the list is an array of key value pairs keys are even values are odd Key may not be null but values may be AbstractProcess sendRequestAndWait MLMessage message long timeout MessageEventDescriptor messageD
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