CHAPTER 7 JAVA AGENT DEVELOPMENT ENVIRONMENT 159
Chapter 7 Java Agent Development Environment For more enhanced information resources it requires that the information system is distributed in a network and communication with different systems in a network. These types of system are difficult to realized with older software skills because of these methods has a limitation in sending data or distribution. The agent-based method is very capable in order to help the understanding of these kind systems as they are ready to use in interoperable and distributed manner [FGAG03] [B07] [B107 [B207]. There are very few systems which are developed using Agent-oriented technologies because agent-based technologies are not yet fully developed and can be made usage for realization in the real world. The standards for agent interoperability s are not yet realized in its full capacity, agent technology is not spread widely till now. In the agent oriented technologies developed by OMG, FIPA have done a tremendous development work for building agent oriented application. They have come up with some new agent oriented tools and models. These steps will definitely help in developing new standards for agent technologies. And these standards will support agent interoperability, communication and coordination among the agent system. [W07][MADO06][MDAO11] Additionally, there is a known agent communication language called as KQML which also helps in agent collaborating with other agent oriented application. Otherwise, it is not enough to make use of a regular communication language for maintaining interoperability connecting different agent systems. The standardization done by FIPA in the development of agent for its easy interoperability is just ahead of the agent communication language, it also specifies some unique solutions for management several agents systems. FIPA also has come up with its anthologies needed for communication among the systems, it also define the transport level protocol. JADELEAP is the important frameworks which permit the execution of special agents on movable devices, JADELEAP, provides the facility of providing services to other element in the system and their extensive shared reception. In this thesis, it is demonstrated how 160
JADE-LEAP framework can be used for developing a personal agent in an emergency environment. In case of an accident on road, a person calls an ambulance in at his multi database system is shown in this thesis. The ambulance node collaborate with many other agents in a multi-agent environment is demonstrated and shown in the thesis. So the mobile device mounted on an ambulance communicated with different hospitals in a multi-database environment to locate an appropriate hospital for that catastrophe situation. [2][3][4][R06][R07] JADE Java Agent Development framework, based on java language is a middleware which is most popular among agent-based system now days. JADE has a flexible infrastructure which can be modifiable according to the user s requirement with JADE S add-on modules. [B_FGD07][B_W09] JADE has its runtime environment with which a development of an application can be facilitated. This runtime environment provided by JADE, gives an implementation of the lifecycle model hold needed by MA, its core logic, and a finally a great graphical tools pack. Jade developed totally in Java, preserving all the advantages of java over all other language features along with third-party libraries, because of these developers can develop a JADE multi-agent system without much knowledge in an agent theory. Initially development of Jade done by the R&D department of Telecom Italia s.p.a., later it is distributed under the LGPL license as open source. 7.1 Jade and the Agents Paradigm JADE middleware layer functionality, is a software platform which are self-governing of the precise purpose and which simplify the realization of distributed applications that exploit the software agent abstraction. [B07][C07][DA13][F05][FAR00] MA can carry its data and control information when moving from one place to other. Agent doesn t carry the object reference and also cannot give call-back. An agent must carry its own state which is nothing but its execution thread so that it can autonomously take decisions like when to do what action. That is the reasons agents are always referred as proactive and autonomous in nature. 161
In a JADE based agent the form of collaboration among two agents is by transmitting asynchronous messages. To do collaboration with other MA, a sender agent sends messages to known destination. In the thesis this is shown with an ambulance agent communicate to a hospital agent and repository agent by sending messages, like Hospital found. A dedicated connection is not formed between a sender and receiver node. While sending, sender is not aware that a receiver is available or not. Or in some case the receiver will get the message when sender is not in network range as well. In this research a very dramatic situation is also taken into consideration that when an ambulance goes through a tunnel (not in a network coverage). Even in this situation a mobile agent is working autonomously and receiving results when ambulance comes out of a tunnel. 7.2 How to Run JADE From the tilab site one can get all the jade software files. Then we have to uncompress all the archive files. After doing so we will get a directory tree with a jade as root created along with a subdirectory lib. The jade.jar jar file are present in a lib subdirectory which is then has to be added to the CLASSPATH on a binary distribution. Then set a class path for java mean where the src sub directory exit. After setting class path, the main container can be launched. There are two agents in the main container of the platform namely DF (Directory Facilitator) agent and AMS (Agent manipulation service). The command for launching the jade is java jade. Boot [options of the java class files] [Agent Specifies list as per the specific program] more containers can then be created on the similar platform if required, or on other remote hosts, which are connected with main container of the AP, which demonstrate a distributed application in a one platform from remote. The other containers can be created with the command Java jade. Boot container [name of the classes] [name list for specifying the agents]. There is another way to execute a jade program, fro that a class path must be set with a command cp a jade, jar path java jade. Boot [classes ] [Agent Specification list]. [5][6][15][16] Managing an agent [B07] 162
Along with agent interoperability, FIPA specification also gives a solution for managing the agent system. FIPA compliant agent is fulfilled with a framework for operating and managing the agent system. For the construction, listing, position, collaboration, movement and function of agents there is a reference model crated in FIPA. The agent management reference model consists of the components namely agent, agent platform (AP), (MTS) Message Transport Service, Directory Facilitator DF, (AMS) agent management system, and jade tools. Following is a more elaboration on these components. Agent: According to Bellifemine an agent is a computational process containing data and states on an Agent platform which provides services. In FIPA complain agent system must have a unique identity which is agent Identifier (AID) labels so that an agent is well-known unambiguously even if it is changing its location. An agent is numbered registered at transport addresses where it can be contacted. Agent Platform (AP): For the deployment of an agent the physical infrastructure is needed that is known as an agent platform (AP). The AP contains the machines, operating systems, and all the FIPA agent management components as listed above, along with the agents and several other maintenance software. Directory Facilitator (DF): The JADE agent platform holds two special agents among that the first one is a DF. The DF is an elective part in an Agent Platform for offering yellow pages services to remaining normal agents. A perfect, absolute and appropriate record about the agents are maintained in DF and be required to provide the all latest update regarding agents in its directory. Agent Platform can offer any amount of DFs which may register with one another to form federations. The DF provides a registration and deregistration to all agent on agent platform. If agent wants to enter in a DF have to take a registration request to DF. On a request from a particular agent a DF can dismiss it by allowing deregistration of that agent. As and when needed, the DF modifies its 163
agent s entire decryption. Search is also possible in order to find a description of related criteria. All the access to DF is through a control of DF so few unwanted request can be denied from a DF. Agent Management System (AMS): The compulsory component of AP is AMS which is conscientious for administrating all the process of an AP, from the making till the destroying of agents, and supervising the movement of agents from and to Agent Platform. To acquire an AID every agent has to register through an AMS. In an authorization control of AMS, Agent descriptions can be later modified. The deregistration from AMS will terminate the life of agent from its AP. Once an agent is deregistering, the AID of a particular agent should delete from the address list and should be made obtainable to other agents on their request. Message Transport Service (MTS): Agent platform also provides an important service the MTS is a service offered by an AP to send FIPA message (Agent communication language) ACL. Every Message is having a proper envelop for reaching the message at an appropriate place. JADE Tools: For making things easier for platform supervision and function progress JADE fulfilled with several tools. There are directory tree for these tools which is in the form of packages, and sub-packages of jade. Tools directory. At present, there several tools in jade like Remote management agent (RMA), Dummy agent, sniffer, Introspector, DF GUI, and LogManagerAgent. Remote Management Agent RMA for managing and controlling the platform, RMA is a graphical console available in jade tool. In order to start a first instance of RMA we have to write a command gui o command prompt window then after more GUI can be launched. After RMA only any other jade tool can be launched. 164
The Dummy Agent for monitoring and debugging there exist a tool in jade called dummy agent, with a GUI and fundamental JADE agent. To compose an ACL messages and transfer to other agents, GUI is very helpful. It also displays a list of ACL message which are sent and received on AP with its timestamp information so that a smooth conversation will happen between the platforms. The Sniffer is used for debugging agents and keeps how an ACL message behaves. Sniffer is a graphical representation like a unified modeling language (UML) sequence diagram, to show the collaboration of different agents by sending ACL messages among themselves. The Introspector is an agent for monitoring the existence of an agent, its transferred ACL messages along with behaviors in entire carrying out. The DF GUI: a default Directory Facilitator (DF) of JADE uses a comprehensive graphical user interface which is nothing but a DF GUI. With the help of DF GUI a user can crated a many domain and sub-domain networks of yellow pages. The LogManagerAgent is an agent which permits executing at runtime logging information, like log level. The SocketProxyAgent is an easy agent, whose role is like a gateway which is bidirectional between a JADE platform and a simple TCP/IP link. 7.3 Features of JADE As a FIPA compliant Jade is full of fascinating advantage, following are the features which JADE offers for programmer. [DA13][FGD07][F07] 1. The main feature of a jade is that it provides a distributed agent platform. The agent platform be capable of be divide between some nodes. Every host runs a single java application and so single java virtual machine. For execution of agent, there is an agent container which gives runtime maintenance and it is constructed as Java threads. [F01][FGTG10a][FGTGR10b] 165
2. Second important future of jade is it Graphical user interface, very useful in managing many agents and their containers from a remote machine. 3. Debugging tools is for developing multi agent s applications on JADE. 4. Interoperability of agent, agent mobility in order to transfer the code and state, Intraplatform. 5. Jade always maintains multiple, concurrent agent activities execution. JADE schedules the agent behaviors in a non-preemptive fashion. Future include all the tools of JADE which are FIPA-compliant Agent Platform, includes the AMS (Agent Management System) and the DF (Directory Facilitator). On the AP the entire component are automatically activated. [F01][FGTG10a][FGTGR10b] In order to implement multi-domain applications, there are many FIPA-complaint DFs may be started at that instant. A common facilitator advertises a domain which is a logical set as agents.gui is a super class and all its properties are inherited in DFs for registering, modifying, searching of agent decryption and finally to deregistering. ACL messages are efficiently transported on same agent platform. All the messages are converted in a coded form as a java object/instance and not as a string messages for avoiding the marshalling and unmarshalling. When ACL messages are going beyond the prescribed platform bounders, it will transport in FIPA complaint syntax, codes and protocols. There are FIPA collaboration protocols available for usage. AMS can facilitate for automatic registration and deregistration of an agent. As per FIPA specification, a FIPA complaint naming service allocated a unique name to all agents at the starting of its life-cycle that is known as a GUID means global unique identifier from it s platform. Ontology and application-defined language are also maintained in jade. 166
7.4 Multi agent System in JADE This section of the thesis describe about JADE classes and how it support the easy way of development of multi-agent system. JADE guarantee the semantic and syntactical compliance with FIPA specifications. The Agent Platform The figure below depicts the agent platforms standard model of agent platform, the arrangement of all component of agent platform, as per FIPA definition. Agent Agent Platform AMS DF MTS Fig 7.1 FIPA-compliant Agent Platform Architecture diagram The access to use an Agent platform is through the supervisory control of Agent Management System (AMS). On a single platform only one AMS can be present. The AMS s white-page and life-cycle service, keep a list of agent identifiers (AID) and agent condition. Each agent must register with an AMS in order to get a valid AID. As discussed earlier the Directory Facilitator (DF) is responsible to give the default yellow page service in the platform. The Message Transport System, for sending message through the platform is also called Agent Communication Channel (ACC), is the software element scheming entire exchange of messages inside the platform, together with messages on remote platforms. A JADE platform is 167
Ambulance Agent Data Assistant agent Hospital agent Data Assistant agent Hospital A agent Hospital B agent Hospital C agent started; the AMS and DF are immediately initiated, because JADE completely complies with the reference architecture of FIPA. On a single agent platform, there can be several machines as hosts. Still only single Java Virtual Machine (JVM), is executed on each machine because only one java application can be run on one host machine. JVM act as a main container of agents that provide an entire run time setting for agent implementation and facilitate all agents to parallel execution on the identical host. The AMS and DF lives on the main-container. The other non-main containers, as an alternative, join to the main container and give a full run-time execution environment for set of JADE agents. Java virtual machine environment in Jade based Multi-database Decision making for Catastrophe healthcare system (JMDCH) is illustrated in following Figure 7.2. Ambulance Host Repository Host Hospital Host JADE Agent Platform Main Container Container Container JRE JRE JRE Fig 7.2 Java Virtual Machine Environment in agent In JMDCH, the main-container is a container where ambulance agent is launched first then two more agents namely hospital and data assistant are launched. On the other hand there are two ordinary containers one is repository host and other one is a hospital host i.e. on container there are three different hospital agents are started and data is fetched from three 168
different hospital namely hospital A, hospital B, hospital C. and on repository there is agented named data assistant exist. All are using a same JVM for execution is shown in Figure 7.3. Fig 7.3 Execution environment of JADE-LEAP JADE is a collection of Java classes that allocate programmers to build a FIPA-compliant multi-agent application pretty simply. JADE-LEAF comes up with bundles of graphical tools that facilitate the difficult assignment of execution a multi-agent application. 7.5 Architectural details of JADE The main architectural component of a JADE platform is shown in the Figure 7.4. A JADE platform is composed of agent containers that can be distributed over the network. Agents live in containers which are the Java process that provides the JADE run-time and all the services needed for hosting and executing agents. There is a special container, called the main container, which represents the bootstrap point. It is the first container to be launched and all remaining containers ought to connect to a chief container by enrolling with it. The Unified Modeling Language diagram in Figure 7.5 shows the associations linking the main architectural essentials of JADE. It is very easy for the programmer to identify containers using simple logical name; by default the main container is named as a Main Container 169
whereas the remaining are named Container-1, Container-2, and so on. We can change the default name with Command-line options that then overrides the default names. Fig 7.4 JADE platform architectural elements Fig 7.5 class diagram of JADE architectural elements The global agent descriptor table (GADT) is managed in jade, with which the registry of all agents presents in the platform including their current status and location; 170
Main-container hold two special agents AMS and DF, that offers the agent management and white page service, and the default yellow page service of the platform, correspondingly. In message passing a main-container is not involved directly but through theses two special agents. When a sender wants to send a message to its receiver it search the recipient in a LADT (local agent descriptor table), then the act. AID is an Agent identity, made up of a collection of slots that comply with the structure and semantics defined by FIPA. The most basic elements of the AID are the agent name and its addresses. The name of an agent is formed using a merging of user given nickname, that is a local name of agent with a platform name, and the global unique identifier is achieved in JADE. 1. The Agent Management System (AMS) is the special agent that governs the complete platform. It is the make contact with all agents that want to work together to contact the white pages of the Agent platform in addition to administer their life cycle. All agents are need to register with the AMS which automatically happens when JADE agent start-up, in order to gain a valid AID. 2. The Directory Facilitator (DF) is the agent that executes the yellow pages service, used by any agent opting to get register its services and to search for other services. To distribute distributes the yellow pages service across several domains, Multiple DFs can be start paralleling. 171
Fig 7.6 A static representation of JADE tool 7.6 Heterogeneous Distributed Database in JMDCHS In case of the integration of heterogeneous, disparate database management systems to present a user with a single, unified query interface, a heterogeneous database system is a prevalent solution. Heterogeneous database systems (HDBs) are computational models and software implementations that provide heterogeneous database integration. [RGT13][SKP95][X96][WN97][SE06][AMAZZ11] 172
Fig 7.7 Heterogeneous environment in a JMDCHS In this research, it is demonstrated that all different hospitals are heterogeneous. All hospitals are having different as and different kinds of database. Still while communicating the mobile agent captures all these heterogeneous information and give the result in an appropriate manner. Relational database are in the form of tables structure, in JMDCH, all the hospital are situated at different locations and with different attributed and field in the tables. The format of all hospital database is different, still agent are able to communicate in such an heterogeneous environment achieving a global data access and fetch all appropriate information from different hospital nodes. [RD98][MKSNRH13][KM08][JH98][GWWCM94][G08] 173