M. Straer, J. Baumann, and F. Hohl. Mole - A Java based mobile agent system. In ECOOP '96 Workshop on Mobile Object Systems, 1996.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....as a new design paradigm for distributed computing potentially permit network applications to operate across heterogeneous systems and dynamic network connectivities, to reduce their bandwidth needs, and to avoid overheads caused by large communication latencies. In addition, mobile agent systems[11, 20, 24, 38] are designed to facilitate the construction of distributed programs that have the flexibility to adapt their operation in response to the heterogeneous nature of or dynamic changes in underlying distributed computing platforms. Agent computing, however, is subject to several inefficiencies. Some ....

....disk archive Selector for data Azimuth Compression Azimuth Compression Azimuth Compression Imagery for processing interesting Fir Filtering Range Compression Range pulse Range pulse Range pulse display and Figure 2: Structure of PSSPS. Usage of interpreted languages, such as Java[38, 20, 24], is a major cause of these problems as is depicted by experiment results listed in table 1. These experiments use the Sun Solaris native C compiler to generate compiled code and use JDK1.2 beta3 package for the Java compiler and runtime environment (including the JIT compiler used in our later ....

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Markus Straber, Joachim Baumann, and Fritz Hohl. Mole-a java based mobile agent system. In ECOOP '96 Workshop on Mobile Object Systems, 1996.

....be allowed to restore their stack from data passed from one host the the next because a corrupt host could illegally construct a stack that would allow an agent to break its security restrictions. This presents a major problem in designing agent based systems. Current Java based implementations [24, 21] require that all state information be kept in the agent s variables or heap storage and that the agent be able to return to that execution state from the contents of its variables (Section 7.4) All stack information must be rebuilt on arrival at a new host from the contents of the agent s ....

....cance of Java to agent systems is that it provides a good starting point to implement such systems. It has a xed set of library routines and a wide user base making it an ideal choice for agent based systems as is demonstrated with IBM s Aglets [24] and the University of Stuttgart s Mole project [21] (Section 7.4) 5.2 The Safe Tcl restricted instruction set. Safe Tcl started out as a language based on Tcl to allow Enabled Mail by using the application Safe Tcl MIME type as proposed by Borenstein and Rose [1] The motivation was to provide a secure environment in which to execute emailed ....

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Markus Straer, Joachim Baumann, and Fritz Hohl. Mole - A Java Based Mobile Agent System. Institute for Parallel and Distributed Computer Systems, University of Stuttgart, Denmark, October, 1996.

....(e.g. network destinations, directory segment) and making capabilities location dependent. Java programming language and runtime environment [2] illustrate the nature of the recently developed techniques listed above. There are many agent systems based on Java, including Aglets [3] Mole [8], and Voyager [9] The Java environment includes built in security controls such as sandboxing for isolation of code into mutually exclusive execution domains, and byte code verification to check the safety of class file downloads. It also inherently supports code mobility, dynamic class loading, ....

Markus Straer, Joachim Baumann, Fritz Hohl, "Mole - A Java Based Mobile Agent System," in M. Mhlhuser (ed.), Special Issues in Object Oriented Programming, Verlag, 1997, pp. 301-308 <URL: http://www.informatik.uni-stuttgart.de/ipvr/vs/projekte/mole/ECOOP96.ps.gz>

....Information Provider Information Provider Article Key Credit Institution Remark: Each actor knows its own private public key pair 12 Dissemination of Commercial Electronic Information should provide identical behavior on all architectures. In principle all existing agent platforms (MOLE [15][16], JDK etc. provide this feature. The second requirement, which for our needs was the most important, concerns the security offered by the platform. From one hand we ask that the platform protect the agent executing on it from other executing agents; that is, one agent should not be able to ....

Markus Strasser, Joachim Baumann and Fritz Hohl, "Mole - A Java Based Mobile Agent System", Second ECOOP Workshop on Mobile Object Systems, University of Linz, July 8-9, 1996.

....point in the object code and at an arbitrary place may happen. The last update of the Java Development Kit [8] introduces object serialization, which is a first step in this direction. But problems persist in the form of what happens to active threads and how to migrate the execution stack [9]. Agent Tcl Interpreter Operating System (Unix, Windows, Agent B Agent Tcl Agent Server Machine gameboy JAVA Virt. Machine AgentServer Java Agent Figure 1: Functional architecture HP OVUA 97 Oliver Huber 4 Application of the functionality of mobile agents in active networks ....

Markus Straer, Joachim Baumann, Fritz Hohl, "MOLE - A JAVA Based Mobile Agent System ", ECOOP '96, Workshop on Mobile Object Systems, Linz, Austria.

....over formality and provability. Our core method of building applications from distributed agents is inspired in part by Actors [1] albeit without the strong formalism of Actor theory. Hive s mobility is in many ways a reimplementation of systems such as D Agents [14] 16] Aglets [17] and Mole [29]. We have tried to implement a simple version of mobility, ultimately intending to create our own solutions to the hard problems such as versioning and shipping complete code. By contrast to many multi agent systems, Hive does not have any formal model of agent communication or negotiation [34] ....

Markus Straer, Joachim Baumann, and Fritz Hohl. Mole -- A Java Based Mobile Agent System. In 2nd ECOOP Workshop on Mobile Object Systems, pages 28--35, Linz, Austria, July 1996. http://www.informatik.uni-stuttgart.de/ipvr/ vs/projekte/mole/ECOOP96.ps.gz

....Magic Telescript[20] which offered services for real world deployment of agent technology. These platforms, more in relation to the distributed systems eld, usually have weak denition of what an agent is, and are often focused on agent mobility. Platforms like Aglet [13] Odyssey [8] Mole [18] or Sodabot [2] fall into this category. The later ooeers good heterogeneity, as agent designers have full freedom for internal agent architecture but induces poor overall structuring. At the opposite, having a strong structural model for agents allows seamless integration within the system, but ....

Markus Strasser, Joachim Baumann, and Fritz Hohl. Mole a Java based mobile agent system. In Proceedings of the 2nd ECOOP Workshop on Mobile Object Systems, pages 2835, Linz, Austria, July 1996. 15

....agent systems. It was followed by systems like Tacoma [3] and Agent Tcl [1] which supported mobile agents written as Tcl scripts. The emergence of Java has led to the development of several Java based mobile agent systems [11] such as Aglets, Odyssey, Voyager, and Concordia. Sumatra [5] and Mole [7] were among the first generation of Java based mobile agent systems. Ajanta 2 is a Java based system that we have developed for programming mobile agent applications in an open system such as the Internet. It has been designed with the goal of supporting secure and robust agentbased ....

Markus Straer, Joachim Baumann, and Fritz Hohl. Mole - A Java Based Mobile Agent System. In Proceedings of the 2nd ECOOP Workshop on Mobile Object Systems, 1996.

....supports code mobility, dynamic code downloading, digitally signed code, remote method invocation, object serialization, platform heterogeneity, and other features that make it an ideal foundation for agent development. There are many agent systems based on Java, including Aglets [3, 14] Mole [8], Ajanta [25] and Voyager [9] However, limitations of Java to account for memory, CPU, and network resources consumed by individual threads [40] and to support thread mobility [2] have been noted. Probably the best known of the safe interpreters for script based languages is Safe Tcl [12] ....

Markus Straer, Joachim Baumann, Fritz Hohl, "Mole - A Java Based Mobile Agent System," in M. Mhlhuser (ed.), Special Issues in Object Oriented Programming, Verlag, 1997, pp. 301-308. ECOOP96.ps.gz>

....x n 7 y n g. Then the composition f is defined to be a finite mapping fx 1 7 y 1 ; x n 7 y n g. 22 CHAPTER 1. INTRODUCTION Chapter 2 A Calculus with Code Mobility Distributed programming language systems in which code, data and or execution states move around among computer systems [1, 16, 23, 44, 45, 62, 68, 92, 94, 101] have been proposed with the development of telecommunication networks. These systems are usually equipped with their own features that are hard to simulate by other systems even with respect to their agent movement (migration) mechanisms. The difference is due to the different presuppositions on ....

....Compared to non transparent migration, transparent migration is more desirable [32, 40, 45] for writing programs to be migrated and understanding the semantics of migration. The migration transparency of existing mobile systems is, however, not satisfactory. ffl Almost all existing mobile systems [64, 76, 92] based on Java do not preserve the calling stack. ffl Telescript [100, 101] an early mobile agent system, provides transparent migration, but the unit of migration is restricted to only one object (agent) 41] at a time. 63 64 CHAPTER 4. AN IMPLEMENTATION ffl In the few systems [32, 40, 45, ....

Markus Straer, Joachim Baumann, and Fritz Hohl. Mole -- A Java based Mobile Agent System. ECOOP'96 Workshop on Mobile Object Systems, 1996.

....[24] and object serialization [18] were added to Java. Hence, objects communicate through the awkward sockets interface. Other systems developed since that time also leverage the Java virtual machine to provide distributed or parallel computing platforms on heterogeneous computing environments [6, 3, 1, 5, 15, 25, 19]. JavaParty [15] introduces the remote class modifier to the Java language. Adding this new keyword to the class definition denotes that the class should be used in a distributed fashion. To accomplish this, JavaParty uses a preprocessor which converts remote classes into pure Java code with RMI ....

....not both. Ajents overcomes this problem by providing two distinct interfaces for synchronous and asynchronous method invocations. An additional benefit of our approach is that it does not require the use of a modified stub compiler. Agent oriented Java systems, some examples of which include Mole [19] and Aglets [11] are designed to support Java based autonomous software agents. Remote objects (agents) may be created, and are provided with mechanisms for mobility and communication. This independence allows objects free reign, but limits ties to the original client who created the object. ....

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M. Straßer, J. Baumann, and F. Hohl. Mole - A Java based mobile agent system. In ECOOP '96 Workshop on Mobile Object Systems, 1996.

....mobile agent programming. It was followed by systems like Tacoma [11] and Agent Tcl [6] which supported mobile agents written as Tcl scripts. The emergence of Java has led to the development of several Java based mobile agent systems, such as Aglets [9] Voyager [19] Sumatra [21] and Mole [24]. The Ajanta system s architecture and programming facilities can be compared and contrasted with the other mobile agent systems based on the following aspects [16] security mechanisms for protecting hosts and agents, remote agent control and communication, location independent naming, migration ....

....quotas on resource use. Security mix in classes can be used to protect objects from unauthorized modification, copying or migration. Aglets [9] has only limited security functionality, and a security architecture for this system has recently been proposed [13] Voyager [19] Sumatra [21] and Mole [24] do not address security issues. Among Tcl based systems, Tacoma does not address security. Agent Tcl supports coarse grained access control lists based on host names, and uses PGP for encryption and authentication. In Ara [20] agent servers use access control lists (called allowances ) to ....

Markus Straßer, Joachim Baumann, and Fritz Hohl. Mole - A Java Based Mobile Agent System. In Proceedings of the 2nd ECOOP Workshop on Mobile Object Systems, 1996.

....of Clone Generating Server . 19 7 Conclusions and Future Work 22 A Coordinator Algorithm 25 B The CP nets model 26 1. Introduction 1.1. Background A mobile agent is an autonomous computer program which can migrate between heterogeneous machines[7, 5]. The concept of a mobile agent is being applied to areas such as workflow systems, electronic commerce and information retrieval systems. But, the security weakness of mobile agent systems limit their application areas. In order to ensure the secure execution of mobile agents, it is necessary to ....

....internal information which produces agent s action, and expect the next agent action from the outputs, produced through parallel execution of clones providing different input to each one of them. 3. Problems in existing mobile agent system A simple mobile agent application operating on Mole system[5] (a popular existing mobile agent systems) was developed for purposes of investigation. Further, a simple malicious agent server which generates clones of incoming agents was also constructed. The experimental results show that a clone can be easily generated without much knowledge about the Mole ....

Markus Straser, Joachim Baumann, and Fritz Hohl. "Mole -- a Java based mobile agent system," In 2nd ECOOP Workshop on Mobile Object Systems, pages 28-35, Linz, Austria, July 1996.

....in the message containing the submitted code to make them available at the destination CE. Therefore, M0 is a weak MCS providing shipping of stand alone code (whose execution is asynchronous and immediate) and data space management is by copy. C. 7 Mole Developed at University of Stuttgart, Mole [37], 38] is a Java API that supports weak mobility. Mole agents are Java objects which run as threads of the JVM, which is abstracted into a place, the Mole CE. A place provides access to the underlying operating system through service agents which, differently from user agents, are always ....

M. Straßer, J. Baumann, and F. Hohl, "Mole---A Java Based Mobile Agent System," in Special Issues in Object-Oriented Programming: Workshop Reader of the 10 th European Conf. on Object-Oriented Programming ECOOP'96, M. Muhlauser, Ed. July 1996, pp. 327--334, dpunkt.

....states. Keywords Mobile agent; operational semantics; code movement. 1 INTRODUCTION Distributed programming language systems in which code, data and or execution states move around among computer systems (Cardelli 1995, Colusa 1995, White 1996, Gosling et al. 1995, Knabe 1995, Marzo et al. 1995, Stra er et al. 1996, Gray 1995) have been proposed with the development of telecommunication networks. Such distributed systems are often called agent systems . There is, however, a serious terminological gap among the people who build and study agent systems. In this paper, we use an agent system to mean a system ....

Straßer, M., Baumann, J. and Hohl, F. (1996) Mole -- a java based mobile agent system. ECOOP'96 Workshop on Mobile Object Systems.

.... paper has been influenced mainly by our previous experience with designing and building the Sumatra system [RASS97] Our work is also related to several other systems that offer mobility as a feature such as TACOMA [JVS95] Voyager 5 [OSVoy] Aglets [V97] Odyssey 6 [GMOd] ARA [P98] and MOLE[SBH96] and to earlier systems such as such as Emerald [JLHB88] and Obliq [Ca95] Our main innovations in this work are resource control mechanisms and separation of naming and location from functionality features that we believe eases the task of building distributed systems. The other significant ....

....having an explicit continuation point is again the ease of constructing debugging tools and has also facilitated the controller mechanism that we described earlier. Making the continuation points explicit also has the advantage of being able to have the system re configure the application. MOLE [SBH96] is another JAVA based mobile agent system that uses a mobile server model of mobility. MOLE agents communicate with each other either by establishing a session and then exchanging messages or by global events. Our system of inter agent communication utilizing MStreams comes closer to the ....

Markus ### ############Baumann and Fritz Hohl, "Mole -- a Java-based mobile agent system", in 2 nd . ECOOP Workshop on Mobile Object Systems. Linz, Austria, 1996.

....machine. This allows us to take advantage of Java s ubiquity, while writing agents that have more obvious control flow and fewer side effects than their Java equivalents. We illustrate this with a higher order version of an existing Java mobile agent. 1 Introduction Some recent developments [Chang96, Stra er96, ObjSpace97, Mitsubishi97, GenMag97] have provided frameworks for running mobile agents written in Java. They allow certain agent state to be shipped over a network between virtual machines. The values of object fields are preserved by movement but information about which code the agent is running at the time is not. That is, the ....

Markus Straßer, Joachim Baumann, and Fritz Hohl. Mole --- A Java Based Mobile Agent System. In ECOOP '96 Workshop on Mobile Object Systems, Linz, Austria, July 1996. (p. 1)

....role within the search scenario thoroughly examined. The paper concludes with a summary of the article s key issues and future work. 2 AGENT BASED SYSTEMS OUR AGENT MODEL In this section we will give you only a short overview of our agent model, that has been described in much more detail in Stra er, Baumann, Hohl(1996) and Baumann et.al (1997) Our model of an agent based system as various other models is mainly based on the concept of agents and locations. An agent system consists of a number of (abstract) locations, being the home of various services. Agents are active entities, which may move from ....

....groups, groups implementing system protocols, high level application groups, etc. This will allow us to structure groups in appropriate classes with different complexity that can be tailored to the programmer s needs. The proposed agent group model will be embedded into our agent system Mole Stra er, Baumann, Hohl(1996). In order to allow efficient distribution of events generated by the group members a distributed event service is also currently build complying to the needs of an agent based environment (e.g. agent migration, creation history of agent groups) Future work will finally encompass the evaluation ....

Straßer, Markus and Baumann, Joachim and Hohl, Fritz (1996) Mole: A Java based mobile agent system. In Proceedings of the 2nd ECOOP Workshop on Mobile Object Systems, (ed. J. Baumann, C. Tschudin, J. Vitek), dpunkt.

....carrying the programs code and its current state. Applications can exploit this mobility by, for example, moving client code closer to a server to reduce network latency or bandwidth. There is growing interest in mobile agents, and several other systems that support mobility have been reported on [1,3,7,14,20,23]. The Knowbot Operating Environment is a system for mobile agents developed at CNRI. In this paper, we report on experiments conducted across the Internet over the past year. We have experimented with a prototype application that uses Knowbot Programs to track updates to World Wide Web pages. One ....

Markus Straßer, Joachim Baumann, and Fritz Hohl. Mole --- a Java based mobile agent system. In Proceedings of the 2nd ECOOP Workshop on Mobile Object Systems, pages 28-35, Linz, Austria, July 1996.

....migrated, instead of a single thread within it. On the other hand, in Java [31] the class loader can be programmed to enable a Java program to link dynamically code downloaded from the network, hence providing support for weak mobility. Java derivatives like Odyssey, Aglets, Voyager [17] or Mole [30], as well as languages like TACOMA [15] Facile [18] and M0 [32] support weak mobility by allowing a procedure or function to be sent to another node for remote execution, with the portion of the global environment that is needed to proceed with execution but with no execution state. Dip. di ....

M. Straßer, J. Baumann, and F. Hohl. Mole---A Java Based Mobile Agent System. In M. Muhlauser, editor, Special Issues in Object-Oriented Programming: Workshop Reader of the 10 th European Conf. on Object-Oriented Programming ECOOP'96, pages 327--334. dpunkt, July 1996.

....component running on a given computational environment can download and link code on the fly from a different, remote component (a code server) Languages and systems supporting mobile code are also known as weakly mobile technologies. Examples of weakly mobile technologies include Java, Mole [SBH96] TACOMA, M0, Facile, Obliq and Safe Tcl [CGPV96] To put it simply, we can contrast mobile agents from mobile code systems by noting that mobile agents are active program objects, or threads, while mobile code is passive and has to be explicitly downloaded and linked before being executed. ....

....agents depart significantly from the traditional distributed objects paradigm and open a whole new world of considerations, especially in the area of security. For this reason, this work doesn t cover mobile agent systems. Discussions of strongly mobile technologies can be found in [CGPV96, Kat96, SBH96, Vig97, VST96, Vit96] The use of mobile code, especially on the Internet, raises serious security concerns. Because users are not always aware that remote code is being linked with their applications, and because such code has potential access to all of the machine resources, security mechanisms ....

Markus Straßer, Joachim Baumann, and Frits Hohl. Mole -- a java based mobile agent system. In Proceedings of the Second International ECOOP Workshop on Mobile Object Systems, Linz, Austria, July 1996.

....recent approaches have been inspired by applications development on the Internet. As we mentioned, the Java class loader allows the programmer to customize the resolution of a class name, possibly downloading the corresponding code from any machine on the network. An extension of Java, called MOLE [17], adds the capability of sending code to another Java interpreter without modifying the Java interpreter. TACOMA [9] is an extension of Tcl that allows the programmer to send code together with any kind of data to a remote machine, in order to be executed there. Facile [5] is a higher order ....

M. Straßer, J. Baumann, and F. Hohl. MOLE - A Java Based Mobile Agent System. In Proceedings of the Second International Workshop on Mobile Object Systems, Linz, July 1996.

.... Systems Classified Systems Remote Execution Java Servlets (push, Sun, 1996) Remote Evaluation (Stamos, 1986) Tacoma (Johansen, van Renesse and Schneider, 1995) Code on Demand ActiveX (Microsoft, 1996) Java Applets (Sun, 1994) Java Servlets (pull, Sun, 1996) Weak Migration Aglets (IBM, 1996) Mole (Stra er, Baumann and Hohl, 1997) Odyssey (General Magic, 1997) Strong Migration AgentTcl (Gray, 1996) Ara (Peine, 1997) Telescript (General Magic, 1996) 3 ADVANTAGES OF CODE AND AGENT MOBILITY In the following, we will examine the advantages resulting from code and agent mobility. During our discussions, for each of the ....

Straßer, M., Baumann, J. and Hohl, F. (1997) Mole: A Java based mobile agent system, in Proceedings of the 2nd ECOOPWorkshop on Mobile Object Systems (eds.

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M. Straer, J. Baumann, and F. Hohl. Mole - A Java based mobile agent system. In ECOOP '96 Workshop on Mobile Object Systems, 1996.

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M. Stra#er, J. Baumann, and F. Hohl. Mole - A Java Based Mobile Agent System. In Proceedings of the ECOOP'96 workshop on Mobile Object Systems, 1996.

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