-In ubiquitous computing environments to use distributed services and devices efficiently the basic information should be provided about types or locations of services in advance. A process explores such information that meets a user's needs. We call it as service discovery which is the most primitive system in distributed mobile computing environment such as ubiquitous. It is a trend that use of a combination of developed agent technology and service discovery to manage efficiently and flexibly distributed services, devices, and users. A number of agent platforms have been developed by many academic institutes; however there exist problems about interoperability among agent platforms. FIPA suggest a discovery middleware module that provides to interoperate between agent platforms. In this paper, we developed the prototype of ontology based discovery middleware based on FIPA specification to facilitate sharing services between FIPA-OS, JADE, and SLP platforms.
Ucomputer use by making many computers available
BIQUITOUS computing is the method of enhancing
throughout the physical environment, but making them
effectively invisible to the user [
The famous agent platforms are JxTA [
The domain reiteration of agent platforms can be occurred in
ubiquitous environments. Therefore, a standard mediation is
necessary to support compatibility. FIPA suggest a discovery
middleware module that provides to resolve such problems [
In this paper, we present the prototype of ontology based discovery middleware to facilitate sharing services between heterogeneous agent platforms. The use of suggested discovery middleware make it possible to share a service of agent platforms and also to perform as following operations 'registration', 'deletion', and 'modification' between heterogeneous agent platforms.
The rest of this paper is divided into three sections. In section 2, we introduce several agent platforms. In section 3, we describe discovery middleware and the design of our system architecture. Finally we discuss conclusion and future works.
SLP is a protocol for automatic resource discovery on IP
based networks. It is possible to operate registration, deletion,
and modification in SLP domain [
As mentioned above, the purpose of SLP is acquisition of location of services. Because cannot provide implementation of application. Therefore SLP needs some expansion of application level for interoperation of heterogeneous agent platforms.
The Foundation for Intelligent Physical Agents (FIPA) is an
international organization that is dedicated to promoting the
industry of intelligent agents by openly developing
specifications supporting interoperability among agents and
agent based applications [
The current version of FIPA-OS agent platform does not provide the implementation of discovery middleware. In this paper, we implement the prototype system of discovery middleware on the FIPA-OS agent platform and provide the interoperability to heterogeneous agent platforms.
JAVA Agent DEvelopment Framework (JADE) is a
software framework fully implemented in Java. It allows
reducing the time-to-market for developing distributed
multi-agent applications by providing a set of ready and
easy-to-use functionalities that comply with the standard FIPA
specifications and a set of tools that supports the debugging and
monitoring phases [
The current version of JADE agent platform does not provide the implementation of discovery middleware such as FIPA-OS. Therefore it needs additional expansions.
Figure 4 illustrates the service discovery mechanism
suggested by FIPA [
However the implementation of discovery middleware is not easy. There are several considerations. For example, it needs communication protocols between heterogeneous agent platforms, and also needs data consistency mechanisms to manage inconsistency caused by service registration, deletion, and modification. Therefore, it is a trend of development that considers a specific subject of agent platform. In this paper, our approach concentrates on providing a real service between heterogeneous agent platforms.
In following paragraphs will represent the considerations of design a discovery middleware.
First, it should be satisfied data consistency between heterogeneous agent platforms. The problem of data inconsistency is inevitably occurred between agent platforms when use operations as follow registration, deletion, and modification. This problem is ongoing study, and we consider several solutions such as using a time stamp, real-time synchronization of database, and etc. Using the time stamp method, it attaches a time stamp to each service when it created. It is not available to use, if a service pass the validate time. The real-time synchronization method is that changes in one database are reflected in the other database.
Second, it needs a standard definition of resources such as service, device, agent, and etc. The difference of resource description between JADE and SLP should be mapped a standard description, because JADE and SLP have there's own description. Therefore we define ontology for resource description as shown in the table 1. In our system, we represent Subject PrintAgent1 PrintAgent1 PrintAgent1 PrintAgent1 PrintAgent1 PrintAgent2 PrintAgent2 PrintAgent2 PrintAgent2 PrintAgent2 resources in first-order predicate calculus. The basic model consists of Subject, Predicate, Object, and GraphID, in which
Object : the set of all values of Subjects (for example, Room 27, Yes, Agent, or empty)
GraphID : the number linked with an OWL file To illustrates, (PrintAgent1, Type, Agent, 11) means that the type of PrintAgent1 is an agent, and linked with an OWL file #11.
Finally, it needs a defined method of service invocation between JADE and SLP. It needs some additional works, because agent platforms have there's own service invocation method each other. This part is ongoing study. We consider several methods about web application or socket invocation or etc.
Figure 5 illustrates our architecture of discovery middleware using JADE and SLP. According to the FIPA specification, a service discovery of heterogeneous agent platforms passes through many communication procedures, because an agent platforms have service information its own database. If an agent an agent query a specific service to ADS, ADS requests the same query to DM. And then DM requests the service to heterogeneous agent platform. After, reply procedures inverse of request procedures. Precisely, Agent ↔ ADS ↔ DM ↔ AP.
Our architecture of DM reduces replying time of query, because it has simpler discovery procedures than current procedures. Figure 5 illustrates our mechanism that stores services of SLP on JADE agent platform in advance such as container. It simplifies communication procedures each time of requests. When an agent needs to discover a certain service, it first looks at its local container to check whether that service is available. On failure, by looking at its own container for heterogeneous agent platforms, it checks the service of SLP to discovery the service. The service information of providing SLP is retrieved to JADE agent platform when JADE agent platform or SLP starts its running. After the service information of SLP is periodically synchronized with container of JADE agent platform.
In ubiquitous computing environments to use distributed services and devices the functions of service discovery should be provided about types or locations of services. In this paper, we developed the prototype of ontology based discovery middleware to facilitate sharing services between heterogeneous agent platforms. Using this prototype make it possible to construct multi agent platform systems. And our architecture of DM reduces replying time of query, because it more simplifies discovery procedures than suggested by FIPA. However several problems should be proved for providing the complete service such as data consistency, communication protocol, standard service description, and SLP applications.
In future, we concentrate on development of a real service application and proving data inconsistency. And we'll extend our discovery middleware to conform FIPA-OS agent platform. Additionally, we are also interested in context-aware service discovery. Sejung Oh received the B.E degree in Engineering of Advanced Materials from Sungkyunkwan University, Korea, in 2003.
He is currently a M.E. student in the Department of Computer Engineering in Sungkyunkwan University. His main areas of research include service discovery, agent platform, context-aware system and ontology building. For service discovery, he is interested in ontology based service discovery, discovery middleware for sharing services between heterogeneous agent platforms.
Juryon Paik received the B.E. degree in Information Engineering and the M.E. degree in Computer Engineering from Sungkyunkwan University, Korea, in 1997 and 2005, respectively.
She is currently a Ph.D. student in the Department of Computer Engineering in Sungkyunkwan University. Her main areas of research include xml mining, xml data replication and ontology building. For xml mining, she is interested in mining frequent tree patterns, mining association rules from xml documents and similarity computation between xml documents.
Heeyong Youn received the BS and MS degrees in electrical engineering from Seoul National University, Seoul, Korea, in 1977 and 1979, respectively, and the PhD degree in computer engineering from the University of Massachusetts at Amherst, in 1988. From 1979 to 1984, he was on the research staff of Gold Star Precision Central Research Laboratories, Korea.
He is presently an endowed professor in the School of Information and Communication Engineering, Sungkyunkan University, Suwon, Korea. His research interests include storage systems, distributed computing and networking, Internet and mobile computing, and fault-tolerant computing. He has published more than 120 papers in international journals and conference proceedings, and received an Outstanding Paper Award from the 1988 International Conference on Distributed Computing Systems, 1992 Supercomputing, and the 2001 Korean Society Internet Information Spring Symposium, respectively. He also served as a lecturer of the ACM Lectureship Series from 1993 to 1997.
Dr. Youn is a senior member of the IEEE. Since 2002, Prof Youn works for 21C Frontier Ubiquitous Computing and Networking project (supporting by ministry of information and communication republic of Korea) and Korea Research Foundation project (KRF – 2003 – 041 –D20421) and Brain Korea 21 Project.
Ungmo Kim received the B.Sc. degree in the Department of Mathematics in Sungkyunkwan University, Korea, in 1981, and the M.Sc degree in Computer Science from Old Dominion University, USA, in 1986, and the Ph.D. degree in Computer Science from Northwestern University, USA, in 1990. He has worked several years as consultant and analyst in universities and private companies, and since 2001, he has been working for the Silver-Net Campaign Society as a Regional Chief-in-Committee Member.
He is a Professor in the School of Information and Communication Engineering in Sungkyunkwan University, Korea. His current research interests include XML/Web mining, Data Mining, Access Control, and Domain-Specified ontology modeling.
Dr. Kim is the Inquiry and Consulting Member of Korea Information Processing Society.