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Service Brokering
Yu-sik Park
Index
Introduction Brokering system Ontology Services retrieval using ontology Example
Introduction In service-oriented distributed systems,
software services are located in different computers
The broker acts as middlemen between consumers and providers, aggregating, repackaging and adding value to services or information
The brokering function in a distributed systems matches a request for a specific service with a remote process that can perform that service, based on subtask’s need for that service
The general broker model
Tasks of brokers Locational Task
The broker should maintain an up-to-date repository of all of the agents available for access within an agent system.
Matching Task The broker should maintain a knowledge base of advertised i
nformation about other agents, and uses this knowledge to match agents with requested services
Advertising Process An agent announces itself to broker by advertising to t
hem, using the terms and vocabulary described in ontologies
Broker that received the advertisement store all of the advertised information about agent in its repository
Querying Process The broker may receive queries from agents that are l
ooking for other agent that can provide specific services.
A query is represented as an individual capability specified over some set of focused ontologies.
Syntactic Brokering and Semantic Brokering Syntactic brokering uses the structure or format of
a task specification to match a requester with a service provider, matching requests to object interfaces or query/scripting languages to decide which service providers to recommend
Unfortunately, within an open agent-based system there may be situations where agents present the same interface, but implement different functions
So, the agent system can add semantic functions to complement the syntactic brokering process
What is the Ontology? W3C defines the ontology in Requirements for
a Web Ontology Language, “An ontology defines the terms used to describe and represent an area of knowledge”.
Hence, a service ontology defines how a service is represented in the area of service discovery.
Why ontology? Sharing common understanding of the structure of information a
mong people or software agents is one of the more common goal in developing ontologies
Enabling reuse of domain knowledge was one of the driving forces behind recent surge in ontology research
Making explicit domain assumptions underlying an implementation makes it possible to change these assumptions easily if our knowledge about the domain changes
Separating the domain knowledge from the operational knowledge is another common use of ontologies
Focused Ontologies and Ontology Fragments When we consider how to represent the ontological kn
owledge, there are basically two approaches Incorporate everything into a single, very large ontolog
y Allow for multiple, focused ontologies
Simple ontology example
Class
Attribute
Agent Capabilities, Advertisements and Queries Agent capabilities provides a mechanism for
agents to advertise their abilities and characteristic to a broker agent, and to query the broker for sets of agents meeting specific criteria
When more than one agent capability is advertised, semantic interpretation is similar to a disjunction
Example : Sembots The SemBots project is developing software technolog
ies to realize self-growing robot software systems that enable robots to improve their high-level software configurations based on their experiences and user feedback in handing unknown situations.
In project, we are developing Component broker Ontology based representation
Component broker of Sembots
http://webeng.icu.ac.kr/Sembot.htm
References Marian Nodine, “Scalable Semantic Brokering over Dy
namic Heterogeneous Data Sources in InfoSleuth”, MCC, April 20, 2001
A. Tokmakoff, “Service Brokering in Object-Based Systems: Advanced Information Services, IEEE 1996
http://webeng.icu.ac.kr/Sembot.htm
Thank you!