Information Technology Reference
In-Depth Information
specification allows to extend the message with additional information like Web
service endpoint references (WS-Addressing
10
) to ensure an end-to-end commu-
nication with only one single message encoding. In this case, agents are able to
register themselves with a specific address to publish their services as a REST
service. The resulting advantage of this combined message format is the support
of more complex interaction patterns beside request/response interactions.
A still problematic issue, concerning the use and composition of RESTful
services, is the change of state of a resource and the corresponding update of
clients. Especially Web clients have to constantly send
GET
requests to check if
the state has changed, which will result in heavy trac and unnecessarily high
load of Javascript. For a bidirectional communication, as used for instance in a
User Interface Framework S. Aghaee et al. [1, Section 5.2] recommend the use of
W3C WebSockets [12]. The WebSocket API provides a mechanism to sent data
in various representations (JSON, XML, etc.) to clients only when the resource
has changed.
4
Conclusion and Future Works
In this paper, we presented a gateway architecture that makes it possible to inter-
connect multi-agent systems and Web services. In contrast to most other solutions
in this area, we rely on a RESTful architecture where agents and their services are
treated as resources. Our approach offers a very intuitive way of resource address-
ing and a very accessible way of resource representation. In our current work, we
especially focus on the latter point. We work on a Javascript-based framework that
assists the creation of Web-based graphical resource representations. We use this
framework specifically to provide graphical user interfaces (GUI) for humans in
order to gain access to agents and their services in the context of an agent-based
collaboration platform. On this platform, so-called
Agentlet
applications are de-
ployed where agents carry information about their graphical Web representation.
For this purpose, we are developing a Web component catalogue, where the rep-
resentation of each component can be switched between JSON and FIPA-SL in
order to make it both readable on the agent and the Web service side. Thus, ac-
cess to agents and their services is possible via any browser and is consequently
very lightweight and nearly platform-independent.
Besides the large potential for further improvements of our Web component
framework (new components, more extensive functionality) and WebGateway
(support of additional content language encodings), the simplicity of the used
service description is not always an advantage with respect to automation of
service workflows. A possible improvement in this area could be the integration
of WADL
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, which plays a similar role for RESTful Web service as WSDL for
SOAP Web services. The further use of our approach in future student projects
and the continuous advancement of our agent-based collaboration platform will
help to improve the introduced components step by step.
10
WS-Addressing:
http://www.w3.org/Submission/ws-addressing
11
Web Application Description Language (WADL):
http://java.net/projects/wadl
