Information Technology Reference
In-Depth Information
1. Host: URI of the Web server inclusive port.
2. Platform: Name of the running
platform.
3. Agent: Name of the agent that owns a service.
4. Service: Name of a specific service.
Mulan
With this structure it is possible to provide a unique address even if several agent
platforms and agents exist on the same host at the same time. The technical
counterparts of the REST resources on the Web server side are implemented as
Java Servlets
7
(interpreting the above mentioned JSPs). They are responsible
for providing the resource representations. They also act as connection endpoints
for HTTP and WebSocket connections and forward all incoming messages to the
responsible WebGateway-agent. Each resource (see Figure 3) has its own Servlet.
For once, we have default Servlets offering default representations in the form of
lists of the respective nested resources (e.g. a platform resource displays a list of
registered agents). But it is also possible to customize Servlets for resources.
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Fig. 3.
Resource Addressing and Servlet Binding
2.3 Message Translation
Translation of messages is essential to ensure a transparent and loosely coupled
interconnection. The gateway has to deal with different content languages and
has to convert a received message to the corresponding encoding of the recipient.
Actually, the WebGateway-agent supports a set of languages:
-
JSON: The major language that is used to communicate with Web services.
It has advantages over XML because of its simplicity and its perfect inte-
gration in Javascript applications.
-
SL: The Semantic Language (SL) [9] is part of the FIPA specification and is
used as a message content language for agent communication.
-
Form Content: HTML FORM
8
content that is transferred by HTTP POST
requests as
application/x-www-form-urlencoded
or
multipart/form-data
en-
coded message data.
7
Java Servlets:
http://www.oracle.com/technetwork/java/index-jsp-135475.html
8
HTML forms:
http://www.w3.org/TR/html4/interact/forms.html
