R. Y. MY, J. LIU 351
Figure 4. Client modulecalling relationships.
Service calls, and service discovery module man-
ager by invoking the meter records, records various data
in the evaluation pro cess;
Service evaluation requires a service call and ser-
vice discovery, and call and find that it is based on the
configuration, so you need to call a service call, service
discovery and evaluation configuration module;
Evaluation results show that the module needs to
call meter records management module for data statistics,
and then obtain statistical data for display;
Project management module is configured to facili-
tate user management evaluation established and is
therefore not dependent on any other modules;
UI interactions interface is in the top level of the
software architecture. But shielding the low-level opera-
tion, only need to call the service evaluation module for
service evaluation, call the evaluation configuration
module configuration management, project management
module called the project management, evaluation results
display module call monitoring / evalu ation results show,
thus ensuring the user on the e va l u ation of the controls ;
3. The Key Technologies Used in the System
3.1. Lightweight Service Invocation Protocol
Mobile service evaluation system designed lightweight
Web services technology is built on XML, SOAP,
WS-Discovery protocol based on criteria such as a dis-
tributed application architecture. Lightweight design ser-
vice protocol's main task is how to reduce the service
invocation packet size. In the mobile environment, how
to use SOAP-based message format to complete a large
number of data transfers, and to ensure efficient transfer
process and accuracy, a feasible way is to use compres-
sion technology to compress the SOAP message. Since
SOAP messages generally use HTTP, FTP and other
connection-based standard protocol for data transmission,
this transmission is the essence of stream-based data
transmission, without compressing the SOAP message
itself, so this paper directly to the Web service SOAP
messages this layer to achieve the flow compression of
the data stream, the input and output streams are encap-
sulated protocol that is added to the structure lightweight
service SOAP message compression and decompression
module.
Lightweight call protocol module structure includes
the following five modules:
Applications call interface: provides a convenient
interface to application calls;
Message Packaging: As in the message encapsula-
tion process, only basic types (int, boolean, string, etc.)
can be directly encapsulated into XML. As for complex
objects, such as the Date object, as well as custom ob-
jects, you cannot directly encapsulate them to XML. In
order to solve complex objects and custom objects en-
capsulation issues, as well as reduce equipment burden
and the amount of data transmitted as much as possible,
the paper design a unified object encapsulation mecha-
nism, which creates a lightweight service message and
Soap Object object, fills the message content intoSoap
Object, then convertes Soap Object to XML.
Message serialization:
After completing the message encapsulation, Soap
Object object cannot be transferred, so you need to con-
vert Soap Object into XML, then serialize it into byte
code, finally send it out. This module just finishes this
job.
Compression / decompression: This module’s func-
tion is to reduce the service data packet, and compress
the XML serialized data stream before sending it to the
client. The client then uses the corresponding decom-
pression algorithm to decompress.
Transmission module:
Since the overhead of TCP protocol is relatively large,
plus there are many additional HTTP protocol overhead
and it is difficult to establish a stable connection in mo-
bile networks. Therefore, this article uses UDP transmis-
sion in the mobile environment. On one hand, eliminate
the need for managing TCP link state control overhead.
On the other hand, save HTTP data header and effec-
tively reduce the packet size.
3.2. Lightweight Service Discovery Protocol
Traditional mode of service calls are on the premise that
clients know in advance the design target address of the
service, and create a client endpoint for the service call
based on this address. The service discovery protocol in
our mobile service evaluation system is the client does
not know in advance the target service address and dy-
namically invoke the detected available services. Service
Discovery lifts the dependencies between client and
server, which allows the server dynamically change its
address. The client and server can also dynamically join
and exit.
Lightweight service discovery protocol defines two
basic service discovery mechanisms to achieve the oper-
ating mode: Ad-Hoc mode and Managed mode.
Ad-Hoc Mode:
In Ad-Hoc mode, the client in a certain form of net-
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