Information Technology Reference
In-Depth Information
CHAPTER
5
Web Service Configuration
with Multiple Quality-of-
Service Attributes
5.1 INTRODUCTION
Web services and their related design and composition methodologies are
increasingly used to integrate disparate software components to accom-
plish many challenging tasks. AWeb service is defined as a Web-accessible
function that is well defined, self-contained, and does not depend on the
context of other Web services. WhenanysingleWebservicefailsto
accomplish a service requestor's multiple function requirements, multiple
Web services need to be dynamically configured together to form a Web
service composition to satisfy both functional and nonfunctional require-
ments. The latter are characterized by quality of service (QoS). The QoS
study is important and covers the following areas:
1.
QoS specification and description, that is, QoS modeling. QoS
serves as a key index for discriminating candidate Web services
and Web service compositions with identical functionality.
Quantifiable QoS parameters and measurements include reli-
ability, capacity, availability, and cost. The QoS information
can be collected from service providers, for example, cost; or
from service requesters' feedback, for example, execution time;
