Table 1 describes examples
of Web services classes implementing different QoS properties.
QoS Measurement in Web Services
Measurement is fundamental for dealing with quality. Indeed, quality should be measured
prior to its evaluation and management. A metric defines a qualitative or quantitative property
of the elements that users want to evaluate. It is characterized by: its name, data type,
type of element to be measured, and computation logic. Operational metrics characterize
the QoS that Web services exhibit when they are invoked. Paradoxically, when Web services
users need to identify metrics that exhibit operational properties at run-time, the autonomy
characteristic of Web services prohibits that exhibition. Nevertheless, when composing a
process, it is indispensable to inquire the Web services operational metrics. In Web services
environments, metrics and reports (log files) are not ???static???, and they should always be
modified to handle the changes. In spite of this, it is difficult to manage the computational
resources (metrics values) of Web services when the workload is unpredictable.
Quality metrics (e.g., service time, cost, reliability, fidelity of results) are useful in many
regards.
Pages:
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609