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You will also need a property of sustainment. The quality
of a service (a set of measures to which a service provably
conforms) must also include the measure of the capacity of
the service to sustain some value of those measures. This
is an entropic measure. Means of observation (direct or
reported) are the tough issue.
About to give web services a logical positivist spin?
From: Chiusano Joseph [mailto:email@example.com]
Lately I've been thinking about what's around the corner for Web
services (whether we're close to that corner yet or not is a separate
issue). The notion of dynamic discovery and collaboration of Web
services comes to mind (choreography, business processes, etc.) - but
I'm also thinking in terms of how a Web service can judge the "quality"
of another Web service. My question is: is anyone aware of any current
efforts on rating Web services?
To put this question in context, please consider the following scenario:
- A travel agency needs to access hotel reservation Web services when
making reservations. Rather than have a fixed list of Web services that
it always accesses, the travel agency would like to instead dynamically
discover Web services at each transaction. This allows the travel agency
to avoid having a pre-negotiated agreement with each Web service.
- This dynamic approach allows the travel agency to be able to
dynamically include newly available Web services (i.e. those not
available on a previous transaction), and exclude existing Web services
that may no longer be available.
- It is assumed that dynamic discovery is through means described by the
various Semantic Web-related initiatives taking place (i.e. a Web
service can discover another Web service that - for instance - accepts a
given credit card, offers fligts by a given airline, etc.).
- Since there is no pre-negotiated agreement in this scenario, the
travel agent needs a way of determining whether a given Web service is
"legitimate" or not. This goes beyond the security/trust realm that can
be covered by security tokens, to encompass whether or not the business
behind the Web service is legitimate, and not a front for a phony
operation. This could be done through the use of a third-party Web
Service "certification" authority that is "trusted" by the travel agent.
Once the travel agent's Web service agent sees this certification on a
Web service, it moves farther with that Web service in its discovery
- Additionally, the Web services (those that the travel agent's Web
service attempts to discover) could have some sort of "quality rating"
that reflects various factors such as reliability (i.e. whether or not
the Web service offers a reliable messaging feature), up time, etc.
- Assuming that the travel agent's Web service has initiatlly "selected"
a Web service based on its legitimacy and quality rating: the travel
agent's Web service may have a list of criteria specific to its request
(hotel reservation) that are required of the discovered Web service, and
at various levels (weights). These may reflect the travel agency's
business policies. For instance, the travel agency may (for whatever
reason) require a 3-day (more lenient) cancellation policy (instead of
1-day notice). Therefore, the requesting Web service may require that
any discovered Web service provide information on its cancellation
policy - and it subsequently "rates" that policy.
- The requesting Web service calculates an overall "weighted score" for
each discovered Web service, and returns to the travel agency
information from the Web services with the top X scores (X is determined
by the travel agency's policies). The aggregated results are then
organized according to the travel agency's policies (e.g. sorted by
price in ascending order).