Copyright © 2012 the Contributors to the Cloud Computing 1.0 Specification, published by the Cloud Computing Community Group under the W3C Community Final Specification Agreement (FSA). A human-readable summary is available.
This specification was published by the Cloud Computing Community Group. It is not a W3C Standard nor is it on the W3C Standards Track. Please note that under the W3C Community Final Specification Agreement (FSA) other conditions apply. Learn more about W3C Community and Business Groups.
| 1 Introduction |
| 1.2 Namespaces |
| 3 The Service Query |
| 4 The Work Request |
| 4.1 Computational "Style" |
| 4.1.1 The "Availability" Property |
| 4.2 Computation parameters |
This specification details the procedure required to "engage" (that is, to initialise the use of) a cloud service.
Generally, this procedure consists of:
A service Query is sent by a cloud consumer in an attempt to find an appropriate cloud service to which future work requests will be sent
This query consists of an "all routers" multicast request, to which listening services send a response consisting of an XML document representing a rule-set, drawn from the Core sub-set of RIF [ RIF], which will, when implemented, yield the charging regime of the service, expressed in units of US cents per GHz-minute
In this way, a consumer is able, in knowing the required amount of computation, to estimate the cost imposed by each service for the desired work
the consumer, after receiving all responses from "interested" cloud services, may then choose from among those services using whatever selection policy is desired.
Note that the charging regime provided by a cloud service is purely a guide: consumers are not required to implement a RIF processor in order to make a service selection
Once a cloud service has been engaged, the intention of a consumer to have that service perform some computational work is communicated in the form of a "work request",
This request consists of an XML document (as shown in example 1), itself consisting of a single element consisting of an empty element with the tag "work_request", having the attributes named "params", containing a reference to the requested computation parameters, "style", containing the computational "style" of the task and "content" containing a reference to a model of the computational task to execute (all these attributes will be explained further below)
The "style" with which a computation takes place consists of the minimum "availability" of the computation which, itself, consisting of a proportion of some period, expressed as a percentage, over which a computation is expected to be running and responsive.
The availability of a computation is calculated as follows, where "MTTF" is Mean Time to Failure and "MTTR" is Mean Time to Repair:
This example lists the "style.css" from Example 1, which itself specifies that those elements (of the model given in that example) having a class of "abc" have a minimum availability of 99%, and the model element with ID "xyz" should have a minimum availability of 99.5%
.abc {
availability: 99%
}
#xyz {
availability: 99.5%
}
the parameters to effect the model's execution appear in the form of a "params" element, the element children of which, each representing a parameter, containing a "name" attribute, the value of which contains the name of a parameter, and a "value" attribute, the value of which contains a reference to the value (the meaning of which is outside this specification) of the parameter value
The following example illustrates the parameter list, containing two parameters named "x" and "y", referenced by the above work request
<params xml:id="params">
<a name="x" value="#a">
<b name="y" value="#b">
</params>