: Public Boundary

Created:	5/10/2022 1:04:42 PM
Modified:	5/10/2022 1:15:22 PM

Project:
Author:	Natha Paquette
Version:	1.0
Phase:	1.0
Status:	Proposed
Complexity:	Easy
Difficulty:
Priority:
Multiplicity:
Advanced:
UUID:	{616AF182-C3B0-4303-837A-791B46F16699}
Appears In:	Figure A-6 NIST Metrics Model

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<li>Overview of the NIST Cloud Computing Metrics </li></ol>
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NIST RATAX-CloudServiceMetricsDescription-DRAFT-V2.3d9 <a href="file://http://collaborate.nist.gov/twiki-cloud-computing/pub/CloudComputing/RATax_CloudMetrics_WAs_Docs/RATAX-CloudServiceMetricsDescription-DRAFT-v2-3d9.pdf">http://collaborate.nist.gov/twiki-cloud-computing/pub/CloudComputing/RATax_CloudMetrics_WAs_Docs/RATAX-CloudServiceMetricsDescription-DRAFT-v2-3d9.pdf</a> The NIST Metrics model defines terms and concepts which can be represented by Templates which can be used to formally define metrics for cloud computing. The Model does not assume the availability of an underlying Structured model for the system being measured. As such the binding of the Metrics to real world entities and entity types is informal. The following terms are defined for the NIST Cloud Computing Metrics model. Measure (noun) Value that expresses a qualitative or quantitative assessment of a property of an entity. Is produced as result of a Measurement and is conforming to a Measure Definition. Note: The definition above is based on the definition of Measure in ISO/IEC 15939:2007. As a result of concerns regarding alignment with other Metric models, which use the term Measure for the abstract definition of the process of measuring, the NIST Metrics WG is considering changing this term to "Measurement Result". Measure Definition A definition of the Measure(s) produced in assessing a property of an entity Measurement Set of operations having the object of determining a Measure Note: Based on the definition of Measurement in ISO/IEC 15939:2007. As a result of concerns regarding alignment with other Metric models, the NIST Metrics WG is considering removing this class from the Model, since the semantics are captured by the combination of the Metric and the Measurement Definition concepts. Metric A standard of Measurement for a particular Measure Definition, which defines the conditions and the rules for performing the Measurement. A metric can be understood as a standard set of procedures and rules for generating values for its associated measure definition. Stakeholders define the scenario of use for a metric. The scenario represents the expectations of an underlying business or operational process (e.g. SLA or Operation) and how the metric will be used to assist such process, what range of values represent acceptable performances of the measured cloud service properties. The scenario also defines the way the metric will be applied – what Cloud resource or service is being measured, under which conditions is the metric evaluation triggered, frequency of the evaluation, etc. The metrics define the cloud service properties to be measured, their related measure definitions, parameters, formulas and constraints (measurement rules, context conditions). Typically, a metric is based on a primary measure definition, but may involve other secondary – or underlying – measure definitions, that are subordinate to the primary – i.e. are used by the definition of the primary measure. The measures define the measurement results of the properties observed. The UML class diagram for the NIST metrics model is shown in Figure A-6. In the definitions below the term “element” refers to a UML Class of the model and the term “attribute” refers to a UML Attribute of a UML Class. ContextCondition A ContextCondition element is expressing the conditions under which this metric is applicable, in a real environment or context. The description attribute is a summary of a particular condition of applicability. The targetCharacterization attribute characterizes the type of Cloud resource(s) to which this metric applies, i.e. the type of resource of which some property can be measured. For example, an availability metric might be exclusively defined for “storage services”, and therefore would not be appropriate to measure the availability of a compute server or of a network. The applicabilityRestriction attribute is expressing particular constraints to be observed when using the metric. For example, measurement rules in the metric definition may depend on some regulatory environment (e.g. a particular definition of “business time”), which in turn might reduce the scope of applicability to certain countries. Measure A Measure element holds the necessary information to understand a value resulting from a measurement of the attribute being observed. The value attribute represents the result of the observation. The unit attribute represents the unit of the value at the time of measurement. The uncertainty attribute represents the uncertainty at the time of measurement. A Measure element is associated to one MeasureDefinition element. It determines the nature of the Measure element. Both uncertainty and unit attributes carry run-time values that should be related respectively to the uncertainty budget derived from the measurement rules and the measure definition unit metadata. MeasureDefinition A MeasureDefinition element holds the basic information necessary to understand the property to be observed. The name attribute represents the measure definition. The referenceId attribute identifies uniquely the measure definition. The scale attribute gives information on how the measurement value can be interpreted and what sort of operations can be performed on it. The type attribute represents the kind of the measure. The unit attribute represents the base unit that will be associated to MeasureDefinition element. The expression attribute represents the function used to assemble the underlyingMeasureDefinitions that compose the MeasureDefinition. The underlyingMeasureDefinitions association represents the possibility that a MeasureDefinition element can be composed of other MeasureDefinition elements. This means the MeasureDefinition element expression is using the outcome of other MeasureDefinition elements. MeasurementRule A MeasurementRule element is used to further constrain some parts of a Measure element and indicate possible method(s) for measurement. For instance, an “AvailabilityDuringBusinessHour” Metric element could be defined with a scope that constrains some piece of a generic “Availability” Measure element to limit the observation period to defined business hours. Measurement rules are necessary for the measurement The description attribute is a summary of a particular measurement rule. The method attribute represents the method of measurement of the targetMeasure. The uncertainty attribute represents the estimate associated with the targetMeasure. It can be used to help determine the Metric accuracy or precision. A measurementRule element can influence more than one targetMeasure element (targetMeasureDefinitions association). For instance, a measurement rule could define that all targeted time measures be of unit second. Metric A Metric element helps define a cloud service property to be measured, its related measures, parameters, formulas and measurement rules so it can be used in a given context. The name attribute represents the metric. The referenceId attribute represents a unique way to identify the metric in a repository. The category attribute represents the type of the metric (i.e. business, technical, security). The parameterList attribute lists a set of variable names that can appear at various places under the Metric element – e.g. in some measurement rule or measure definition. The parameterList attribute can be what is needed by an implementer of the Metric element – to use the variables or attribute names inside the list either as parts of a run-time Metric interface, or in a Metric configuration file. A Metric element is associated to one or more ContextCondition elements (contextConditions association). A Metric element is associated to one or more MeasurementRule elements (measurementRules association). A Metric element is associated to one primary MeasureDefinition element (primaryMeasureDefinition association).