Copyright 2005 Digital Enterprise Research Institute. All rights reserved.

www.deri.org

WSLA Language Specification

http://www.research.ibm.com/wsla/

WSMO Working Group PresentationAdina Sirbu & Ioan Toma

18 January 2006

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Presentation Overview

• Short recap of WSLA Framework• WSLA Language

– Parties– Service definition– Obligations

• Conclusions

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Short recap of WSLA

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WSLA Language

• An XML-based language used by both service providers and consumers

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Parties

• Signatory parties:– Service provider– Service consumer

• Supporting parties:– Measurement– Management– Condition

evaluation

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Service Definition – Service Object

• A ServiceObject is an abstraction of all conceptual elements for which SLA parameters and the corresponding metrics can be defined

• A ServiceObject includes any number of: Schedules, Triggers, Constants, MetricMacroDefinition, MetricMacroExpansion, SLAParameters and Metrics

• ServiceDefinition, Operation and OperationGroup are all subtypes of ServiceObject

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Service Definition - SLA Parameter

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Service Definition - Metric

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Service Definition - Metric

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Obligations

Service Level Objective

Elements:• the obliged party• one or more validity

periods• the state = a logical

expression• an evaluation event

or an evaluation schedule

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Obligations

Action Guarantee

Elements:• the obliged party• the precondition = a

logical expression• an evaluation event

or an evaluation schedule

• the qualified action• the execution

modality

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Obligations

Logic Expressions:• “follow first-order logic”• contain AND, OR, NOT,

IMPLIES operators which connect predicates or, again, expressions

• could be extended e.g., to contain variables and quantifiers

Predicates:• can have SLA parameters and

scalar values as parameters • new domain-specific predicates

are introduced by extending the abstract predicate type

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Conclusions & Relevance to WSMO/L/X

• Conclusions– WSLA allows to express: what to measure, how to measure,

who does what and guarantees– WSLA Language – a XML based language for specifying SLAs

related information

• Relevant for:– WSMO -> describe semantically the services of WSLA

framework (measurement, evaluation, management)

-> QoS representation, reasoning, measurement – WSMT -> the monitoring part (

www.alphaworks.ibm.com/tech/ettk)– WSMX -> the negotiation component