15/09/2015semantic week - 2009page 1 enhancing service selection by semantic qos henar muñoz frutos...
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19/04/23 Semantic Week - 2009 Page 1
Enhancing Service Selection by Semantic
QoSHenar Muñoz FrutosTelefónica I+D
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Introduction
Conclusions and Future Directions
Proposed Approach
Implementation
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Context
• Marketplace model: customers and providers interact for trading services– Introduction of Grid and Cloud technologies – New services included: infrastructure services
• Services: Storage, computing, infrastructure, software as a Service
• Provided by Amazon, Google, HP…– Services encapsulate resources
• Resources: machines, hard disk, applications, licenses• Key element: Service Selection based on QoS metrics
– Due to the increase of functionally similar services – Due to the importance of non-functional properties: QoS metrics
availability, performance, price, reliability, infrastructure properties– To find the best service to meet user requirements and assure
QoS
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Context
• Important is to have a contract between the involved entities (customer-providers)– Need Service Level Agreement
• terms for the provision of the service (service description),
• Quality of service (QoS) level to be maintain, • Information about resources to be provided, • the liability to compensation if SLAs are not met.
• SLA templates used for achieving an agreement between customers and provider specifying the terms under the provision of the service
• SLA templates can be used as input for the service selection based on QoS metrics
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Problem statement
• Main SLA specifications– WS-Agreement (OGF-GRAAP)-WSLA (IBM)– They covers the syntactic aspects in the description of SLA:
• a schema for specifying an agreement and an agreement template,
• no focus on vocabulary domain– WS-Agreement non-goals: Defining Specification of metrics
associated with agreement parameters i.e., how and where these are measured
• Specification assumes that other complimentary specifications will address these requirements
• Current SLA specifications lack in interoperability:– Open marketplace: Providers and consumers are collaborating on a
global scale competing for offering and consuming services – Different terminologies to describe the vocabulary domain
(performance vs. response time)– Different language (performance vs. rendimiento)
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Example
ANSYS request
•CPUName: IntelCore Duo•CPU Speed: 2 GHz•Capacity: 400 MB•Price: 27 euros per day•DiskSpace: 250GB
-RAMMemory: 7.5 GB-ComputeUnit: 4 ECU-Storage: 850GB-Platform: 64 bit-Price: $0.4 per instance hour
CUSTOMER
AMAZON
Software engineering company
-MemoryPerTask: 7.5 GB-ClockCPUSpeed: 100 MHz / process-StorageCapability: 850GB-Cost: 5 euros/task/hour
BSC
PROVIDERSCloud and Grid providers
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Objectives
• Improve interoperability between service providers and clients– Providing semantic interoperability by the introduction of semantic
annotations– Beyond syntax to semantics, mapping of data exchanged between the involved
parties
• Be backwards compatible – Compatible with current SLA specification e.g. WS-Agreement, WSLA– Compatible with current components (which do not understand the
specification…)• If specification is used, then extra reasoning is feasible• If NOT then the process continues normal operation
• A lightweight approach, so that, a easy way for providers to introduce these annotations.
• Increase automation in the selection process to reduce human intervention
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Conclusions and Future Directions
Related Work
Implementation
Introduction
Proposed Approach
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Proposed ApproachSpecification for semantic Annotations (SA-SLA)
- Backwards compatible
- Lightweight approach
Conceptual model - QoS ontology
Implementation
- Semantic Enhanced service Selection (SESS)
Selection algorithm- ranking services- taken from [Wang2006]
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SA-SLA• Introduction of semantic annotations in current SLA
template files– Based on SA-WSDL– WS-Agreement + WSLA compatible
• Allow for annotating SLA description with pointers to semantic concepts
• Annotation of: SLA Parameters. Metrics
Metric Parameter SLO
modelReferences SchemaMappings
Non-semantic descriptions
Semantic descriptions
RDF, OWL, WSML
SA-SLA
SLA template
QoS metrics SLA terms
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SA-SLA
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Conceptual Model
• Framework capturing the QoS provided by the suppliers and required by the customer to match between the two
• Conceptual model in QoS which is shared by customers and providers and formalized as OWL– It can be extended by domain requirements (domain
specific)
• QoS ontology: specify SLA parameters and metrics for infrastructure services and their relationships– Based on [Wang2006], [Lee2003], [Tsesmetzis2006],
[Ren2007]
• QoS categorization: infrastructure, system, network, and security and cost
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QoS ontology
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Conceptual Model
• To solve the terminology problem (different terms for the same concept)– Simple Knowledge Organization System (SKOS)– Standard way to represent knowledge organization using
RDF
• SKOS is used for solving terminology problem
<rdf:Description rdf:about="http:// brein.com/ontology/Upper/QoS#ResponseTime">
<skos:inScheme rdf:resource="http://eu-brein.com/thesaurus/QoSmetrics"/> <rdf:type rdf:resource="http://www.w3.org/2004/02/skos/core#Concept"/> <skos:prefLabel xml:lang="en">Response Time</skos:prefLabel> <skos:altLabel xml:lang="es">Tiempo de Respuesta</skos:altLabel></rdf:Description>
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Conclusions and Future Directions
Proposed Approach
Introduction
Implementation
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Architecture
Comon conceptual
model
SESS SESS
SLA framework SLA framework
SA-SLA(WS-Agreement
WSLA)
Local domain
knowledge
Local domain
knowledge
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Ontology Manager
Local domain
ontologySKOS representation
SKOS Manager
SA-SLA
TSLA Parser
Customer Request
TSLASelector
SLA template scores
SA-SLA
Provides Offers
Architecture
Semantic Enhanced Service Selector
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Implementation
• Ontologies– Common conceptual model: OWL– Local knowledge: OWL + RDF (SKOS)
• Local knowledge repository– Query engine: Jena– Query language: SPARQL– Reasoner: Pellet
• Semantic Enhanced Service Selector– Parse the SLA templates files (JAXB and XPATH) and– match providers offers with customers’ requirements
(selection algorithm taken from [Wang2006])– Interact with local domain repository for semantic
support (create SLA instances, obtain local metrics)
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Proposed Approach
Introduction
Implementation
Conclusions
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Conclusions
• The increasing number of functionally similar services requires non-functional selecting process
• Non-functional properties as QoS which are described as part of the SLA templates files
• The introduction of semantic annotations in current SLA specifications allows solving the QoS metric definition problem
• Using semantic technologies in a non-intrusive way addresses the issue of backwards compatibility and eases development of tools
• Our proposal is based on existing specifications (WS-Agreement, SAWSDL)
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References
• [Wang2006] Wang, X, Vitvar, T., Kerrigan, M., and Toma, I.; A QoS-aware selection model for semantic Web Services. In 4th International Conference on Service Oriented Computing (ICSOC 2006), Chicago, USA, Dec. 2006.
• [Lee2003] Lee, K, Jeon, J, Lee, W, Jeong, S., and Park, S., QoS for Web Services: Requirements and Possible Approaches, W3C Working Group Note 25, 2003. http://www.w3c.or.kr/kroffice/TR/2003/ws-qos/
• [Tsesmetzis2006] Tsesmetzis, D. T., Roussaki, I. G., Papaioannou, I. V., and Anagnostou, M. E. 2006. QoS awareness support in Web-Service semantics. AICT-ICIW. IEEE Computer Society, Washington, 128.
• [Ren2007] Ren, K.; Jinjun Chen; Tao Chen; Junqiang Song; Nong Xiao; Grid-Based Semantic Web Service Discovery Model with QoS Constraints, Semantics, Knowledge and Grid, Third International Conference on 29-31 Oct. 2007 Page(s):479 – 482
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