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Semantic Aware Service Quality Negotiation

Semantic Aware Service Quality Negotiation. Marco Comuzzi, Kyriakos Kritikos and Pierluigi Plebani Dipartimento di Elettronica e Informazione Politecnico di Milano, Italy Service Wave Madrid, Spain, Dec. 10 - 13, 2008. Outline. Problem Definition Solution Quality Model Requirements

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Semantic Aware Service Quality Negotiation

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  1. Semantic Aware Service Quality Negotiation Marco Comuzzi, Kyriakos Kritikos and Pierluigi Plebani Dipartimento di Elettronica e Informazione Politecnico di Milano, Italy Service Wave Madrid, Spain, Dec. 10 - 13, 2008

  2. Outline Problem Definition Solution Quality Model Requirements OWL-Q Semantic Aware Quality Negotiation Example Future Work

  3. Problem Definition SOA promises automation from service discovery, negotiation until service execution Our focus is on automating all of these processes • Functional discovery is executed once • Many satisfactory research solutions proposed • Service quality must be taken into account for discovery and negotiation • Our previous work proposed solutions for both quality-based service discovery and negotiation • First problem: Main assumption that quality-based service specifications contain the same set of quality dimensions • Second problem: User interaction/input required both at beginning of service discovery and negotiation • Third problem: Different models used to capture user input

  4. Solution Use of ontologies for describing service quality dimensions • Formal, semantic and extensible description model • Semantic Web (SW) techniques for ontology reasoning and mapping • Lead to syntactic and semantic matching of service quality terms • Better discovery process with higher precision and recall • Very complex reasoning tasks can be supported like service discovery, mediation, negotiation Use of ontology model for quality-based service description along with rules for the alignment of the description Extend an existing semantic quality-based language (OWL-Q) with negotiation concepts Use this extended language with rules for supporting and automating negotiation

  5. Architecture of Negotiation Framework

  6. Service Quality Model Requirements (I) Define quality both as a capability and a requirement Rich and extensible semantic service quality model compliant with standards (e.g. WS-Policy) Syntactically separate from functional specification Rich description of both service quality dimensions & metrics • Value set for the metric • Domain the dimension belongs to • Weight of the metric (for both service providers and requesters) • Temporal characteristic of the metric values • Function indicating the quality delivered according to metric value • Formal description of how value of metric of complex WS is computed from values of same metrics of component WSs

  7. Service Quality Model Requirements (II) • A set of reference ontologies (measurement and currency units, measurement methods • Distinguish between negotiable and non-negotiable quality dimensions Cost model of the provider • Cost(avail)=avail*3, cost([0.95,0.97])=[7.85,7.97] Requester’s budget and negotiation strategy • Weights on quality dimension specify how budget should be split • Wavail=0.5, Wrt=0.5, Avail_r=[0.95,0.99], budget=20

  8. OWL-Q (I) Ontology for rich, semantic, extensible QoS-based WS description Fulfils all requirements except the negotiation ones Complements OWL-Q Comprises of many facets/sub-ontologies Offers mid and low level ontologies for domain-independent and dependent QoS dimensions

  9. OWL-Q (II)

  10. OWL-Q (III)

  11. Semantic Aware Quality Negotiation (I) Three elements should be defined: • Negotiation Object • Negotiation Protocol • Negotiator’s decision Model Quality-related and Negotiation-specific extensions of OWL-Q Quality-related: • Negotiable and Non-negotiable quality dimensions • Admissible values set of a quality dimension mapped to service levels according to a function Negotiation-specific • Negotiation Actor and strategy • Cost model

  12. Semantic Aware Quality Negotiation (II)

  13. Example (I) WS provider advertizes: • Avail=[0.9,0.99], RT=[0.5,2.0], coverage={Orange, Verizon, Cingular} WS provider’s cost model: price=cost_avail+cost_rt+cost_cov where: • cost_avail=Avail*3 • cost_RT=3*(2-RT)/1.5 • cost_cov=|cov_ad ∩cov_req| WS requester needs: • Avail=[95,99], RT=[100,1000], coverage={Orange, Verizon} WS requester has budget: 7

  14. Example (II) Use rules for matchmaking and producing useful negotiation facts: • matches (ad, req) ⇐ ∀qdi1 ∈ req ∃qdi2 ∈ ad s.t match (qdi1, qdi2) • match (qdi1, qdi2) ⇐ equiv (qdi1, qdi2) ∧ c_values (qdi1, qdi2) • c_values (qdi1, qdi2) ⇐ ∃v1 ∈ qdi1.values∧ ∃v2 ∈ dqi2.values s.t utfqdi1.unit→qdi2.unit (v1) = v2 • compatible (ad, req) ⇐ matches (ad, req) ∧ req.Bugdet ≥ MinCost (ad, req) Plus another set of rules for finding equivalence of quality attributes, utility functions and functions solving optimization problems

  15. Future Work More extensions to OWL-Q regarding the negotiation protocol perspective • Specify negotiation capabilities of participants Investigate if other aspects/parts of the negotiation process can be automated or assisted by reasoning with ontologies • E.g in negotiation protocol establishment • Reducing some actions of the actual negotiation protocol

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