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S-CUBE LP: Quality of Service Models for Service Oriented Architectures

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S-CUBE LP: Quality of Service Models for Service Oriented Architectures

  1. 1. S-Cube Learning Package Quality Definition: Quality of Service Models for Service Oriented Architectures Politecnico di Milano (POLIMI), Vienna University of Technology (TUW), MTASZTAKI (SZTAKI), Tilburg University (TILBURG), Universidad Politécnica de Madrid (UPM) Kyriakos Kritikos, Barbara Pernici, Pierluigi Plebani,Cinzia Cappiello (POLIMI), Marco Comuzzi (TuE), Salima Benbernou (Paris), IvonaBrandic (TUW), Attila Kertész (SZTAKI), Michael Parkin (TILBURG), Manuel Carro (UPM) www.s-cube-network.eu
  2. 2. Learning Package Categorization S-Cube Quality Definition, Negotiation and Assurance Quality Definition and SLA Negotiation Quality of Service Models for Service Oriented Architectures © S-Cube
  3. 3. Learning Package Overview Problem Description QoS and Service life-cycle Service Quality Models (SQM) Service Quality Meta-Models (SQMM) Service Level Agreements Meta-Models (SLA-MM) Discussion Conclusions © S-Cube
  4. 4. The importance of QoS QoS – is a combination of several qualities attributes (e.g., availability, security, response time) of a service – can be generally seen as a important factor in distinguishing the success of service providers. If QoS can be defined the users: – Can express their needs – Can select the best service with respect to their needs … and the providers: - Can better advertise their services © S-Cube
  5. 5. Why QoS Model QoS is used to define a contract between a service provider and a service user in order to guarantee that their expectations are met – Before building a service the offered QoS must be defined - Class of Service – Before using a service provider and user must agree on QoS - Service Level Agreement So, both service users and providers must share the same lexicon for expressing QoS QoS model is needed! © S-Cube
  6. 6. QoS Models In this learning package, we will discuss how the service quality can be described according to what is proposed in the literature The is performed by inspecting the characteristics of the available approaches to reveal which are the consolidated ones and which are the ones specific to given aspects and to analyze where the need for further research and investigation is The approaches considered have been selected based on a systematic review of conference proceedings and journals spanning various research areas in Computer Science and Engineering including: Distributed, Information, and Telecommunication Systems, Networks and Security, and Service-Oriented and Grid Computing © S-Cube
  7. 7. Learning Package Overview Problem description QoS and Service life-cycle Service Quality Models (SQM) Service Quality Meta-Models (SQMM) Service Level Agreements Meta-Models (SLA-MM) Discussion Conclusions © S-Cube
  8. 8. Main steps 1/5: Advertisement Requesters and providers publish or exchange quality requests and quality offers, respectively Such quality documents are called Quality- Based Service Descriptions (QSDs) © S-Cube
  9. 9. Main steps 2/5. Discovery The service discovery phase is split into two sub- phases: – Service matchmaking concerns filtering the advertised services according to the requesters functional and quality requirements – Service selection concerns sorting the matchmaking results according to the requester’s preferences. In result, the requester is presented with an ordered list of services and selects the one that best matches his needs © S-Cube
  10. 10. Main steps 3/5: Negotiation QSDs are exchanged between service providers and requesters The possible agreement on quality levels between the parties involved leads to the definition of another quality document, the Service Level Agreement (SLA) © S-Cube
  11. 11. Main steps 4/5: Monitoring andUtilization The qualities in the SLA are monitored in order to discover customers and/or providers violations of its functional and quality terms Monitoring may also signal potential dangerous situations, that may lead to a violation of the SLA if recovery actions are not timely undertaken © S-Cube
  12. 12. Main steps 5/5: Adaptation When an SLA is violated, recovery/adaptation reactive and proactive actions may be taken A possible recovery action might require a re- negotiation of the SLA or the execution of the matchmaking activity to find an alternative service It might also happen that an alert is sent to the assessment component of the monitoring activity that continues to execute © S-Cube
  13. 13. Service Quality Models and Meta-Models In order to automate as much as possible the above activities, a clear and formal description of QoS is required Service providers (SPs) and service requesters (SRs) should agree on the same language (Service Quality Model, SQM) for expressing their quality documents (QD). In this way, all the mechanisms used for supporting the service lifecycle can be properly enacted. Nowadays, in the literature many meta-models and languages for describing service quality exist, which can be distinguished in two main types: – Service Quality Meta-Models (SQMMs) – SLA Meta-Models (SLAMMs). © S-Cube
  14. 14. Service Quality Models and meta-models relationships © S-Cube
  15. 15. Learning Package Overview Problem description QoS and Service life-cycle Service Quality Models (SQM) Service Quality Meta-Models (SQMM) Service Level Agreements Meta-Models (SLA-MM) Discussion Conclusions © S-Cube
  16. 16. Definition SQMs are descriptions of a taxonomy or concrete list of QoS categories, attributes, metrics, and relationships that connect all of these quality entities A typical SQM may contain the Performance QoS category which includes the QoS attributes of response time and throughput Relying on a SQM means that Service Providers (SPs) and Service Requesters (SRs) have to preliminary select which is the exact set of relevant quality attributes © S-Cube
  17. 17. Role of SQM SQMs provide the concrete semantics of the quality terms that may be used in QSDs and SLAs, that is in other types of quality documents All the service lifecycle activities, such as matchmaking and monitoring, are designed around this set of quality attributes Although the above procedure assists in producing suitable mechanisms for supporting the service life-cycle activities, the suitability of these mechanisms is specific for the considered scenario © S-Cube
  18. 18. Quality Service Description 1/2 QSDs are often associated with a validity period or expiration time which signifies when they become outdated. Depending on which party is producing them, QSDs can be separated into – Service Quality Offers (produced by an SP) – Service Quality Request (produced by an SR). Further separated into - Service Quality Requirements - Service Selection Models denoting the significance of each quality attribute or metric to the SR by associating it with a specific weight and are used for ranking Service Descriptions (SDs). © S-Cube
  19. 19. Quality Service Description 2/2 Both Service Quality Offers and Requirements are expressed as a set of quality constraints – A quality constraint usually contains a comparison operator that is used to compare a quality metric or attribute with a value – A quality constraint may also contain the unit of the compared value. Thus, QSDs describe all the appropriate information that is required for matchmaking and negotiating service quality In this way, they are used in the respective service life-cycle activities. © S-Cube
  20. 20. ISO 9126 - 1/3 If services are considered as standalone software modules, then their quality can be determined by the attributes that traditionally characterize software quality and, thus, by the attributes defined in the ISO 9126 model [ISO/IEC 2001] ISO 9126 is an international standard for the evaluation of software Quality is defined as: “The totality of features and characteristics of a product or service that bear on its ability to satisfy stated or implied needs” Stated needs are explicitly declared by the users Implied needs refers to requirements users do not know © S-Cube
  21. 21. ISO 9126 – 2/3 Quality is a combination of three types of qualities: – In use: related to the quality perceived by the user – Internal: regardless of the context in which it is used – External: related to context in which it is used ISO 9126 reflects this combination since it is composed by four main parts: – ISO/IEC 9126-1:2001 Part 1: Quality model – ISO/IEC TR 9126-2:2003 Part 2: External metrics – ISO/IEC TR 9126-3:2003 Part 3: Internal metrics – ISO/IEC TR 9126-4:2004 Part 4: Quality in use metrics © S-Cube
  22. 22. ISO 9126 – 3/3 © S-Cube
  23. 23. ISO 9126 is not enough ISO 9126 quality model is not adequate for representing service quality. It applies only to software services and not to other service types, such as infrastructural services For this reason, different contributions can be found in the literature that propose various SQMs taking inspiration from ISO 9126 – The structure of these SQMs is based on the use of taxonomies in which categories, related to different analyzed aspects, are defined. – Each category contains a set of attributes that are entities which can be verified or measured in the service – Most of the models associate each attribute with a definition and, in some cases, also provide the related metric and assessment formulae © S-Cube
  24. 24. Ideal meta model for SQM © S-Cube
  25. 25. Typical Service Quality Attributes Performance:  Security – Response time – Authentication – Latency – Authorization – Throughput – Non-repudiation – Availability  Configuration: – Accuracy – Cost – Reliability  Network: Data Quality – network delay – Accuracy – Jitter – Completeness – packet loss – Consistency – TimelinessThe complete S-Cube Quality Reference Model is available athttp://www.s-cube-network.eu/km/qrm © S-Cube
  26. 26. Relevant SQM in SotA [Sabata et al. 1997] [Ran 2003] [Colombo et al. 2005] [The OASIS Group 2005] [Cappiello 2006] [Truong et al. 2006] [Brandic et al. 2006] [Sakellariou and Yarmolenko 2008] [Cappiello et al. 2008] [Frutos et al. 2009] [Nessi Open Framework 2009] [Kritikos and Plexousakis 2009] [Mabrouk et al. 2009] © S-Cube
  27. 27. Learning Package Overview Problem description QoS and Service life-cycle Service Quality Models (SQM) Service Quality Meta-Models (SQMM) Service Level Agreements Meta-Models (SLA-MM) Discussion Conclusions © S-Cube
  28. 28. Definition SQMMs provide the means for describing QoS in a more general and extensible way than SQMs An SQMM is a conceptualization of the appropriate quality concepts and their relationships that can be used to capture and describe a SQM A typical SQMM will contain the concepts of – QoS category – QoS attribute – QoS metric the relationships – contains (from QoS categories to attributes) – measuredBy (from QoS attributes to metrics) © S-Cube
  29. 29. Role of SQMM SQMM can describe many different SQMs, where the number of those SQMs and their actual difference mainly depends on the richness of the SQMM SQMMs are used to specify QSDs, which are usually described by a set of constraints on some QoS attributes and metrics © S-Cube
  30. 30. Elements defining a SQMM Enumeration of all possible quality attributes Modeling the attributes domain (e.g., phone service provisioning) (i.e., the entity and its relation to the “attribute" entity) Modeling of inter-attribute relationships/dependencies (either quantitative or qualitative or both) Modeling the attributes compositionality (i.e., if it is composite or not and what are its child attributes) Modeling the different views which an attribute may concern, i.e., the SPs, SRs or both views Distinguishing by using appropriate constructs between QoS and QoE attributes Distinguishing by using appropriate constructs between domain- dependent and domain-independent attributes Modeling the service layer an attribute refers to Modeling the association/relationship between quality attributes and metrics © S-Cube
  31. 31. Ideal SQMM © S-Cube
  32. 32. Relevant SQMM in SotA 1/2 Pure (only focused on SQMM) – WS-QoS [Tian et al. 2003] – WSAF-QoS [Maximilien and Singh 2004] – DAML-QoS [Zhou et al. 2004] – QoSOnt [Dobson et al. 2005] – QRL [Cortes et al. 2005] – UML QoS [The OMG Group 2005] – WSMO-QoS [Wang et al. 2006] – OWL-Q [Kritikos and Plexousakis 2006] – onQoS-QL [Giallonardo and Zimeo 2007] – PCM [De Paoli et al. 2008] © S-Cube
  33. 33. Relevant SQMM in SotA 2/2 SLA-enabled (also consider SLA-MM elements) – QML [Frlund and Koistinen 1998] – WSOL [Tosic et al. 2003] – WSLA [Keller and Ludwig 2003] – SWAPS [Oldham et al. 2006] Security-based (specific for the security enviroment) – Trust-Serv [Skogsrud et al. 2004] – PeerTrust [Nejdl et al. 2004] – P3P [Cranor et al. 2006] – WS-Trust [Nadalin et al. 2007] © S-Cube
  34. 34. Learning Package Overview Problem description QoS and Service life-cycle Service Quality Models (SQM) Service Quality Meta-Models (SQMM) Service Level Agreements Meta-Models (SLA-MM) Discussion Conclusions © S-Cube
  35. 35. Definition SLA-MMs allow the definition of SLAs and SLA Templates between the interacting parties Since the agreement terms include Service Level Objectives (SLOs), which denote constraints on quality attributes or metrics listed in an SQM, and both SQMs and constraints may be defined by an SQMM, we have three possible cases – there is a specific SQMM type, called SLA-enabled SQMM (SLA- SQMM), that can define SLA specifications – SLA-MMs may use one or more SQMMs to dene and reference quality attributes and even specify SLOs – SLA-MMs may reference the contents of one or more SQMs © S-Cube
  36. 36. Service Level Agreement SLA documents contain the following class of components – Technical (e.g., metrics, actions) – Organizational (monitoring and reporting) – Legal (legal responsibilities, invoicing and payment modes). Since it is difficult to automate and enforce the legal components of SLA documents, these are either omitted or neglected SLAs contain more information than QSDs in terms of supporting the service provisioning activity There is no uniform and common quality document to be used across all the activities This is a major drawback that requires time, as document transformations should take place from one format to the other, and reduces the automation degree of the activities © S-Cube
  37. 37. SLA components The most common components are: – involved parties: signatory parties and supporting parties – contract validity period: species for how long the SLA will be valid and enforceable. – service definitions: service characteristics (i.e., functionality), components (i.e., operations, input, output, internal and external services for a composite service), and observable parameters (i.e., QoS metrics for the service and its components). – the set of QoS guarantees and the obligations of the various parties: - QoS guarantees are widely known as Service Level Objectives (SLOs) and are expressed as conditions on one or more QoS metrics, thus indicating the metrics allowed values. - A set of SLOs constitutes a specic Service Level (SL). There can be different SLs defined in an SLA, expressing the different modes a service may execute in different time periods, or degradation/upgrade levels if the agreed SL is violated/surpassed. – action guarantees: a commitment that a particular activity is performed by an obliged party if a given precondition is met (e.g., a violation occurs). The committing activities include compensation, reward, recovery, and management actions. © S-Cube
  38. 38. SLA templates Before SLAs are established, they are in a form which is called SLA template These SLA templates – are used to describe, matchmake, and negotiate the SLs to be offered by a service of an SP to an SR. – are produced by both SPs and SRs. – can be complete or incomplete SLAs: - Complete SLA templates are commonly agreed among all participants in a restricted domain or are used as bilateral agreements between two organizations or as SLA offerings advertised by an SP to specific customer classes. Thus, they are offered in a “take it or leave it" basis - Incomplete SLA templates can be seen as a skeleton with fields which must be completed according to the directives of the desired relationship between two organizations. So, they are generic forms or templates that can be tailored to the specific circumstances of a SLA instance © S-Cube
  39. 39. Relevant SLA-MM in SotA SLA (only for quality issues):  Contract Type (consider all – QML [Frlund and Koistinen the elements of a contract): 1998] – X-Contract [Molina-Jimenez et – WSLA [Keller and Ludwig al. 2003] 2003] – BCL [Linington et al. 2004] – WS-A [WS-AGREEMENT 2003] – SweetDeal [Grosof and Poon – SLAng [Lamanna et al. 2003] 2004] – WSOL [Tosic et al. 2003] – CTXML [Farrell et al. 2004] – RBSLA [Paschke 2005] – SWCL [Oren et al. 2005] – QoWL [Brandic et al. 2006] – GXLA [Tebbani and Aib 2006] – TrustCom [TrustCoM Consortium 2007] © S-Cube
  40. 40. Learning Package Overview Problem Description QoS and Service life-cycle Service Quality Models (SQM) Service Quality Meta-Models (SQMM) Service Level Agreements Meta-Models (SLA-MM) Discussion Conclusions © S-Cube
  41. 41. On SQM Various SQMs have been proposed, from small or at categories of service quality attributes to sophisticated taxonomies containing many categories and attribute types In average, the SQMs have a satisfactory category number, where each category contains a small quality attribute number. Most SQMs mainly cover general (i.e., domain-independent) quality attributes, while a small number of them also covers specific (i.e., domain-dependent) ones Most SQMs contain both composite and atomic quality attributes along with the connecting relation between them. This is very important during service monitoring as it may be used to validate or enrich the monitoring results of a service monitoring engine or component Another interesting finding is that the majority of the SQMs includes only QoS attributes but only the most recent approaches also include QoE attributes. © S-Cube
  42. 42. On SQMM The majority of SQMM use either ontologies or informal formalisms. Ontology is widely selected in pure SQMMs, while the informal is the best modeling choice in the other two partitions, i.e., the SLA-enabled and security-based ones. A recent trend for pure and SLA-enabled SQMMs is to use ontologies for their representation. The adoption of ontologies can be explained by their ability to provide unambiguous semantics to quality terms and, thus, to enable machines to automatically process and reason on ontology-specified QSDs in order to support service life-cycle activities like discovery and negotiation © S-Cube
  43. 43. On SLA-MM Current SLA-MM are not capable of fully supporting most of the SLA management activities apart from those of SLA Monitoring & Assessment and Settlement This can be explained by the focus of SCL design on service functionality, which was inevitable during SCL modeling time. Thus, although these languages were designed to accommodate for any electronic contract type, they cannot be used to specify SLAs unless they are extended appropriately Based on the above analysis, there is a need for a new language able to express SLAs in a satisfactory way © S-Cube
  44. 44. Learning Package Overview Problem Description QoS and Service life-cycle Service Quality Models (SQM) Service Quality Meta-Models (SQMM) Service Level Agreements Meta-Models (SLA-MM) Discussion Conclusions © S-Cube
  45. 45. Summary Service quality definition is fundamental for the SBA A lot of approaches are now available In this presentation we: – Highlighted which are the main elements of the definition of Service Quality: SQM, SQMM, SLA-MM – How these elements are organized – Which are the approaches in the state of the art that are considered useful © S-Cube
  46. 46. Further S-Cube ReadingKritikos, K., Pernici, B., Plebani, P., Cappiello, C., Comuzzi, M., Benbernou, S., Brandic, I., Kertész, A., Parkin,M., Carro, M. A Survey on Service Quality Description (accepted with major revision on ACM ComputingSurvey, 2011).Brandic, I., Pllana, S., and Benkner, S. 2006. An Approach for the High-level Specification of QoS-aware GridWorkflows Considering Location Anity. Scientific Programming Journal 14, 3-4, 231-250.Colombo, M., Nitto, E. D., Penta, M. D., Distante, D., and Zuccala, M. 2005. Speaking a Common Language:A Conceptual Model for Describing Service-Oriented Systems. In ICSOC. 48-60.Cappiello, C. 2006. Mobile Information Systems Infrastructure and Design for Adaptivity and Flexibility.Springer-Verlag, Chapter The Quality Registry, 307-317.Cappiello, C., Kritikos, K., Metzger, A., Parkin, M., Pernici, B., Plebani, P., and Treiber, M. 2008. A qualitymodel for service monitoring and adaptation. In Workshop on Monitoring, Adaptation and Beyond (MONA+) atthe ServiceWave 2008 Conference. Springer.Kritikos, K. and Plexousakis, D. 2006. Semantic QoS Metric Matching. In ECOWS 06: Proceedings of theEuropean Conference on Web Services. IEEE Computer Society, Zurich, Switzerland, 265-274. © S-Cube
  47. 47. References (SQM) 1/2 [Brandic et al. 2006] Brandic, I., Pllana, S., and Benkner, S. 2006. An Approach for the High-level Specification of QoS-aware Grid Workflows Considering Location Anity. Scientific Programming Journal 14, 3-4, 231-250. [Colombo et al. 2005] Colombo, M., Nitto, E. D., Penta, M. D., Distante, D., and Zuccala, M. 2005. Speaking a Common Language: A Conceptual Model for Describing Service-Oriented Systems. In ICSOC. 48-60. [Cappiello 2006] Cappiello, C. 2006. Mobile Information Systems Infrastructure and Design for Adaptivity and Flexibility. Springer-Verlag, Chapter The Quality Registry, 307-317. [Cappiello et al. 2008] Cappiello, C., Kritikos, K., Metzger, A., Parkin, M., Pernici, B., Plebani, P., and Treiber, M. 2008. A quality model for service monitoring and adaptation. In Workshop on Monitoring, Adaptation and Beyond (MONA+) at the ServiceWave 2008 Conference. Springer. [Frutos et al. 2009] Frutos, H. M., Kotsiopoulos, I., Gonzalez, L. M. V., and Merino, L. R. 2009. Enhancing Service Selection by Semantic QoS. In ESWC. 565-577. [Kritikos and Plexousakis 2009] Kritikos, K. and Plexousakis, D. 2006. Semantic QoS Metric Matching. In ECOWS 06: Proceedings of the European Conference on Web Services. IEEE Computer Society, Zurich, Switzerland, 265-274. © S-Cube
  48. 48. References (SQM) 2/2 [Mabrouk et al. 2009] Mabrouk, N. B., Georgantas, N., and Issarny, V. 2009. A Semantic End-to-End QoS Model for Dynamic Service Oriented Environments. In PESOS Workshop at ICSE 2009. IEEE. [Nessi Open Framework 2009] Nessi Open Framework. 2009. Quality Model for NEXOF-RA Pattern Designing. Tech. rep. [Ran 2003] Ran, S. 2003. A model for web services discovery with QoS. SIGecom Exch. 4, 1, 1-10. [Sabata et al. 1997] Sabata, B., Chatterjee, S., Davis, M., Sydir, J., and Lawrence, T. 1997. Taxonomy for QoS Specifications. In Object-Oriented Real-Time Dependable Systems, 1997. Proceedings., Third International Workshop on. 100-107. [Sakellariou and Yarmolenko 2008] Sakellariou, R. and Yarmolenko, V. 2008. High Performance Computing and Grids in Action. Chapter Job Scheduling on the Grid: Towards SLA-Based Scheduling. [The OASIS Group 2005] The OASIS Group. 2005. Quality Model for Web Services. Tech. rep., The Oasis Group. September. [Truong et al. 2006] Truong, H.-L., Samborski, R., and Fahringer, T. 2006. Towards a Framework for Monitoring and Analyzing QoS Metrics of Grid Services. In International Conference on e-Science and Grid Computing. IEEE Computer Society Press, Amsterdam, The Netherlands. © S-Cube
  49. 49. References (SQMM) 1/3 [Cortes et al. 2005] Cortes, A. R., Martn-Daz, O., Toro, A. D., and Toro, M. 2005. Improving the Automatic Procurement of Web Services Using Constraint Programming. Int. J. Cooperative Inf. Syst. 14, 4, 439-468. [Cranor et al. 2006] Cranor, L., Dobbs, B., Egelman, S., Hogben, G., Humphrey, J., Langheinrich, M., Marchiori, M., Presler-Marshall, M., Reagle, J., Schunter, M., Stampley, D. A., and Wenning, R. 2006. Platform for Privacy Preferences (P3P). Working group note, W3C. November. [De Paoli et al. 2008] De Paoli, F., Palmonari, M., Comerio, M., and Maurino, A. 2008. A Meta-model for Non-functional Property Descriptions of Web Services. In ICWS 08: Proceedings of the 2008 IEEE International Conference on Web Services. IEEE Computer Society, Beijing, China, 393-400. [Dobson et al. 2005] Dobson, G., Lock, R., and Sommerville, I. 2005. QoSOnt: a QoS Ontology for Service-Centric Systems. In EUROMICRO 05: Proceedings of the 31st EUROMICRO Conference on Software Engineering and Advanced Applications. IEEE Computer Society, Porto, Portugal, 80-87. [Frolund and Koistinen 1998] Frolund, S. and Koistinen, J. 1998. Quality of services specification in distributed object systems design. COOTS98: Proceedings of the 4th conference on USENIX Conference on Object-Oriented Technologies and Systems 5, 4, 179-202. [Giallonardo and Zimeo 2007] Giallonardo, E. and Zimeo, E. 2007. More Semantics in QoS Matching. In International Conference on Service-Oriented Computing and Applications. IEEE Computer Society, Newport Beach, CA, USA, 163-171. © S-Cube
  50. 50. References (SQMM) 2/3 [Keller and Ludwig 2003] Keller, A. and Ludwig, H. 2003. The WSLA Framework: Specifying and Monitoring Service Level Agreements for Web Services. Journal of Network and Systems Management 11, 1, 57-81. [Kritikos and Plexousakis 2006] Kritikos, K. and Plexousakis, D. 2006. Semantic QoS Metric Matching. In ECOWS 06: Proceedings of the European Conference on Web Services. IEEE Computer Society, Zurich, Switzerland, 265-274. [Maximilien and Singh 2004] Maximilien, E. M. and Singh, M. P. 2002. Conceptual model of web service reputation. SIGMOD Rec. 31, 4, 36-41. [Nadalin et al. 2007] Nadalin, A., Goodner, M., Gudgin, M., Barbir, A., and Granqvist, H. 2007. WS-Trust specification, http://www.ibm.com/developerworks/webservices/library/specication/ws-trust/. In Technical report. OASIS Working Draft. [Nejdl et al. 2004] Nejdl, W., Olmedilla, D., and Winslett, M. 2004. PeerTrust: Automated Trust Negotiation for Peers on the Semantic Web. In SDM 2004: Proceedings of the VLDB 2004 International Workshop on Secure Data Management in a Connected World. LNCS, vol. 3178. Springer, Toronto, Canada, 118-132. [Oldham et al. 2006] Oldham, N., Verma, K., Sheth, A., and Hakimpour, F. 2006. Semantic WS-Agreement Partner Selection. In WWW 06: Proceedings of the 15th International conference on World Wide Web. ACM Press, Edinburgh, Scotland, 697- 706. © S-Cube
  51. 51. References (SQMM) 3/3 [Skogsrud et al. 2004] Skogsrud, H., Benatallah, B., and Casati, F. 2004. Trust-Serv: Model-Driven Lifecycle Management of Trust Negotiation Policies for Web Services. In Proc. 13th World Wide Web Conf. [The OMG Group 2005] The OMG Group. 2005. UMLTM Prole for Modeling Quality of Service and Fault Tolerance Characteristics and Mechanisms. Tech. Rep. ptc/2005-05- 02, The OMG Group. May. [Tosic et al. 2003] Tosic, V., Ma, W., Pagurek, B., and Esfandiari, B. 2003. On the Dynamic Manipulation of Classes of Service for XML Web Services. Research Report SCE-03-15, Department of Systems and Computer Engineering, Carleton University, Ottawa, Canada. [Tian et al. 2003] Tian, M., Gramm, A., Nabulsi, M., Ritter, H., Schiller, J., and Voigt, T. 2003. QoS integration in web services. Gesellschaft fur Informatik DWS 2003, Doktorandenworkshop Technologien und Anwendungen von XML. [Wang et al. 2006] Wang, X., Vitvar, T., Kerrigan, M., and Toma, I. 2006. A QoS-Aware Selection Model for Semantic Web Services. In ICSOC, A. Dan and W. Lamersdorf, Eds. Lecture Notes in Computer Science, vol. 4294. Springer, 390-401. [Zhou et al. 2004] Zhou, C., Chia, L.-T., and Lee, B.-S. 2004. DAML-QoS Ontology for Web Services. In ICWS 04: Proceedings of the IEEE International Conference on Web Services. IEEE Computer Society, San Diego, CA, USA, 472-479. © S-Cube
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  54. 54. Acknowledgements The research leading to these results has received funding from the European Community’s Seventh Framework Programme [FP7/2007-2013] under grant agreement 215483 (S-Cube). © S-Cube

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