1. PaaSport Offerings Recommendation Layer & Semantic Models
Nick Bassiliades
International Hellenic University (IHU)
Final Review Meeting - 12/01/ Brussels

2. PaaSport Architecture
Final Review Meeting - 12/01/ Brussels

3. Semantic Models & PaaS Offering Recommendation Layer
PaaSport Semantic Models (IHU)
conceptual and modelling pillars of the marketplace infrastructure.
Semantic annotation of the registered PaaS offerings and the deployed applications profiles.
PaaS Offering Recommendation Layer (NUIG, IHU)
implements core functionalities offered by the PaaSport Marketplace Infrastructure.
PaaS offering discovery, recommendation and rating.
Final Review Meeting - 12/01/ Brussels

4. The role of the PaaSport Semantic Models
Common vocabulary for the various modules of the system
PaaSport Offering Recommendation layer
Matchmaking is performed using concepts and properties of the offering and application ontologies.
Persistence layer
The DB schema follows exactly the conceptual model of the ontologies; No mismatch.
PaaS Offering profiles stored in the DB are mapped onto the Semantic Model layer (RDF graph) using a relational-to-ontology mapping tool (D2RQ platform).
Adaptive front-ends layer
The UIs for managing application and PaaS offering semantic profiles use concepts and properties from the semantic models.
Final Review Meeting - 12/01/ Brussels

5. Semantic Models Objective
Define a formal pattern for modelling various aspects of PaaS concepts (offerings, applications and SLAs)
Basic modelling requirements
User roles, e.g. providers, clients
Conceptual modelling of properties/attributes for PaaS
Further descriptions of properties through e.g. n-ary relations, container classes, etc.
Units of measurements
Easy to reuse/inject any existing domain vocabulary
Matchmaking-oriented attributes, e.g. value ranges
Easily extendable
Well-defined steps to be followed
Final Review Meeting - 12/01/ Brussels

6. PaaSport Semantic Models
Extension of the DUL upper ontology (DOLCE+DnS Ultralite)
Well established and widely used
Semantic Interoperability with other similar research efforts (e.g. SSN)
Extensibility
Adding new concepts and parameters related to PaaSport offerings and applications
Without compromising the Table Schema of the Persistence Layer.
Final Review Meeting - 12/01/ Brussels
<Event/Title> <date> <Location>

7. PaaSport Semantic Models Overview
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8. A PaaS Offering Example
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9. An Application Request Example
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10. PaaS Concepts & Parameters
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11. PaaS Offerings Recommendation layer Objective
To allow the user to select the most appropriate PaaS offering published at the PaaSport marketplace based on the semantic description and deployment profile of the business applications that the user wishes to deploy in the Cloud.
Final Review Meeting - 12/01/ Brussels

12. Final Review Meeting - 12/01/2017 - Brussels
PaaS Offerings Recommendation layer Architecture – Component Interaction
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13. Matchmaking and Ranking algorithm
The heart of the PaaS Offering Recommendation Layer
The algorithm selects, scores and ranks the most appropriate PaaS offerings that best match the requirements of the application a developer wants to deploy.
Requirements / Objectives
Efficiency / scalability
Extensibility
When the semantic model is extended with new offering / applications instances, concepts and parameters.
The algorithm should not (or minimally) change.
Final Review Meeting - 12/01/ Brussels

14. Matchmaking and Ranking algorithm
GUI
Initialization
GetOfferings
Input
Check Functional
For each concept, offering and parameter
Run SPARQL query
Keep offering or not
Rank Non-Functional
Retrieve parameter values
Score parameter values
Sort Results
Application Requirement Instance
Offerings
Concepts
Functional Parameters
Non-Functional Parameters
Coefficients
Difference Functions
Functional?
Steep-ness Factor
PaaS Offering profiles
Offerings
Offerings + Score
Final Review Meeting - 12/01/ Brussels

15. Final Review Meeting - 12/01/2017 - Brussels
Scoring PaaS Offerings How much do we care for better parameter values?
OfferScore= 𝑝∈𝑁𝑜𝑛𝐹𝑢𝑛𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑐𝑜𝑒𝑓𝑓 𝑝 ∗ 𝑃𝑎𝑟𝑆𝑐𝑜𝑟𝑒 𝑝
Final Review Meeting - 12/01/ Brussels

16. Final Review Meeting - 12/01/2017 - Brussels
Implementation
Java for programming all components
Including the matchmaking algorithm
Jena Framework for handling Ontologies / RDF
Querying via SPARQL query language for RDF
D2RQ for mapping relational DB to RDF triples
Mapping rules in the D2RQ Mapping Language
Spring framework for retrieving the application requirement from the persistence layer.
Final Review Meeting - 12/01/ Brussels

17. Final Review Meeting - 12/01/2017 - Brussels
Matchmaking Workflow
When new offerings are added, the mapping procedure is incrementally run to update the KB of PaaS offerings.
Final Review Meeting - 12/01/ Brussels

18. Algorithm Performance
Query time scales linearly to the number of:
Offerings
Requirement parameters
Final Review Meeting - 12/01/ Brussels

19. The PaaSport Rating and Selection Components
Rating Component
The user can rate PaaS Offerings based on his criteria.
Selection Component
The user can sort the PaaS Offerings based on their ratings and his priorities/criteria.
Criteria
Quality of Service
Quality of Support
Maintenance Activity
SLA Reliability
Value of Money
Final Review Meeting - 12/01/ Brussels

20. …so How Does Rating & Selection Work?
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21. Final Review Meeting - 12/01/2017 - Brussels
Technical Example
User priorities {"QualityOfService": 4, "QualityOfSupport": 5, "MaintenanceActivity": 2, "SLAReliability": 1, "ValueForMoney": 3},
Service 1 {"QualityOfService": 2, "QualityOfSupport": 3, "MaintenanceActivity": 2, "SLAReliability": 1, "ValueForMoney": 3},
Service 2 {"QualityOfService": 3, "QualityOfSupport": 2, "MaintenanceActivity": 5, "SLAReliability": 1, "ValueForMoney": 1},
Service 3 {"QualityOfService": 2, "QualityOfSupport": 3, "MaintenanceActivity": 2, "SLAReliability": 1, "ValueForMoney": 3}
Service 4 {"QualityOfService": 4, "QualityOfSupport": 5, "MaintenanceActivity": 4, "SLAReliability": 2, "ValueForMoney": 2}
Output ranking scores attached to the services.
[1] "service 1 score "
[2] "service 2 score "
[3] "service 3 score "
[4] "service 4 score "
Final Review Meeting - 12/01/ Brussels

22. Final Review Meeting - 12/01/2017 - Brussels
Relevant Publications
F. Ahmadi Zeleti, I. Hassan, S. Abbas, A. Ojo and L. Porwol, "Architecting the Recommendation Layer of a Platform-as-a-Service e-Marketplace", Proc. 11th International Joint Conference on Software Technologies - Volume 1: ICSOFT-EA, pp DOI: /
N. Bassiliades, M. Symeonidis, G. Meditskos, E. Kontopoulos, P. Gouvas and I. Vlahavas, "A semantic recommendation algorithm for the PaaSport platform-as-a-service marketplace", Expert Systems with Applications (IF: 2.981), Elsevier, Vol. 67, Jan. 2017, pp ,
N. Bassiliades, M. Symeonidis, G. Meditskos, E. Kontopoulos, P. Gouvas and I. Vlahavas, “PaaSport Semantic Model: An Ontology for a Platform-as-a-Service Semantically Interoperable Marketplace”, under review.
Contact:
Nick Bassiliades
International Hellenic University &
Aristotle University of Thessaloniki
Final Review Meeting - 12/01/ Brussels