Web Service Capability Meta Model

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The concept of capability is a cornerstone element in service description. Nevertheless, despite its fundamental role little effort has been seen to model service capabilities. Current approaches either fail to consider capabilities as feature-based entities and confuse them with annotated invocation interfaces or fail in modelling capabilities at several abstraction levels and establishing links between them. In particular, they are not able to model and deal with concrete capabilities (i.e., capabilities that reflect real customers' needs). In this paper, we propose a conceptual model as an RDF-schema for describing service capabilities. Our model defines capabilities as an action verb and a set of attributes and their values. It is also able to define capabilities at different levels of abstractions/concreteness and establish links between them. Most importantly, our model enables describing concrete capabilities which directly correspond to consumer needs. Our meta model is based on RDF and makes use of Linked Data to define capability attributes as well as their values.

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Web Service Capability Meta Model

  1. 1. Digital Enterprise Research Institute www.deri.ie Web Service Capability Meta Model Sami Bhiri, Wassim Derguech and Maciej Zaremba WebIST, Porto, Portugal, 2012 Copyright 2009 Digital Enterprise Research Institute. All rights reserved. 1
  2. 2. Capability: Informal DefinitionDigital Enterprise Research Institute www.deri.ie  Central concept in (semantic) information systems  A service is an access mechanism to a certain capability.  A Business process is a set of ordered activities aiming to achieve a business goal.  Capability = What an action (Program, Business Process, Task) does from a functional perspective.  Synonyms: Business Function, Functionality  Related terms: Business Goal, Consumer Request 2
  3. 3. Examples of capabilitiesDigital Enterprise Research Institute www.deri.ie  FedexShipment: is a capability for Shipping  packages under 50 Kg,  serving certain routes,  the price depends on the source, destination and the weight of the package; i.e. different formulas for computing the price based on other attributes.  FedexOffer:  Shipping of a 10Kg Package from Ireland to Singapore on 2012- 02-15 for 200 Dollars. 3
  4. 4. Capability modelling problemsDigital Enterprise Research Institute www.deri.ie  Attribute dependency  :From and :To attributes are interdependent.  The :Price attribute depends on the attributes :From, :To and :Package.  Dynamic attributes  The :Price may depend on the current exchange rate or the company workload.  make it hard if not impossible to model non static and attribute-interdependent capabilities. 4
  5. 5. Limitations of current approachesDigital Enterprise Research Institute www.deri.ie  Current approaches consider capabilities as (annotated) invocation interfaces and not as functionalities.  Capabilities are described at several levels of abstraction in terms of IOPE. However, there is no explicit links between these levels. And a manual intervention is needed to determine the concrete capability.  Especially do not represent (and manipulate) concrete capabilities which correspond to consumers requests 5
  6. 6. Principles of our meta modelDigital Enterprise Research Institute www.deri.ie  Three principles  A capability is described via domain specific features.  A concrete capability often depends on the Customer’s Request and is dynamically generated.  Capabilities are described at different levels of abstraction and links between these levels are explicitly captured. 6
  7. 7. Principles of our meta modelDigital Enterprise Research Institute www.deri.ie  Three principles  A capability is described via domain specific features.  A concrete capability often depends on the Customer’s Request and is dynamically generated.  Capabilities are described at different levels of abstraction and links between these levels are explicitly captured. 7
  8. 8. Domain Specific AttributesDigital Enterprise Research Institute www.deri.ie  A capability is described by an action verb and a set of attribute values pairs.  Each attribute describes a particular intrinsic property of the capability.  The action verb as well as the attributes are defined in domain related ontology. Such ontology gives all possible attributes a particular capability needs in addition to their possible values. 8
  9. 9. Cap. meta Model: one basic principleDigital Enterprise Research Institute www.deri.ie  A capability is described by an action verb and a set of attribute values pairs. hasAttribute hasValue Capability Attribute AttributeValue owl:Thing do ActionVerb 9
  10. 10. Principles of our meta modelDigital Enterprise Research Institute www.deri.ie  Three principles  A capability is described via domain specific features.  A concrete capability often depends on the Customer’s Request and is dynamically generated.  Capabilities are described at different levels of abstraction and links between these levels are explicitly captured. 10
  11. 11. Dynamic generation of capability offersDigital Enterprise Research Institute www.deri.ie  FedexShipment: is a capability for Shipping  packages under 50 Kg,  serving certain routes,  the price depends on the source, destination and the weight of the package; i.e. different formulas for computing the price based on other attributes.  FedexOffer:  Shipping of a 10Kg Package from Ireland to Singapore on 2012- 02-15 for 200 Dollars. 11
  12. 12. Capability Category and Offer (1/2)Digital Enterprise Research Institute www.deri.ie A capability Offer corresponds to a concrete functionality that corresponds to a consumer need.  The attributes of a capability offer have concrete or a set of concrete values. A capability Category corresponds to a category of capability Offers.  A capability category does not correspond to a concrete need of a particular consumer. Analogy with OOP: a capability Category corresponds to a Class, a capability Offer corresponds to an object. 12
  13. 13. Capability Category and Offer (2/2)Digital Enterprise Research Institute www.deri.ie  A capability Category can be seen as a factory for generating capability Offers according to consumers’ requests.  A capability offer is dynamically generated for a specific customer.  We say that a certain capability offer is a variantof the corresponding capability Category.  Current meta models can not describe capability offers. However, what consumers are interested in are capability offers. 13
  14. 14. BF meta Model: Complete pictureDigital Enterprise Research Institute www.deri.ie Capability ActionVerb do hasAttribute hasMax hasValue hasMin Attribute AttributeValue hasElement RangeAttValue CoAttribute ProAttribute Co&Pro Attribute EnumerationAttValue ConstrainedAttValue DynamicAttValue CondAttValue hasEvaluator hasEvaluator hasCondition constrainedBy Expression Constraint hasExpression ExprType: String ExprValue: String 14
  15. 15. Matching of a consumer requestDigital Enterprise Research Institute www.deri.ie Consumer Request BF Category Values of Possible Values of Values or how to compute Hard Co Preferences Co and Co&Pro the values of Pro and Constraints attributes attributes Co&Pro attributes 1. Does the Capability category support the No There is input values requested by the consumer? no match Yes 2. Generate the Capability offer(s) that corresponds to the consumer request Yes Capability offer 3. Does the generated Capability offer satisfy the No There is hard constraints specified by the consumer request? no match Control flow Capability offer Data flow Cability Offer(s) That matches the CR 15
  16. 16. Principles of our meta modelDigital Enterprise Research Institute www.deri.ie  Three principles  A capability is described via domain specific features.  A concrete capability often depends on the Customer’s Request and is dynamically generated.  Capabilities are described at different levels of abstraction and links between these levels are explicitly captured. 16
  17. 17. Example of capabilitiesDigital Enterprise Research Institute www.deri.ie ShippingCap1 ShippingCap2 ShippingCap3 From: International From: Europe From: Europe To: International To: Europe To: Europe Express: Boolean ShippingCap4 ShippingCap5 ShippingCap6 From: International From: Europe From: International To: International To: Europe To: International Express: Boolean PickUpDate: Date PickUpDate: Date ShippingCap7 ShippingCap8 From: International From: Europe To: International To: Europe PickUpDate: Date PickUpDate: Date Express:Bool Express:Bool 17
  18. 18. Specification RelationDigital Enterprise Research Institute www.deri.ie  Definition: Let Cap1 and Cap2 be two capabilities, Cap1 specifies Cap2 if  |Cap1.attributes| = |Cap2.attributes| and  ∀ at1 ∈ Cap1.attributes and ∀ at2 ∈ Cap2.attributes / at1 is a subtype or sametype of at2  ∃ at1 ∈ Cap1.attributes and ∃ at2 ∈ Cap2.attributes / at1 is a subtype of at2 ShippingCap2 ShippingCap1 From: Europe specify From: International To: Europe To: International 18
  19. 19. Extension RelationDigital Enterprise Research Institute www.deri.ie  Definition: Let Cap1 and Cap2 be two capabilities, Cap1 extends Cap2 if  Cap2.attributes ⊂ Cap1.attributes and  |Cap1.attributes| > |Cap2.attributes| ShippingCap5 ShippingCap2 extend From: Europe From: Europe To: Europe To: Europe PickUpDate: Date 19
  20. 20. Explicit links between abstraction levelsDigital Enterprise Research Institute www.deri.ie Capability rdf:type rdf:type rdf:type ShippingCap ActionVerb: d:Shippment cap:variantOf From: ship:SourceAddress cap:variantOf To: ship:TargetAddress Fedex Pckg: ship:Package TNT ActionVerb: Price: ship:ShippingPrice ActionVerb: From: …. From: …. To: …. FedexOffer To: …. ship: …. cap:variantOf From: Ireland ship: …. Pckg: .... To: Singapore Pckg: .... …. 20
  21. 21. Back To Our PrinciplesDigital Enterprise Research Institute www.deri.ie  Three principles  A capability is described via domain specific features.  Domain specific ontology for defining the action verb and attributes  A concrete capability often depends on the Customer’s Request and is dynamically generated.  Attribute types allow for generating capability offers during the matching process  Capabilities are described at different levels of abstraction and links between these levels are explicitly captured.  Specification and extension relations between capabilities 21
  22. 22. What Can This Meta Model Do?Digital Enterprise Research Institute www.deri.ie  Describes capability categories and capability offers in a uniform way.  Especially, it is able to describe concrete capabilities that correspond to consumers’ concrete needs.  In addition, it draws the relation between capability categories and capability offers.  Attributes as well as their values are first class citizens, clearly and easily identifiable.  Makes use of linked open data for describing capabilities. 22
  23. 23. Future WorkDigital Enterprise Research Institute www.deri.ie  Investigate other kinds of relations that might exist between capabilities.  Zoom into global relations to define fine grained relations.  Automation support for maintaining the capabilities cloud/hierarchy. 23

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