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.

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.
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2. Capability: Informal Definition
Digital 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
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3. Examples of capabilities
Digital 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.
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4. Capability modelling problems
Digital 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.
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5. Limitations of current approaches
Digital 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
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6. Principles of our meta model
Digital 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.
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7. Principles of our meta model
Digital 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.
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8. Domain Specific Attributes
Digital 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.
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9. Cap. meta Model: one basic principle
Digital 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
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10. Principles of our meta model
Digital 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.
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11. Dynamic generation of capability offers
Digital 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.
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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.
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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.
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14. BF meta Model: Complete picture
Digital 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
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15. Matching of a consumer request
Digital 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
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16. Principles of our meta model
Digital 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.
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17. Example of capabilities
Digital 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
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18. Specification Relation
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 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
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19. Extension Relation
Digital 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
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20. Explicit links between abstraction levels
Digital 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: ....
….
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21. Back To Our Principles
Digital 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
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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.
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23. Future Work
Digital 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.
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