Thesis full text (PDF) - Politecnico di Milano

More documents

Recommendations

Info

elements that correspond to UML attributes of datatypes. The rest of the UML properties are defined with property restrictions added apart allowing for the same property to have multiple domains and ranges. • Generalizations: They organize classes and associations hierarchically with additional restrictions of disjointness and completeness. The subClassOf and subPropertyOf constructs in DAML+OIL and OWL have similar meaning. • Instances: Instances appear in class diagrams as values for enumeration types and static attributes. Similar is the use of hasValue and oneOf in OWL for individuals. 2.9 Reasoning Capabilities for UML Models 2.9.1 Representation Formalisms Although the formalization of UML class diagrams has been already addressed in First Order Logic [40] [41] [42], theorem proves do not guarantee complete automatic reasoning because of the FOL undecidability. DL languages have been widely used to formalize UML components [43], because their computational complexity and decidability are well studied. Interpretations have been given with DLRifd [44], ALCQI [45], and sROIQ [46]. We adopt sROIQ because it overcomes the limitations of ALCQI by supporting nominal’s, role inclusion axioms and transitivity, and inference systems are highly optimized. 2.9.2 Reasoning Engines For reasoning upon the description logic languages used to formalize UML class and object diagrams, three widely used tableau-based provers: Pellet, Fact++, and RacerPro. All of them provide sound and complete reasoning based upon the tableau method. The features they support, and evaluate: • their expressivity in terms of the inferences they provide upon Tboxes and Aboxes, • the advanced features they support for ontologies development, • their access mechanisms for clients. 24
2.9.2.1 Pellet Pellet 1 [47] is an open-source, description logic reasoning engine for sROIQ(D) models. sROIQ supports qualifying number restrictions, role hierarchies, disjoint, inverse, reflexive and irreflexive roles, and nominals. sROIQ(D) provides restrictions on integer and string datatypes, and supports user-defined datatypes. The worst case complexity of the KB satisfiability reasoning task in sROIQ has been proven to be NExpTime-hard [48]. All the reasoning services offered by Pellet are reduced to consistency checking which is determined with tableau algorithms. The standard reasoning tasks are: • Concept Satisfiability: it determines if a concept may be instantiated. Unsatisfiable concepts result from modeling errors at the knowledge base, and therefore, detecting them is the first step for the correction of these errors. • Consistency Checking: it determines if the knowledge base contains any contradictory definitions. Contradictions may occur because (i) an unsatisfiable concept has been instantiated, (ii) an individual does not respect the number restrictions defined upon its participating roles, or (iii) there are contradictions in the definition of concepts resulting from the presence of nominal’s. Detecting the consistency of the knowledge base may reveal modeling errors and illegal role assertions for individuals. • Classification: it creates the hierarchy of concepts. The hierarchy is further used in other retrieval mechanisms, like in getting all the concepts of an individual. • Realization: it retrieves the direct concepts instantiated by an individual. It also supports retrieval of individuals that satisfy certain criteria like participation in certain roles and instantiation of indirect concepts. Besides the above standard reasoning tasks, Pellet offers features that are not found often in other reasoning engines. It allows the incremental update of the instances base (Abox). It keeps tracks of the changes by indicating the dependencies between individuals and by updating them during 1 http://pellet.owldl.com 25
Page 1 and 2: POLITECNICO DI MILANO V Facoltà di
Page 3 and 4: Table of Contents Abstract ........
Page 5 and 6: 1. Introduction At present the Web
Page 7 and 8: • Definition of the formal repres
Page 9 and 10: This approach overcomes the develop
Page 11 and 12: Both the teleological and the ontol
Page 13 and 14: consists of a data schema, describi
Page 15 and 16: high-level business rules, written
Page 17 and 18: Thanks to the automatic generation
Page 19 and 20: 2.4.2 RDF Resource Description Fram
Page 21 and 22: Third, besides the aforementioned r
Page 23: The XMI serialization of UML [33] e
Page 27 and 28: 3. Semantics Web based Recommendati
Page 29 and 30: them by invoking respectively the c
Page 31 and 32: etrieves the properties by their ca
Page 33 and 34: Figure 3.6: Instance Component 3.1.
Page 35 and 36: 3.1.8 Add Components The Add compon
Page 37 and 38: Add Class Component ClassDisjointOf
Page 39 and 40: PropertyDisjointOfProperty (for ins
Page 41 and 42: first-class citizens, we have more
Page 43 and 44: Figure 3.17: Remove Datatype Compon
Page 45 and 46: 3.1.19 Remove Instance component Th
Page 47 and 48: 3.2.4 Export-XMI-from-KB component
Page 49 and 50: 3.3.1.2 Properties of a class patte
Page 51 and 52: 3.3.1.5 Instances of a class assumi
Page 53 and 54: 3.3.1.8 Instances of a class assumi
Page 55 and 56: 3.3.2.2 Remove property value for a
Page 57 and 58: 3.4.2 Application Specification In
Page 59 and 60: Action • View Notification: Group
Page 61 and 62: Send Group Invitation Actor: Group
Page 63 and 64: A user can recommend friend as Frie
Page 65 and 66: In the figure 3.37, a User browsing
Page 67 and 68: Through the entry unit in figure 4.
Page 69 and 70: Figure 4.2: Example of WebML hypert
Page 71 and 72: Description Classes Hierarchy Unit
Page 73 and 74: Add PropertyValueAxiom Input: manda
Page 75 and 76:
4.4. The top segment of the page is
Page 77 and 78:
page otherwise it will go to the er
Page 79 and 80:
We are showing current user’s inf
Page 81 and 82:
current user is sending a friend in
Page 83 and 84:
The information of a particular gro
Page 85 and 86:
Figure 4.20: HTML view to Post New
Page 87 and 88:
the application domain as extended
Page 89 and 90:
Knowledge Instances Yes Yes Yes Yes
Page 91 and 92:
OWL DL KB Framework CLASS HIERARCHI
Page 93 and 94:
of a specific group members of the
Page 95 and 96:
[22] OMG UML (2007), Unified Modeli
Page 97:
[56] BRAMBILLA, M., CERI, S., FRATE
show all

Thesis full text (PDF) - Politecnico di Milano

Create successful ePaper yourself

Delete template?

Save as template?