Thesis full text (PDF) - Politecnico di Milano

More documents

Recommendations

Info

2.4.3 OWL OWL (Web Ontology Language) is the latest recommendation of W3C [21], and is probably the most popular language for creating ontologies today. It is also the last technical component. The good news is that it is built on RDF schema; as you have already established a solid understanding of RDF schema, much of the material here is going to look familiar to you. OWL = RDF schema + new constructs for expressiveness Therefore, all the classes and properties provided by RDF schema can be used when creating an OWL document. OWL and RDF schema have the same purpose: to define classes, properties, and their relationships. However, compared to RDF schema, OWL gives us the capability to express much more complex and richer relationships. The final result is that can construct agents or tools with greatly enhanced reasoning ability. Therefore, OWL often used for the purpose of ontology development. RDF schema is still a valid choice, but it’s obvious limitations compared to OWL will always make it a second choice. Compared to RDFS, OWL has much more powerful expressiveness. 2.5 Ontology There are several aspects of this definition that need to be clarified. First, this definition states that ontology is used to describe and represent an area of knowledge. In other words, ontology is domain specific; it is not there to represent all knowledge, but an area of knowledge. A domain is simply a specific subject area or sphere of knowledge, such as photography, medicine, real estate, education, etc. Second, ontology contains terms and the relationships among these terms. Terms are often called classes, or concepts; these words are interchangeable. The relationships between these classes can be expressed by using a hierarchical structure: super classes represent higher-level concepts and subclasses represent finer concepts, and the finer concepts have all the attributes and features that the higher concepts have. 20
Third, besides the aforementioned relationships among the classes, there is another level of relationship expressed by using a special group of terms: properties. These property terms describe various features and attributes of the concepts, and they can also be used to associate different classes together. Therefore, the relationships among classes are not only super class or subclass relationships, but also relationships expressed in terms of properties. To summarize, ontology has the following properties: • It is domain specific. • It defines a group of terms in the given domain and the relationships among them. By clearly defining terms and the relationships among them, ontology encodes the knowledge of the domain in such a way that it can be understood by a computer. This is the basic purpose of ontology. We can summarize the benefits of ontology as follows (and you should be able to come up with most of these benefits yourself): • It provides a common and shared understanding/definition about certain key concepts in the domain. • It provides a way to reuse domain knowledge. • It makes the domain assumptions explicit. • Together with ontology description languages (such as RDF schema), it provides a way to encode knowledge and semantics such that machines can understand. • It makes automatic large-scale machine processing possible. Among all these benefits, we in fact pay more attention to the fourth one in the preceding list. 21
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: 2.4.2 RDF Resource Description Fram
Page 23 and 24: The XMI serialization of UML [33] e
Page 25 and 26: 2.9.2.1 Pellet Pellet 1 [47] is an
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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?