Group IT Semantic Web Krzysztof Kaminski
8/7/2019 Semantic Web - Group IT v0.4 - draft
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Group IT
Semantic Web
Krzysztof Kaminski
8/7/2019 Semantic Web - Group IT v0.4 - draft
http://slidepdf.com/reader/full/semantic-web-group-it-v04-draft 2/14
Information Management
Group IT
Agenda
What is Semantic Web?
Main principles of Semantic Web?
What are the benefits of using Semantic Web Technologies?
How we can use Semantic Web Technologies?
Building Ontology
Questions
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What is Semantic Web?
³The Semantic Web is an extension of the current web in which information isgiven well-defined meaning, better enabling computers and people to
work in co-oper ation.³
[Berners-Lee et al , 2001]
Semantic Web - is a mesh of information linked up in such a way as to be easilyprocessable by machines, on a global scale.
Semantic web - provides a way of using common language to tag data so that
information exchange can occur in databases and produce an outcome that is
perceptive to the user. It relies on machine-readable information and metadataexpressed in RDF.
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Main pr inciples of Semantic Web
Explicit Metadata: metadata capture part of the meaning of data. HTML is used
to express meaning of its content in not machine processable way (text). If HTML is replaced by more appropriate languages, then the Web page can
carry their content on its sleeve (currently XML and RDF).
Ontologies: defined as ³an explicit and formal specification of a
conceptualisation³ [R. Studer] are ways of declaring what types of things exist,
and what types of relationships they have with each other. Provide shared
understanding of a domain to use in machine-understandable content.
The ter ms denote important concepts (classes) of domain.
The r elationships typically include hierarchies of classes.
Proper ties i.e. (X surveys Y), (A hasLoad C)
Value r estr ictions (only X can survey B)
Disjointness statement (bulk carrier and oil carrier are disjoint)
Specification of logical r elations between objects (every surveyable
ship must have at least 100 Gross tonnage)
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Main pr inciples of Semantic Web
Logic : is the discipline that studies principles of reasoning. In general it offers:
Formal languages for expressing knowledge
Well-understood formal semantics
Automated reasoners that can deduct (infer) conclusions from the given
knowledge
Logic can be used to uncover ontological knowledge that is implicitly given. It can
also help to uncover unexpected relationships and inconsistencies (ensure
correctness of model).
Agents: Semantic Web Agents use all technologies we have outlined:
Metadata will be used to identify and extract information from Web sources.
Ontologies will be used to assist in Web searches, to interpret retrievedinformation, and to communicate with other agents.
Logic will be used for processing retrieved information and for drawing
conclusions.
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What ar e the benef its of using Semantic Web
Technologies?
The main advantages of Semantic Web are:
I nteroperability ± two or more software systems or/and people can function
with each other to achieve common goal.
Knowledge Sharing ± share common structure of information among people
and software agents
I nference
± Usage of reasoner infer relations and inconsistencies (ensurecorrectness of the model)
Disadvantages:
Subscribe for a single predefined meaning of the terms
(cannot be predefined globally)
Require manual mark up of all existing web pages (impossible)
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What ar e the benef its of using Semantic Web
Technologies?
Semantic Web Enabled Knowledge Management:
Knowledge will be organized in conceptual spaces according to its meaning.
Automated tools for maintenance and knowledge discovery
Semantic query answering
Query answering over several documents
Defining who may view certain parts of information (even parts of documents)will be possible.
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How we can use Semantic Web Technologies?
Knowledge Base (Rules and Regulations)
Data Integration (Marine Systems)
Knowledge Base (Intranet: The Hub)
Knowledge Base (Marine Domain)
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Knowledge Base (Rules and Regulations)
Knowledge Base of particular domain:
Effective Search
Machine and human understandable
Evolves at ontology level
Rules and Regulations Knowledge Base:
Serve as a human and machine searchable source of LR Rules and
Regulations
Can be expand over the time to other languages
Versioning capabilities enable storing different releases of Rules and
Regulations throughout the timeline
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Knowledge Base (The Hub, Mar ine Domain)
The Hub Knowledge Base:
Serve as a human and machine searchable source of The Hub content
Can serve as a glossary of business terms organised in logical hierarchy
Ontology visualisation tools can be used to browse ontology
Marine Domain Knowledge Base:
Serve as a human and machine searchable source of Marine Domain
Can ensure reusability of the same, logically organised objects during
development of enterprise architecture models
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Mar ine Systems Data Integr ation
General ontology for integration of different data sources and systems
Mappings of concepts
Single queries for multiple systems
Example:
Ship-types rationalised across heterogeneous systems
Note:Oracle 11g has support for RDF and OWL, its own reasoner and
Support for Java API (Jena)
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Mar ine Systems Data Integr ation
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Building Ontology
Logical Data Model developed during discovery of Ship life-cycle store crucial
information and structure that can be reused, saving substantial amount of effort allocated for development of ontologies.
Ontology development is necessarily an iterative process.
An ontology is a model of reality of the world and the concepts in the ontology
must reflect this reality.
The analytical work is similar to building a conceptual enterprise data model
and involves many of the same skills
One of the interesting differences is that as the ontology is being built it can be
used in connection with data profiling to see whether the information that iscurrently being stored in information systems does in fact comply with the rules
that the ontology would suggest.