3. The Web of Documents
Traditional Web, Hypertext Web
Analogy
A global file system
Designed for
Human consumption
Primary objects
Documents
Links
Untyped
Between documents (or parts of documents)
Degree of structure in object
Fairy low
Semantics of content and links
implicit
3
5. The Web of Data
Analogy
A global data space
Designed for
Machines first, humans later
Primary objects
Things (description of things)
Links
Typed
Between things
Degree of structure in objects
High
Semantic of content and links
Explicit
5
7. Linked Data
• Is about using the Web to create typed links
between data from different sources
• Refers to data published on the Web in
such a way that
– It is machine-readable
– Its meaning is explicitly defined
– It is linked to other datasets
– It can be linked to from external datasets
7
8. Properties of the Web of Data
• It is generic
– Can contain any type of data
• Data about anything
– Anyone can publish data
– No constraints on choice of vocabularies
– entities are connected by RDF links
8
12. Ontology , RDF
• Ontology provides a means to vocabularies
and link’s semantics on linked data.
• RDF provides a generic, graph-based data
model to structure and link data that
describes things
• A triple [subject, predicate, object]
– Subject: a URI
– Predicate: a URI
– Object: a URI or a string literal
12
22. Retrieval Process
22
• a) Query construction
• b) Search algorithm of the system
• c) Presentation of the results
Search Engines
Query A lot of related Web Pages
QA Systems
Question Exact Answer
23. Retrieval Process (Cont.)
23
Query Analyzer
Query
A lot of
Web Pages
WWW
Crawler
RequestWeb Pages
Index
File
Indexer
Web Pages
Index TermsSearch
Ranking
Results Doc
Datastore
Web Pages
UI
Query
Ranked Results
Web Pages
• Traditional SE
25. Therefore, what is needed?
25
• Assign meta data to information objects
• Content description with concepts and relations between
them
• Provision of background knowledge
• Provision of the semantics of relations for query
extension, ontology integration, etc.
RDF
RDF Schema, OWL, Rules
26. 26
Question Answering
• Question answering (QA) systems take users’
natural language questions and automatically locate
answers from large collections of documents.
• Two types of QA systems
– Closed-Domain (or restricted domain) Question Answering
– Open-Domain Question Answering
27. 27
Question Answering (Cont.)
• Open Domain QA System
Question
Analysis
Answer
Selection
Question Query
Answer
Type
Documents
Answer (s)
Question
Answer (s)
UI
Document
Analysis
Passages
Document Retrieval
Systems
Document
Retrieval
Open Domain
Ontology
28. 28
Question Answering (Cont.)
• Restricted Domain QA System
Question
Analysis
Answer
Post Processing
Question Query
Answer (s)
Question
Answer (s)
UI
Answer
Retrieval
Answer (s)
Data
Open Domain
Ontology
Lexicon
Domain
Ontology
Knowledge Base
29. Related Works
• AquaLog
– Vanessa Lopez, Victoria Uren, Enrico Motta, Michele Pasin.
• PowerAqua
– Vanessa Lopez, Andriy Nikolov, Marta Sabou, Victoria Uren, Enrico Motta,
Mathieu d’Aquin
• QASYO
– for YAGO Ontology
• AutoSPARQL
29