01: Semantic Web Vision & Structured Web Documents in XML

Question 1

What are the problems with the current keyword-based search engines?

Answer 1

• Key Problem: the meaning of Web content is not machine-accessible: a lack of semantics
• High recall, low precision
• Low or no recall
• Results are highly sensitive to vocabulary
• Results are single Web pages
• Human involvement is necessary to interpret and combine results
• Results of Web searches are not readily accessible by other software tools

Question 2

What are the three key points with Semantic Web approach?

Answer 2

• Representing Web content in a form that is more easily machine-processable
• Using intelligent techniques to take advantage of these representations
• Evolving out of the existing Web

Question 3

What are the limitations of current knowledge management technologies in four dimensions?

Answer 3

1. Searching information
   
   • ​​Keyword-based search engines
2. Extracting information
   
   • ​​Human involvement necessary for browsing, retrieving, interpreting, combining
3. Maintaining information
   
   • ​​Inconsistencies in terminology, outdated information
4. Viewing information
   
   • ​​Impossible to define views on Web knowledge

Question 4

What are the characteristics of a Semantic Web Enabled knowledge management?

Answer 4

• Advantages:
  
  • ​Organizing knowledge in conceptual spaces according to its meaning
  • Having automated tools for maintenance and knowledge discovery
  • Answering any query semantically
  • Answering any query over several documents
  • Defining who may view certain parts of information (even parts of documents) will be possible

Question 5

What are the benefits of Web Enabled B2B electronic commerce?

Answer 5

• Businesses enter partnerships without much overhead
• Differences in terminology will be resolved using standard abstract domain models
• Data will be interchanged using translation services
• Auctioning, negotiations, and drafting contracts will be carried out automatically (or semi-automatically) by software agents

Question 6

What are some problems with HTML?

Answer 6

• Humans don’t have an issue, but machines (software agents) do
  
  • How to distinguish “therapists” for a “secretary”?
  • How to determine exact consultation hours?
  • They would have to follow the link to the State of Origin games to find when they take place
• XML would be a better representation

Question 7

What is explicit metadata?

Answer 7

“Data about data”–metadata capture part of the meaning of data

Question 8

What is an ontology?

Answer 8

An explicit and formal specification of a conceptualization

Question 9

What are the typical components of an ontology?

Answer 9

• Terms denote important concepts (classes of objects) of the domain
  
  • e.g. professors, staff, students, courses, departments
• Relationships between these terms: typically class hierarchies
  
  • A class C to be a subclass of another class C’ if every object in C is also included in C’
  • e.g. All professors are staff members

Question 10

Draw an example of a class hierarchy.

Answer 10

Question 11

What is the role of ontologies on the Web?

Answer 11

• Ontologies provide a shared understanding of a domain: semantic interoperability
  
  • ​Overcome differences in terminology
  • Mappings between ontologies
• Useful for the organization and navigation of Web sites
• Useful for improving the accuracy of Web searches
• Web searches can exploit generalization/specialization information

Question 12

What is the tradeoff between expressive power and computation complexity?

Answer 12

The more expressive a logic is, the more computationally expensive it becomes to draw conclusions

Question 13

What are software agents?

Answer 13

• Work autonomously and proactively
  
  • Evolved out of object-oriented and component-based programming

Question 14

What will a personal agent on the Semantic Web do? Name its operations one after another chronically (in a time-based sequence).

Answer 14

1. Receive some tasks and preferences from the person
2. Seek information from Web sources, communicate with other agents
3. Compare information about user requirements and preferences, make certain choices
4. Give answers to the user

Question 15

What are the principles of a layered approach to the development of the Semantic Web?

Answer 15

• Downward compatibility
• Upward partial understanding

Question 16

Draw the general Semantic Web layer stack.

Answer 16

Question 17

Draw the specific Semantic Web layer stack.

Answer 17

Question 18

What are the differences between the specific and the general ​Semantic Web layer stacks?

Answer 18

• Ontology layer is instantiated with two alternatives:
  
  • Current standard Web ontology language (OWL)
  • A rule-based language

Question 19

Name the layers of the Semantic Web and their functionalities.

Answer 19

• XML layer
  
  • ​Syntactic basis
• RDF layer
  
  • ​RDF basic data model for facts
  • RDF schema simple ontology language
• Ontology layer
  
  • ​More expressive languages than RDF schema
  • Current Web standard: OWL
• Logic layer
  
  • ​Enhance ontology languages further
  • Application-specific declarative knowledge
• Proof layer
  
  • ​Proof generation, exchange, validation
• Trust layer
  
  • ​Digital signatures
  • Recommendations, rating agencies, …

Question 20

XML is the separation of ____ from ____.

Answer 20

XML is the separation of content from display.

Question 21

Provide an example of a meaningful empty element in XML.​

Answer 21

• An empty element is not inherently meaningless
  
  • It may have some properties in terms of attributes
• ​An attribute is a name-value pair inside the opening tag of an element

Question 22

What is a comment and how would you write one in XML?

Answer 22

A piece of text that is to be ignored by the parser

Question 23

How do you prevent name clashes in XML documents that have been developed independently?

Answer 23

By using a different prefix for each DTD or schema

Question 24

How do you declare a namespace?

Answer 24

Can be declared within an element and can be used in that element and any of its children