ch 12.txt

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ch 12.txt
2015-04-06 19:40:18
diane cs111
diane cs111 ch 12
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  1. What are information systems?
    Information systems are software applications that facilitate the organization and analysis of data.
  2. Give an example of an information system.
    Spreadsheet software allows users to place raw data in tables and then utilize formulas and basic graphical mechanisms to generate calculations and illustrations from it.
  3. Database structures are a/an _______________ to a distributed information system based on files.
  4. What are the three layers of data in a database system?
    • From outside in:
    • Database (the stored data of the system)
    • Database management system (system of programs controlling how data is accessed)
    • Application software (system of programs specifying how to present data to the user)
  5. In a database, what are tuples and attributes?
    Tuples are rows (records) and columns are attributes (fields).
  6. What does the SELECT operator do in a database?
    It is a query. It removes rows (from your view) that don't meet the criteria. Or, it determines which tuples have particular attributes.
  7. What does the PROJECT operator do in a database?
    It limits the view of the database to particular columns (attributes).
  8. What does the relational operator JOIN do?
    It combines multiple tables that have common attributes.
  9. What is meant by 'concurrency control'?
    It refers to the possibility of the loss of data integrity due to concurrent access to data from multiple access points. It can be avoided by locking records, and by setting rollback points to recover database to its state prior to transaction being processed.
  10. What is encryption?
    It is encoding a message in such a way that only the receiving station can decode it.
  11. What are the steps to sending a message with public-key encryption?
    • 1) create message
    • 2) look up recipient's public key
    • 3) encrypt message with recipient's public key
    • 4) transmit encrypted message
    • 5) decrypt message with recipient's private key
  12. What is meant by authentication?
    Authentication is validating that the message sender is who it appears to me.
  13. What are the steps to sending a message for the purpose of key-based authentication?
    • 1) create message
    • 2) encrypt message with sender's private key
    • 3) transmit encrypted message
    • 4) decrypt message with sender's public key