As with all the other notes, the full package is available here. Otherwise, the rest of this article includes the first set of notes which cover the Basic Concepts of Database Systems and include some of the definitions that were likely to show up on the first exam. These are word for word of what Dr. Uckan wrote on the board.

Basic Concepts of Database Systems

Wednesday, August 27, 2008
09:07

  • A DATABASE (DB) is a data-oriented model of subset of the universe
    of interest, called a "    miniworld"
  • In a miniworld, we are interested in:
  • Entities
  • Relationships
  • Events (time-varying
    relationships)
     
  • An ENTITY is an object, or a being, or an abstraction of
    interest, that can be distinguished from similar entities.
    • EX:
    •  A student in a college
    • An employee in a company
    • A DVD in my collection
    • A particular school of
      thought (e.g., existentialism) in philosophy
       
  • An ENTITY SET is a set of entities of the same type.
    • EX:
    • All students in a college
    • All human emotions
    • All books in a
      library
       
  • A RELATIONSHIP is an association (mapping) within, or between,
    or among several entity sets
    • EX:
    • A student enrolls in a class
    • A man marries a woman
    • A book belongs
      to       a
      student
       
  • A  RELATIONSHIP
    SET     is a set of
    all distinguishable relationships of all the same type.
    • EX:
    • Enrollment between students and
      courses
    • Is_married_to between Men and Women
    • Is_married_to in the set of people
    • Belongs_to between Students and
      Computers
       
  • A RELATIONSHIP
    (R)  SET cannot stand alone, and
    must rely on some ENTITY (E) SETS.
  • A R SET has a
    degree
    • The DEGREE of an R SET is
      the number of the E SETS on which the R set depends.
    • EX:
    • Enrollment is of degree 2
      (binary)
    • Is_married_to is binary or
      unary
    • Medical_Tests_Prescribed by
      Doctors for patients from Std. Medical_Tests is of degree 3 (i.e.
      ternary)
       
  • Mapping
    Properties (Mapping Constraints) for relationship sets specify in a
    semi-quantitative manner the number of entities involved in each
    relationship.
    • Types
    • One-to-One (1:1) (examples-
      Is_married_to (1:M or 1:∞)
    • Ex: Exclusive  ownership of Cars by People
    • One-to-Many
    • Many-to-Many
    • EX: Enrollment between
      Students and Courses
       
  • E and R sets are
    described by their attributes. An     ATTRIBUTE is a measurable or observable property of an E or R
    that takes its admissible values from on an associated     DOMAIN SET. A Domain Set is a set of
    acceptable values for an attribute.
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