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Jarrar: Uniqueness

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Lecture video by Mustafa Jarrar at Birzeit University, Palestine. ...

Lecture video by Mustafa Jarrar at Birzeit University, Palestine.
See the course webpage at: http://jarrar-courses.blogspot.com/2011/09/knowledgeengineering-fall2011.html
and http://www.jarrar.info

and on Youtube:
http://www.youtube.com/watch?v=3_-HGnI6AZ0&list=PLDEA50C29F3D28257

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Jarrar: Uniqueness Jarrar: Uniqueness Presentation Transcript

  • © Mustafa Jarrar
    Lecture Notes, Knowledge Engineering (SCOM7348)
    University of Birzeit
    1st Semester, 2011
    Knowledge Engineering (SCOM7348)
    Uniqueness
    (Chapter 4)
    Dr. Mustafa Jarrar
    University of Birzeit
    mjarrar@birzeit.edu
    www.jarrar.info
  • Conceptual Schema Design Steps
    1. From examples to elementary facts
    2. Draw fact types and apply population check
    3. Combine entity types
    4. Add uniqueness constraints
    5. Add mandatory constraints
    6. Add set, subtype, & frequency constraints
    7. Final checks, & schema engineering issues
  • Uniqueness Constraint
    For each state taken individually, each person has at most one weight.
    How can we record such information without redundancy?
    View slide
  • Uniqueness on Unary Fact Types
    Is their any problem with this schema?
    How can we prevent people adding such redundant information?
    View slide
  • Uniqueness on Unary Fact Types
    The uniqueness constraint ensures entities are unique (no duplicates)
  • Uniqueness on Binary Fact Types
    EachPolitician was born in at most one Country
    EachPolitician heads government of at most one Country
    EachCountry has at most one head Politician
  • Uniqueness on Binary Fact Types
    Means many to many
    It is possible that the same Politican visited more than one Country
    and that the same Country was visited by more than one Politician
    Who can give more examples?
  • Uniqueness on Binary Fact Types
    What is unique here?
  • Uniqueness on Binary Fact Types
    What is unique here?
  • Uniqueness on Binary Fact Types
    The four uniqueness constraint patterns for a binary.
    No duplicates are allowed in a's column
    Each a R's at most one b
    No duplicates are allowed in b's column
    Each b is R'd by at most one a
    Both the foregoing constraints apply
    No duplicate (a,b) rows are allowed
    Each a may R many b and vice versa
  • How to think about Uniqueness
    Is the population significant?
    Adding counterexamples to test the constraints

  • Uniqueness on Binary Fact Types
    Which is more realistic?
  • Uniqueness on Ternary Fact Types
    What are the uniqueness constraints?
    Each (Person, Subject) combination is unique.
  • Uniqueness on Ternary Fact Types
    Allowed basic uniqueness constraints for a ternary.
  • Uniqueness on Ternary Fact Types
    What this uniqueness means?
  • Uniqueness on Ternary Fact Types
    Allowed uniqueness constraint combinations for a ternary.
  • Uniqueness on Ternary Fact Types
    Which of this constraint patterns is illegal? Why?



  • Example of Uniqueness on n-ary fact types
    Each (a,c,d) combination occurs on at most one row.
  • Uniqueness with Nested Fact Types
    This constraint is particularly important! Why?
     Explain what is unique
  • What is the difference between these?
     Explain the Joins
     Do we need uniqueness?
  • External Uniqueness constraints
    What is missing?
    u
  • External Uniqueness constraints
    The meaning of the External Uniqueness
    Each (b,c) combination is paired with at most one a
    Each population Rjoin S has bc unique
    (where “join” denotes “conceptual inner join”)
  • Example with nest fact types
  • Key Length Check
    What is wrong?
    Splits into
    Each UC in an elementary n-aryrelationship must span at least n-1 roles
  • Key Length Check
    What is wrong?
    Splits into
  • Discussion
    Summarize what did you learn until now?
    Problem of uniqueness in your day-life?
    Compare the uniqueness constraint in ORM
    with the cardinality constraints in UML and EER?
  • Project 1 (Higher Education Governance)
    The Ministry of Higher Education is planning to build an information system about all students in the Palestinian universities. Such that, each university will be asked to submit its student profiles (i.e., a copy of the mark sheet, for every student who graduated from it). All details in these mark sheets will be then recorded in the information system. Please remark that, a student may have more than one mark sheet, as she/he may have more than a degree.
    • Develop a conceptual model (in both Arabic and English separately) for this information system, which must be suitable for mark sheets in all Palestinian universities (Tip: you may start with your own mark sheet).
    Deadline: September 22, 2010
    Deliver printed copy to my office, and upload a soft copy to Google Docs, and share it with me:
    • File name must be, (ORMProject1.HigherEducation.AntonDeik.V03.zip)
    • The .zip file must contain the source files, and report in .doc and .pdf