Dr. Mustafa Jarrar. Knowledge Engineering (SCOM7348) (Chapter 4) University of Birzeit

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1 Mustafa Jarrar Lecture Notes, Knowledge Engineering (SCOM7348) University of Birzeit 1 st Semester, 2011 Knowledge Engineering (SCOM7348) Uniqueness (Chapter 4) Dr. Mustafa Jarrar University of Birzeit mjarrar@birzeit.edu Jarrar

2 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 Jarrar

3 Uniqueness Constraint For each state taken individually, each person has at most one weight. How can we record such information without redundancy? Jarrar

4 Uniqueness on Unary Fact Types Is their any problem with this schema? How can we prevent people adding such redundant information? Jarrar

5 Uniqueness on Unary Fact Types The uniqueness constraint ensures entities are unique (no duplicates) Jarrar

6 Uniqueness on Binary Fact Types Each Politician was born in at most one Country Each Politician heads government of at most one Country Each Country has at most one head Politician Jarrar

7 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? Jarrar

8 Uniqueness on Binary Fact Types What is unique here? Jarrar

9 Uniqueness on Binary Fact Types What is unique here? Jarrar

10 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 Jarrar

11 How to think about Uniqueness Is the population significant? Adding counterexamples to test the constraints Jarrar

12 Uniqueness on Binary Fact Types Which is more realistic? Jarrar

13 Uniqueness on Ternary Fact Types What are the uniqueness constraints? Each (Person, Subject) combination is unique. Jarrar

14 Uniqueness on Ternary Fact Types Allowed basic uniqueness constraints for a ternary. Jarrar

15 Uniqueness on Ternary Fact Types What this uniqueness means? Jarrar

16 Uniqueness on Ternary Fact Types Allowed uniqueness constraint combinations for a ternary. Jarrar

17 Uniqueness on Ternary Fact Types Which of this constraint patterns is illegal? Why? Jarrar

18 Example of Uniqueness on n-ary fact types Each (a,c,d) combination occurs on at most one row. Jarrar

19 Uniqueness with Nested Fact Types This constraint is particularly important! Why? Explain what is unique Jarrar

20 What is the difference between these? Explain the Joins Do we need uniqueness? Jarrar

21 External Uniqueness constraints What is missing? u Jarrar

22 External Uniqueness constraints The meaning of the External Uniqueness Each (b,c) combination is paired with at most one a Each population R join S has bc unique (where join denotes conceptual inner join ) Jarrar

23 Example with nest fact types Jarrar

24 Key Length Check What is wrong? Splits into Each UC in an elementary n-ary relationship must span at least n-1 roles Jarrar

25 Key Length Check What is wrong? Splits into Jarrar

26 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? Jarrar

27 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 Jarrar