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Revision. CS-1Q IM Lecture 10 Phil Gray. Simon Gay. The Class Test. Friday 31st January, 1.30 - 2.45 pm, Hunter Halls (East and West) Two questions: ANSWER BOTH! one question on HCI, of similar structure to the practice questions and past exam questions

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  1. Revision CS-1Q IM Lecture 10 Phil Gray Simon Gay

  2. The Class Test • Friday 31st January, 1.30 - 2.45 pm,Hunter Halls (East and West) • Two questions: ANSWER BOTH! • one question on HCI, of similar structure to thepractice questions and past exam questions • one question on Mathematics and Information Management • 30 minutes per question, + 15 minutes reading/checking time

  3. A Word from Chris about HCI • You need to know what a mental model is. • Revise the section on Elicitation.

  4. Overview • Basic Division between • Information Management (~ 75-80%) • Sets & Relations (~20-25%)

  5. Types of Questions • objective content • what is • define • list • explain the difference between • worked examples • e.g., ER diagrams, queries • questions on sets & relations • critical question • compare, assess • explain the relationship between

  6. Content • Lecture 1: Issues in Managing Data • Lecture 2: Data Modelling & ER Diagrams • Lecture 3: The Relational Data Model • Lecture 4: Creating Database Tables from an ER Diagram • Lectures 5-6: Sets and Relations • Lecture 7: Querying Relational Databases • Lectures 8-9: SQL

  7. Content • Data, information and knowledge • Databases & DBMSs • definitions • layered architecture • ER Modelling • what’s a model? • be able to define the elements • be able to produce a simple ER diagram

  8. Content • Relational Model • be able to define the elements • keys • constraints • transforming from / comparing to ER Model • Sets & Relations • based around the tutorial exercises

  9. Content • Querying Relational Databases • understand the operations • be able to relate them to sets & relations • SQL • know the syntax & semantics • be able to write and explain simple queries

  10. Model Answer (a) (3 marks) A database is one or more structured sets of persistent data, usually held on computer and associated with software to update and query the data. A database management system is a suite of programs that manage databases (or an information system where the data may be shared by different applications). Other functions: (1) multiple views of the same data (1) controlled concurrent access to data (1) management of security and integrity

  11. N 1 stored in Widget Warehouse identifier type price identifier address description street city postcode Model Answer (b) 1 mark for entities, 1 mark for attributes, 1 mark for composite attribute, 1 mark for relationship, 0.5 marks for cardinality, 0.5 marks for total participation of widgets, 1 mark for primary keys

  12. Model Answer (b) (continued) (2 marks) The association should be represented by including an attribute in the Widget table to hold a foreign key referring to the primary key in the Warehouse table.

  13. Model Answer (c) (i) (1 mark) True, because  stands for the empty set, and the empty set is a subset of every set. (ii) (1 mark) True, because A is the set of all elements of U that are greater than 2. The order of listing elements is not significant. (iii) (1 mark) 3, 1

  14. 1 3 2 4 Model Answer (c) (iv) (2 marks) Not transitive because, for example, we have tuples <1,2> and <2,3> but not <1,3> (there are 2 other examples) Transitive means: if xRy and yRz then xRz.

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