sol-01-02(1) - SOLUTIONS - CIS209 - INTERNAL - 2002 PROBLEM...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
SOLUTIONS - CIS209 - INTERNAL - 2002 PROBLEM 1 [25] Question 1 [3] Define the relational model. What is a relational database management system (DBMS)? Answer The relational model is a data model (or a model for representing data). The (relational) data objects or, rather, data structures it consists of are domain and relation . The relational operators include set specific operators – union , intersection , difference and Cartesian product – and relation specific operators – restriction , projection , join , division . [2] A relational DBMS is a DBMS that provides/implements the elements of a relational model (i.e. the relational data objects/structures and the relational operators) [1] TOTAL [3] Question 2 [3] Define the notion of “foreign key”. Give an example. Answer Consider two relations R 1 and R 2 . A set of attributes S of R 2 is a foreign key referencing R 1 if and only if S is a candidate key in R 1 . [2] For example: Customer (Customer-id, Name, Address, Job-details) Account (Account-number, Type, Overdraft-Limit, Balance, Customer-id) Customer-id is a FK in Account referencing Customer. [1] TOTAL [3] Question 3 [4] Explain the two types of program–data independence on the basis of the three level ANSI/SPARC architecture of a database system. Answer Introduction/description of the three ANSI/SPARC levels – i.e., internal (physical), conceptual and external. A diagram is sufficient (see Study Guide page 11), but other correct ways of defining/introducing these levels should be accepted. [2] Physical program-data independence is the immunity of application programs to changes at the internal (or physical) level (assuming that the conceptual level does not change). [1] Logical program-data independence is the immunity of application programs to changes at the conceptual level (assuming that the external level remains unchanged). [1] TOTAL [4] CIS209 – IS52003A 2002 Internal Solutions 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Question 4 [5] What is a system catalogue? Give example of two types of data/information it usually includes and explain what data/information is/can-be used for (one or two sentences per type of data/information). Answer A system catalogue is a component of a database system which contains information about the database. [1] Types of data/information contained in a catalogue include: 1. schemas: 1.1. conceptual schema (or description of base tables) – used, for example, for checking the correctness of SQL queries; 1.2. external schemas (or description of views) – used for evaluating queries at the external level; 2. integrity rules – used for enforcing the integrity of the database between transactions; 3. security rules – used for enforcing the security of the database; 4. statistical information about the data (extension) of the database – used by the optimiser; 5. transaction log – used in data recovery. Award 2 marks per correct example of type of data/information contained in a catalogue, up to
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 14

sol-01-02(1) - SOLUTIONS - CIS209 - INTERNAL - 2002 PROBLEM...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online