Lecture Review Week 9

Database --- This week's lecture was rather difficult to understand. What in the world is relational algebra.. Weren't algebra supposed to be some letter that represent numbers?

Anyhow, there are eight operations in relational algebra. Selection, projection, union, intersection, difference, cartesian product, natural join and renaming operator.

Projection is equivalent to the selection clause in SQL. As there could be duplicate tuples, the rows with duplicate are removed - Distinct. Projection is represented by PI (R)

Selection correspond to the Where clause. Since it always selects the whole tuple, all the tuples are distinct, thus there won't be a need for distinct keyword. Selection is represented by SIGMA(R).

Union is the combined of the different relations, removing duplicate tuple. Intersection is the duplicate tuples in the relations being considered. Set difference is the tuples that appear in the first relation but not in the second relation.

Cartesian product gives all the possible combination of the tuples between the first and the second relation. No duplicate is possible. Theta-join does a cartesian product of the two relations on some conditions given.

Natural join joins two relations with relations of the same name and projects only one of the attribute. Renaming allows attributes to be renamed, similar to the keyword -As in SQL.


Business Law --- The first lecture on Company Law. First off, the 3 types of business was introduced - Sole-proprietorship, partnership (up to 19 partners), and company (more than 19).

A company is a legal person but do not have the senses like a natural person. The two primary organs of a company are the board of directors and shareholders. The directors are people who run the company in accordance to the Companies Act. The qualification of a director is just that you have to be above 21 years old and is a natural person.


Business Correspondence --- The second Oral Presentation lecture focuses on making the talk a memorable one for the audience. Visual aids must be attractive, and must not be filled with lines and lines of words. Everything should be written in point form.

Contents must be audience centred, difficult to understand terms and abbreviations must be explained.

Use catchy phrases with memory devices and word painting techniques. Give your points in words that give the same sound - alliteration. Repeats your catchy phrase to make an impression. Make comparison using simile, metaphor. Other techniques include allusion, counterpoint, hypothesis and rhetorical question


Artificial Intelligence --- The lecture continues on Logics. To infer from first order logic, there are three ways, forward chaining, backward chaining, and resolution. Basically, I still don't understand forward and backward chaining. For resolution, it is trying to form a proof by refutation / contradiction. By adding the negation of the statement to be proven to the knowledge base, you try to derive that the statement is unsatisfiable. This will therefore prove that the statement is true.


Software Engineering --- This week's lecture basically converts state diagrams into codes and see what should be done to enforce that the states are not violated. Converting from designs to codes are usually quite intuitive and nothing much can be said about this lecture. Anyway, the test is done after the mid-term test, and I really can't concentrate well thereafter. Just hope the test is not too badly done like the other two modules.