Business Proposal

CS682 D1 Information Systems Analysis and Design

Homework March 21, 2013

Pruthvi Thummalapally

BU ID: U32-34-9973

1) Study Questions Chapter # 8 (Found on www.courseinfo.bu.edu CS682) Questions # 15, 104, 150 and 153.

A)

15. The domain value for an attribute is the value that will be recorded if not specified by the user. True

104. The number of entities that can participate in a relationship is known as:

A) The domain of the relationship

B) The cardinality of the relationship

C) The degree of the relationship

D) The association of the relationship

E) None of these

150. Nonspecific relationship is where many instances of one entity are associated with many instances of another entity.

153. Nonidentifying relationships are those in which each of the participating entities has its own independent primary key.

2) Differentiate between entities and entity instances. Why don’t we try to model instances? (2 points)

A) An entity is a class of persons, places, objects, events, or concepts about which we need to capture and store data. An entity is something that may exist independently and so there is often a one-to-one relationship between entities and database tables, where as an entity instance is a single occurrence of an entity

Because entity instances are single occurrences of entity these values wary and are different so if we use entity instances for data modeling there will be no consistency in the data model i.e. independent relationships might not be possible.

3) Differentiate between candidate keys, primary keys and alternate keys. Can each of these be a concatenated key? (2 points)

A) Candidate key – one of a number of keys that may serve as the primary key.

Primary key – is a candidate key used to uniquely identify a single entity instance. It should be unique and not null.

Alternate key or Secondary key – is a...