MIS 375 EXAM 2 QUESTIONS AND ANSWERS
Provide three different options that are available when selecting an identifier for a
student entity. What are the pros and cons of each choice? - Answer -The three options
available for selecting an entity identifier: (1) Put together a combination of attributes to
serve as the identifier (such as first_name and last_name). (2) Sometimes, a single
attribute is available that can serve as the identifier (such as social security number,
though there may be legal constraints on use of this data in this way). (3) A new
attribute can be created to serve as the identifier (such as student_id). Creating a new
attribute is normally done in the design phase.
Any of these ways of selecting an identifier is acceptable. The important point is to
ensure that the chosen identifier uniquely identifies each instance of the entity.
What is the purpose of developing an identifier for an entity? - Answer -One of the
aspects of the definition of an entity is the fact that there are multiple occurrences of the
entity. If there are not multiple instances of something that is a potential entity, that
something is not an entity in the system. Consequently, there must be a way of
identifying each individual occurrence of an entity so that it can be picked out from
amongst all the other instances of the entity. That is the purpose of having identifiers
with unique values.
What type of high-level business rule can be stated by an ERD? Give two examples.
- Answer -A business rule is a constraint or guideline to follow during operation of the
system. Examples of business rules are: an order belongs to just one customer; a
customer cannot cancel an order that has been shipped; a backorder can be created for
an out of stock product. Business rules are expressed on ERDs by the kinds of
relationships that the entities share.
, Define what is meant by an entity in a data model. How should an entity be named?
What information about an entity should be stored in the CASE repository? - Answer -
An entity is a person, place, thing, or event about which data is collected and stored.
Entities names are nouns. Information stored in a CASE repository regarding an entity
includes:
• Name
• Definition
• Special Notes
Define what is meant by an attribute in a data model. How should an attribute be
named? What information about an attribute should be stored in the CASE repository? -
Answer -An attribute is a characteristic that describes an entity. Attribute names are
nouns. Information stored in a CASE repository regarding an attribute includes:
• Name
• Definition
• Alias
• Sample Values
• Acceptable Values
• Format
• Type
• Special Notes
Define what is meant by a relationship in a data model. How should a relationship be
named? What information about a relationship should be stored in the CASE
repository? - Answer -A relationship describes the association between entities.
Relationship names are labeled as active verbs. Information stored in a CASE
repository regarding a relationship includes:
• Verb Phrase
• Parent Entity
• Child Entity
• Definition
• Cardinality
• Modality
• Special Notes
A team of developers is considering including 'warehouse' as an entity in their data
model. The company for whom they are developing the system has just one warehouse
location. Should warehouse be included? Why or why not? - Answer -Entities represent
something for which there exist multiple instances or occurrences. If there is only one
instance of a warehouse, then it would not be best represented by an entity. However, if
multiple warehouses were planned in the future, then a warehouse entity should be
included.
What is meant by a concatenated identifier? - Answer -A concatenated identifier is one
in which a combination of attributes serves to uniquely identify an entity. For instance,
Provide three different options that are available when selecting an identifier for a
student entity. What are the pros and cons of each choice? - Answer -The three options
available for selecting an entity identifier: (1) Put together a combination of attributes to
serve as the identifier (such as first_name and last_name). (2) Sometimes, a single
attribute is available that can serve as the identifier (such as social security number,
though there may be legal constraints on use of this data in this way). (3) A new
attribute can be created to serve as the identifier (such as student_id). Creating a new
attribute is normally done in the design phase.
Any of these ways of selecting an identifier is acceptable. The important point is to
ensure that the chosen identifier uniquely identifies each instance of the entity.
What is the purpose of developing an identifier for an entity? - Answer -One of the
aspects of the definition of an entity is the fact that there are multiple occurrences of the
entity. If there are not multiple instances of something that is a potential entity, that
something is not an entity in the system. Consequently, there must be a way of
identifying each individual occurrence of an entity so that it can be picked out from
amongst all the other instances of the entity. That is the purpose of having identifiers
with unique values.
What type of high-level business rule can be stated by an ERD? Give two examples.
- Answer -A business rule is a constraint or guideline to follow during operation of the
system. Examples of business rules are: an order belongs to just one customer; a
customer cannot cancel an order that has been shipped; a backorder can be created for
an out of stock product. Business rules are expressed on ERDs by the kinds of
relationships that the entities share.
, Define what is meant by an entity in a data model. How should an entity be named?
What information about an entity should be stored in the CASE repository? - Answer -
An entity is a person, place, thing, or event about which data is collected and stored.
Entities names are nouns. Information stored in a CASE repository regarding an entity
includes:
• Name
• Definition
• Special Notes
Define what is meant by an attribute in a data model. How should an attribute be
named? What information about an attribute should be stored in the CASE repository? -
Answer -An attribute is a characteristic that describes an entity. Attribute names are
nouns. Information stored in a CASE repository regarding an attribute includes:
• Name
• Definition
• Alias
• Sample Values
• Acceptable Values
• Format
• Type
• Special Notes
Define what is meant by a relationship in a data model. How should a relationship be
named? What information about a relationship should be stored in the CASE
repository? - Answer -A relationship describes the association between entities.
Relationship names are labeled as active verbs. Information stored in a CASE
repository regarding a relationship includes:
• Verb Phrase
• Parent Entity
• Child Entity
• Definition
• Cardinality
• Modality
• Special Notes
A team of developers is considering including 'warehouse' as an entity in their data
model. The company for whom they are developing the system has just one warehouse
location. Should warehouse be included? Why or why not? - Answer -Entities represent
something for which there exist multiple instances or occurrences. If there is only one
instance of a warehouse, then it would not be best represented by an entity. However, if
multiple warehouses were planned in the future, then a warehouse entity should be
included.
What is meant by a concatenated identifier? - Answer -A concatenated identifier is one
in which a combination of attributes serves to uniquely identify an entity. For instance,
