Week_4 Flashcards
What is a Data Model?
Integrated collection of concepts for describing data, relationships between data, and constraints on the data in an organization.
Describe the basis of a Relational Data Model.
Data and relationships are all represented as tables, and each table has columns and a unique name.
What is conceptual modelling?
Conceptual Modelling is the process of developing a model of information use that is independent of implementation details.
What is a Relationship in a Entity-Relationship model?
A Relationship describes the association between entities.
What is an Attribute?
An attribute is a property of an entity or a relationship type.
What is meant by Domain in association with an attribute?
The domain defines the potential values that an attribute may hold. (e.g. Domain for the Australian postcode is a sequence of 4 digits)
What is the difference between an Entity type and Entity Occurrence?
An Entity occurrence is a uniquely identifiable object of an entity type where as an Entity type is a group of objects with same properties, identified by the enterprise as having an independent existence.
What is Multiplicities in a Relationship?
They show the maximum and minimum number of possible occurrences of an entity type and how it relates to another entity type.
What is a Relation? (Relational Model terminology)
A relation is a table with columns and rows.
What is an attribute?
A attribute is a named column of a relation.
What is a domain?
A domain is the set of allowable values for one or more attributes.
What is a Tuple?
A Tuple is a row of a relation.
What is a Degree?
A Degree is the number of attributes in a relation.
What is the Cardinality?
The Cardinality is the number of tuples in a relation.
