31) Developers generally construct a logical representation of database data, called a data model, after building a database.
32) A data model describes data and relationships that will be stored in the database.
33) In data models, physical objects are represented as entities, whereas logical constructs and transactions are represented as attributes.
34) Attributes are used to describe characteristics of entities.
35) An identifier is an attribute or a group of attributes whose value is associated with one, and only one, entity instance.
36) In an entity-relationship (E-R) diagram, an entity is represented by a triangle, and the relationships between entities are represented by dotted lines.
37) A line in an E-R diagram is used to represent the attributes of the entities.
38) A many-to-many (N:M) relationship means that more than one entity is allowed on each side of the relationship and that the number of entities on each side can be different.
39) The crow's-foot notation in an E-R diagram shows the maximum number of entities that can be involved in a relationship.
40) Minimum cardinalities represent the lower limit on the number of entities required in a relationship.