Which of the following can data models be used to describe?

A. data
B. data relationships
C. data semantics
D. data constraints

Which of the following models can be used to describe object-based logical models?

A. semantic data model
B. entity-relationship model
C. physical data model

What are the possible relationships between two entity sets?

A. one-to-one
B. one-to-many
C. many-to-one
D. many-to-many

The data models are divided into three classes：­­____________ ­­____________ models, ­­____________ ­­____________ models and ­­____________ ­­____________ models.

An ____________ is an object, which can be uniquely distinguished from other objects.

The set of all entities of the same type and relationships of the same type are termed as ____________ ____________ and ____________ ____________ respectively.

Entities and relationships are to be distinguished using the concept of ____________ ____________.

Object-based logical models are used for describing data at the ­­____________ and ____________ levels.

The three widely used record-based logical models are ____________ Model、____________ Model and ____________ Model.

Well known physical data models are ____________ model and ____________ ____________ model.