Block 2, Part 3: The Database Context

Question 1

What is an information system?

Answer 1

A collection of hardware, software and processes that enables organisations to manage and process data and to produce information.

Question 2

What constitutes the processing of data?

Answer 2

Any activity involved in collecting, filtering, integrating and exploring the data.

Question 3

What is a replicated database?

Answer 3

A single database whose contents are replicated to multiple server sites, allowing ‘local’ access requests to a copy of the data.

Question 4

What is a federated database?

Answer 4

A collection of DBMSs on multiple servers that collectively manage data content.

Question 5

What is a relational database?

Answer 5

A DBMS built on the relational model of data, typically using SQL for data definition, control and access.

Question 6

What is a non-relational database?

Answer 6

A DBMS using non-relational models of data - hierarchical, object-oriented, etc.

Question 7

What is the domain of discourse?

Answer 7

The collection of data that is significant to an organisation.

Question 8

What is meant by ‘persistent data’?

Answer 8

Data is held in long-term storage and endures beyond the execution time of the software that manages and accesses it.

Question 9

What is meant by ‘shared data’?

Answer 9

Data is available to multiple processes.

Question 10

What is meant by ‘interrelated data’?

Answer 10

Individual data elements held in the database can be managed and processes as collections.

Question 11

What is a database management system?

Answer 11

Any software system that manages one or more databases.

Question 12

What is a schema?

Answer 12

A data definition that describes a data collection.

Question 13

What is a logical schema?

Answer 13

A schema which defines the logical properties of data in a database - the representation and associated constraints.

Question 14

How many logical schemas does a database have?

Answer 14

Just one.

Question 15

What does a logical schema comprise in a relational database?

Answer 15

The relational tables, the logical links between them (foreign keys), and any constraints on the data values.

Question 16

What is a storage schema?

Answer 16

A schema that defines how a database is stored in files and accessed, which must relate to the definitions in a logical schema (via a mapping).

Question 17

How many storage schemas does a database have?

Answer 17

Just one.

Question 18

What is an external schema?

Answer 18

A schema which defines data accessible through the DBMS for a specifies group of user processes, which must relate to the definitions in a logical schema (via a mapping).

Question 19

How many external schemas does a database have?

Answer 19

There can be several external schemas, depending on the differing needs of the users and applications.

Question 20

When does logical data independence exist?

Answer 20

When a change to a logical schema has no impact on application code.

Question 21

When does physical data independence exist?

Answer 21

When a change to the storage schema has no impact on the applications.