Page 107 - DCAP516_COMPUTER_SECURITY

Unit 8: Introduction to Databases

File manager: manages allocation of disk space and data structures used to represent Notes
information on disk.
Database manager: The interface between low-level data and application programs and
queries.
Query processor: translates statements in a query language into low-level instructions the
database manager understands (May also attempt to find an equivalent but more efficient
form).
DML pre-compiler: converts DML statements embedded in an application program to normal
procedure calls in a host language. The pre-compiler interacts with the query processor.
DDL compiler: converts DDL statements to a set of tables containing metadata stored in a
data dictionary.
In addition, several data structures are required for physical system implementation:
Data files: store the database itself.
Data dictionary: stores information about the structure of the database. It is used heavily.
Great emphasis should be placed on developing a good design and efficient implementation
of the dictionary.

Indices: provide fast access to data items holding particular values.

Self Assessment

Give one word for following:
7. A program that converts DDL statements to a set of tables containing metadata stored in
a data dictionary.
8. A place that stores information about the structure of the database.
9. The interface between low-level data and application programs and queries.
10. A processor that translates statements in a query language into low-level instructions the
database manager understands.
11. A program that converts DML statements embedded in an application program to normal
procedure calls in a host language.
8.21 Summary

Information and data are different. Information is understood by a person. Data are values
stored on a passive medium like a computer disk. The purpose of a database management
system (DBMS) is to bridge the gap between information and data - the data stored in
memory or on disk must be converted to usable information.

A database is a model of a real world system. The contents (sometimes called the extension)
of a database represent the state of what is being modeled. Changes in the database
represent events occurring in the environment that change the state of what is being
modeled. It is appropriate to structure a database to mirror what it is intended to model.

The basic processes that are supported by a DBMS are:
Specification of data types, structures and constraints to be considered in an
application.

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