• DBMS is a collection of programs which enables the users to create and maintain a DB.

• DBS is constituted from a DB and a DBMS.

• Data elements
• Data type
• Data manipulation

• Self-contained Nature of a DBS:catalog(meta-data) - describes the structure of the primary database
• Insulation between programs and data: program data independence
• Data abstraction: conceptual representation of data
• Data model is a type of data abstraction that is used to provide the conceptual representation

• High cost of dbms
• Higher hardware costs
• Higher programming costs
• Higher conversion costs
• Slower processing of some applications
• Increased vulnerability
• More difficult recovery

• Create the views of DB

• Casual end users (middle or high level managers)
• Naive or parametric end users - use canned transactions (bank tellers)
• Sophisticated end users (engineers, scientists, business analysts)

• Develop and implement specifications for transactions

• Design and implement the dbms as a software package

• Design and implement software packages

Operators and maintenance personnel

Database schema - the description of a database.

Schema diagram - a displayed schema.

Schema construct - each object in the schema.

Database instance (occurrence of state) - the data in the database at a particular moment in time.

Schema diagram

Data Independence - a degree of independence or insulation of the correct functioning of an application program or query from a wide variety of changes in the logical and physical organization, access paths, and storage mapping of the database

• Logical data independence
• Physical data independence

• Single-user
• Multi-user

• Centralized
• Distributed
• Homogeneous
• Heterogeneous

• General
• Special

Director file
 

DIRNUMB	DIRNAME	DIRBORN	DIRDIED
1	Allen, Woody	1935	-
2	Hitchcock, Alfred	1899	1980
3	De Mille, Cecil B	1881	1959
4	Kubrick, Stanley	1928	-
5	Preminger, Otto	1906	-
6	Ford, John	1895	1973

Star file
 

STARNUM	STARNAME	BIRTHPLACE	STARBORN	STARDIED
1	Allen, Woody	New York	1935	-
2	Keaton, Diane	Los Angeles	1946	-
3	Sellers, Peter	Southsea, Eng.	1925	1980
4	Scott George C	Wise, Va.	1927	-
5	Mcdowell, M	Leeds, Eng	1943	-
6	Grant, Cary	Bristol, Eng	1904	1986

Movie file
 

MVNUM	MVTITLE	YEARMADE	MVTYPE	NUMNOMS	NUMADS	DIRNUM
1	Annie Hall	1977	com	5	4	1
2	Dr Strangelove	1964	com	4	0	5
3	Clockwork Orange	1971	sci-fi	3	0	5
4	Psycho	1960	horror	3	0	2
5	The Birds	1963	horror	0	0	2
6	Grapes of Wrath	1940	drama	4	2	7

Entities, Attributes and Relationships

Entity like a noun, a person, place or thing.

[eg for eloise they are directors, movies and movie stars]

Attribute this is a property of an entity. For the entity person, the list of attributes may include eye colour and height.

[for eloise the attributes of interest for the entity movie include movie title, type of movie, year of production etc.]

Examples of entities & attributes

Relationship - this is an association between entities.

For example there is an association between directors and movies.

A director is associated with all the movies she or he has directed, and a movie is associated with its director. i.e. A director is related to all the movies he or she had directed, and a movie is related to its director.

This is an example of a one-to-many relationship. One director is associated with many movies, but each movie is only associated with one director.

relationship

Here the relationship is represented by an arrow.

The 'one' part of the relationship, in this case director, is indicated by a single headed arrow, and the 'many' part of the relationship, in this case movie is indicated by a double-headed arrow.

We can use this knowledge to update our definition of a database.

A database is a structure that can house information about multiple types of entities, the attributes of these entities, and the relationships among the entities.