Introduction to Databases & their Environment
• A file based system is a collection of application
programs that perform services for the users wishing to
access information.
• Each program within a file based system defines and
manages its own data. Because of this, there are limits
as to how that data can be used or transported.
• File based systems were developed as better
alternatives to paper based filing systems.
• By having files stored on computers, the data could be
accessed more efficiently. It was common practice for
larger companies to have each of its departments
looking after its own data.
,
, Limitations of File-based Approach
• Separation and isolation of data
– Each program maintains its own set of data.
– Users of one program may be unaware of potentially useful data held by other programs.
• Duplication of data
– Same data is held by different programs.
– Wasted space and potentially different values and/or different formats for the same item.
• Data dependence
– File structure is defined in the program code.
• Incompatible file formats
– Programs are written in different languages, and so cannot easily access each others files.
• Fixed Queries/Proliferation of application programs
• Programs are written to satisfy particular functions. Any new requirement needs a
new program
, Various Database definitions
• DB:
– Shared collection of logically related data (and a description of this
data), designed to meet the information needs of an organization.
– System catalog (metadata) provides description of data to enable
program–data independence.
– Logically related data comprises entities, attributes, and relationships
of an organization's information.
• DBMS:
– A software system that enables users to define, create, and maintain
the database and which provides controlled access to this database.
• DBMS is the software that interacts with the users’ application
programs and the data
• A file based system is a collection of application
programs that perform services for the users wishing to
access information.
• Each program within a file based system defines and
manages its own data. Because of this, there are limits
as to how that data can be used or transported.
• File based systems were developed as better
alternatives to paper based filing systems.
• By having files stored on computers, the data could be
accessed more efficiently. It was common practice for
larger companies to have each of its departments
looking after its own data.
,
, Limitations of File-based Approach
• Separation and isolation of data
– Each program maintains its own set of data.
– Users of one program may be unaware of potentially useful data held by other programs.
• Duplication of data
– Same data is held by different programs.
– Wasted space and potentially different values and/or different formats for the same item.
• Data dependence
– File structure is defined in the program code.
• Incompatible file formats
– Programs are written in different languages, and so cannot easily access each others files.
• Fixed Queries/Proliferation of application programs
• Programs are written to satisfy particular functions. Any new requirement needs a
new program
, Various Database definitions
• DB:
– Shared collection of logically related data (and a description of this
data), designed to meet the information needs of an organization.
– System catalog (metadata) provides description of data to enable
program–data independence.
– Logically related data comprises entities, attributes, and relationships
of an organization's information.
• DBMS:
– A software system that enables users to define, create, and maintain
the database and which provides controlled access to this database.
• DBMS is the software that interacts with the users’ application
programs and the data
