31271 Lecture Notes - Lecture 1: Meed, Business Rule, Conceptual Schema
Lecture 1: Introduction to DBMS and Data Modelling Part 1
Database Development (Basic Concepts)
• Data is stored representations of objects and events that have meaning and
ipotae i the use’s eioet. There are two types of data:
o Structured – numbers, text, dates
o Unstructured – images, video, documents
o Structured data refers to facts related to objects and events of importance
i the use’s eioet ad epeset the taditioal data that is easily
stored and retrieved in traditional databases and data warehouses.
Unstructured data refers to multimedia data, such as images, sound and
ideo segets that ae o stoed as pat of the use’s usiess
environment.
• Metadata is data that describes the properties or characteristics of end-user data
and the context of that data. Essentially, it is data about data.
• Information is data that has been processed in such a way to increase the
knowledge of the user. It creates useful information for the company who is after
the data. Eg. graphical displays turn data into useful information that managers can
use for decision making and interpretation.
• Data consist of facts, text, and other multimedia objects, while information is data
that have been processed in such a way that it can increase the knowledge of the
person who uses it.
Why Databases & Intro to DBMS
• Traditional file processing systems create duplicate data, and the use of a database
allows centralisation of data, removing the chance of these duplicates as well as any
issues that might arise from duplicate data. The duplication of data is wasteful as
well, as it requires additional storage space and an increased effort to keep all files
up to date. This can lead to compromises in data integrity.
• A database is an organized collection of logically related data.
• Other disadvantages of traditional file processing systems include:
o Program data dependence – all programs maintain metadata for each file
they use
▪ If there are files which rely on other files, a single change to the
master file would result in the other files all being altered to align
with the changes. However, if there are many connections it would
be difficult to locate all the files/programs which are affected by the
changes.
o Limited Data Sharing – no centralized control of data
▪ In the traditional approach, each application would have its own
private files, in their own format. This means that if a manger
requested a report, there would be a major programming effort to
draw data from several incompatible files in separate systems.
o Lengthy development times – programmers must design their own file
formats
▪ Traditional file processing systems require developers to start from
scratch by designing new file formats and descriptions, and then
writing the file access logic for each new program. These
deelopet ties ae iosistet ith today’s fast paed
business environment, in which time to market is a key business
success factor.
find more resources at oneclass.com
find more resources at oneclass.com
o Excessive Program Maintenance – 80% of information systems budget
devoted to maintenance.
▪ All of the above issues contributed to the heavy program
maintenance required from organizations which relied on a file
processing system.
• Further issues of data redundancy (duplication of data) can result from the use of
spreadsheets rather than databases. In a spreadsheet, each row is intended to stand
on its own. As a result, the same information may be entered several times. The way
to fix this is to use two tables with a One-to Many relationship which is linked by a
Foreign Key.
• The problem with storing redundant data is that when you delete data, you may
delete some but not all instances of the data. When you update, you may only be
updating some and not all instances. And when you insert new data, multiple data
entry can introduce inconsistency. Also, it is very important to note that multiple
data entry is expensive!
• Thus arose the database approach, which has a central repository of shared data
which is managed by a controlling agent and stored in a standardized, convenient
form.
• A database requires a database management system, which is a software system
used to define, create, maintain a database, and provide controlled access to user
databases. It is the connection between the database and various systems in place.
• A database application is an application program that is used to perform a series of
database activities (create, read, update and delete) on behalf of database users.
• Advantages of this approach include:
o Program-data independence – allos a ogaizatio’s data to hage ad
evolve without changing the application programs that process the data.
o Planned data redundancy – good database design attempts to integrate
previously separate data files into a single, logical structure. Ideally, each
primary fact is recorded in only one place in the database.
o Improved data consistency – by eliminating or controlling data redundancy,
the opportunity for inconsistency is greatly reduced.
o Improved data sharing – a database is designed to be a shared corporate
resource which allows other users access.
o Increased application development productivity – database approach
greatly reduces cost and time for developing new business applications thus
increasing productivity
o Enforcement of standards – the data repository provides database
administrators with a powerful set of tools for developing and enforcing
standards that have been established. However, the failure to implement a
strong database admin function is the most common source of database
failures within organisations.
o Improved data quality – the database approach provides a number of tools
and processes to improve data quality.
o Improved data accessibility and responsiveness – end users without
programming experience can often retrieve and display data, even when
they cross traditional departmental boundaries.
o Reduced Program Maintenance – stored data must be changed frequently
for a variety of reasons: new data item types are added, data formats are
changed etc. Due to the way that file processing environments work,
changes to data formats and access methods inevitable resulted in the meed
find more resources at oneclass.com
find more resources at oneclass.com
to modify the application programs. However, in a database environment
data is more independent of the programs that use them.
o Improved decision support – Some databases are designed expressly for
decision support applications.
• Costs and risks of database approach:
o New, specialised personnel – often, organizations that implement the
database approach have to hire new personnel that are skilled in the area of
database management in order to reap the benefits of the new approach.
Further, because of rapid changes to technology, employees will have to be
constantly retrained or upgraded to keep up.
o Installation and management cost and complexity – initial set up cost of
multiuser database management systems are high, and require staff and
trained personnel to install and operate it. Additionally, complex additional
software may be needed to provide security and ensure concurrent updates
of shared data.
o Conversion Costs – the cost of converting older systems to modern database
technology is often seen as extravagant and prohibitive.
o Need for explicit backup and recovery – Comprehensive procedures are
required to provide backup copies of data and for restoring the database
when damage occurs, as shared corporate databases must be accurate and
available at all times.
o Organizational conflict – shared databases require a consensus on data
definitions and ownership, as well as the responsibilities for accurate data
maintenance. It has been found that these are often difficult issues to
resolve when disputes arise.
Components of the Database Environment
▪ There are nine major components of a typical database environment:
o Data modelling and design tools – automated tools used to design databases
and application programs.
o Repository – centralized storehouse of metadata
o Database Management System (DBMS) – software system for managing the
database.
o Database – storehouse of the data. It is the organized collection of logically
related data.
o Application Programs – Software using the data that maintains the database
and provides information to users.
o User Interface – text, graphical displays, menus etc. for the user
o Data/Database Administrators – personnel responsible for maintaining the
database.
o System Developers – personnel responsible for designing databases and
software.
o End Users – people who use the applications and databases.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 1: introduction to dbms and data modelling part 1. Information is data that has been processed in such a way to increase the knowledge of the user. It creates useful information for the company who is after the data. The duplication of data is wasteful as well, as it requires additional storage space and an increased effort to keep all files up to date. If there are files which rely on other files, a single change to the master file would result in the other files all being altered to align with the changes. However, if there are many connections it would be difficult to locate all the files/programs which are affected by the changes: limited data sharing no centralized control of data. In the traditional approach, each application would have its own private files, in their own format. In a spreadsheet, each row is intended to stand on its own.
