Transcript Introduction to Module

44220: Database Design & Implementation
Introduction to Module
Ian Perry
Room: C49
Ext.: 7287
E-mail: [email protected]
http://itsy.co.uk/ac/0506/sem2/44220_DDI/
The Structure of the Module

Database Design & Implementation is
concerned with three things:



Ian Perry
Why data storage (and information
retrieval) needs to be organised in some
manner.
How such a data storage system might be
designed in such a way that it is
demonstrably robust.
How such a design might be implemented
using a Relational DataBase Management
System (RDBMS).
44220: Database Design & Implementation: Introduction to Module
Slide 2
Lectures & Workshops
Mon, 1:15 (CG7)
18.
19.
20.
21.
22.
23.
24.
------------------- Tue, 11:15 (IT4)
Introduction to Module
Modelling the ‘Real’ World
Conceptual Data Modelling
ER Diagramming
Logical Data Modelling
Avoiding Data Anomalies
Review & Ass 1 Reqs.
18.
19.
20.
21.
22.
23.
24.
Information For All?
Modelling Exercises
Conceptual Modelling Ex.
Drawing ER Diagrams
Logical Modelling - Part 1
Logical Modelling - Part 2
Assignment 1 Support
[ Ass 1 Deadline – 01 Mar ]
Physical Data Modelling
Implementing Domains
Review & Ass 2 Reqs.
-- No Lecture --
26.
27.
28.
29.
26.
27.
28.
29.
MS Access – Workshop 1
MS Access – Workshop 2
Assignment 2 Support
Assignment 2 Support
----------------- Easter Break ----------------[ Ass 2 Deadline – 28 Apr ]
Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 3
Assessment – based on a Case Study

Learn-By-Post




Read the Case Study Carefully



… handles the assessment and examination of students who
are taking modules by mail order.
There are currently 12 modules on offer (there are plans to
increase this number to 18); with each student taking a
maximum of 3 modules per year.
Each module takes one year to complete, at the end of which
an examination is taken at one of five examination centres
around the country.
There is a lot more to it than you might think initially.
It would, therefore, pay you to re-read it from time to time.
Your database ‘solutions’ must be able to ‘answer’ 10
specific questions, e.g.:




Ian Perry
Who are our students?
What is the assessment/examination weighting for all of the
available modules?
Which students should be sent a certificate for module X?
Etc.
44220: Database Design & Implementation: Introduction to Module
Slide 4
Two Assignments

Assignment 1 (50%) – 01 March 2006
Develop and document an appropriate
Conceptual Data Model.
 Develop and document a robust Logical
Data Model.
Assignment 2 (50%) – 28 April 2006
 Implement your logical database model as a
Physical Data Model, using Microsoft
Access.
 Test this physical data model by building a
number of Database Queries, to make sure
that it ‘works’.


Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 5
Data & Information

Data?


A series of observations, measurements,
or facts.
Information?

Data that have been transformed into a
meaningful and useful form for people.
Data
Information
Process
(perhaps!)
Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 6
Information Attributes

Information (or do I mean data?) can be
thought of as having three dimensions:

Time


Content


Accuracy, Relevance, Completeness, etc.
Form


Timeliness, Currency, Frequency, etc.
Clarity, Detail, Order, Presentation, etc.
Information is often affected by more
than one of the above.
Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 7
Information = ?

Structure & Context
People tend to look for a familiar structure
& place data in a familiar context, e.g.:
120506:
=> DD/MM/YY = 12/05/06 = 12 May 2006.
 We use structure & context to transform
the data we receive into information.
Information = Data + Structure + Context
 The same data can be ‘interpreted’ as
different information if a different
structure and/or context is applied.


Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 8
To sum up so far!

Data  Information.


Information is a people thing, only they can:



Data are simply facts relating to ‘things’ like
events, transactions, etc.
determine the structure & context with which data
might become information.
and make decisions based upon the knowledge
gained by the possession of that information.
Must understand the difference between
Data & Information:

Ian Perry
in order to Design & Implement a Database System
that is both Efficient & Effective.
44220: Database Design & Implementation: Introduction to Module
Slide 9
Traditional Data Storage



Computing has often been introduced to organisations
in piecemeal manner.
With the addition of each new software application
comes the need to create a new set of files;
 containing that application’s required records.
 with each record containing that application’s
required fields.
 and each field storing an ‘important’ data item.
Over time the same data items will tend to be stored
again and again (and again?) in the file systems of
multiple applications:
 which leads to a number of problems!
Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 10
Data Redundancy

The repetition, in two or more files, of
the same data item.

There are an uncontrolled number of
copies, which is:
Expensive in Storage
 Expensive in Time

Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 11
Data Inconsistency

The problem of version control.

With many versions of the data likely:
Which one is the most up to date?
 Which one should I believe?


Destroys user confidence.
Very confusing.
 Potentially very expensive.

Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 12
Data Dependence

Applications and their data are ‘bound’
(i.e. stored) together.


Ian Perry
This doesn’t represent the way business
organisations need to use data.
The road to ‘information’ is impeded by
the binding ‘glue’.
44220: Database Design & Implementation: Introduction to Module
Slide 13
Data Sequencing

If (when?) we need to combine the data
from two, or more, business areas then
the physical HOWs can be complex.

Which often requires complicated
patching systems; in order to:
extract the data from one system.
 enter that data into the next.


In extreme cases this may mean:
printing out the data from one system.
 manually re-entering it into the next.

Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 14
A Database Approach

Take a holistic view of an organisation’s
information requirements, so that:


Laying a foundation of:



data is thought of as a pivotal, company
wide, resource.
shared, common, data in which all have
confidence.
with well maintained & controlled access to
that data.
In other words:

Ian Perry
a Database!
44220: Database Design & Implementation: Introduction to Module
Slide 15
Definitions

A database is:


A database management system
(DBMS) is:


an organised collection of data.
software designed to assist in maintaining
and utilising large collections of data.
A relational database management
system (RDBMS) is:

Ian Perry
a specific type of DBMS.
44220: Database Design & Implementation: Introduction to Module
Slide 16
What does a RDBMS do?

Main Features:




Data is stored independently of the means of
data manipulation.
Data addition, alteration, retrieval are all
controlled, consistent tasks.
Different users see different data collections.
Which gives us some advantages, i.e.:



Ian Perry
Minimal Data Redundancy (+ Data Consistency)
Data Independence (+ Data Flexibility)
Data Sharing (+/- Data Security)
44220: Database Design & Implementation: Introduction to Module
Slide 17
Why should we care?
“Data is only potential information; information is potential knowledge; and
knowledge is potential competitive advantage if it is used in a creative, flexible,
and above all, accurate way.” Adrian M (1990) Let’s Get Serious. Focus News. Winter.
Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 18