Transcript Introduction to Module

44220: Database Design & Implementation
Introduction to Module
Ian Perry
Room: C41C
Ext.: 7287
E-mail: [email protected]
http://itsy.co.uk/ac/0809/sem2/44220_DDI/
The Structure of the Module
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The Database Design & Implementation
Module is concerned with three things:
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Ian Perry
Why data storage (and information
retrieval) needs to be organised in some
manner.
How a data storage system might be
designed in such a way that it is
demonstrably robust.
How such a robust design might be
implemented using a Relational DataBase
Management System (RDBMS).
44220: Database Design & Implementation: Introduction to Module
Slide 2
Lectures & Workshops
Fri, 10:15 (C17a) ------------------ Fri, 11:15 (IT3)
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Introduction to Module
Modelling the ‘Real’ World
Conceptual Data Modelling
ER Diagramming
Logical Data Modelling
Avoiding Data Anomalies
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Explore the DD&I Web-site
Modelling Exercises
Conceptual Modelling Ex.
Drawing ER Diagrams
Logical Modelling - Part 1
Logical Modelling - Part 2
[ Ass 1 Deadline – Wednesday, 18th of March ]
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Physical Data Modelling
Implementing Domains
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MS Access – Workshop 1
MS Access – Workshop 2
----------------- Easter Break ----------------30.
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Review & Ass 2 Reqs.
-- No Lecture –
-- No Lecture –
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Assignment 2 Support
Assignment 2 Support
Assignment 2 Support
[ Ass 2 Deadline – Wednesday, 13th of May ]
Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 3
Assessment – based on a Case Study
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Perry’s Newsagents
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Read the Case Study Carefully
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There is a lot more to it than you might think initially; and don’t
forget to re-read it from time to time.
Your Role
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Deliver a variety of Daily/Weekly/Monthly Newspapers and
Magazines to a large number of customers in the town of Beverley
(East Yorkshire).
You have been asked take part in the development of a Database
System for Perry’s Newsagents that can:
 record the Newspapers and/or Magazines supplied by specific
Suppliers.
 record Customer Orders for Newspapers and/or Magazines.
 plan the Daily Delivery of Newspapers and Magazines to
Customers.
Your database ‘solution’ MUST be able to ‘answer’ 10 specific
questions (i.e. at the end of the Case Study), e.g.:
A. What Newspapers & Magazines do we sell?
C. Which Newspapers & Magazines are supplied by Supplier X?
F. Which Newspapers and Magazines has Customer X ordered?
Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 4
Two Assignments
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Assignment 1 (50%) – 18th of March, 2009
Develop and document an appropriate
Conceptual Data Model.
 Develop and document a robust Logical
Data Model.
Assignment 2 (50%) – 13th of May, 2009
 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’.
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Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 5
Data & Information
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Data?
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A series of observations, measurements,
or facts.
Information?
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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
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Information (or do I mean data?) can be
thought of as having three dimensions:
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Time
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Content
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Accuracy, Relevance, Completeness, etc.
Form
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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 = ?
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Structure & Context
People tend to look for a familiar structure
& place data in a familiar context, e.g.:
120509:
=> DD/MM/YY = 12/05/09 = 12 May 2009
 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.
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44220: Database Design & Implementation: Introduction to Module
Slide 8
To sum up so far!
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Data  Information.
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Information is a people thing, only they can:
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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:
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in order to Design (Ass 1) & Implement (Ass 2) a
Database that is both Efficient & Effective.
44220: Database Design & Implementation: Introduction to Module
Slide 9
Traditional Data Storage
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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
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The repetition, in two or more files, of
the same data item.
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There are an uncontrolled number of
copies, which is:
Expensive in Storage
 Expensive in Time
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Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 11
Data Inconsistency
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The problem of version control.
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With many versions of the data likely:
Which one is the most up to date?
 Which one should I believe?
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Destroys user confidence.
Very confusing.
 Potentially very expensive.
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Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 12
Data Dependence
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Applications and their data are ‘bound’
(i.e. stored) together.
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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
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If (when?) we need to combine the data
from two, or more, business areas then
the physical HOWs can be complex.
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Which often requires complicated
patching systems; in order to:
extract the data from one system.
 enter that data into the next.
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In extreme cases this may mean:
printing out the data from one system.
 manually re-entering it into the next.
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Ian Perry
44220: Database Design & Implementation: Introduction to Module
Slide 14
A Database Approach
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Take a holistic view of an organisation’s
information requirements, so that:
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Laying a foundation of:
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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:
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a Database!
44220: Database Design & Implementation: Introduction to Module
Slide 15
Definitions
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A database is:
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A database management system
(DBMS) is:
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an organised collection of data.
software designed to assist in maintaining
and utilising large collections of data.
A relational database management
system (RDBMS) is:
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a specific type of DBMS.
44220: Database Design & Implementation: Introduction to Module
Slide 16
What does a RDBMS do?
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Main Features:
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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.:
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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