Lecture 7 and 8 Databases and Information Management

8/12/2019 Lecture 7 and 8 Databases and Information Management

1/33


2/33

The need for a database

solution

Organisations have to collate, process and

output vast amounts of data and information

Manual or multiple system options not viablewhen dealing with possibly millions of

customers in a global market

Need for accessible informationtouch of a

button/key Need for up-to-date information

Need for information security


3/33

The need for structure Our ability to use data improves when we

introduce more structure in how data is stored. The need to go through all the data to reach a

specific item or customer is now not arequirement.

The more the structure, the easier to sift or minethrough large amounts of data.

Think of a structure as an address. The moreprecise the address we have, the easier it is to find

the associated data. Similarly the structure of the data tells the system

where to look for data and avoid unnecessaryeffort.


4/33

Structure example Ever wondered why an Internet search can

return the addresses of home pages thatcontain a word so quickly.

The answer is because the addresses arestored under a list of words arrangedalphabetically.

When you enter a word, the computer jumpsto the appropriate row of the Table without

any processing of information in other rows. Thus, it is possible to peruse very large

databases in a fraction of a second.


5/33

Database models and

structures

There are four main types of databases:

flat

relational

hierarchical

distributed


6/33

Flat structure databases Flat data models have the least amount of

structure. They typically take the form of onelarge table, where the first row is the list of thevariables and subsequent rows are data

Each case has a row of data

Many statisticians use flat models

Advantages

Most software include free access to flat datafiles. For a small number of cases, flatdatabases do a reasonably fast job


7/33

Flat structure databases

Disadvantages

Flat databases waste computer storageas it is required to keep information onitems that logically cannot be available.

For example, if information onpostcodes/zip codes is required, flat files

require us to enter missing information forzip codes in foreign countries.


8/33


Hierarchical and structural databasesavoid this problem by defining different

tables for classes of countries in whichpost/zip code is not available.

Thus flat files keep large sparse data full ofmissing information.

When the size of database is large, searchthrough the data takes a long time


9/33

Flat structure databases Flat databases are not conducive to complicated

search queries that divide the database further.

For example, in a flat file about students it wouldbe difficult to find all students that live in a certainpost/zip code that have received a grade C.

Such a query will require repeated pass throughthe data.

First pass may identify all students who live in a

post/zip code, second pass may identify allstudents who have a grade C and the third passmay find students in both groups


10/33


Such multiple passes through data areinefficient and take a long time:

Since every simple ifstatement (ifpost/zipcode is equal to SE1 then ...) takes afraction of a secondeach subsequentsearch accumulates more time

Efficient search methods are important forlarge databases


11/33

Flat structure database

example

Student ID Name Mid termgrade

Finalgrade

Address Post/zipcode

... .....

4561 Alison Safaie B A 13 Manor Park SE1 ... ... ..

7878 Mike Smith C B 24 Curzon Street NW14 ... ... ..

8954 SherifMohamed

A C 21a High Street NW14 ... ... ..

Table 1: Example of a flat file


12/33


13/33

Relational databases This information in essence says that the patient ID

number, name and medical record numberbelong to the same person.

To effectively store both information items and therelationships among these items, relational data iskept in table formats.

The first row of the table shows the name of thevariables and subsequent rows are data. All itemsin the same row usually belong to the same case

and are related. One column of the table istreated as the key to the table. Numbers orcharacters in this column corresponds to items inother tables. Thus it is possible to move from onetable to another.


14/33

Relational databases

StudentID

Keycolumn

Name Mid-term

Final

4561 AlisonGhadiri

B A

7878 Mike Smith C B

8954 SherifMohamed

A C

Table 2: Table for "Students grades"

StudentID

Keycolumn

Address Post/zip code

4561 13 Manor Park SE1

7878 24 CurzonStreet

NW14

8954 21a HighStreet NW14

Table 3: "Students' contact information

ExampleHere is an example of a Table ofgrades for the example introducedunder flat files

This is an example of an additional tablefor contact information:


15/33

Relational database queries

When a query is made, the relationaldatabase searches through its tables to find

the answer. Often the answer involves information pooled

together from different tables.

For example, a query for names of peoplewith grade of A, can be answered from the

table of grades. The query for grades ofpeople in post/zip code area NW14 must beanswered from both tables.


16/33


17/33

Hierarchical databases Hierarchical database models are one type

of relational data models based on a parent-

child relationship Hierarchical database models resemble al

tree structure

Example

The file directory on your desktop is an

example of a hierarchical database system. A folder may contains other folders which may

contain other files, which contain data.


18/33

Hierarchical databases

advantages

In hierarchical models, children inherit therelationships and characteristics of theirparents.

An operation on the parent affects thechildren; if you tell the computer to do anoperation on a folder, the operation affectsall the folders/children and files that itcontains.

For example, if you delete the top folder, youwould delete all of the folders and files itcontains. This feature saves time for theperson maintaining the files.


19/33

Distributed databases Most databases physically reside in one

place. They may be backed up to another placebut the elements of the database are notmaintained in different places.

In a distributed database, data is kept in differentsettings and on different computers. One orseveral central computers maintain indexes towhere the data is. Using the address of the data

computers can then communicate and find theinformation needed.

Distributed databases need not only addresses forwhere the data is but they also need an audit trailof who has updated data or retrieved it.


20/33

Distributed databases Audit data is needed in order to pinpoint errors in

the system and in order to understand whereconfidentiality of the system breaks down.

When a computer requests data from another, anaudit trail is created by storing who sent the datawhere and when.

When this computer passes the data to another,the information needs to be updated in theoriginal computer.

As the number of computers receiving the dataincreases the task of auditing becomes moredifficult.


21/33

Distributed database example

A good example of a distributed database isWorld Wide Web pages. These pages of data arekept on a different computers, often referred to asWeb servers.

The address of each file is the location addressyou enter when you want to see the page. Thislocation address is an index to the Web pages.

Centralised computers keep the beginning of

these addresses, called domains. Subsequent detailed addresses are kept at the

Web servers.


22/33

Distributed database searches

When searching a distributed database, two stepsmust occur.

First a program, sometimes called crawler, mustindex the content of the databases, then anotherprogram, often called a search engine, wouldsearch the index for your request.

When a match is found, the index is used to findthe address of the information. This address is

provided to the engine that assembles a list foryou.

When you click on the items identified by thesearch engine, you use the address to retrieve thedata items it has found.


23/33

Database considerations for

an organisation

In terms of database management anorganisation has to consider the following:

How to store their datawhichmodel/approach

Data security

Cost of a DBMS (database management

system) initial and maintenanceCentralised or de-centralised approach


24/33

Data considerations for an

organisation What suits there needs, size and works with their

business processes and functions How is the data going to be stored on a single

DBMS or distributed across a number of databases(centralised v decentralised approach)

How to protect the data from internal andexternal threatshackers, viruses, natural disasters,incompetence of end users

Cost of design, implementation, management of

the systemneed for a database manager oradministrator(s)

Decentralised or centralised approach (see nextslides)


25/33

Decentralised or centralised?

Decentralised databases exchange files andtherefore may exchange corrupted files or

viruses that may affect the entiresystem. Security of these databases aredifficult to maintain.

In decentralised databases the type of datato be exchanged, the process of addressingthe data, and the protocol for updating thedata must be agreed upon ahead of timeand plans must be in place for updating theprocess.


26/33


27/33


28/33

Data-less information systems A data-less information system contains no

centralised data and relies on distributeddatabases.

The Data-less Information System relies on rapidcommunication to construct the data at the pointof need for the data.

A data-less information system also does notrequire any additional hardware; instead it relieson the hardware of existing organisations and

institutions. e.g. Wavenet relying on weather and climate

systems around the world


29/33

Components of a data-less IS

There are three components to a data-less information system:

Decoder

Communicator

Analysis


30/33

Decoder This software resides in the database of

participating organisations. It reads andanalyses the structure of the other systems

records. It uses known characteristics of the data,

national and international standard of data,and the supplied format of the data todecipher the format and structure of thedata.

When it is finished understanding the structureof the data, it sends a message to other unitsacknowledging participation


31/33

Communicator This software resides in the database of participating

organisations systems. I

It verifies any consent that is required (if required e.g.

patient medical records), the nature of data to becollected, and the systems suggestion about whereto look for the data.

This software contacts all sites that have a reportingdecoder and collects the necessary information,including the possibility of different possibleinterpretation of the same data at different sites. The

data collected by the software is for one time useand would be erased after the use.


32/33


33/33

Lecture 7 and 8 Databases and Information Management

Documents

Transcript of Lecture 7 and 8 Databases and Information Management