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Lecture 7

Database requirements

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When asked if the change created in the clients work environment by the IT project led to problems for RD answered,

“Yes, problems. Advancing technology erodes certain skills. In reality - fundamentals remain the same, management depends a good understanding of concepts and should not be technology tied. The real risk to good systems is rooted in the ease of use of applications, not their difficulty. This encourages rapid development of applications with insufficient analysis. The old guard “Analyst” is often forgotten, the process as a discrete job may be defunct - but the process as a process is still crucial.” [Extract of Interview with Technical Director R.D June 1999]

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RequirementsIs there an existing system?What can improve that system?

Hardware? Software? Process re-engineering?

Chance for improvement But is that within your remit?

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Requirements data

QuestionnairesGroup discussions

Joint Application Design (JAD)Interviews Action research

Pre-understanding Using consultancy to do research More methodology

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RequirementsConversion of medium

Existing forms

Awareness of custom end user ‘information systems’Defn: All users of computers by people in organizations

who are not Information Systems professionals. Purchase, development, operation of CBIS by users

rather than an IS department

Look for duplication, redundancy in existing processes

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Data characteristicsWhat form is it in?Conversion?Is the data item necessary?

E.g. recent debate by MSP’s on salary, language, religion for census

Values, range, size of data fields Remember VARCHAR(5), NULL, MAX,

MIN etc.

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Data characteristics

Length of time period of storage

Permissions to access DBA User hierarchy Personnel records

Data protection

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Operational requirementsHow large, how many usersPhysical location of the users,

connection via Local Area Network (LAN) Wide Area Network (WAN) Dial up connection (infrequent use)

Location of data

9Figure 2. A typical Local Area Network (LAN) configuration in a medical practice

Client PCs attached to the central server by category 5 twisted pair cableEthernet LAN

technology for the PC to server connection.

Uninterrupted Power Supply: In the event of a power cut allows enough time for a controlled shut down of the system

Server: manages network resources and controls user access to GPASS application. Also carries out regular data backups to tape drive.

Printers: one line printer for printing prescriptions and a general purpose laser for admin.

Hub the server to network cables connection point

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Operational requirements

Support for hardware and softwareCostType of use

Varying queries Static queries

Service Level Agreements See example

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User Phoned Back 80% within 2 hours 95% within 3 hours 100% within 4 hours‘Critical’ Site Visit 75% within 3 hours 90% within 5hours 100% within 8 hours‘Sub-Critical’ Site Visit 75% within 4 hours 90% within 6 hours 100% within 8 hours‘Critical’ systems reinstatement 75% within 3 hours 90% within 6 hours 100% within 8 hours‘Sub-Critical’ systems reinstatement 75% within 4 hours 90% within 6 hours 100% within 8 hours

Service Level Targets ( the response that IT company aim to meet or exceed)

Level Of Support

Example of level of support from actual IT company

Should be measurable in practice

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Area in which networks have been implemented and

supported

The geographical area covered (in this case) has determined the SLA shown in the previous slide

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Operational requirementsResponse time for queriesReliability (MTBF)Security

Prevention of unauthorised access Back up of data Restoration of data

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Naming (Dowling)

Avoid ambiguityAvoid abbreviationsAvoid generic names ? On the end of data values denotes a

yes/no questionCross reference if that is the only optionUse a naming convention

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Next weekCreating the Data ModelE-R DiagramsNormalisationOther Reading

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