IB CompSci HL 1.1/1.2 System Design

Before a system is designed, what the new system should do needs to be identified

Systems analyst

Evaluation

Factors

(SA, E, F)

Systems analyst

Designed and analysed by them

Document how current system works

Surveys interviewing users, observing, tracing information

(D&A, D, S)

Evaluation of current system

What works fine, what doesn't?

Proposal for new system that increases productivity

(Good, bad, improvements)

Factors system analyst considers

What existing infrastructure can be used?

What requirements on hardware and software will the new system have?

Ethical issues (redundancy, loss of jobs, retraining)

(Existing, H&S, Ethics)

When developing a new system

How current system works

Provide requirements for the new system

Employee training

When considering change

Proper plan on implementation

Employee training

How new system will be implemented

Type of change over

(Plan, training, how, type - P, T, H, T)

Why does change need to be managed?

Ensure that changes are smoothly implemented

Benefits of change achieved

Focus on wider impact of change: How individuals move from current situation to new one

Simple process to major change (E.g. changes in policy, strategy to achieve potential)

(Smooth implementation. Benefits, Wider impact, simple to major change)

Legacy system

An old method, technology, computer system or application program that may or may not be supported/available for purchase anymore

Merger

Combination of two things (companies) into one

Complications in mergers

Language difference

Part of business operating in a different country than host using an older version of a system

Workers delegate, will laptops work in other departments?

Units

Software environment

(L, C, H, U, S)

Software as a service (Saas)

Client doesn't run its own computer system, but lends servers from the software manufacturer that are managed and maintained by the software manufacturer (E.g. Netflix)

Advantages of SaaS

No maintenance cost

Provide help in cases of malfunction

Maintenance and updates managed by software manufacturer

Client enjoys the professional know how of software manufacturer

(MC, M, M&U, P)

Disadvantages of SaaS

Data security issues from trusting your information to someone else (loss of control)

Host may be in different time zone so maintenance is inconvenient

User feedback hard to get if host is not user

(DS, TZ, UF)

Local vs Remote

Local hardware or use the cloud

Computing models offered in the cloud

Infrastructure as a service (IaaS)

Platform as a service (PaaS)

Software as a service (SaaS)

Networks as a service (NaaS)

(I, P, S, N)

Advantages of cloud computing

Convenience, Security, Back ups, Collaboration and Environmentally Friendly.

(C, S, B, C, EF)

Disadvantages of cloud computing

Security, Service outage, storage limits, slow speeds and limited features.

(S, SO, SL, S, LF)

Advantages of local computing

Security, Back up control, legacy software, software control and feature control.

(S, BU, LS, SC, FC)

Disadvantages of local computing

Cost of hardware, technical support and lack of collaboration

(CoH, TS, C)

Types of installations

Direct, Parallel, Pilot and Phased

(D, PPP)

Direct change over

Old system stopped and new system started

Advantages of direct change over

Minimal time and effort

New system is available immediately

(T&E, I)

Disadvantages of direct change over

If new system fails, no back up (BU)

Parallel change over

The new system is started but the old system is kept running alongside and data inputted into both systems

Advantages of parallel changeover

New system fails = old systems run as a back up

Outputs from the two systems can be compared to see if the new one is running correctly

(BU, CoO)

Disadvantages of parallel changeover

Running two systems is costly in terms of time and money

(T, M)

Pilot changeover

New system is trialed in a small part of business, once it's running correctly then new system is implemented across organisation

Advantages of pilot changeover

All features can be trialed

New system fails, only small part of organisation suffers - impact of fail

Staff who were part of pilot can train others

(T, I, ToO)

Disadvantages of pilot changeover

For the section that is piloting, if system fails there's no back up (BU)

Phased changeover

New system introduced in phases as parts of the old system are gradually replaced with new system

Advantages of phased changeover

Allows people to get used to new system

Training done in stages

(UC, T)

Disadvantages of phased changeover

If new part of system fails, no back up for that area (BU)

Problems with data migration

Incompatible file formats

Data structure differences

Validation rules

Incomplete data transfers

International conventions on data, currencies & character sets

(I [FF], DS, V, I, IC)

Importance of testing

Ensure system works

Systems that don't work decrease productivity and end user satisfaction

Two stages of testing

Before system is delivered (Alpha) and after it has been set up (Beta)

Alpha

Involved engineers developing system testing themselves

Beta

Involves testing by real users with real data

Types of testing

Alpha, Beta, White box (tracing data on paper as it proceeds through algorithm), Blackbox (Comparing input with expected outcome) and Debugging (Automatic program - Debugger)

(A, B, Wb, Bb, Db)

Importance of user documentation

Very crucial as it explains working of a system to user. Increases productivity and makes system implementation easier

(Explanation, Productivity, Implementation)

Requirements in user documentation

Hardware and Software requirements, Installation guide, How to start system and use different features, main features of systems, Example inputs and outputs, Error messages and troubleshooting guides and Information on how to contact developer of system.