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comp sci > 1.5 systems analysis > Flashcards

1.5 systems analysis Flashcards

1
Q

user documentation

A
  • describe how to use the system contents
  • detailed instructions on how to navigate, input data, produce reports
  • actions to take when error messages are produced
  • installation guide
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2
Q

maintenance documentation

A
  • be used by the og developer or by a different programmer at a future date
    contents
  • algorithms for all code which are unambiguous list of instructions to solve a problem (pseduo code or flow charts)
  • annotated listings which is the program code with comments
  • data dictionary is a file or printout containing descriptions of and other information about, the structure of the data system testing
  • variable list
  • subroutine list
  • class diagram
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3
Q

back up and recovery procedures

A
  • describe how and when data is/should be backed up and how to recover the data in event of loss
    contents
  • when data is backed up
  • where data is backed up
  • clerical procedures to follow after back up (eg. how to securely stored backed up data)
  • instructions or steps to recover data after loss
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4
Q

what is the waterfall approach

A
  • sequential process
  • developers draft the design of a system up front and it does not change
  • once the analysis and design stages are complete, developers cannot go back to make any changes
  • if the analysis or design of the project are inaccurate or incorrect in any way, the project will fail due to the rigidness of the waterfall methodology
  • requires less communication between the client and the developer
  • client input is only required during the analysis and at times the design stage
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5
Q

what is the agile approach

A
  • incremental approach to development
  • developers start with a simple project design and requirements
  • iterative approach as analysis and design relies on each other
  • analysis informs design and the design informs further analysis to be undertaken
  • changes can be made after each phase of development, analysis can be revisited and designs can be changed
  • strong communication between the client and the developer should be regular
  • clients are involved during all stages of development
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6
Q

what is decomposition

A
  • the process of breaking a complex problem down into smaller subproblems
  • these subproblems are easier to manage throughout the entire software development process
  • if a complex problem is not decomposed, the project will be too difficult to solve and become unmanageable
  • if a problem is too complex it is prone to errors, bugs and going over its initial costs
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7
Q

what is abstraction

A
  • the process of ignoring or removing specific information and data to allow developers to focus on the important details of a specific subproblem
  • allows developers to think about a problem in more general terms
  • allows developers to identify common solutions to the general problem they have abstracted
  • if a problem is not abstracted, the solution can become unnecessarily complicated
  • stops a solution becoming unnecessarily complicated
  • doesn’t solve problems but allows us to simplify them (for example: ‘the data will be sorted’ but without thinking about the method of sorting required - this will be dealt with later)
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8
Q

advantages of decomposition

A
  • different members of a team can work on different sub problems
  • makes maintenance easier
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9
Q

disadvantages of decomposition

A
  • may be difficult to combine the subproblems to solve the original problem
  • poorly understood problems are difficult to decompose
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10
Q

what is abstraction similar to

A

the ‘black box programming’ technique where we only need to know what a subroutine/procedure does and the parameter it requires and we do not need to know how to do it

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11
Q

extra advantages of agile

A
  • because the products are tested so thoroughly the product can be launched at the end of any cycle and is therefore, more likely to reach launch date
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12
Q

disadvantages of agile

A
  • needs a very good project manager to keep the project focused otherwise it could come in late and over budget - can be hard to establish a firm delivery data
  • the final project can be very different to what was initially intended
  • documentation is often neglected as working software usually takes priority over comprehensive documentation
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13
Q

explain the purpose of a feasibility study

A
  • is to decide whether a solution is possible and how it may be completed or to decide whether the current system can be replaced/ is worth replacing
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14
Q

what are the different stages of feasibility and what do they check

A
  • technical feasibility :
    • will the proposed system meet its objectives?
    • does the technology exist to allow the system to work?
  • social feasibility :
    • the effects on the employees and customers of the proposed system
    • unemployment, redundancies, retraining,
      relocation
    • consider customer service
  • legal feasibility :
    • are there any legal constraints that would prohibit
      aspects of the system (eg. will the system
      contravene the Data Protection act)
  • time feasibility :
    • can the system be implemented within the required
      time scale
  • cost effective :
    • costs include capital/development costs and
      running costs - should not over or under utilise
      developers, resources, methods and technologies
    • hardware and software should be researched to ensure it is cost effective
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15
Q

what are the 4 types of investigation methods

A
  • interview
  • observation
  • questionnaire
  • document collecting
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16
Q

what does observation involve, and what are the advantages and disadvantages

A
  • the analyst shadows employees of the customer, making notes on how to do their job

advantages:
- can actually see what is happening and do not have to rely on what people tell you they think is happening
- pick up parts of the system that are not immediately obvious to the customer
- confirm information gathered through different fact-finding methods
- the analyst sees parts of the system that employees may not realise are important or consider important to discuss

disadvantages:
- time consuming and expensive to carry out
- staff may feel they are being watched and act differently so you do not actually see what goes on every day
- cost of sending analysts around the world
- there is no guarantee that some of the more subtle parts of the system will show up during the observation period

17
Q

what does questionnaire involve, and what are the advantages and disadvantages

A
  • designing a questionnaire requires knowledge of the system to be built and the range of people who are the target audience for the questionnaire
  • can allow the analyst to get a range of responses on a specific subset of requirements

advantages:
- cheap to produce for a large number of people
- can be distributed worldwide
- could be completed online so results can be available very quickly
- can be anonymous - more honest responses
- cheaper than interviewing in terms of time spent gathering data

disadvantages:
- hard to create and design a good questionnaire (have to be designed by experts or information could be unusable)
- not all questionnaires sent out will be completed
- people don’t always take questionnaires seriously as interviews and may not give correct answers
- no follow up questions

18
Q

what does document collection involve, and what are the advantages and disadvantages

A
  • the analyst gathers any business documents that relate to the new system to be constructed (orders, invoices, financial records and any other document that it is use on a day to day basis)

advantages:
- analyst can see how the current system should be operating
- inexpensive method of gathering lots of information fairly quickly
- can identify storage requirements
- documents are reliable and show most of the data stored in the system and that data that is used

disadvantages:
- staff may not be following procedures in documentation and may be using system in their own way
- documentation may be out of date and not updated to reflect system changes
- documents give a limited view of the system and do not say how they were created
- documents may contain sensitive information and there may be restrictions on seeing them

19
Q

what does interviews involve, and what are the advantages and disadvantages

A
  • carefully planned to extract maximum amount of information about the current system
  • these can take place at all levels within the organisation are not just directed at management

advantages:
- can gather large amount of detailed information
- can make judgements on validity of information from personal contact or body language
- can ask follow up questions or open ended questions to gather more detailed information in selected areas

disadvantages:
- time consuming and expensive to carry out
- has to be carried out by trained interviewer or closed questions written by experts
- difficult to analyse large amount and wide variety of information

20
Q

what are the possible effects if increasing the use of computers in the work place

A
  • new jobs have been created
  • computers speed up the repetitive, boring parts of the jobs, leaving the people to do the creative, interesting parts
  • computers are cheaper to run, so have led to a reduction in the cost pf manufactured goods
  • repetitive job such as copying documents or stamping metal are carried out more reliably by computers
  • some jobs have disappeared completely
  • people worry about not being able to use new systems
  • learning new systems can take time
  • new computer systems can be expensive to install
  • teleworking/ video conferencing
21
Q

hardware selection criteria

A
  • hardware must meet requirements of proposed system
  • hardware must support current software
  • hardware must be upgradable and expandable to meet the needs of the next planning interval
22
Q

software selection criteria

A
  • software must meet requirements of proposed system
  • software must be compatible with the current and future hardware over the next planning interval
  • software must be standardised throughout the business to improve purchasing power, simplify training
23
Q

what is carried out in the design stage

A
  • design the data structures
  • files/ database structures
  • algorithms ( flowcharts or pseudo code for example)
  • user interface design
  • use prototyping to try out how the system might look and work long before it is complete
  • design the test data to be used (typical, extreme and erroneous)
  • all this needs to be implemented/coded by the programmers using suitable techniques such as annotation and self documenting code
24
Q

what is alpha testing

A
  • is conducted in-house by developers or highly skilled testers and occurs before the customer agrees to accept the final program
  • alpha builds are not shared with either the end user or with the customer
  • alpha builds are not final piece of software and often include limited functionality and many bugs
25
Q

what is beta testing

A
  • beta testing is conducted after alpha testing and later on in the software development life cycle
  • beta builds are shared with a limited number of end users to beta test the system with live data
  • beta builds contain all the main functionality but will still include some bugs
  • bugs reported by the beta testers are corrected by the development team
26
Q

what is acceptance testing

A
  • is the final phase of testing during the software development life cycle
  • is undertaken by the actual end users of the system with real data
  • the purpose is to ensure the system has met the original requirements and the specifications of the customer
27
Q

what is the changeover phase and what are the 4 methods

A
  • direct
  • pilot
  • phased
  • parallel
  • once a system has been designed, coded and tested, it needs to replace the old system
28
Q

describe the direct changeover

A
  • sudden change to new system
  • could be used where failure would not be catastrophic or most likely where there isn’t an existing system already
  • can be cheaper to implement
  • new system is available immediately if required
  • can be the least disruptive if implemented well
  • new system may not work as well until staff are fully used to using it
  • if new system fails, organisation have no system which could be costly or dangerous
29
Q

describe the pilot changeover

A
  • used by part of the organisation
  • a department is selected in the organisation and they run the new system while the remainder continue with the old system
  • all features of the new system can be fully trialed
  • if something goes wrong with the new system, only a small part of the organisation is affected
  • the staff who were part of the pilot scheme can help train other staff
  • all staff can focus on one area to resolve any problems
  • difficulties identified in one area can be resolved and managed in the next area
  • for the office / department doing the pilot, there is no backup system if things go wrong
  • might cause problems in the changeover period when they need to communicate with each other and have different systems
  • slower to get new system up and running compared to some other methods
30
Q

describe the parallel changeover

A

-both old and new system running at the same time
- the old system continues alongside the new system for weeks or months
- safest option as if new system fails, they still have the existing system
- often used for critical systems such as hospitals and banks
- new system is available immediately if required
- the outputs from the old and new systems can be compared to check that the new system is running correctly
- expensive as require temporary staff or overtime for current staff to operate both systems
- could cause confusion for staff/ customers having two systems

31
Q

describe the phased changeover

A
  • phasing in parts of the system
  • this is used with larger systems that can be broken down into individual modules that can be implemented separately at different times
  • it could also be used where for example only a few customer accounts are processed using the new system, while the rest remain for time on the old system
  • phased conversion could be direct or parallel
  • may be compatibility issues between the new and existing modules
  • allows users to gradually get used to the new system
  • staff training can be done in stages
  • all staff can focus on one area to resolve any problems
  • problems can be fixed quicker as more experts to resolve one functionality problem at a time
  • difficulties identified in one area can be resolved and managed in the next area
  • might cause problems in the changeover period when they need to communicate with each other and have different systems
  • slower to get new system up and running compared to some other methods
  • if a part of the new system fails, there is no back up system, so data can be lost
  • some systems cannot easily be broken down by functionality
32
Q

what is the maintenance phase and what are the 3 different types

A
  • maintenance starts from the day the new system begins to be used until the time when the system is no longer used
  • perfective, adaptive, corrective
33
Q

what is perfective maintenance

A
  • this type of maintenance improves the current system being used
  • making improvements that are not major enough to justify a new system
  • when the system functionality is improved
34
Q

what is adaptive maintenance

A
  • the current system being used is changed to suit new working requirements, for example, perhaps it is now a requirement to allow emails to be sent to customers
  • it could also be related to changes needed because of a new operating system version or hardware
  • when the system is changed to run on a new hardware or software platform
35
Q

what is corrective maintenance

A
  • this involves fixing errors found in the current system while it is being used
  • no substantial program code can claim to be ‘bug free’
  • some bugs can remain dormant for years only to be triggered by a specific event
  • others become immediately apparent
  • in any cases, corrective maintenance will attempt to eliminate these errors - this will involve recoding, but not changing the design of the system
  • fixing bugs that were not detected during development or system testing
36
Q

why are data flow diagrams useful

A
  • because of the central importance of data/ picture useful to ease complexity
  • makes it easier to understand

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