CSSE3002 Lecture Notes - Lecture 9: Fault Tree Analysis, Risk Management, Brainstorming
28 Jun 2018
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Lecture week 9A
Non-functional Requirements
- Specifically, what are the constraints of the system, what are the properties of the system
that needs to be ensured for the system to do what we expect it to do?
- Functional requirement: what system does (book a ticket)
- Non-functional requirement: usually applicable across many of the functional requirements
(security of transaction), constraints of the behaviour of the system (very important,
system could be a failure if it is not achieved)
NFR Sources
Categorise them: based on where they come from
Product requirements: requirements of the product or constraints and behaviour
of product (encryption of data, security of transaction, execution speed, reliability,
privacy of access)
Process requirements: how we do the project, revolve around the development
process, standards we need to follow, procedures that need to be put in place,
implementing requirements
External requirements: things that are external to the direct impact of the system
(e.g. talking to another system, using API format that must be used etc) something
that is decided by external party and that needs to be follows (little to no control
over it)
Could also break down the three types of requirements
Process Requirements:
Standards: must conform to a particular standard
Implementation: must use a particular language/database/coding standard
Delivery: things that must be demonstrated (with a particfular fashion
Product Requirements:
Usability: human engineering factor, how easy it is to use, how easy to adapt to diff
situation
Efficiency: performance/ space (slides are connected wrongly)
Performance: Memory limitations, time limitations
e.g. must be able to complete this task in 0.01sec, able to handle concurrency
Space: main memory/ secondary memory
Reliability: how likely it is to not fail/ is it always available when user needs it
find more resources at oneclass.com
find more resources at oneclass.com
Portability: implemented the system in a particular platform, expect it to be able to
work in other platforms as well (e.g. mobile phone, PC, tablet)
External requirements
Legislative: all big international companies have to ensure their system stores data
in a way that is required and the privacy also impacts on how you disclose
information, how you sort and what you do with the data - needs to be secure, terms
and condition needs to update to customers
Interoperability: interact with another system, another system already exist, means
have to conform to the interface that is provided to you
Cost: how much money you’ve got for your budget, a constraint
NFR Examples
Product requirement: must use HTML5, only some javascript libraries can be used
Process requirement: must follow a particular process, usually machine critical or
safety critical systems, organisational or national or international standards that are
critical, must follow the standard. (climate control system for the metro system in
Hong Kong, must follow railway safety standard, although there are a lot of rules)
External requirement: who can access what kind of data (role-based requirements)
Verifiable
Have to be able to test (describe it in a testable fashion)
Non-functional requirements have to be measurable in order to verify
Measures
Things that needs to be measured
Speed: things that are used to determine the appropriate response time or
performance of the system (how quickly system responses, how quickly the UI
responses)
Size: How much space are you allowed to use, how much memory
Ease of use: training time, amount of support/help material, no of errors after
training or all types of things we use to measure ease of use
Reliability: availability/ probability of failure
Robustness: when it doesn’t do what it should do, what will happen? Being
able to cater for disastrous events (e.g. live backup system, restart after crash)
Requirements Conflicts
Conflict occurs because different stakeholders want different things or want similar
things in a different way. Have to negotiate between stakeholders because it is not
easy to do both (more expensive)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Functional requirement: what system does (book a ticket) Non-functional requirement: usually applicable across many of the functional requirements (security of transaction), constraints of the behaviour of the system (very important, system could be a failure if it is not achieved) Categorise them: based on where they come from. Product requirements: requirements of the product or constraints and behaviour of product (encryption of data, security of transaction, execution speed, reliability, privacy of access) Process requirements: how we do the project, revolve around the development process, standards we need to follow, procedures that need to be put in place, implementing requirements. Could also break down the three types of requirements. Standards: must conform to a particular standard. Delivery: things that must be demonstrated (with a particfular fashion. Usability: human engineering factor, how easy it is to use, how easy to adapt to diff situation.
