chapter 1 - software requirement fundamentals

8/10/2019 Chapter 1 - Software Requirement Fundamentals

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CHAPTER 1

SOFTWARE REQUIREMENTFUNDAMENTALS

ISS 2113 SOFTWARE REQUIREMENT

MDM. MARINA BINTI HASSAN, CTFL


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Requirements Determination

Objectives Understand how to create a requirements definition.Become familiar with requirements analysis techniques.Understand when to use each requirements analysistechnique.Understand how to gather requirements using interviews,JAD sessions, questionnaires, document analysis, andobservation.Understand when to use each requirements-gatheringtechnique.

ISS 2113 SOFT. REQ, CHAPTER 1 MDM. MARINA BINTI HASSAN, CTFL


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What is a Requirement

A requirement is a statement of what

the system must do orcharacteristics it must have written from businessperson perspective (what ofsystem) and sometimes called business or userrequirementslater in design, requirements become more

technical (how of system) and written fromdevelopers perspective. So sometimes calledsystem requirements



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What Are Requirements?

System Requirements :Functional requirementsNon-functional requirements

Functional Requirements the activities thesystem must performBusiness uses, functions the users carry outUse cases

Non-Functional Requirements other systemcharacteristicsConstraints and performance goals



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Product vision and project scope

Establish business requirements and align them with software requirements specs

Clear vision and scope lead to more focused requirements

Document contains 3 sections:Business requirements and contextProduct visionProject scope and limitations



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Business requirements and context

Brief description of the rationale and businessopportunity for the product to be developed.Main business objectives and some quantifiable

success criteria for financial or technical benefitsobjectives.

A quantifiable financial benefit is: The product helpsreduce customer support cost by 30% during the first

year of operations. A quantifiable technical benefit is: The average delay todeal with and service a customer complaint will bearound 8 hours.



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Business requirements and context (cont)

Risks associated with the business requirements andtheir management.

Risk assessment, prioritization, monitoring,mitigation and control. (Elaboration on thetechnical and non-technical project risks will beincluded in the software project plan document).

Description of the different types of product usersand other stakeholders.Context and environment in which the product will be operating.



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Product vision

Clear statement of the product goals.Capture the views of possibly many stakeholders and types ofusers

Identify main functionalities and product featuresList all the assumptions and dependencies



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Project scope and limitations

List functionalities and features to be included indifferent releases or versions of the product.

Scope for each release is developed in line with the

stakeholders objectives and priorities.Describe limitations - includes the functionalitiesand features that will not be provided by the productin any of its future releases.



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FURPS+ Requirements Acronym

Functional requirementsUsability requirements

R eliability requirementsPerformance requirements

Security requirements+ even more categories



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Requirements definition: Functional vs.Nonfunctional Requirements

Requirement definition report usually justcalled Requirement definition- is a straightforwardtext report that simply list the functional and

nonfunctional requirements in an outline format. A f u n ct i o n a l r eq u i r em en t relates directly to aprocess the system has to perform or information itneeds to contain.

N o n f u n ct i o n a l r eq u i r em en t s refer to behavioralproperties that the system must have, such asperformance and usability.



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FURPS+ Requirements Acronym


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System Requirements

System requirements specifications that define the newsystem

Functional requirements Activities system must perform (use cases) Based on procedures and business functions Documented in analysis models

Nonfunctional requirementsTechnical requirement hardware and software

Performance requirement workload measuresUsability requirement user interface, workflowReliability requirement outages, error detectionSecurity requirement access & protection



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Models and Modelling

Analyst describes information systemrequirements using a collection of models

Complex systems require more than one type

of model Models represent some aspect of the system

being built

Process of creating models helps analystclarify and refine design Models assist communication with system

usersISS 2113 SOFT. REQ, CHAPTER 1 MDM. MARINA BINTI HASSAN, CTFL


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Some Analysis and Design Models


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Reasons for Modelling



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Types of Models

Different types of models are used in informationsystems development

Mathematical formulas that describe

technical aspects of the system Descriptive narrative memos, reports, or lists

that describe aspects of the system Graphical diagrams and schematic

representations of some aspect of the system



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StakeholdersThe Source ofSystem Requirements

People with interest in successful systemimplementation

Three primary groups of stakeholders Users (use system) Clients (pay for and own system) Technical staff (ensure system operation)

Every type of stakeholder is identified byanalyst



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Stakeholders Who do you involve and talk to?

Stakeholders persons who have an interest in thesuccessful implementation of the systemInternal Stakeholders persons within theorganizationExternal stakeholders persons outside theorganizationOperational stakeholders persons who regularlyinteract with the system

Executive stakeholders persons who dont directlyinteract, but use the information or have financialinterest


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Avoid vague and unverifiable requirements whichdepend for their interpretation on subjective

judgment

This is critical for non-functional requirements

Quantifiable Requirements



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System Requirements and SoftwareRequirements

System requirements - are for the system as a whole; sometimes referred to as user requirements

Includes hardware, software, firmware, people,information, techniques, facilities, services, and othersupport elements

Software requirements derived from systemrequirements



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chapter 1 - software requirement fundamentals

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