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Requirements Analysis & Requirements Specification. Originally developed by Michael Madigan StorageTek Manager, PAL Engineering Software Engineering of Standalone Programs University of Colorado, Boulder. Requirements Engineering . Requirements Engineering. Requirements Elicitation.

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Requirements Analysis & Requirements Specification


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requirements analysis requirements specification

Requirements Analysis&Requirements Specification

Originally developed by Michael Madigan

StorageTek

Manager, PAL Engineering

Software Engineering of Standalone Programs

University of Colorado, Boulder

requirements engineering
Requirements Engineering

Requirements Engineering

Requirements Elicitation

Requirements Analysis

Requirements Verification

Requirements Specification

Requirements Management

requirements analysis specification definitions
Requirements Analysis & Specification Definitions
  • Requirements Analysis
    • The process of studying and analyzing the customer and the user/stakeholder needs to arrive at a definition of software requirements.1
  • Requirements Specification
    • A document that clearly and precisely* describes, each of the essential requirements of the software and the external interfaces.
      • (functions, performance, design constraint, and quality attributes)
    • Each requirement is defined in such a way that its achievement is capable of being objectively verified by a prescribed method; for example inspection, demonstration, analysis, or test.2
types of requirements
Types of Requirements
  • Functional requirements
  • Performance requirements
    • Speed, accuracy, frequency, throughput
  • External interface requirements
  • Design constraints
    • Requirements are usually about “what”, this is a “how”.
  • Quality attributes
    • i.e. reliability, portability, maintainability, supportability
what vs how dilemma 3
What vs. How Dilemma3

User Needs

WhatHow

System Requirements

WhatHow

System Design

WhatHow

SoftwareRequirements

WhatHow

SoftwareDesign

software quality attributes 4
Software Quality Attributes4
  • Correctness
  • Reliability
    • Rating = 1 – (Num Errors/ Num LOC)
    • Can be allocated to subsystems
  • Efficiency
  • Integrity
  • Usability
  • Survivability
  • Maintainability
  • Verifiability
  • Flexibility
  • Portability
  • Reusability
  • Interoperability
  • Expandability
analysis of elicitation results helps to create a vision
Analysis of Elicitation results helps to create a Vision

Settle on which problem

- Explain in the problem statement (2.2)

Marketing group establishes positioning of the product (2.3)

Stakeholder and User Summaries

- User is a special case of stakeholder

- Identify all stakeholders w.r.t. development:

Name Represents Role

- Identify all users w.r.t. system:

Name Description Stakeholder

stakeholder profiles 3 5
Stakeholder Profiles (3.5)

Representative - who (name) is representing this stakeholder type.

Description - brief description of the stakeholder type

Type - Qualify s-h’s expertise, technical background, degree of sophistication

Responsibilities - List s-h’s key responsibilities with regard to the system being developed - why a stakeholder?

Success Criteria - How does the stakeholder define success? How rewarded?

Involvement - involved in the project in what way? Requirements reviewer, system tester, ...

Deliverables* - required by the stakeholder

Comments/Issues - Problems that interfere w/ success, etc.

user profiles 3 6
User Profiles (3.6)

Representative - Who represents this user? (might be a stakeholder)

Description - of the user type

Type - qualify expertise, technical background, degree of sophistication

Responsibilities - user’s key resp.’s w.r.t. system being developed

Success Criteria - how this user defines success? rewarded?

Involvement - How user involved in this project? what role?

Deliverables - Are there any deliverables the user produces? For whom?

Comments/Issues - Problems that interfere w/ success, etc.

This includes trends that make the user’s job easier or harder

user environment 3 4 working environment of target user
User Environment (3.4)-- working environment of target user

Number of people involved in doing this now? Changing?

How long is a task cycle now? Changing?

Any unique environmental constraints: mobile, outdoors, in-flight, etc.

Which system platforms are in use today? future?

What other applications are in use? Need to integrate?

key stakeholder or user needs 3 7
Key Stakeholder or User Needs (3.7)

List key problems with existing solutions as perceived by the stakeholder or user.

What are the reasons for this problem?

How is it solved now?

What solutions does the stakeholder want?

What is relative importance of solving each problem?

Alternatives and Competition (3.8)

product overview 4 at last
Product Overview (4.)(at last!)

4.1 Product perspective (context)

Put the product in perspective to other related products and the user’s environment.

Independent?

Component of a larger system?

How do the subsystems interact with this?

Known interfaces between them and this component?

Block diagram

slide14

Product Overview (4.)(at last!)

4.2 Summary of Capabilities

Customer Benefit Supporting Features

1.

2.

3.

4.

slide15

Product Overview (4.)(at last!)

4.3 Assumptions and dependencies

What factors affect the features above?

List assumptions that, if changed, ALTER this document

4.4 Cost and pricing -- not done by engineering

4.5 Licensing and installation -- different types of license enforcement will create more requirements for the development effort

slide16

Product Features (5.)

What’s a feature?

- high level capability necessary to deliver benefit to the user

- externally desired service that typically requires inputs to achieve

Level of detail must be general -- this is not the requirements spec for the developers.

Provide the basis for product definition, scope management, and project management.

Each will be expanded in the use-cases or other requirements

Externally perceivable by users or external systems

what is not in the product features section
What is not in theProduct Features Section?
  • Design
  • Constraints -- These go in section 6.
    • Design constraints
    • External constraints
  • Quality Ranges -- These go in section 7
    • ranges for performance, robustness, fault tolerance, etc. that are not really features (specific capabilities, functions)
precedence and priority 8
Precedence and Priority (8.)
  • Which features essential?
    • We will delay shipment in order to have these
    • We will postpone the feature in order to meet first-release goal
other product requirements
Other Product Requirements
  • These are requirements that are not features (functions) of the product
    • hardware platform requirements --
    • system requirements -- supported host o.s.’s, peripherals, companion software
    • environmental requirements -- temperature, shock, humidity, radiation, usage conditions, resource availability, maintenance issues, type of error recovery
    • applicable standards -- legal, regulatory, communications
documentation requirements
Documentation Requirements
  • What must be developed to support successful deployment?
    • User Manual?
    • Online Help?
    • Installation guide? Read Me file?
    • Labeling, packaging?
use case internals compare to example in larman text p 68 ff terms 73 78
Use Case Name

Scope

Level

Primary Actor

Stakeholders & interests

Preconditions

Success Guarantee (post-conditions)

Basic Flow

Alternate Flows (extensions)

Error Flows

Subflows

Special requirements

Technology & data variations list

Frequency of occurrence

Open Issues

Use Case Internals -- Compare to example in Larman text (p. 68 ff.). Terms: 73-78
fully dressed example process sale larman text p 68 ff
Fully Dressed Example: Process Sale, Larman text, p. 68 ff.

Primary Actor: Cashier

Stakeholders and Interests:

- Cashier:Wants accurate, fast entry, and no payment errors, as cash drawer shortages are deducted from his/her salary.

- Salesperson:Wants sales commissions updated.

- Customer:Wants purchase and fast service with minimal effort. Wants proof of purchase to support returns.

- Company:Wants to accurately record transactions and satisfy customer interests. Wants to ensure that Payment Authorization Service payment receivables are recorded. Wants some fault tolerance to allow sales capture even if server components are unavailable. Wants automatic and fast update of accounting and inventory.

fully dressed example process sale larman text p 68 ff continued
Fully Dressed Example: Process Sale, Larman text, p. 68 ff. - continued

- Government Tax Agencies: Want to collect tax from every sale. May be multiple agnecies such as national, state, and county.

- Payment Authorization Service: Wants to receive digital authorization requests in the correct format and protocol. Wants to accurately account for their payables to the store.

Preconditions:Cashier is identified and authenticated.

Success Guarantee (Postconditions): Sale is saved. Tax is correctly calculated. Accounting and Inventory are updated. Commissions recorded. Receipt generated. Payment authorization approvals are recorded.

fully dressed example process sale larman text p 68 ff continued25
Main Success Scenario (of Basic Flow):

1. - 10.

Extensions (Alternative Flows):

*a.

*b.

1a

2-4a

3a.

3b.

3c.

3-6a-c

4a

5a-c

6a

7a-f

9a-c

Fully Dressed Example: Process Sale, Larman text, p. 68 ff. - continued
fully dressed example process sale larman text p 68 ff cont
Fully Dressed Example: Process Sale, Larman text, p. 68 ff. – cont.

Special Requirements:

- Touch Screen UI on a large flat panel monitor. Text visible from 1 meter.

- Credit auth. response within 30 seconds 90% of the time.

...

Technology and Data Variations List:

...

Frequency of Occurrence: Could be nearly continuous.

Open Issues:

- What are the tax law variations?

- Explore the remote service recovery issue.

- What customization is needed for different businesses?

now what after development of use case s
Now what -- after development of use case(s)
  • Look for consistency, correctness, completeness
    • Most important for core requirements likely to be implemented soon
  • By translation to other formats
    • See Vision Document
    • State diagrams and tables
    • Event tables
    • Condition tables
    • Domain diagram (UML)
references
References
  • 1 “Requirements Analysis,” Richard Thayer, SMC 10/97 Version 2, 1997
  • 2 “IEEE Guide for Software Requirements Specification,” IEEE 830-1998
  • 3 “Software Requirements:Objects, Functions, and States”, Prentice Hall, 1993
  • 4 Software Quality Measurement for Distributed Systems, RADC-TR-83-175