CSCI 4050 Quiz 2: Key Concepts in Requirements Engineering and UML Diagrams

What is Requirements Engineering

- what services are required

- Identify constraints on these services

- ensure software will meet the user expectations and ending-up with a high quality software

What are the steps in the Requirements Engineering proccess

Feasibility Study and Report --> Elicitation, Analysis, System Models -->Requirements Specification --> Requirements Validation

Elicitation

"work with the customer on gathering requirements"

What are the different techniques to elicit requirements

- interviews

- questionnaires (list of pre-selected questions)

- task analysis (observing in environment)

- user stories (short description of features)

- scenarios (describe use of system as a series of interactions between end user and system)

- use cases (abstractions describe a class of scenarios)

Analysis

"process the gathered information to understand it, classify in various categories and relate the customer needs to possible software requirements"

System Models

output of elicitation and analysis; plan driven approach

Specification

structure the customer input and derived requirements as written documents (user requirements) and diagrams (system requirements)

Validation

"The process of testing the requirements to ensure that they conform with customer needs, accurate, complete,..."

What are the requirements for validation

- correctness (represent the client's view)

- completeness (all possible scenarios/user stories)

- consistency (no contradicting requirements)

- clarity (interpreted in one way)

- realism (implementable and deliverable)

- traceability (behavior can be traced as a set of functional requirements)

- verifiability (written so they can be tested)

The Requirements Engineering Process is an _______________ process that continues thought requirements development; No single standard approach to requirements development

iterative

How do we write requirements?

depends on the development model

- traditional approach (waterfall) - shall, should langauge

- SCRUM - user stories

- RUP - use cases

- mix

What is a requirement?

a statement of one of the following:

- what a system must do

- a known limitation or constraint on resources or design

- how well the system must do what it does

What is a functional requirement?

what a system must do

describe the interaction between the system and its environment independent from the implementation

What is a non functional requirement?

a known limitation or constraint on resources or design and how well the system must do what it does (quality of the sysyem)

aspects not directly related to functional behavior

What are constraints

imposed by the client or the environment (any language, algorithm or regulations)

"pseudo requirements"

Types of non functional requirements (quality requirements)

- usability

-reliability (robustness, safety, security)

- performance (response time, throughput)

- supportability (adaptability, maintainability, modifiability)

Types of non functional requirements (constraints/pseudo requirements)

- implementation

- interface

- operation

- packaging

- legal (licensing, certification, regulations)

Usability definition

must be measurable, the ease of which actors can use a system to perform a function

Robustness definition

ability of a system to maintain function (even if there is wrong input or changes in the enviornment)

loss of data/recovered data

Availability definition

ratio of the expected uptime against aggregate of the expected up and down time

Performance definition

response time, throughput

Efficiency definition

minimal use of resources (memory, processor, disk, network...)

Reliability definition

how precise the computations are

Portability definition

does it work for several platforms

Modifiability definition

addition of new functionalities

Reusability definition

of components, code, design and even requirements in other systems

Maintainability definition

changes to functionalities, repairs

Readability definition

of code, documents

Testability definition

ease of testing and error reporting

Understandability definition

of design, architecture, code

Integrability definition

ability to integrate components

UML Use Case Diagram

Used during requirements elicitation and analysis to represent external behavior

Actor definition

represents a role that is a type if user of the system

Use case definition

represents a class of functionality provided by the system