The document outlines the importance of clear and complete software requirements, highlighting different types such as functional, non-functional, domain, inverse, and design constraints. It emphasizes the need for requirements to be unambiguous to prevent poor software quality and details how non-functional requirements impact system performance and usability. Additionally, it discusses the sources of requirements and the implications of domain-specific constraints on system design.

1. Software
Requirements
(OOAD Tutorial Series)
By: UPSOL ACADEMY

2. Requirements ?
Required
Wanted
Needed

3.  requirements must be complete and unambiguous.
 Incomplete and ambiguous requirements are open to
multiple interpretations and assumptions
 This can lead to the development of poor quality, or
faulty, software products
Tips for Requirements

4. Source of Requirements
Stakeholders
Documents
Existing System
Domain/Business area

5.  Functional Requirements
 Non-Functional requirements
 Domain Requirements
 Inverse Requirements
 Design and Implementation Constraints
Requirements Types

6.  Statements describing what the system does.
 Functionality of system
 Statements of services the system should provide
 Reaction to particular inputs
 Behavior in particular situations
 Customers and developers usually focus on functional
requirements.
 Example: Login, Browse, Add to cart etc.
Functional Requirements

7.  Most non-functional requirements (NFRs) relate to the
system as a whole. They include constraints on:
 Performance
 Reliability
 Security
 Maintainability
 Usability
 Standards
More critical and may make system unusable if failed to apply..
Non-functional Requirements

8.  Example:
 If a real-time control system fails to meet its
performance requirements, the control functions will
not operate correctly e.g. ATM in banking system.
 NFRs come up/depends through:
 User needs, budget & interoperability,
 Organizational policies(s/w developing),
 External factors such as safety regulations, privacy
legislation, etc.
Non-Functional Requirements

9. • Architecture: where non-functional decisions are cast, and functional
requirements are partitioned.
• Design: where functional requirements are accomplished
Non-Functional Requirements
Architecture vs design

10.  requirements that come from
 Application domain
 Reflect fundamental characteristic of application domain.
 These can be both Functional and Non-Functional
requirements
 Domain requirements can impose strict constraints on
solutions
Domain Requirements

11.  They explain what the system shall not do.
 Example:
 The system shall not use red color in the user
interface, whenever it is asking for inputs from the
end-user
Inverse Requirements

12.  They are development guidelines within which the
designer must work.
 These requirements can seriously limit design and
implementation options
 Can also have impact on human resources
 Example:
Design and implementation
Constraints

13.  Example:
 The system shall be developed using the Microsoft .Net
platform
 The system shall be developed using open source tools and
shall run on Linux operating system
Design and implementation
Constraints