Software Requirement Engineering

1. Software Requirement Engineering

2.  Managing your Customer
 Software Requirements
 Software System Behaviour
 Relationship between Features and Software Requirements

3. Managing Your Customer

4.  Feature creep, which Weinberg [1995] notes
can increase scope by as much as 50 percent
to 100 percent after the start of a project.
 Official Changes
Customer requests a new system capability
(Official Change) that is not part of baseline
then the impact must be assessed.
 If the new feature is critical.
 If the feature is important, but not
critical

5.  Un-Official Changes
 Requirements Leakage which are invisible to team managing
schedule, budget and quality criteria.
 Contributes up to half of the total scope of one project.
 These Un-official sources for changes can be,
 Direct Customer requests to programmers
 Functionality inserted by the programmers with
consideration of What’s good for the customer
 Programmer “Easter Eggs”

7.  Software capability that must be met or possessed by a system
or a system component to satisfy a contract, standard,
specification, or other formally imposed documentation
 Features and use cases sufficient to understand the system at a
macro-level view.
 Software requirements are those things that the software does on
behalf of the user.

8.  Davis [1999] suggests that we need five major classes of things in
order to fully describe the behavior of a software system (Figure
1).
 Inputs to the system
 Outputs from the system
 Functions of the system
 Attributes of the system
 Attributes of the system environment

9. Figure 1:: System elements
Software System Behavior

10.  Mapping relationship between features and software requirements.
Vision Document Feature Software Requirements
Simple descriptions of systems
services in brief form.
Express features in much more
detailed terms.
Cites features in user’s language. Express features in technical
terms, using one or more specific
Software requirements that must
be fulfilled to provide the
features to the user

11.  Suppose we are developing a defect-tracking system
 Backbone of a requirements management concept known as
"traceability“.
Vision Document Feature Software Requirements
Feature 30: The defect-tracking
system will provide trending
information to help the user
assess project status.
SR30.1:Trending information
will be provided in histogram
report showing time on x-axis
and defects on the y-axis
SR30.2: The user can enter the
trending period in units of days,
weeks or months.
SR30.3: An example trending
report is shown in Figure1.