Transcript bhc-reqs.ppt

Purpose of Requirements
Analysis
Process of discover, refinement, modeling,
and specification
• o Bridge gap between system level SW
allocation and
•
design
• o Enable system engineer to specify
software function
•
and performance
• o Indicate SW interface with other system
Analysis Tasks
•
•
•
•
•
o
o
o
o
o
Problem Recognition
Evaluation and synthesis
Modeling
Specification,
Review
Role of Analyst
• o Evaluate flow and content of
information
• o Define and elaborate all SW functions
• o Understand SW behavior in context of
events affecting
•
system
• o Establish system interface
characteristics
• o Uncover design constraints
Problem Areas
• o Communication Skills (different levels)
•
- High-level interaction
•
- More detail extraction from customer
•
- Tailor communication approach
towards customer
• o Facilitated Application Specification
Techniques (FAST)
•
Joint team of customer with developers
(marketing, an-
Analysis Principles
• o Information domain of problem must
be represented
•
and understood.
• o Develop models that illustrate system
info, function,
•
and behavior
• o Models and problem should be
decomposed into hier•
archical organization
Information Domain
• o All SW applications can be called data
processing.
•
Software is built to process data
• o SW also processes events
• o data and control (events) both reside
within the Info
•
Domain
• o 3 views of data and control as processed
by computer
Modeling and Specification
• o Modeling____
•
- Aid in understanding information,
function, and be•
havior of system.
•
- Focal point for review (determine
completeness, con•
sistency, and accuracy of
specification)
•
- Foundation for design: ("mapping"
Essential and Implementation
Views
• o Essential_View____
•
of SW requirements:
•
- Presents functions to be accomplished
•
- Information to be processed
•
- Without regard to implementation
details
• o Implementation_View________
•
of SW requirements:
Prototyping
• o Prototype is mostly for customer
assessment
• o Several_steps_of_prototyping:_______
•
1. Evaluate SW request and determine if
feasible.
•
2. Develop abbreviated representation of
requirements
•
3. Develop abbreviated design
specification from re-
Specification
• Formal spec languages lead to formal
representation of
• requirements that may be verified or further
analyzed
• Specification_Principles:_____
• o Cognitive model (take user's
perspective)
• o Operational (be able to verify)
• o Tolerant of incompleteness and
Representation Guidelines
• o Representation format and content
should be relevant
•
to problem
• o Information contained within
specification should be
•
nested
• o Limited number of and consistent use of
diagrams and
•
other notational forms
Software Requirements
Specification
• o Function and performance allocated to
SW from sys•
tem engineering should be refined by:
•
- establishing complete information
description
•
- detailed functional description
•
- performance requirements and design
constraints
•
- validation criteria
Specification Contents
•
- Introduction states goals and
objectives of SW
•
describe context of computer-based
system
•
- Information Description gives
detailed descrip•
tion of problem
–
O Information flow and structure
documented
Specification Contents
• - Behavioral Description examines
operation of SW
•
as consequence of
–
–
•
O external events and
O internally generated control
characteristics
- Validation Criteria: (very important)
–
O "How do we know if SW is successful
implemen-