1. Prepared by Stephen M. Thebaut, Ph.D. University of Florida
Why is Requirements Engineering Difficult? Software Specification Lecture 2
Prepared by
Stephen M. Thebaut, Ph.D.
University of Florida

2. Once upon a time, the IBM engineer who managed the development of OS/360 wrote…
The hardest single part of building a software system is deciding precisely what to build. No other part of the conceptual work is as difficult… No other part of the work so cripples the resulting system if done wrong. No other part is more difficult to rectify later.
– Fred Brooks, “No Silver Bullet…”

3. So WHY is RE so hard? Difficulty of anticipation
Unknown or conflicting requirements / priorities (“I’ll know what I want when I see it.”)
Conflicts between & among users and procurers
Fragmented nature of requirements
Complexity / number of distinct requirements for large or complex systems

4. an·tic·i·pa·tion [an-tis-uh-pey-shuhn]
noun, 14th century
1. a prior action that takes into account or forestalls a later action;
2. the act of looking forward;
3. visualization of a future event or state.
We can never know about the days to come, but we think about them anyway…Anticipation, anticipation is makin' me late, Is keepin' me waitin’. -Carly Simon

5. So WHY is RE so hard? Difficulty of anticipation
Unknown or conflicting requirements / priorities (“I’ll know what I want when I see it.”)
Conflicts between & among users and procurers
Fragmented nature of requirements
Complexity / number of distinct requirements for large or complex systems

6. So WHY is RE so hard? Difficulty of anticipation
Unknown or conflicting requirements / priorities (“I’ll know what I want when I see it.”)
Conflicts between & among users and procurers
Fragmented nature of requirements
Complexity / number of distinct requirements for large or complex systems

7. So WHY is RE so hard? Difficulty of anticipation
Unknown or conflicting requirements / priorities (“I’ll know what I want when I see it.”)
Conflicts between & among users and procurers
Fragmented nature of requirements
Complexity / number of distinct requirements for large or complex systems

8. So WHY is RE so hard? Difficulty of anticipation
Unknown or conflicting requirements / priorities (“I’ll know what I want when I see it.”)
Conflicts between & among users and procurers
Fragmented nature of requirements
Complexity / number of distinct requirements for large or complex systems

9. So WHY is RE so hard? (cont’d)
Some analogies:
Working a dynamically changing jigsaw puzzle
Blind men describing an elephant
Different medical specialists describing an ill patient

10. The terminology problem:
problem definition
problem specification
requirements (functional or non-functional)
requirements definition
requirements specification
requirements analysis
systems analysis
specifications (functional or non-functional)
software specifications
systems specification
design specifications

11. Requirement:
...something required; something wanted or needed; an essential requisite.
Elicit:
...to draw forth or bring out; to derive by reason or argument; to evoke.

12. Analysis:
...separation of a whole into its component parts; an examination of a complex, its elements, and their relations; resolving complex expressions into simpler or more basic ones; clarification of an expression by an elucidation of its use in discourse.
Specify:
...to name; to state explicitly or in (sufficient) detail.

13. Prepared by Stephen M. Thebaut, Ph.D. University of Florida
Why is Requirements Engineering Difficult? Software Specification Lecture 2
Prepared by
Stephen M. Thebaut, Ph.D.
University of Florida