Allegedly ???unfixable??? bugs merit close management attention. Why
are they being raised? What cannot be fixed? (See Figure A.60.)
FIGURE A.57 Release history
FIGURE A.58 Release interval analysis
FIGURE A.59 Bug-finding ability of test environments
800
700
600
500
400
300
200
100
0 0.3.10.3.140.3.9
1.0.231.1.31.1.342.0.352.0.372.0.392.0.412.0.432.0.452.0.472.0.492.0.52.0.542.0.562.0.582.0.602.0.62.0.642.1.662.2.13.5.0
Critical High Medium Low
70
Intervals between releases (in days)
60
50
40
30
20
10
0
1200
1000
800
600
400
200
0
26
60
32
19
154
91
Low
Medium
High
Critical
209
374
239
299
302
386
20 126 276
0
100
DEV DIT DPS Integration Production
406 Manage Software Testing
A.11 Case Study: Testing a Formal Requirements Specification
(TransitCard Ticketing System)
This section provides the context and background details of a system fragment called the TransitCard
Ticketing System. It:
??? Identifies the document structure of the TransitCard development
??? The context of the system to be developed
??? Illustrates an approach to testing a safety-critical system
??? . . .
A.11.1 Documentation Structure
This section identifies the relationships between the various kinds of documents used in this example
(Figure A.61).
A.11.2 System Context
This system is concerned with a ticketing subsystem to be employed on an underground system. It has
four parts: the ticket, the ticket charger, the ticket reader and access controller, and the station computer.
Pages:
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693