Study Problem Solutions
CSCI 6231 Mid Term
Chapter 1
1.1:
Postdelivery maintenance will cost about 3 times as much as the
original development, that is, about $1,275,000.
1.2:
No. Temporally defined maintenance is a subset of operationally
defined maintenance. That is, all changes to a software product constitute
operational maintenance, but only those performed after installation
constitute temporal maintenance.
1.3:
Try to find a solution using off-the-shelf software (packages). If this
fails, determine which of the constraints (time, cost, functionality) can be
relaxed, and provide a solution that fits the remaining constraints. If this fails,
do not make promises that cannot be kept, but rather provide data such as
hardware invoices and software development schedules showing the
unreasonableness of the total request.
Chapter 1 Continued
1.4:
Acceptance criteria must be stipulated in the contract, as must a full list of
deliverables. Clauses should include: software shall meet specifications, be delivered
on time, within budget; all faults shall be corrected at no further charge for a period of
one year, say, after acceptance of product; documentation shall be full and complete,
and shall include source code, specifications, design, and operating instructions;
training shall be provided (stipulate type and duration). Terms of the maintenance
contract should be included. You might try to include a clause holding the developer
responsible for damages caused by faults in the software.
Chapter 1 Continued
1.5:
Late delivery: Underestimation of size of product; failure to obtain complete
and accurate requirements; poor planning; failure to specify the product correctly;
poor management techniques; failure to detect faults early in the life cycle; ineffective
or badly trained personnel; poor quality testing; personnel turnover; poor
documentation of the development process; poor communication between members
of the development team; continual hardware and/or system software failures.
Project over budget: All of the above, plus unexpected price increases for
hardware, programming tools, and so on.
Product does not meet specifications: All of the above, plus poor quality
specifications; poor testing; poor quality assurance.
Operational faults, such as injuries to sailors firing the missiles: Poor testing,
and hence residual faults; poor quality documentation.
Inadequate documentation: Badly trained personnel; poor management.
Chapter 1 Continued
1.6: $136. From Figure 1.6 of Object-Oriented Software Engineering, the ratio of cost of detecting and correcting a fault
during postdelivery maintenance to the cost of detecting and
correcting it during the analysis phase is 368 to 3 (approximately
123 to 1).
Chapter 2
2.3: Because of Miller’s Law we cannot develop
a software product in a single step, and therefore we need to use stepwise refinement.
2.4: Incrementation.
Chapter 2 Continued
2.8:
Experience and skills of the development team; computer literacy of the
client; extent to which the client seems to appreciate his or her real needs.
2.9:
The product may not be what the client really needs, so construct a rapid
prototype. The design may not permit future development as the corporation grows
or changes the way it does business, so ensure that the design is as open-ended as is
reasonable. There may be cost and or time overruns, so estimate carefully (see
Chapter 9). The users may not be comfortable with the product, so a rapid prototype
of the user interface is needed; also, involve the purchasing clerks, factory supervisors,
sales clerks, and so on, in the development loop. A competitor may produce off-theshelf software before the product has been delivered — there is no ethical way to
resolve this risk. A critical member of the development team may leave, so keep management of the development organization abreast of major decisions being made,
thereby making it easier to integrate a replacement into the team. The development
team may not be properly managed, so ensure that managers are competent and
well-trained.
Chapter 9
9.3: From Figure 9.2 of Object-Oriented and Classical
Software Engineering, Seventh Edition,
UFP = 7 x 3 + 2 x 4 + 10 x 6 + 56 x 5 + 8 x 3 + 12 x 10 + 17 x 10 =
683
Chapter 9 Continued
9.8:
Nominal effort for this organic mode product is 3.2 x 521.05 = 190
person months
(i)
At $9,900 per person-month, the project costs $1,881,000.
(ii)
Replacing the staff with team A from Problem 9.7, the cost
for the project becomes (190 x 0.35) x 12,900 = $857,850, or a gain of
$1,023,150.
Chapter 9 Continued
9.9:
First obtain independent COCOMO and function point estimates as a
check. Assuming that the predictions do not change, the next step is to
discuss the product with experienced software engineers, and ask them to
come up with estimates based on their experience (“expert judgment by
analogy”). Use their estimates to try to decide whether the COCOMO or
function point estimator is more likely to be an accurate predictor of the cost
of the product. If this, too, fails, use the function point estimate on the
grounds that it is generally less damaging in the long run to overestimate than
to underestimate cost.
Alternatively, the Delphi technique could be used to try to achieve
agreement within an accepted tolerance.
Chapter 9 Continued
9.7:Nominal effort (organic mode) = 3.2 x 431.05 = 126 person-months
Multiplier for P1 = 1.65
Multiplier for P2 = 0.70
Multiplier for team A = 0.71 x 0.82 x 0.70 x 0.90 x 0.95 = 0.35
Multiplier for team B = 1.46 x 1.29 x 1.42 x 1.21 x 1.14 = 3.69
(i)If team A develops P1, total effort = 126 x 1.65 x 0.35 = 73 person-months.
If team B develops P2, total effort = 126 x 0.70 x 3.69 = 325 person-months.
Total = 398 person-months
(ii)If team B develops P1, total effort = 126 x 1.65 x 3.69 = 767 person-months.
If team A develops P2, total effort =126 x 0.70 x 0.35 = 31 person-months.
Total = 798 person-months.
(iii)Assignment (i) makes more sense, and is backed by COCOMO predictions.
Chapter 4
4.1:
Use a (modified) chief programmer team. This is a standard
application area, so an experienced chief programmer with a team of two
reasonably competent programmers should do a credible job.
Chapter 4 Continued
4.2:
The team should be organized as in Figure 4.6 of Object-Oriented
Software Engineering. The difficulty of the problem requires the synergistic
effect of group interaction at each level, but the scale of the problem and the
need for strict controls (military project) require a hierarchy. Regulatory and
budgetary considerations require nontechnical management.
Chapter 5
5.11:
Build tool: Promotes stepwise refinement by making it easy to perform
numerous compilations and linkages.
Coding tool: Promotes stepwise refinement by making it easy to add,
modify, or delete code.
Configuration-control tool: Promotes stepwise refinement by making it easy
to find the appropriate version of a module or artifact.
Data dictionary: Promotes stepwise refinement by allowing the team to
add, modify, or delete entries while the product is being developed or maintained.
(E-mail: Does not hinder stepwise refinement.)
Interface checker: Promotes stepwise refinement by checking interfaces
when a module is added, modified, or deleted.
Online documentation: Promotes stepwise refinement by allowing the
documentation to be modified easily.
Operating system front end: Promotes stepwise refinement by making it
easy to perform numerous compilations and linkages.
Pretty printer: Promotes stepwise refinement by ensuring that the code is
readable even after changes have been made.
Chapter 5 Continued
Report generator: Promotes stepwise refinement by making it easy to add
or modify reports.
Screen generator: Promotes stepwise refinement by making it easy to add
or modify screens.
Source-level debugger: Promotes stepwise refinement by making it easier to
find faults after making an addition, modification, or deletion to the software.
(Spreadsheet: Does not hinder stepwise refinement.)
Structure editor: Promotes stepwise refinement by making it easy to add,
modify, or delete code.
Version-control tool: Promotes stepwise refinement by making it easy to
find the appropriate version of a module or artifact.
(Word processor: Does not hinder stepwise refinement.)
(World Wide Web browser: Does not hinder stepwise refinement.)
Chapter 6
6.2:
If the organization is restructured so that 26 professionals, including five
managers, are concerned solely with SQA, increased productivity and product
quality can be expected. The costs to the company will include reorganization
time (two day’s labor, approximately 77 x $825 + 19 x $1,100, or about $84,500)
and training time and costs for the five SQA managers (perhaps $75,000). The
total cost of under $160,000 should be recouped in a year even if productivity
increases by only 3%.
6.10:
The proof stands.
Chapter 6 Continued
6.12:
An annotated flowchart is shown in Figure 6.1.