An Anemometry System Case

This system architecting dealt with a severe climate anemometry system (SCAS) and was the only case of the four that was hardware-based. A toplevel functional decomposition for this system is shown in Figure A.5. The requirements for each of the decomposed elements were defined in considerable detail, and are not presented here because the definition and evaluation of alternatives were particularly well-executed. Table A.8 shows three alternative designs, represented as (1) an as-is design, (2) a moderate upgrade, and (3) a major upgrade. We note that each element of these alternatives is set forth at the second level of functional decomposition, all shown in one figure.

The evaluation framework for this system is presented in Table A.9. Here we see the three system alternatives mapped against a set of evaluation criteria listed in the following six categories:

1. Performance

2. Human factors

3. Maintainability

4. Cost

5. Risk

6. Other

The evaluation was carried out at the subcriterion level, with both a weighting and rating set of numerics. Values were normalized to the ''as-is'' case. As shown in the table, the total scores for the three alternatives are:

2. Moderate upgrade: score = 128.44

3. Major upgrade: score = 125.67

TABLE A.6 Requirements Traceability Matrix—SEE

Requirements

Needs/goals/objectives Mission engineering Requirements analysis Functional analysis Functional allocation Specification development Performance analysis Alternative evaluation System design analysis Scheduling Life-cycle costing Technical performance Measurement

Program/decision analysis

Risk analysis

Logistics and integration

Interface definition and control Integrated logistics support Integration

Configuration management Test and evaluation Quality assurance Requirements traceability Operational evaluation & reengineering Operation

Operational evaluation Modeling Prototyping Mathematical models Simulation models

Architecture 1

Architecture 2

Architecture 3

IDEF IDEF IDEF IDEF IDEF IDEF

CORE, IDEF CORE, IDEF CORE, IDEF CORE, IDEF CORE, IDEF CORE, IDEF

RDD-100, RDD-100, RDD-100, RDD-100, RDD-100, RDD-100,

CORE, IDEF CORE, IDEF CORE, IDEF CORE, IDEF CORE, IDEF CORE, IDEF

Object-Time Fast Track COCOMO Lisa-2B

Expert Choice System-Developer Microsoft Project COCOMO Lisa-2B

Expert Choice TeamWork Microsoft Project COCOMO, PRICE Lisa-28

Decide @Risk RELAX

Expert Choice

@Risk

Expert Choice

@Risk

SLIC

OMEGA OMEGA OMEGA OMEGA

SLIC SLIC SLIC SLIC

SLIC SLIC SLIC SLIC

TRACE TRACE

MATRIX MATRIX

RTM RTM

MODSIM II MODSIM II

Demo Demo

Demo Demo

Demo IThink

Extend+BPR

Demo

MATLAB

GPSS

Demo

MATLAB

NETSIM

TABLE A.7 Architecture Selection

I-SEE

Architecture 1 (All Macintosh)

Architecture 2 (All PC)

Architecture 3 (MAC & PC)

Evaluation Criteria

Weight

Require.

Perf. Anal. Log.

* Int.

T&E OE

■z. Reeng.

Require.

Perf. Anal. Log.

* Int.

T&E OE

■z. Reeng.

Require.

Perf. Anal. Log.

* Int.

T&E OE

>; Reeng.

Method 1

Cost

35%

7

7

7

7

7

9

9

9

9

9

3

3

3

3

3

Speed

5%

3

5

5

5

5

5

7

5

5

7

7

7

5

7

9

Ability to handle

10%

5

5

5

7

7

5

7

5

7

7

7

7

7

7

9

large problems

Ability to handle

10%

5

5

5

5

5

5

5

5

5

5

7

9

7

7

7

growth in users

Ability to meet new

10%

5

5

5

5

5

5

5

5

5

5

7

9

7

9

7

requirements

Capability to meet

5%

5

6

5

5

5

7

7

7

7

7

9

9

9

9

9

new applications

Operability

15%

7

7

7

7

7

5

5

7

7

5

5

7

5

7

5

Currency of

10%

5

7

5

5

7

7

7

5

7

7

5

5

5

7

5

software

Total

100%

Total score

6.2

7

5.9

(benefit)

Total cost

190

170

340

Method 2

Speed

10%

3

5

5

5

5

5

7

5

5

7

7

7

5

7

9

Ability to handle

15%

5

5

5

7

7

5

7

5

7

7

7

7

7

7

9

large problems

Ability to handle

15%

5

5

5

5

5

5

5

5

5

5

7

9

7

7

7

growth in users

Ability to meet new

15%

5

5

5

5

5

5

5

5

5

5

7

9

7

7

7

requirements

Capability to meet

10%

5

5

5

5

5

7

7

7

7

7

9

9

9

9

9

new applications

Operability

20%

7

7

7

7

7

5

5

7

7

5

5

7

5

7

5

Currency of

15%

5

7

5

5

7

7

7

5

7

7

5

5

5

7

5

software

Total

100%

Total score

5.7

6

7.5

(benefit)

Total cost

190

170

340

Benefit-to-Cost

0.03

0.035294

0.022059

Ratio

Severe climates anemometry system

Atmospheric sensing

Mechanical service

Environmental service

Power service

Indoor/outdoor transmission

Data handling

Wind speed

Wind direction

Barometric pressure

Instrument housing

Instrument orientation

Ice control

Main supply

Regulation/ conditioning

Backup power

Power

Signal

Physical linkages

Collection

Processing/ storage

Reporting, distribution and display

Figure A.5. Top-level SCAS functional decomposition.

We thus see that both upgrades represent significant improvements over the as-is alternative, according to the evaluator.

The architect then displayed some of the results in graphical form. Figure A.6 shows a cost-effectiveness plot using an effectiveness metric based on the criteria of performance, human factors, and maintainability. This graph distinctly indicates a ''knee-of-the-curve'' phenomenon. There is a large gain in effectiveness for relatively little cost increase in moving from the as-is alternative to the moderate upgrade. The major upgrade carries with it a large cost increase for only a modest increase in effectiveness. A rather imaginative next step for the architect was to examine the relationship between effectiveness and risk, as illustrated in Figure A.7. Although risk increases monoton-ically in moving from the as-is to the major upgrade, there is almost no ''knee-in-the-curve'' as compared with the previous figure.

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