A A Software Defects Assessment System Case

The software defects assessment system provides the software manager with an automated decision-support tool to assist in the software maintenance process by prioritizing software defects both accurately and efficiently. The system is called SD-DSS (Software Defects—Decision Support System).

The top-level functional identification for this system is shown in Figure A.2, which shows the various requirement areas under the following four major functional categories:

SD-DDS

Data management

Model management

■ Extraction capability

■ DBMS access function

■ Data dictionary Control

■ Model building

■ Modeling manipulation

■ Model maintenance

■ Modeling access functions

Dialog management

■ User I/F with data and models base

■ Support many user outputs

■ Robust Help facility

■ Track dialogs

■ Flexibility and adaptiveness

System requirements

- Performance

- Capacity

- Reliability

- Maintainability

Figure A.2. Top-level functional identification.

1. Data management

2. Model management

3. Dialog management

4. System requirements

Exhibit A.2 provides an overview of requirements for each of these functional areas.

Given these functional areas and requirements in each area, the next step is to structure alternative architectures for such a system. Three alternatives are depicted in Exhibit A.3. In broad terms, the alternatives reflect different choices in terms of host hardware and the associated software that would normally be attendant to different computer configurations.

The evaluation of the three alternatives is represented in Table A.3. This ''comparison matrix'' lists the evaluation in three categories: (1) cost, (2) functionality, and (3) system. Each of these categories is broken down so that it is then possible to assess each alternative at a lower level of detail. Expansion of the subcriteria in terms of ideas as to how to make the calculations is shown in Table A.4.

With respect to the category of cost, the following points are relevant:

• Total life-cycle cost was based on the following components over a ten-year period:

—Research, Development, Test, and Evaluation (RDT&E): engineering design, software development, and documentation —Production and Construction: Commercial off-the-shelf (COTS) hardware and software and facility modifications —Operations & Maintenance (O&M): system operations, maintenance personnel, activation, and materiel support —Retirement and Disposal: retirement personnel, transportation, and handling

• Parametric cost estimation:

—Constructive Cost Model (COCOMO) used for RDT&E and O&M costs

• Bottom-up unit cost estimation used for production, construction, retirement, and disposal costs

A summary of life-cycle costs (LCC) over a ten-year period is provided in Table A.5. The percent of costs by cost category is also listed in the far-right column.

The system architect assessed all evaluation categories with the assistance of a commercial software package known as Expert Choice [A.2], as illustrated in Figure A.3. Functionality measures were analyzed by performing

Exhibit A.2: Functional Requirements—SD-DSS

Data Management Requirements

• The system shall collect/extract software-defect-related data from the following sources for inclusion into the DSS database management system (DBMS):

—Automated configuration management system —Financial/accounting system —Personnel system

—Software reliability information (i.e., metrics)

• The system shall provide the basic data manipulation functions such as select, update, delete, and insert. The query capability shall support ad hoc query and report generation capability.

• The system shall provide a catalog of all data with definitions and the ability to provide usage information on those data.

• The system shall provide comprehensive data security, providing protection from unauthorized access, recovery capabilities, archival capabilities, etc.

Model Management Requirements

• The system shall allow users to create models that will structure and evaluate the qualitative and quantitative factors involved in prioritizing software defects.

• The system shall create models easily and quickly, either from scratch or from existing models contained in the model base.

• The system shall allow users to manipulate models to include sensitivity analysis, ''what if'' analysis, goal seeking, and cost-benefit analysis.

• The system shall generate a directory of models for use by different individuals of the organization.

• The system shall manage and maintain the model base with management functions analogous to database management: store, access, run, update, link, catalog, and query.

• The system shall track models, data, and application usage. Dialog Management Requirements

• The system shall have a user-friendly graphical user interface.

• The system shall be able to interact with several different dialog styles.

• The system shall be able to accommodate a variety of input devices.

• The system shall be able to present data with a variety of formats and output devices (i.e., color graphics, three-dimensional presentations, and data plotting).

• The system shall provide ''help'' capabilities, diagnostics, training, and suggestion routines to assist to user.

• The system shall be able to capture, store, and analyze dialog usage to facilitate improving the dialog system.

• The system must provide flexibility and adaptiveness to accommodate different problems and technologies.

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