Ada Projects Research Articles

Poisson analyses of defects for small software components

Poisson analyses are proposed for the identification of the determinants of defects in small software components such as subprograms, modules, or functional units. Software complexity (which can be measured during design or implementation) and software development environment characteristics influence the numbers of defects emerging in the testing phase. Poisson models are calibrated using software complexity measures from several Ada projects along with their associated software change report data. One of the models is used to estimate defects at the subprogram, subsystem, and project levels for the calibration data, and these estimates are then compared to the actual defects. Notable results from this analysis are that extensively modified reused subprograms (> 25% changed) have substantially more defects than new code of otherwise comparable characteristics and that software development environment volatility (as measured by non-defect changes per thousand source lines of code) is a strong determinant of subprogram defects. To demonstrate cross-language applicability, defect predictions are made at the subsystem level for a project coded in the C programming language and compared to the actual subsystem defects. Finally, for software projects developed through multiple builds, we show that a Poisson model that incorporates a measure of testing effort is applicable.

The impact of Ada and object-oriented design in NASA Goddard's Flight Dynamics Division

This paper presents the highlights and key findings of 10 years of use and study of Ada and object-oriented design in NASA Goddard's Flight Dynamics Division (FDD). In 1985, the Software Engineering Laboratory (SEL) began investigating how the Ada language might apply to FDD software development projects. Although they began cautiously using Ada on only a few pilot projects, they expected that, if the Ada pilots showed promising results, the FDD would fully transition its entire development organization from FORTRAN to Ada within 10 years. However, 10 years later, the FDD still produced 80 percent of its software in FORTRAN and had begun using C and C++, despite positive results on Ada projects. This paper presents the final results of a SEL study to quantify the impact of Ada in the FDD, to determine why Ada has not flourished, and to recommend future directions regarding Ada. Project trends in both languages are examined as are external factors and cultural issues that affected the infusion of this technology. The detailed results of this study were published in a formal study report [1] in March of 1995. This paper supersedes the preliminary results of this study that were presented at the Eighteenth Annual Software Engineering Workshop in 1993 [2].

Modeling the effort to correct faults

An approach is proposed for analyzing the determinants of fault locality and fault correction effort during unit, system, and acceptance testing. The approach uses a Poisson analysis to model fault locality and a categorical multivariate regression analysis based on an ordered response model to model effort. Ordered response models are applicable when effort data are available on a categorical basis (e.g., 0–1 hour, 1 hour to 1 day, etc.) rather than on a continuous scale (e.g., measured in hours and fractions thereof). The usual ordinary least-squares regression assumptions of a continuous normally distributed dependent variable are not valid in the case of categorical dependent variables. Fault data from five Ada projects are analyzed to yield estimates for various fault locality variables and the probabilities for a fault to be in the various effort categories. The results are used to estimate the fault correction effort at the project level. These estimates are then compared with the actual fault correction efforts.

A pragmatic Ada software design/development methodology

A pragmatic design method is described which has been successfully applied to two medium size Ada projects. This design method parallels (albeit at a much less sophisticated level) the domain oriented methodologies currently becoming popular with the advent of products such as Microsoft Visual Basic (TM).

A composite complexity approach for software defect modelling

An approach is proposed to develop defect models for software components based on a categorical multivariate regression analysis. This modelling technique is useful when the software components are sufficiently small so that the assumption of a continuous normally distributed defect distribution is not valid. Library unit aggregations from five Ada projects are analysed to yield a composite complexity measure which is a function of both software complexity characteristics and development environment characteristics. The probabilities of various numbers of defects are derived from this composite complexity measure. The probability distributions are used to calculate subsystem level defects which are then compared to the actual defects.

Object oriented requirements analysis in an Ada project

Among the methodologies that have appeared related to Ada, Object Oriented Development is emerging as the one of choice for a wide range of applications. Although Object Oriented Development is understood as covering more than just the design phase of the software life cycle, most Ada projects adopt these methodologies only in the design phase, using other kinds of methodologies for the requirements analysis, like structured analysis. We believe that if a single coordinated methodology is used throughout all the phases of the software life cycle, it will increase the traceability in the system, decrease the integration problems, and improve conceptual integrity of the design, leading to a more consistent final system.Although there are already many well known Object Oriented Design methods for Ada, Object Oriented Requirements Analysis methods are not so common. Notwithstanding, having a project to be carried out in Ada, we decided to use Object Oriented methodologies from the very beginning, using the Object Oriented Requirements Analysis method proposed by the company EVB Software Engineering, Inc. That work, however, was not completely straightforward. We faced many practical difficulties, that had to be dealt with, and some problems that had to be solved. In this way, a variant of the original method emerged, which we believe is better suited to real word projects.

Prediction and control of ADA software defects

A study of two Ada projects shows that software defects can be predicted in the development phase. Of all metrics tested, measures of package size proved to be the best predictors of defect densities. The prediction function derived suggests that defect density is very high for small Ada packages, decreases rapidly to reach a minimum for intermediate-sized packages, and then rises gradually as package sizes increase. During the design and coding phases, package sizes can be evaluated against this criterion, and such strategies as consolidation, further decomposition, redesigning, or recoding can be considered. Since the study found that packages with system integration and test (SI&T) defects are six times more likely to exhibit postdelivery defects as those without, a two-phased SI&T is suggested.

IDEA - an incremental development environment for Ada

This paper decribes an incremental environment which has been developed to meet the needs of developers and maintainers of large Ada projects. This environment assists the user to develop valid Ada text while consulting other Ada packages and documents. It is built around an embedded syntax-directed editor which controls text inspection, modification and, subsequently, re-compilation. In addition, the data accumulated by a translator is available during editing to provide semantic assistance on request.

A Preliminary Study of Ada Expansion Ratios

Abstract Since the mandate (DoDD 5001.31) requiring the use of the Ada language in all mission critical software, a need for revised expansion ratios for estimating Ada software has emerged. This paper describes a study to determine a set of preliminary Ada expansion ratios. Three classes of Ada programming features were identified during this study. These classes are based on the use of Ada specific constructs within the software modules. Each of the classes identified also has a corresponding expansion ratio. These ratios are used to determine memory requirements which are input to cost estimation models such as COCOMO and SLIM (1). The results of this research will have direct bearing on future Ada projects by helping to develop improved software costing and sizing estimates. This will lead to improved reliability on design requirements for program memory and execution timing specifications. A special note on the effect of timing and compiler optimization is also included in this paper.

A preliminary study of Ada expansion ratios

Since the mandate (DoDD 5001.31) requiring the use of the Ada language in all mission critical software, a need for revised expansion ratios for estimating Ada software has emerged. This paper describes a study to determine a set of preliminary Ada expansion ratios. Three classes of Ada programming features were identified during this study. These classes are based on the use of Ada specific constructs within the software modules. Each of the classes identified, also has a corresponding expansion ratio. These ratios are used to determine memory requirements which are input to cost estimation models such as COCOMO and SLIM [1].The results of this research will have direct bearing on future Ada projects by helping to develop improved software costing and sizing estimates. This will lead to improved reliability on design requirements for program memory and execution timing specifications. A special note on the effect of timing and complier optimization is also included in this paper.