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NASA NTRS1992

Software-Engineering Process Simulation (SEPS) model

The Software Engineering Process Simulation (SEPS) model is described which was developed at JPL. SEPS is a dynamic simulation model of the software project development process. It uses the feedback principles of system dynamics to simulate the dynamic interactions among various software life cycle development activities and management decision making processes. The model is designed to be a planning tool to examine tradeoffs of cost, schedule, and functionality, and to test the implications of different managerial policies on a project's outcome. Furthermore, SEPS will enable software managers to gain a better understanding of the dynamics of software project development and perform postmodern assessments.

Lin, C. Y.↗

NASA NTRS1991

Framework Programmable Platform for the Advanced Software Development Workstation: Preliminary system design document

The Framework Programmable Software Development Platform (FPP) is a project aimed at combining effective tool and data integration mechanisms with a model of the software development process in an intelligent integrated software environment. Guided by the model, this system development framework will take advantage of an integrated operating environment to automate effectively the management of the software development process so that costly mistakes during the development phase can be eliminated. The focus here is on the design of components that make up the FPP. These components serve as supporting systems for the Integration Mechanism and the Framework Processor and provide the 'glue' that ties the FPP together. Also discussed are the components that allow the platform to operate in a distributed, heterogeneous environment and to manage the development and evolution of software system artifacts.

Mayer, Richard J.↗

NASA NTRS1992

Software design for automated assembly of truss structures

Concern over the limited intravehicular activity time has increased the interest in performing in-space assembly and construction operations with automated robotic systems. A technique being considered at LaRC is a supervised-autonomy approach, which can be monitored by an Earth-based supervisor that intervenes only when the automated system encounters a problem. A test-bed to support evaluation of the hardware and software requirements for supervised-autonomy assembly methods was developed. This report describes the design of the software system necessary to support the assembly process. The software is hierarchical and supports both automated assembly operations and supervisor error-recovery procedures, including the capability to pause and reverse any operation. The software design serves as a model for the development of software for more sophisticated automated systems and as a test-bed for evaluation of new concepts and hardware components.

Herstrom, Catherine L.↗

NASA NTRS1992

SSE software test management STM capability: Using STM in the Ground Systems Development Environment (GSDE)

This report is one of a series discussing configuration management (CM) topics for Space Station ground systems software development. It provides a description of the Software Support Environment (SSE)-developed Software Test Management (STM) capability, and discusses the possible use of this capability for management of developed software during testing performed on target platforms. This is intended to supplement the formal documentation of STM provided by the SEE Project. How STM can be used to integrate contractor CM and formal CM for software before delivery to operations is described. STM provides a level of control that is flexible enough to support integration and debugging, but sufficiently rigorous to insure the integrity of the testing process.

Church, Victor E.↗

NASA NTRS1991

Software component quality evaluation

The paper describes a software inspection process that can be used to evaluate the quality of software components. Quality criteria, process application, independent testing of the process and proposed associated tool support are covered. Early results indicate that this technique is well suited for assessing software component quality in a standardized fashion. With automated machine assistance to facilitate both the evaluation and selection of software components, such a technique should promote effective reuse of software components.

Clough, A. J.↗

NASA NTRS1992

LV software support for supersonic flow analysis

The software for configuring a Laser Velocimeter (LV) counter processor system was developed using structured design. The LV system includes up to three counter processors and a rotary encoder. The software for configuring and testing the LV system was developed, tested, and included in an overall software package for data acquisition, analysis, and reduction. Error handling routines respond to both operator and instrument errors which often arise in the course of measuring complex, high-speed flows. The use of networking capabilities greatly facilitates the software development process by allowing software development and testing from a remote site. In addition, high-speed transfers allow graphics files or commands to provide viewing of the data from a remote site. Further advances in data analysis require corresponding advances in procedures for statistical and time series analysis of nonuniformly sampled data.

Bell, William A.↗

NASA NTRS1992

Data collection procedures for the Software Engineering Laboratory (SEL) database

This document is a guidebook to collecting software engineering data on software development and maintenance efforts, as practiced in the Software Engineering Laboratory (SEL). It supersedes the document entitled Data Collection Procedures for the Rehosted SEL Database, number SEL-87-008 in the SEL series, which was published in October 1987. It presents procedures to be followed on software development and maintenance projects in the Flight Dynamics Division (FDD) of Goddard Space Flight Center (GSFC) for collecting data in support of SEL software engineering research activities. These procedures include detailed instructions for the completion and submission of SEL data collection forms.

Heller, Gerard↗

NASA NTRS1992

The software-cycle model for re-engineering and reuse

This paper reports on the progress of a study which will contribute to our ability to perform high-level, component-based programming by describing means to obtain useful components, methods for the configuration and integration of those components, and an underlying economic model of the costs and benefits associated with this approach to reuse. One goal of the study is to develop and demonstrate methods to recover reusable components from domain-specific software through a combination of tools, to perform the identification, extraction, and re-engineering of components, and domain experts, to direct the applications of those tools. A second goal of the study is to enable the reuse of those components by identifying techniques for configuring and recombining the re-engineered software. This component-recovery or software-cycle model addresses not only the selection and re-engineering of components, but also their recombination into new programs. Once a model of reuse activities has been developed, the quantification of the costs and benefits of various reuse options will enable the development of an adaptable economic model of reuse, which is the principal goal of the overall study. This paper reports on the conception of the software-cycle model and on several supporting techniques of software recovery, measurement, and reuse which will lead to the development of the desired economic model.

Bailey, John W.↗

NASA NTRS1992

Generic domain models in software engineering

This paper outlines three research directions related to domain-specific software development: (1) reuse of generic models for domain-specific software development; (2) empirical evidence to determine these generic models, namely elicitation of mental knowledge schema possessed by expert software developers; and (3) exploitation of generic domain models to assist modelling of specific applications. It focuses on knowledge acquisition for domain-specific software development, with emphasis on tool support for the most important phases of software development.

Maiden, Neil↗

NASA NTRS1993

Software engineering

Today's software systems generally use obsolete technology, are not integrated properly with other software systems, and are difficult and costly to maintain. The discipline of reverse engineering is becoming prominent as organizations try to move their systems up to more modern and maintainable technology in a cost effective manner. The Johnson Space Center (JSC) created a significant set of tools to develop and maintain FORTRAN and C code during development of the space shuttle. This tool set forms the basis for an integrated environment to reengineer existing code into modern software engineering structures which are then easier and less costly to maintain and which allow a fairly straightforward translation into other target languages. The environment will support these structures and practices even in areas where the language definition and compilers do not enforce good software engineering. The knowledge and data captured using the reverse engineering tools is passed to standard forward engineering tools to redesign or perform major upgrades to software systems in a much more cost effective manner than using older technologies. The latest release of the environment was in Feb. 1992.

Fridge, Ernest M., III↗

NASA NTRS1992

LV software support for supersonic flow analysis

The software for configuring an LV counter processor system has been developed using structured design. The LV system includes up to three counter processors and a rotary encoder. The software for configuring and testing the LV system has been developed, tested, and included in an overall software package for data acquisition, analysis, and reduction. Error handling routines respond to both operator and instrument errors which often arise in the course of measuring complex, high-speed flows. The use of networking capabilities greatly facilitates the software development process by allowing software development and testing from a remote site. In addition, high-speed transfers allow graphics files or commands to provide viewing of the data from a remote site. Further advances in data analysis require corresponding advances in procedures for statistical and time series analysis of nonuniformly sampled data.

Bell, W. A.↗

NASA NTRS1992

Information models of software productivity - Limits on productivity growth

Research into generalized information-metric models of software process productivity establishes quantifiable behavior and theoretical bounds. The models establish a fundamental mathematical relationship between software productivity and the human capacity for information traffic, the software product yield (system size), information efficiency, and tool and process efficiencies. An upper bound is derived that quantifies average software productivity and the maximum rate at which it may grow. This bound reveals that ultimately, when tools, methodologies, and automated assistants have reached their maximum effective state, further improvement in productivity can only be achieved through increasing software reuse. The reuse advantage is shown not to increase faster than logarithmically in the number of reusable features available. The reuse bound is further shown to be somewhat dependent on the reuse policy: a general 'reuse everything' policy can lead to a somewhat slower productivity growth than a specialized reuse policy.

Tausworthe, Robert C.↗

NASA NTRS1991

Data systems and computer science: Software Engineering Program

An external review of the Integrated Technology Plan for the Civil Space Program is presented. This review is specifically concerned with the Software Engineering Program. The goals of the Software Engineering Program are as follows: (1) improve NASA's ability to manage development, operation, and maintenance of complex software systems; (2) decrease NASA's cost and risk in engineering complex software systems; and (3) provide technology to assure safety and reliability of software in mission critical applications.

Zygielbaum, Arthur I.↗

NASA NTRS1990

General purpose optimization software for engineering design

The author has developed several general purpose optimization programs over the past twenty years. The earlier programs were developed as research codes and served that purpose reasonably well. However, in taking the formal step from research to industrial application programs, several important lessons have been learned. Among these are the importance of clear documentation, immediate user support, and consistent maintenance. Most important has been the issue of providing software that gives a good, or at least acceptable, design at minimum computational cost. Here, the basic issues developing optimization software for industrial applications are outlined and issues of convergence rate, reliability, and relative minima are discussed. Considerable feedback has been received from users, and new software is being developed to respond to identified needs. The basic capabilities of this software are outlined. A major motivation for the development of commercial grade software is ease of use and flexibility, and these issues are discussed with reference to general multidisciplinary applications. It is concluded that design productivity can be significantly enhanced by the more widespread use of optimization as an everyday design tool.

Vanderplaats, G. N.↗

NASA NTRS1992

Experimental software engineering: Seventeen years of lessons in the SEL

Seven key principles developed by the Software Engineering Laboratory (SEL) at the Goddard Space Flight Center (GSFC) of the National Aeronautics and Space Administration (NASA) are described. For the past 17 years, the SEL has been experimentally analyzing the development of production software as varying techniques and methodologies are applied in this one environment. The SEL has collected, archived, and studied detailed measures from more than 100 flight dynamics projects, thereby gaining significant insight into the effectiveness of numerous software techniques, as well as extensive experience in the overall effectiveness of 'Experimental Software Engineering'. This experience has helped formulate follow-on studies in the SEL, and it has helped other software organizations better understand just what can be accomplished and what cannot be accomplished through experimentation.

Mcgarry, Frank E.↗

NASA NTRS1994

Software Management Environment (SME): Components and algorithms

This document presents the components and algorithms of the Software Management Environment (SME), a management tool developed for the Software Engineering Branch (Code 552) of the Flight Dynamics Division (FDD) of the Goddard Space Flight Center (GSFC). The SME provides an integrated set of visually oriented experienced-based tools that can assist software development managers in managing and planning software development projects. This document describes and illustrates the analysis functions that underlie the SME's project monitoring, estimation, and planning tools. 'SME Components and Algorithms' is a companion reference to 'SME Concepts and Architecture' and 'Software Engineering Laboratory (SEL) Relationships, Models, and Management Rules.'

Hendrick, Robert↗

NASA NTRS1994

Software for continuum modeling of controls-structures interactions

It is clear that computer software is needed to assist in the generation of the equations of motion for complex, flexible spacecraft. Daniel Poelaert of ESTEC has developed the software DISTEL with which he has modeled the structural dynamics for different satellites. He is interested in expanding the capabilities of DISTEL to include structural damping and control systems. Unfortunately, the software has not been released. The author has developed similar software, PDEMOD, which has been used to model the Spacecraft control Laboratory Experiment (SCOLE), the Solar Array Flight Experiment (SAFE), the Mini-MAST truss, and the LACE satellite. PDEMOD has been used also for optimal parameter estimation and integrated control-structures design. PDEMOD is also being extended to include structural damping and control systems which are imbedded into the same equations for the structural dynamics. This paper will address the formulation of the equations for the structural dynamics of spacecraft structures which are constructed of a 3-dimensional arrangement of rigid bodies and flexible beam elements. Control system dynamics are imbedded into the same equations so that model order reduction approximations are not necessary. The input data consists of the physical data of the elements and the topological information describing how the elements are connected. PDEMOD accomplishes the following: (1) automatically assembles the equations of motion for the entire structural model; (2) calculates the modal frequencies; (3) calculates the mode shapes; (4) generates perspective views of the mode shapes; and (5) forms selected transfer functions. The software PDEMOD continues to be developed to provide additional features to assist in analyzing and synthesizing control and structural systems for flexible spacecraft.

Taylor, Lawrence W., Jr.↗

NASA NTRS1993

The (mis)use of subjective process measures in software engineering

A variety of measures are used in software engineering research to develop an understanding of the software process and product. These measures fall into three broad categories: quantitative, characteristics, and subjective. Quantitative measures are those to which a numerical value can be assigned, for example effort or lines of code (LOC). Characteristics describe the software process or product; they might include programming language or the type of application. While such factors do not provide a quantitative measurement of a process or product, they do help characterize them. Subjective measures (as defined in this study) are those that are based on the opinion or opinions of individuals; they are somewhat unique and difficult to quantify. Capturing of subjective measure data typically involves development of some type of scale. For example, 'team experience' is one of the subjective measures that were collected and studied by the Software Engineering Laboratory (SEL). Certainly, team experience could have an impact on the software process or product; actually measuring a team's experience, however, is not a strictly mathematical exercise. Simply adding up each team member's years of experience appears inadequate. In fact, most researchers would agree that 'years' do not directly translate into 'experience.' Team experience must be defined subjectively and then a scale must be developed e.g., high experience versus low experience; or high, medium, low experience; or a different or more granular scale. Using this type of scale, a particular team's overall experience can be compared with that of other teams in the development environment. Defining, collecting, and scaling subjective measures is difficult. First, precise definitions of the measures must be established. Next, choices must be made about whose opinions will be solicited to constitute the data. Finally, care must be given to defining the right scale and level of granularity for measurement.

Valett, Jon D.↗