Posted by

Software Cost Estimation Using a Decision Graph Process: A Knowledge Engineering Approach

Software Track



At The California Institute of Technology/Jet Propulsion Laboratory, methodologies for Flight Software (FSW) cost estimation and documentation are determined that allow for efficient concurrent and consistent analysis within a tight schedule constraint. This knowledge is structured or “engineered ” to facilitate the implementation of FSW cost estimation by others who wish to serve as practitioners in the field.

Knowledge Engineering (as defined by Edward Feigenbaum and Pamela McCorduck in 1983 ) “& is that discipline that involves integrating knowledge into computer systems in order to solve complex problems normally requiring a high level of human expertise”. Embedded in this definition is the acquisition and structuring of the related information characterizing the knowledge domain of interest. The effort described in this presentation relates to these ideas in 2 specific ways: (1) It gives a decision graph relating to the acquisition, structuring and representation of the knowledge used for the computation of FSW estimates for space missions at JPL and (2) Although we do not fully automate the processes described here, various aspects of the work are embedded in and related to computer activity. Further, the work is done in such a way as to facilitate further automation of its procedures.

We present an overview of FSW cost estimation techniques used for Independent Cost Estimates (ICEs), proposals, and for the validation of Cost Analysis Data Requirements (CADRe) submissions. The aforementioned decision graph illustrates the steps taken in the production of these estimated costs and serves as the basis of discussion for this paper and the corresponding presentation.

General principles for the estimation of FSW are presented using the SEER-SEM computer program as an illustration of these principles when appropriate. A discussion of various Source Lines of Code (SLOC) data sources and their uses for the preparation of the estimates is given as code size is a major driver for software costs. A computerized methodology used to map the SEER-SEM output into the JPL Work Breakdown Structure (WBS) is illustrated. Finally, an “Across the Board” tally of the SEER-SEM runs and their corresponding input is given in a single sheet for a set of several proposals at JPL.

This paper is not a description per se of the efforts by two software cost analysts. Rather, it is an outline of the methodology used for FSW cost analysis presented in a form that would serve as a foundation upon which others may gain insight into how to perform FSW cost analyses for their own problems at hand.


Sherry Stukes
The Jet Propulsion Laboratory
Ms. Stukes is a Software Systems Engineer/Cognizant Engineer at The Jet Propulsion Laboratory in Pasadena, California. She specializes in software estimating and software data collection in support of JPL Independent Cost Estimates, proposals, and CADRe development. Ms. Stukes manages a research project that will provide a software estimating tool for NASA Headquarters, which is not dependant on software lines of code.

Some of Ms. Stukes prior accomplishments include: development and maintenance of two large databases for the Air Force Space and Missile Systems Center (AF SMC): the Software Database (SWDB) and the Operations and Support Database (OSDB); instructor for the Army Logistics Management College (ALMC) Software Estimating Models course; and advisor to Air Force Institute of Technology (AFIT) students conducting thesis projects in the area of software model calibration. Ms. Stukes was the
1997 International Society of Parametric Analysts (ISPA) Parametrician of the year.

Ms. Stukes holds a BS degree in Business Administration from California State University, Long Beach and an MBA from California Lutheran University.

Dr. John Spagnuolo
The Jet Propulsion Laboratory
Dr. Spagnuolo is presently serving as an Engineering Cost Analyst in the Engineering Cost Estimation Group at The Jet Propulsion Laboratory in Pasadena, California. He specializes in the preparation of Cost Estimation Data Requirements (CADRes), Cost Estimating relationships (CERs) and software cost estimation and analysis. He holds degrees in mathematics from Clarkson College of Technology, University of California at Los Angeles, and the Doctor’s degree from Rensselaer Polytechnic Institute.

In the past, Dr. Spagnuolo has received several awards and certificates of recognition relating to his work in neural networks and solar physics. He received the Space Act Award for his paper on the Computation and Visualization of Archimedean spirals in 3 dimensions. Along with numerous conference and journal articles, he has published several abstracts in the NASA Tech Briefs Journal. He also developed an architecture for a hierarchical planning system for computerized military war gaming and an expert system for use in automated decision making in a computer war game for which he won best session paper at the Military Operations Research Society (MORS) Conference. Presently, Dr. Spagnuolo is studying Newton’s Principia from a mathematical perspective and doing research in mapping cognition onto an artificial neural network.