Examining Reuse in Lasrs++-based Projects

NASA Langley Research Center (LaRC) developed the Langley Standard Real-Time Simulation in C++ (LaSRS++) to consolidate all software development for its simulation facilities under one common framework. A common framework promised a decrease in the total development effort for a new simulation by encouraging software reuse. To judge the success of LaSRS++ in this regard, reuse metrics were extracted from 11 aircraft models. Three methods that employ static analysis of the code were used to identify the reusable components. For the method that provides the best estimate, reuse levels fall between 66% and 95% indicating a high degree of reuse. Additional metrics provide insight into the extent of the foundation that LaSRS++ provides to new simulation projects. * When creating variants of an aircraft, LaRC developers use object-oriented design to manage the aircraft as a reusable resource. Variants modify the aircraft for a research project or embody an alternate configuration of the aircraft. The variants inherit from the aircraft model. The variants use polymorphism to extend or redefine aircraft behaviors to meet the research requirements or to match the alternate configuration. Reuse level metrics were extracted from 10 variants. Reuse levels of aircraft by variants were 60% 99%. * Senior Member, AIAA Copyright © 2001 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The U.S. Government has a royalty free license to exercise all rights under the copyright claimed herein for Government Purposes. All other rights are reserved by the copyright owner. Acronyms AoR Amount of Reuse Metric DC Dependency Chain Method ERF External Reuse Frequency Metric ERL External Reuse Level Metric F Frequency GUI Graphical User Interface LaRC Langley Research Center LaSRS++ Langley Standard Real-Time Simulation in C++ LOC Lines of Code NOC Number of Classes OC Object Chain Method RO Refined Object Chain Method Rsf Size-Frequency Reuse Metric Introduction The LaSRS++ project had three main goals: 1. Create one simulation framework from which developers could build both single-vehicle and multivehicle simulations for a variety of aircraft. This goal aimed to increase developer utilization. In the 1980’s, each simulator at LaRC had its own code base. With one common framework, developers no longer had to undergo significant training to move from one simulator to the next. 2. Move vehicle models between simulators with minimal additional development. With separate code bases, vehicle models had to be rewritten and re-tested to move to another simulator. 3. Encourage software reuse. With separate code bases leading to segregated development teams, reinvention of features was not only common but sometimes necessary. Designed as an objectoriented framework, LaSRS++ provided a large number of generic components that developers could reuse when writing a new simulation. When AIAA-2001-4119