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A legacy system is an operational, large-scale software system that is maintained beyond its first generation of programmers. It typically represents a massive economic investment and is critical to the mission of the organization it serves. As such systems age, they become increasingly complex and brittle, and hence harder to maintain. They also become even more critical to the survival of their organization because the business rules encoded within the system are seldom documented elsewhere.Our research is concerned with developing a suite of tools to aid the maintainers of legacy systems in recovering the knowledge embodied within the system. The activities, known collectively as "program understanding", are essential preludes for several key processes, including maintenance and design recovery for reengineering.In this paper we present three pattern-matching techniques: source code metrics, a dynamic programming algorithm for finding the best alignment between two code fragments, and a statistical matching algorithm between abstract code descriptions represented in an abstract language and actual source code. The methods are applied to detect instances of code cloning in several moderately-sized production systems including tcsh, bash, and CLIPS.The programmer's skill and experience are essential elements of our approach. Selection of particular tools and analysis methods depends on the needs of the particular task to be accomplished. Integration of the tools provides opportunities for synergy, allowing the programmer to select the most appropriate tool for a given task.

Advances in building automation technology have taken place for a variety of building services including heating, ventilating, and air conditioning (HVAC) control systems, lighting control systems, access control systems, and fire detection systems. In spite of these advances in technology, many building control systems do not work as intended. It is evident that the industry needs to learn how to take advantage of the new ability to interconnect traditionally independent systems in a building. Commissioning, automated fault detection and new approaches to applying system integration are all areas of active research. However, it can be difficult to conduct this research in actual buildings because of the need to maintain comfortable and safe conditions for the building occupants.This report describes two enabling tools that have been developed to advance these research efforts. It focuses on the use of these tools to develop and test automated fault detection and diagnostic (FDD) technology for HVAC systems and their application in the area of Fault Detection and Diagnosis. The two enabling tools are the Virtual Cybernetic Building Testbed (VCBT) and the FDD Test Shell. The VCBT consists of a variety of simulation models that together emulate the characteristics and performance of a cybernetic building system. The simulation models are interfaced to real state-of-the-art BACnet speaking control systems to provide a hybrid software/hardware testbed that can be used to develop and evaluate control strategies and control products that use the BACnet communication protocol. The FDD Test Shell is a data-sharing tool that was developed to enable side-by-side testing and comparison of two or more FDD tools and to support the integration of information from multiple FDD tools.Preliminary tests of some of the faults modeled in the VCBT are described in this report. The primary goal of the tests was to quantify the impact of valve and damper leakage for typical air-handling unit (AHU) with variable-air-volume (VAV) box configurations. In this study, testing revealed that leakage through the outdoor air damper and a stuck open outdoor air damper fault have almost no measurable impact on the operation of the system.

Control of building systems is becoming increasingly more intelligent and complex. This development both necessitates the use of automated diagnostics to ensure fault-free operation and enables diagnostic capabilities for the various building systems by providing a distributed platform that is powerful and flexible enough to perform fault detection and diagnostic (FDD). Most of today's emerging FDD tools are stand-alone software products that do not reside in a building control system. Thus, trend data files must be processed off-line, or an interface to the building control system must be developed to enable on-line analysis. This is a cumbersome process and it does not scale well because all of the data must be obtained at a single point. A better approach would be to develop algorithms that can be embedded in commercial controllers so that the fault detection can be done as close to the source of the fault as possible. Only the result of the analysis needs to be conveyed to an operator or supervisory controller.AHU Performance Assessment Rules (APAR) is a diagnostic tool that uses a set of expert rules derived from mass and energy balances to detect common faults in air-handling units. Control signals are used to determine the mode of operation for the AHU. A subset of the expert rules corresponding to that mode of operation is then evaluated to determine if there is a mechanical fault or a control problem. VAV box Performance Assessment Control Charts (VPACC) is a diagnostic tool that uses a statistical quality control measures to detect faults or control problems in VAV boxes. This report describes the results of a research study to determine the effectiveness of these tools in detecting commonly found mechanical faults and control problems.The research involved a complementary set of laboratory experiments using commercial AHU and VAV box controllers under both normal operating conditions and operation with known faults, computer simulations, and emulations using the NIST Virtual Cybernetic Building Testbed (VCBT). The APAR and VPACC tools were both found to be successful at finding a wide variety of faults. It was also found that some faults could not be detected under certain operating conditions because the control system was able to mask the problem or because sensor data needed to detect the fault is not commonly available in commercial systems. Both tools appear to be suitable for embedding in commercial control products.

Based on a small number of cases, we were able to show for the first time that the use of orthogonal double plating is not associated with an increased rate of complications in patients with periprosthetic femoral fractures and stable components. Moreover, orthogonal double plating can be used successfully as a salvage procedure. At the time of follow up, seven out of ten patients were mobile. More cases must be investigated to validate our findings.