Elicitation, representation, and analysis of requirements are important tasks performed early in the systems engineering process. This remains true with the adoption of Model-Based Systems Engineering (MBSE) methodologies. Existing SysML-based methodologies often choose between (i) using external requirements documents and/or databases as the authoritative source for requirements truth versus (ii) generating requirements directly, as elements in the system model. In either case, there is often need for the systems engineer to manually develop a model-based requirements representation, as this faculty is not automatic in the commonly-used SysML feature set. Additionally, once the system model has been completed, systems engineers typically must prepare traditional "shall-statement" requirements for external review purposes, as not all stakeholders can be expected to be trained in system model interpretation.This paper details a novel effort to address both problems, by automatically transforming text-based requirements (TBR) into SysML model-based requirement (MBR) representations, and vice versa. The text-to-model based transformation direction uses requirement templates and natural language processing techniques, expanding on work from the field of requirements engineering. This paper also presents an aerospace-domain case study application of the developed tool. In the case study, a selected set of requirements were analyzed, and a system model was constructed. Then, the intermediate output system model was updated with additional elements, to represent the progression of the project's systems engineering process. The modified system model was then analyzed, constructing text-based requirements from the structure. The resulting text-based requirements were compared to the initial set of input requirements to assess consistency in both directions of analysis. The methodology developed in this paper improves the systems engineering process by saving the systems engineer time constructing potentially repetitive model elements, and by enabling model-based requirement analyses to methodologies previously only capable of processing text-based requirements. Further, the methodology eases the responsibility of the systems engineer to maintain a copy of the model-based requirements in text-based format.TABLE OF CONTENTS 1. INTRODUCTION .
This work presents an overview of the Segmented Aperture Interferometric Nulling Testbed (SAINT), a project that will pair an actively-controlled macro-scale segmented mirror with the Visible Nulling Coronagraph (VNC). SAINT will incorporate the VNC's demonstrated wavefront sensing and control system to refine and quantify end-to-end high-contrast starlight suppression performance. This pathfinder testbed will be used as a tool to study and refine approaches to mitigating instabilities and complex diffraction expected from future large segmented aperture telescopes.
One major benefit offered by MBSE is the ability to formalize interactions between subsystems in the design process. This formalization eases the transfer of information between parties. The process of government acquisition is likewise characterized by information transfer: diverse requirements must be altered and tracked between the requesting, responding, and evaluating parties. Thus, it is a natural extension of MBSE is to apply it to the acquisition process.This paper demonstrates a set of tools and patterns developed during a surrogate simulation of an MBSE-enabled Request for Proposal between NAVAIR and a responding contractor. In particular, the tools presented were developed from the NAVAIR Systems Model viewpoint. This paper covers four tools developed in this surrogate pilot. The first analyzes the problem of requirement generation. While standards such as the OMG SysML are being adopted by MBSE practitioners, the model literacy of all stakeholders is unlikely and may never be fully guaranteed. Document generation tools, such as OpenMBEE have been developed for SysML software, which enable presentation of descriptive information about the model. This paper demonstrates modeling patterns and a tool that translates information from native-model form into a text-based format. The second and third tools presented assist in the acquirer's source selection process. Making use of the patterns which generate the text requirements above, Evaluation and Estimation Models are presented, which can act directly on contractors' responses. The Evaluation Model assists the verification process by ensuring numerical requirements are satisfied. The Estimation Model compares the contractors' claimed values with historically expected values, to assist directing the source selection experts' focus of examination. The fourth tool presented offers a method of extracting historical traceability for model elements. This aids the acquisition process by enabling digital signoff at any stage of the acquisition process. These four tools were applied in the surrogate acquisition process for a notional UAV, and a description of this case study is presented.TABLE OF CONTENTS 1. INTRODUCTION .
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