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The ''N'' 2 chart, also referred to as ''N'' 2 diagram, ''N''-squared diagram or ''N''-squared chart, is a diagram in the shape of a matrix, representing functional or physical interfaces between system elements. It is used to systematically identify, define, tabulate, design, and analyze functional and physical interfaces. It applies to system interfaces and hardware and/or software interfaces.〔The first version of this article is completely based on the (NAS SYSTEM ENGINEERING MANUAL SECTION ) 4.4 VERSION 3.1 06/06/06.〕 The ''N''-squared chart was invented by the systems engineer Robert J. Lano, while working at TRW in the 1970s and first published in a 1977 TRW internal report.〔Lano, R. (1977). ''The N2 Chart''. TRW Software Series, Redondo Beach, CA.〕 == Overview == The ''N''2 diagram has been used extensively to develop data interfaces, primarily in the software areas. However, it can also be used to develop hardware interfaces. The basic ''N''2 chart is shown in Figure 2. The system functions are placed on the diagonal; the remainder of the squares in the ''N'' × ''N'' matrix represent the interface inputs and outputs. 〔 NASA (1995). "Techniques of Functional Analysis". In: ''(NASA Systems Engineering Handbook )'' June 1995. p.142.〕 Where a blank appears, there is no interface between the respective functions. Data flows in a clockwise direction between functions (e.g., the symbol F1 F2 indicates data flowing from function F1, to function F2). The data being transmitted can be defined in the appropriate squares. Alternatively, the use of circles and numbers permits a separate listing of the data interfaces. The clockwise flow of data between functions that have a feedback loop can be illustrated by a larger circle called a control loop. The identification of a critical function is also shown in Figure 3, where function F4 has a number of inputs and outputs to all other functions in the upper module. A simple flow of interface data exists between the upper and lower modules at functions F7 and F8. The lower module has complex interaction among its functions. The N2 chart can be taken down into successively lower levels to the hardware and software component functional levels. In addition to defining the data that must be supplied across the interface, the N2 chart can pinpoint areas where conflicts could arise.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「N2 chart」の詳細全文を読む スポンサード リンク
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