Another way of looking at this situation is by letting the (first order) differential features <math>\operatorname{d}u, \operatorname{d}v, \operatorname{d}w</math> be viewed as the features of another universe of discourse, called the "tangent universe to <math>X\!</math> with respect to the interpretation <math>c\!</math> " and represented as <math>\operatorname{d}X \cdot c</math> . In this setting, <math>\operatorname{D}q \cdot c</math> , the "difference proposition of <math>q\!</math> at the interpretation <math>c\!</math> ", where <math>c = u\ v\ w</math> , is marked by the shaded region in Figure 4.
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Another way of looking at this situation is by letting the (first order)
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differential features du, dv, dw be viewed as the features of another
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universe of discourse, called the "tangent universe to X with respect
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to the interpretation c" and represented as dX.c. In this setting,
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Dq.c, the "difference proposition of q at the interpretation c",
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where c = uvw, is marked by the shaded region in Figure 4.