Directional derivative in content MathML?

Is there an accepted notation for marking up directional (ie. vector) 
derivatives (http://mathworld.wolfram.com/DirectionalDerivative.html) in 
content MathML?  My first inclination was to use the <gradient> tag, but 
that's not quite correct since it's really the dot product of the 
gradient and the unit direction vector.  Is the <diff/> tag appropriate 
here?  How would I specify the directional vector?  A <bvar> perhaps?

Thanks,
-- Brent

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"The programmer, like the poet, works only slightly removed from pure
  thought-stuff.  He builds his castles in the air, from air, creating
  by exertion of the imagination.  Few media of creation are so
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                         -- Frederick Brooks, Jr., The Mythical Man Month

Received on Monday, 19 May 2003 16:25:42 UTC