Re: [Corpora-List] Wavelet for NLP

From: John F. Sowa (sowa@bestweb.net)
Date: Mon Jun 12 2006 - 14:27:36 MET DST

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    Stefan,

    The analogy with Fourier transforms was the original
    motivation. The primary difference between a wavelet
    and a sine wave (or cosine wave) is that sine waves
    extend to infinity in both directions, but a wavelet
    is zero except on a finite interval.

    > I've always been thinking of wavelet transforms as
    > a "variant" of Fourier transformation, which is also
    > (at least supposed to be) invertible in the continuous
    > case.

    The property of being invertible is central to the
    definition of wavelet transforms. Extending continuous
    methods to discrete structures, such as words and texts,
    introduces difficulties, but the possibility of finding
    an inverse is highly desirable whenever possible. In
    some cases, the inverse is "lossy" -- i.e., much of the
    original detail is lost in the reconstruction.

    John Sowa



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