amenable in Murtaugh 2016
erve as a cautionary reminder to programmers of the
essential violence perpetrated to a text and a call to critically question the
efficacy of methods based on subsequent transformations, the expression's use
seems in practice more like a badge of pride or a schoolyard taunt that would
go: Hey language: you're nothin' but a big BAG-OF-WORDS.
## Bag of words
In information retrieval and other so-called _machine-reading_ applications
(such as text indexing for web search engines) the term "bag of words" is used
to underscore how in the course of processing a text the original order of the
words in sentence form is stripped away. The resulting representation is then
a collection of each unique word used in the text, typically weighted by the
number of times the word occurs.
Bag of words, also known as word histograms or weighted term vectors, are a
standard part of the data engineer's toolkit. But why such a drastic
transformation? The utility of "bag of words" is in how it makes text amenable
to code, first in that it's very straightforward to implement the translation
from a text document to a bag of words representation. More significantly,
this transformation then opens up a wide collection of tools and techniques
for further transformation and analysis purposes. For instance, a number of
libraries available in the booming field of "data sciences" work with "high
dimension" vectors; bag of words is a way to transform a written document into
a mathematical vector where each "dimension" corresponds to the (relative)
quantity of each unique word. While physically unimaginable and abstract
(imagine each of Shakespeare's works as points in a 14 million dimensional
space), from a formal mathematical perspective, it's quite a comfortable idea,
and many complementary techniques (such as principle component analysis) exist
to reduce the resulting complexity.
What's striking about a bag of words representation, given is centrality in so
many text retrieval application is its irreversibility. Given a bag of words
representation of a text and faced with the task of producing the original
text would require in essence the "brain" of a writer to recompose sentences,
working with the patience of a devoted cryptogram puzzler to draw from the
precise stock of available words. While "bag of words" might well serve as a
cautionary reminder to programmers of the essential violence perpetrated to a
text and a call to critically question the efficacy of methods based on
subsequent transformations, the expressions use seems in practice more like a
badge of pride or a schoolyard taunt that would go: Hey language: you're
nothing but a big BAG-OF-WORDS. Following this spirit of the term, "bag of
words" celebrates a perfunctory step of "breaking" a text into a purer form
amenable to computation, to stripping language of its silly redundant
repetitions and foolishly contrived stylistic phrasings to reveal a purer
inner essence.
## Book of words
Lieber's Standard Telegraphic Code, first published in 1896 and republished in
various updated editions through the early 1900s, is an example of one of
several competing systems of telegraph code books. The idea was for both
senders and receivers of telegraph messages to use the books to translate
their messages into a sequence of code words which can then be sent for less
money as telegraph messages were paid by the word. In the front of the book, a
list of examples gives a sampling of how messages like: "Have bought for your
account 400 bales of cotton, March delivery, at 8.34" can be conveyed by a
telegram with the message "Ciotola, Delaboravi". In each case the reduction of
number of transmitted words is highlighted to underscore the efficacy of the
method. Like a dictionary or thesaurus, the book is primarily orga
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