Here is Random House's basic summary of "shall" usage:

The traditional rule of usage guides dates from the 17th century and says
that to denote future time shall  is used in the first person ( I shall
leave. We shall go ) and will  in all other persons ( You will be there,
won't you? He will drive us to the airport. They will not be at the meeting ).
The rule continues that to express determination, will  is used in the first
person ( We will win the battle ) and shall  in the other two persons ( You
shall not bully us. They shall not pass ). Whether this rule was ever widely
observed is doubtful. Today, will  is used overwhelmingly in all three
persons and in all types of speech and writing both for the simple future
and to express determination. Shall  has some use in all persons, chiefly in
formal writing or speaking, to express determination: I shall return. We
shall overcome. Shall  also occurs in the language of laws and directives:
All visitors shall observe posted regulations.  Most educated native users
of American English do not follow the textbook rule in making a choice
between shall  and will.

shall. (n.d.). *Dictionary.com Unabridged*. Retrieved June 04, 2011, from
Dictionary.com website: http://dictionary.reference.com/browse/shall

John

On Sat, Jun 4, 2011 at 10:09 PM, Kathleen Ward <[log in to unmask]> wrote:

> I've always heard it called the deonatic use ofnthe modal -- something
> that imposes an obligation on the hearer of an utterance.  It is a
> characteristic of modals in English that they have both deonatic and
> epistemically (degree of certainty) uses.
>
> Kathleen M. Ware.
>
> University of California, Davis
>
>
> On Saturday, June 4, 2011, Jane Saral <[log in to unmask]> wrote:
> > Friends have just returned from their annual pilgrimage to Ashland,
> Oregon, and on one flight they saw a sign in the flight attendants' area
> that said, "Hands shall be washed before serving food or drink."
> >
> >
> >
> > What is this use of "shall" called?
> >
> > Jane Saral
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> >
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