URL encoding of query variables

Greetings,

	I am doing some URL encoding of query variables in my code, and I wanted
to be sure I have the rules right.  I can think of 4 ways to specify a query
variable and its value, and I want to know which are valid.

1. keyword=value      This is the simplest case and I know what to do with it.
2. keyword=           This represents a null value for the keyword.  Again,
                      I think I know what to do.
3. keyword            This represents a keyword with no associated value, perhaps
                      some true/false type of indicator.  It has no equal sign.  Is
                      this form valid?
4. =value             This is an attempt at some kind of positional value.  I think it
                      is invalid.  Is that true?

Thanks,

Fred Bohle