Blurb::
Allow treatment of discrete variables as continuous

Description::
The variables domain specifies how the discrete variables are treated.
If the user specifies \c mixed in the variable specification block,
the continuous and discrete variables are treated separately. If the
user specifies \c relaxed in the variable specification block, the
discrete variables are relaxed and treated as continuous
variables. This may be useful in optimization problems involving both
continuous and discrete variables when a user would like to use an
optimization method that is designed for continuous variable
optimization. All %Dakota methods have a default value of mixed for
the domain type except for the branch-and-bound method which has a
default domain type of relaxed. Note that the branch-and-bound method
is under development at this time. Finally, note that the domain
selection applies to all variable types: design, aleatory uncertain,
epistemic uncertain, and state.

With respect to domain type, if the user does not specify an 
explicit override of \c mixed or \c relaxed, Dakota infers
the domain type from the method. As mentioned above, 
all methods currently use a mixed domain as a default, except 
the branch-and-bound method which is under development.

Examples::
Theory::
Faq::
See_Also::	variables-mixed
