When one definition form simply macroexpands into another, or otherwise has an identical effect as far as the dspec system is concerned, the dspec system should consider them variant forms of the same class.
Use define-dspec-alias to convert one definer to the other during canonicalization. A pre-defined example of this in LispWorks is
defvar. These cannot be distinguished (other than in the source code), so
defparameter has been defined as a dspec alias for
defconstant are distinct kinds of variable, since we can easily tell which type of definition is in effect by calling the function
constantp. To define their dspecs, LispWorks creates a dspec class called
variable and uses it as the superspace argument when defining the
defconstant dspec classes.
would be a suitable appropriate alias definition. This define-dspec-alias form defines the dspec.
define-dspec-alias is like
defmacro for dspecs, so it could be used to describe complicated conversions, as long as it can be done purely statically and totally in terms of existing dspecs. However, nothing more complicated than
defparameter has been found necessary.
Some definition forms are macros that expand into a group of other definitions, for example
defstruct. When the form is associated with a dspec class, the subdefinitions can be automatically recorded as being subforms of the new definition, by use of the def macro.
def defines a relation between two particular definitions, for example
(defstruct foo) and
(defun make-foo), not between the two dspec classes.
Some definitions are additions to another class of definition, for example methods are additions to generic functions. We call these distributed definitions, consisting of "parts" and "the aggregate".
The primary name of a part gives the primary name of the aggregate it is a part of, and the qualifiers distinguish it from the other parts of the same aggregate. Only a part dspec may have qualifiers.
LispWorks User Guide and Reference Manual - 20 Sep 2017