is not supplied or is
, the current process (that is, the result of calling get-current-process) is used.
In the typical case when only the current process sets the property (even if other processes read it), private properties can be used, and are much faster in SMP LispWorks, because they do not need to deal with parallel setting. See process-private-property.
(process-property 'foo (get-current-process) 'bar)
LispWorks User Guide and Reference Manual - 21 Dec 2011