The instantiation field is purely to enable a message to be addressed
to a unique application. When an application registers, it does not
specify the instantiation - rather this is returned by the CCC library
such that it is unique for the specified <#1997#> type<#1997#> at the specified
<#1998#> address<#1998#>. It is not guaranteed to be globally unique - global
uniqueness is only guaranteed by the triple of <#1999#> (instantiation,
type, address)<#1999#> with no wildcards in any field. When an application
sends a message, it uses one of its unique triples as the source
address. Which one it chooses should depend on to whom the message
was addressed.