1. In a multi-domain graphical modeling environment, a method of 1 invoking domain-specific help callback methods for multi-domain graphical objects, comprising: registering: domain-specific help callback methods for each class of multi-domain graphical objects that occur in a domain of a multi-domain graphical model; the multi-domain graphical model including at least one instance of a multi-domain graphical object, the multi-domain graphical object occurring in more than one domain and having at least one of a different functionality, semantics or property in each domain, the registering occurring by: adding a domain-specific help method for a class of objects to a list of methods stored as a help callback property of the class, or, creating a domain-specific help callback method for a multi-domain graphical object, the registering occurring: when the object is created, or when the object is moved from one domain to another domain, the registering associated with a help facility; receiving a help request from a user for an instance of the multi-domain graphical object; identifying: in response to the received help request, the class of the instance of the multi-domain graphical object associated with the help request, and in response to the received help request, the type of the multi-domain graphical object associated with the help request; identifying dynamically: a class for the instance of the multi-domain graphical object, and a current domain of the instance of the multi-domain graphical object; and invoking a domain-specific callback method registered with the help facility for the type and domain identified for the multi-domain graphical object, the invoking using the identified class for the instance of the multi-domain graphical object and the identified current domain of the instance of the multi-domain graphical object.