Module Management As A System Service

Gilad Bracha, Charles F. Clark, Gary Lindstrom and Douglas B. Orr

Abstract

A new approach to program modularity is presented, based on three
key  ideas: (i) elevating module management to a pervasive system
service, (ii) casting the notion of module as  an  abstract  data
type,  and  (iii)  representing modules as objects for programmed
manipulation and retention.  The result is an  innovative  system
architecture for program construction, with flexible capabilities
for name space management, inter-process sharing, and incremental
loading and re-linking.  The necessary reflective powers are pro-
vided by a permanently running system process  exporting  a  wide
repertory of module manipulation and delivery services.  This ap-
proach draws on insights from both programming languages and sys-
tem  architecture.  From programming languages, we have taken in-
spiration from the power of inheritance in  object-oriented  pro-
gramming  languages,  and  the importance of types as a basis for
secure, evolvable module interfaces.  From  system  architecture,
we  have  profited from the server process approach to system or-
ganization, and respect for the crucial role of module binding as
a system flexibility governor.  A case study applying this archi-
tecture to C++ is presented, as well as a brief assessment of its
role  in  a more comprehensive architecture for persistent object
management.