The Gutenberg operating system kernel
ACM '86 Proceedings of 1986 ACM Fall joint computer conference
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THE GUTENBERG SYSTEM IS A PORT-BASED, OBJECT-ORIENTED OPERATING SYSTEM KERNEL DESIGNED TO FACILIATE THE DESIGN AND STRUCTURING OF PROCESSES IN DISTRIBUTED SYSTEMS. THIS IS ACHIEVED BY PROVIDING PRIMITIVES FOR STRUCT- URING PROCESSES THROUGH CONTROLLED PROCESS INTERCONNECTIONS AND THROUGH ACCESS TO SHARED RESOURCES. ONLY SHARED RESOURCES ARE VIEWED AS PROTECTED OBJECTS AND HENCE, ALL SHARED RESOURCES CAN BE ACCESSED ONLY BY SPECIFIC OPERATIONS DEFINED ON THEM. PROCESSES COMMUNICATE WITH EACH OTHER AND ACCESS PROTECTED OBJECTS THROUGH THE USE OF PORTS. EACH PORT IS ASSOCIATED WITH AN ABSTRACT DATA TYPE OPERATION AND CAN BE CREATED BY A PROCESS ONLY IF THE PROCESS POSSESSES THE PRIVILEGE TO EXECUTE THAT OPERATION. PRIVI- LEGES ARE REPRESENTED BY ONE OR MORE CAPABILITIES. THUS, ACCESS CONTROL TO SHARED RESOURCES IS ACHIEVED BY CONTROLLING THE ACQUISITION OF CAPABILITIES TO CREATE PORTS BY PROCESSES. CAPABILITIES TO CREATE PORTS FOR REQUESTING OPERATIONS ARE CONTAINED IN THE CAPABILITY DIRECTORY WHICH IS A KERNEL OBJECT, I.E., IS MAINTAINED AND MANIPULATED ONLY BY THE KERNEL. THE PURPOSE OF THE CAPABILITY DIRECTORY IS TO RESTRICT THE USE OF CAPABILITIES IN A CONSISTENT AND ORDERLY WAY. AT ANY TIME, EACH PROCESS IS ASSOCIATED WITH A SINGLE SUBDIRECTORY OF THE CAP- ABILITY DIRECTORY DESIGNATED AS ITS ACTIVE DIRECTORY. THE PROTECTION DO- MAIN OF A PROCESS IS DEFINED BY THE SET OF STABLE CAPABILITIES IN ITS ACTIV