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E.3 Consistency of a Distributed System

This clause defines attributes and rules associated with verifying the consistency of a distributed program.

Static Semantics

For a prefix P that statically denotes a program unit, the following attributes are defined:

P'Version

Yields a value of the predefined type String that identifies the version of the compilation unit that contains the declaration of the program unit.

P'Body_Version

Yields a value of the predefined type String that identifies the version of the compilation unit that contains the body (but not any subunits) of the program unit.

The version of a compilation unit changes whenever the version changes for any compilation unit on which it depends semantically. The version also changes whenever the compilation unit itself changes in a semantically significant way. It is implementation defined whether there are other events (such as recompilation) that result in the version of a compilation unit changing.

Bounded (Run-Time) Errors

In a distributed program, a library unit is consistent if the same version of its declaration is used throughout. It is a bounded error to elaborate a partition of a distributed program that contains a compilation unit that depends on a different version of the declaration of a shared passive or RCI library unit than that included in the partition to which the shared passive or RCI library unit was assigned. As a result of this error, Program_Error can be raised in one or both partitions during elaboration; in any case, the partitions become inaccessible to one another.

About DocAda Light: Preface / Preliminary / Help / TOC / Copyright
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