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<H1> E.3 Consistency of a Distributed System</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> This clause defines attributes and rules associated
with verifying the consistency of a distributed program. </DIV>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2/1</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> For a <FONT FACE="Arial, Helvetica">prefix</FONT>
P that statically denotes a program unit, the following attributes are
defined: </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DL Class="Hanging"><DT> P'Version<DD Class="Hanging">
<A NAME="I6719"></A><A NAME="I6720"></A>Yields a value of the predefined
type String that identifies the version of the compilation unit that
contains the declaration of the program unit.</DL>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DL Class="Hanging"><DT> P'Body_Version<DD Class="Hanging">
<A NAME="I6721"></A><A NAME="I6722"></A>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. </DL>
<DIV Class="Paranum"><FONT SIZE=-2>5/1</FONT></DIV>
<DIV Class="Normal"> <A NAME="I6723"></A>The <I>version</I> of a
compilation unit changes whenever the compilation unit changes in a semantically
significant way. This International Standard does not define the exact
meaning of "semantically significant". It is unspecified whether
there are other events (such as recompilation) that result in the version
of a compilation unit changing. <A NAME="I6724"></A></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5.1/1</FONT></DIV>
<DIV Class="Normal"> If P is not a library unit, and P has no completion,
then P'Body_Version returns the Body_Version of the innermost program
unit enclosing the declaration of P. If P is a library unit, and P has
no completion, then P'Body_Version returns a value that is different
from Body_Version of any version of P that has a completion. </DIV>
<H4 ALIGN=CENTER>Bounded (Run-Time) Errors</H4>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Normal"> <A NAME="I6725"></A><A NAME="I6726"></A>In a distributed
program, a library unit is <I>consistent</I> 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. <A NAME="I6727"></A>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. </DIV>
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