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E.2 Categorization of Library Units

1
[Library units can be categorized according to the role they play in a distributed program. Certain restrictions are associated with each category to ensure that the semantics of a distributed program remain close to the semantics for a nondistributed program.]
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{categorization pragma [distributed]} {pragma, categorization [distributed]} {library unit pragma (categorization pragmas) [partial]} {pragma, library unit (categorization pragmas) [partial]} {categorized library unit} A categorization pragma is a library unit pragma (see 10.1.5) that restricts the declarations, child units, or semantic dependences of the library unit to which it applies. A categorized library unit is a library unit to which a categorization pragma applies.
3
The pragmas Shared_Passive, Remote_Types, and Remote_Call_Interface are categorization pragmas. In addition, for the purposes of this Annex, the pragma Pure (see 10.2.1) is considered a categorization pragma.
4/1
{8652/0078} {AI95-00048-01} {shared passive library unit} A library package or generic library package is called a shared passive library unit if a Shared_Passive pragma applies to it. {remote types library unit} A library package or generic library package is called a remote types library unit if a Remote_Types pragma applies to it. {remote call interface} A library unit package or generic library package is called a remote call interface if a Remote_Call_Interface pragma applies to it. {normal library unit} A normal library unit is one to which no categorization pragma applies. 
4.a.1/1
Ramification: {8652/0078} {AI95-00048-01} A library subprogram can be a remote call interface, but it cannot be a remote types or shared passive library unit.
5
[The various categories of library units and the associated restrictions are described in this clause and its subclauses. The categories are related hierarchically in that the library units of one category can depend semantically only on library units of that category or an earlier one, except that the body of a remote types or remote call interface library unit is unrestricted.
6
The overall hierarchy (including declared pure) is as follows: 
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Declared Pure 

Can depend only on other declared pure library units;
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Shared Passive 

Can depend only on other shared passive or declared pure library units;
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Remote Types 
The declaration of the library unit can depend only on other remote types library units, or one of the above; the body of the library unit is unrestricted;
10
Remote Call Interface 

The declaration of the library unit can depend only on other remote call interfaces, or one of the above; the body of the library unit is unrestricted;
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Normal 
Unrestricted. 
12
Declared pure and shared passive library units are preelaborated. The declaration of a remote types or remote call interface library unit is required to be preelaborable. ]

Implementation Requirements

13/1
 This paragraph was deleted.{8652/0079} {AI95-00208-01} For a given library-level type declared in a preelaborated library unit or in the declaration of a remote types or remote call interface library unit, the implementation shall choose the same representation for the type upon each elaboration of the type's declaration for different partitions of the same program. 

Implementation Permissions

14
Implementations are allowed to define other categorization pragmas.

Wording Changes from Ada 95

14.a/2
{8652/0078} {AI95-00048-01} Corrigendum: Clarified that a library subprogram can be a remote call interface unit.
14.b/2
{8652/0079} {AI95-00208-01} Corrigendum: Removed the requirement that types be represented the same in all partitions, because it prevents the definition of heterogeneous distributed systems and goes much further than required. 

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