Difference between revisions of "Agents in SCOOP"

m (Added a page about separate agents)
 
m (Fix typo)
 
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The page reflects current decisions taken for the current SCOOP implementation, in particular without support for processor tags. So it may change in the future.
 
The page reflects current decisions taken for the current SCOOP implementation, in particular without support for processor tags. So it may change in the future.
 +
 +
== Status of agent targets ==
 +
: Because any agent object is created on a processor associated with the agent's target, that target has to be controlled.
 +
'''Agent target validity rule.''' The target of an agent must be controlled.
  
 
== Types ==
 
== Types ==
−
''Rule.'' Formal arguments of a feature used in an agent expression with a separate target should be separate.
+
'''Agent argument types validity rule.''' If an agent has a separate target, every non-expanded argument of the associated feature must be separate.
 +
: Because an agent is created on a processor of a target, without processor tags it is impossible to create an agent on an open target of separate type and then pass the corresponding target object at the agent call. Also there is no way to make an open target controlled (see previous rule).
 +
'''Agent open target type validity rule.''' If the target of an agent is open, it may not be separate.
  
−
''Example.'' <e>
+
'''Example.''' <e>
−
f (p: P; q: Q): R
+
f (p: separate P; q: separate Q): R
 
t: separate T
 
t: separate T
 
...
 
...
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</e>
 
</e>
 
The type <e>t</e> of <e>agent t.f (c, ?)</e> is <e>
 
The type <e>t</e> of <e>agent t.f (c, ?)</e> is <e>
−
       separate FUNCTION [ANY, TUPLE [separate P, separate Q], separate R]
+
       separate FUNCTION [ANY, TUPLE [separate Q], separate R]
 
</e>
 
</e>
  
−
: The separateness status of the type <e>TUPLE</e> used for arguments does not matter, what matters is the types of arguments. In many cases when <e>TUPLE</e> is used, it is used as a value type, i.e. it could even be an expanded type, so that a separate mark is not required. But then we need some conversion rules to attach different types of <e>TUPLE</e>. So far the implementation uses whatever separateness status of a <e>TUPLE</e> type is more suitable, most probably it is <e>separate TUPLE</e>.
+
: The first parameter is not separate because the target and the agent object have the same handler.
−
 
+
: The separateness status of the type <e>TUPLE</e> used for arguments does not matter, what matters is the types of arguments. In many cases when <e>TUPLE</e> is used, it is used as a value type, i.e. it could even be an expanded type, so that a separate mark is not required. But then we need some conversion rules to attach different types of <e>TUPLE</e>. In order to avoid unnecessary processor dependency, it's going to be created on the target processor (as a routine object itself), therefore it is not <e>separate</e>.
  
 
== Agent classes ==
 
== Agent classes ==
 
The first parameter in the class <e>ROUTINE</e> and descendants is not used, so in the future it will be dropped altogether.
 
The first parameter in the class <e>ROUTINE</e> and descendants is not used, so in the future it will be dropped altogether.
  
−
''Example.'' The agent type from the example above becomes<e>
+
'''Example.''' The agent type from the example above becomes<e>
−
       separate FUNCTION [TUPLE [separate P, separate Q], separate R]
+
       separate FUNCTION [TUPLE [separate Q], separate R]
 
</e>
 
</e>
−
 
  
 
== Correctness and wait conditions ==
 
== Correctness and wait conditions ==

Latest revision as of 13:08, 7 May 2013

The page reflects current decisions taken for the current SCOOP implementation, in particular without support for processor tags. So it may change in the future.

Status of agent targets

Because any agent object is created on a processor associated with the agent's target, that target has to be controlled.

Agent target validity rule. The target of an agent must be controlled.

Types

Agent argument types validity rule. If an agent has a separate target, every non-expanded argument of the associated feature must be separate.

Because an agent is created on a processor of a target, without processor tags it is impossible to create an agent on an open target of separate type and then pass the corresponding target object at the agent call. Also there is no way to make an open target controlled (see previous rule).

Agent open target type validity rule. If the target of an agent is open, it may not be separate.

Example. 
f (p: separate P; q: separate Q): R
t: separate T
...
r := agent t.f (c, ?)
x := r.item ([a])
The type t of agent t.f (c, ?) is 
separate FUNCTION [ANY, TUPLE [separate Q], separate R]
The first parameter is not separate because the target and the agent object have the same handler.
The separateness status of the type TUPLE used for arguments does not matter, what matters is the types of arguments. In many cases when TUPLE is used, it is used as a value type, i.e. it could even be an expanded type, so that a separate mark is not required. But then we need some conversion rules to attach different types of TUPLE. In order to avoid unnecessary processor dependency, it's going to be created on the target processor (as a routine object itself), therefore it is not separate.

Agent classes

The first parameter in the class ROUTINE and descendants is not used, so in the future it will be dropped altogether.

Example. The agent type from the example above becomes
separate FUNCTION [TUPLE [separate Q], separate R]

Correctness and wait conditions

The feature {ROUTINE}.precondition should be split into 2 parts: correctness_condition and wait_condition. Then the routine call looks like
call (a: OPEN_ARGS)
          require
              correctness_condition (a)
          do
              from
              until
                  not wait_condition (a)
              loop
                  execute_body (a)
              end
          end

The same change applies to the feature item.

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