SCOOP (Simple Concurrent Object Oriented Programming) is a concurrency model designed for the
Eiffel programming language
Eiffel is an object-oriented programming language designed by Bertrand Meyer (an object-orientation proponent and author of '' Object-Oriented Software Construction'') and Eiffel Software. Meyer conceived the language in 1985 with the goal of i ...
, conceived by Eiffel's creator and designer,
Bertrand Meyer
Bertrand Meyer (; ; born 21 November 1950) is a French academic, author, and consultant in the field of computer languages. He created the Eiffel programming language and the idea of design by contract.
Education and academic career
Meyer rece ...
.
SCOOP defines a way for an object oriented program to be written without the concept of threads, locks, or other typical
multiprogramming
In computing, multitasking is the concurrent execution of multiple tasks (also known as processes) over a certain period of time. New tasks can interrupt already started ones before they finish, instead of waiting for them to end. As a result ...
methods. This allows the compiler or runtime environment to optimize the amount of concurrency as well as eliminate typical design flaws such as deadlock.
The model was first designed in the early 1990s and published in 1993 in the
Communications of the ACM
''Communications of the ACM'' is the monthly journal of the Association for Computing Machinery (ACM). It was established in 1958, with Saul Rosen as its first managing editor. It is sent to all ACM members.
Articles are intended for readers with ...
An updated version was described in chapter 30 of the book ''
Object-Oriented Software Construction
''Object-Oriented Software Construction'' is a book by Bertrand Meyer, widely considered a foundational text of object-oriented programming. The first edition was published in 1988; the second, extensively revised and expanded edition (more than ...
''.
A prototype implementation was developed in 1995 by Eiffel Software. An article by Compton and Walker provides an overview of SCOOP and describes another early implementation. Nienaltowski, Arslan and Meyer have published a description of the model as of 2003. Work on SCOOP proceeded at the Chair of Software Engineering at
ETH Zurich. SCOOP became available as a standard part of
EiffelStudio
EiffelStudio is a development environment for the Eiffel programming language developed and distributed by Eiffel Software.
EiffelStudio includes a combination of tools integrated under a single user interface: compiler, interpreter, debugger, br ...
early in 2011.
[Eiffel Software]
SCOOP: Concurrency for Eiffel
/ref>
Technical overview
SCOOP works by allowing references to certain objects to be declared as separate. In the code below, an entity local_inventory
is declared as a separate type, by specifying the Eiffel language keyword separate
in the declaration.
local_inventory: separate INVENTORY
A separate object may be handled by a SCOOP processor that is different from the processor handling the referencing object. A SCOOP processor is the abstract notion of an autonomous thread of control that handles the execution of operations on one or more objects. SCOOP processors are independent of underlying concurrency mechanisms like processor threads, multiple processor cores, and distributed computer systems.
In addition to the concept of separateness, SCOOP exploits the principles of '' design by contract'' as part of the SCOOP strategy for synchronizing access to shared separate resources. For example, a precondition
In computer programming, a precondition is a condition or predicate that must always be true just prior to the execution of some section of code or before an operation in a formal specification.
If a precondition is violated, the effect of the s ...
for a consumer wishing to access an item in the inventory example above, might be that such an item does currently exist. This would be expressed with a contract on the feature of class INVENTORY
which returns the item.
item: PRODUCT
-- Current item
require
inventory_has_item: has_item
In traditional, sequential processing, a client intending to call local_inventory.item
would be responsible for making certain that the precondition local_inventory.has_item
holds before making the call. If the call to item
were made in a state in which has_item
did not hold, the caller would incur a precondition violation exception.
In the presence of SCOOP and given the separateness of local_inventory
, making the check on has_item
before calling item
would not be reliable. This is because the state of local_inventory
could have been changed by requests from other SCOOP processors between the time that the check was made and the time that item
could be called.
As a result, when SCOOP is enabled, the precondition has_item
is transformed from a correctness condition, which will cause an exception in the case of a violation, to a wait condition. The wait condition will cause the execution of item
to be delayed until such time as has_item
holds. In the Eiffel Software implementation, if SCOOP is not enabled, the separate
keyword is ignored and sequential processing is assumed.
See also
*Eiffel
Eiffel may refer to:
Places
* Eiffel Peak, a summit in Alberta, Canada
* Champ de Mars – Tour Eiffel station, Paris, France; a transit station
Structures
* Eiffel Tower, in Paris, France, designed by Gustave Eiffel
* Eiffel Bridge, Ungheni, M ...
*''Object-Oriented Software Construction
''Object-Oriented Software Construction'' is a book by Bertrand Meyer, widely considered a foundational text of object-oriented programming. The first edition was published in 1988; the second, extensively revised and expanded edition (more than ...
''
References
{{reflist, 30em
External links
* Eiffel Softwar
online documentation for SCOOP
* Th
SCOOP research page at ETH Zurich
1993 software
Concurrent programming languages
Object-oriented programming languages
es:Computación concurrente
fr:Programmation concurrente
nl:Multiprogrammeren
pt:Programação concorrente