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| ==Introduction== | | ==Introduction== |
| SAS/AF software contain an enhanced SAS component Language also known as Screen Control Language. SCOM is an object oriented programming model that provides a framework for SAS/AF component development. SCOM makes it easy to develop plug-and-play components that adhere to simple communication rules, which in turn makes it easy to share information between components. | | SAS (pronounced as "sass") is a collection of software for Statistical Analysis. SAS help analyst to perform data entry, retrieval, management and mining, report writing and graphics, statistical analysis, etc. SAS has business solutions that enable large-scale software solutions for areas such as IT management, human resource management, financial management, business intelligence, customer relationship management etc. SAS was started by Anthony J. Barr in 1966 [http://en.wikipedia.org/wiki/Anthony_James_Barr 1] as a NC state graduate student like us. SAS/AF is application facility, a set of application development tools to create customized desktop GUI applications. In simple words it can be called as a library of drag-and-drop widgets which are object oriented. SAS/AF software contain an enhanced SAS component Language also known as Screen Control Language. SCOM is an object oriented programming model that provides a framework for SAS/AF component development. SCOM makes it easy to develop plug-and-play components that adhere to simple communication rules, which in turn makes it easy to share information between components. |
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| .[http://www.bredemeyer.com/use_cases.htm 2]
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| ==Overview== | | ==Overview== |
| In general '''use cases''' are used to capture the '''who''' i.e the actors, the '''what''' i.e interactions and system reactions, and the '''purpose''' i.e the goal of a particular system without having to worry too much about the internal workings of the system. Use cases originated in the Object oriented community but their applicability is not limited to object oriented systems. [http://en.wikipedia.org/wiki/Use_case 1]
| | SCOM can be used to develop components that adhere to simple communication rules, which in turn make it easy to share information between components. |
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| ==SCOM in detail== | | ==SCOM in detail== |
| ===Purpose of SCOM=== | | ===Purpose of SCOM=== |
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| ===Use case templates ===
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| *'''Use case'''
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| Each use case should have a unique name describing in a manner which describes its purpose. The name usually is a active phrase, in a verb-noun format. Use cases can also have a reference number associated with them, this is to indicate how they relate to other use cases. Also the use case name should maintain creation and modification history of the template, this information should be preceded by the keyword '''history'''.
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| *'''Description'''
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| In the description field of the use case template we maintain the goals of the use case. The description should list the source for the functional requirement, this information should be preceded by the keyword '''sources'''.
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| *'''Actors'''
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| Use cases identify the intent satisfying the role assumed by external '''actors''' interacting with the “system under discussion/test”. The actors can be classified into '''primary actor''' or '''secondary actor'''. A '''primary actor''' is one having a goal requiring the assistance of the system. A '''secondary actor''' is one from which the system needs assistance to satisfy a goal.[http://www.wilsonmar.com/1usecase.htm 8]
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| *'''Assumptions'''
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| Assumptions made in order to achieve the goals defined should be stated in a declarative manner. The assumptions should be evaluated to a true or false and in case if the assumption is false then it is unspecified as to what the use case will do. Behavior in case of an assumption failure can accounted for using use-case extensions.
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| *'''Steps'''
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| The sequence of interactions necessary to successfully meet the goal. The interactions between the system and actors are structured into one or more steps which are expressed in natural language. A step completes when all its component interactions have completed. A step has the form
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| <sequence number><interaction>. If there are multiple steps then each step should have a sequence number showing its position in the list of interactions. The execution of one or more steps can be made conditional by using programming-like IF-then-ELSE constructs.[http://www.bredemeyer.com/pdf_files/use_case.pdf 3]
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| *'''Variations'''
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| Variations represent any variation in the steps of the use case. The format of the variation is <step reference> < list of variations separated by or>.
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| *'''Non functional requirements'''
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| Non functional requirements related to fault tolerance,performance,etc are listed as <keyword> : < requirement>. Here again the non functional requirements are list in a natural and understandable format.
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| *'''Issues'''
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| This section lists the issues which are awaiting the resolution.
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| ===Use case template example===
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| [[Image:usecasetemplateexample.png]]
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| ===Types of Use cases===
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| *'''System use cases''': System use case describes the service which the system provides for the actor. The system use case describes <i>what</i> the system would do in response to the actor's actions. An actor in the system use cases can be wither a human user or another system interacting with the system under consideration.
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| *'''Business use cases''': Business use cases are used to define the processes which will be used by the external actors. The business use cases treat the system under consideration as a black box in which the actors are given a description as to <i>what</i> the process does by specifying a value. [http://www.agilemodeling.com/artifacts/systemUseCase.htm#Informal 5]
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| ==Use case extension==
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| In order to deal with the case of assumption failure, a variant of the use cases can defined using the use case extension.
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| ===Use case extension template===
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| *'''Use case extension''' [http://www.bredemeyer.com/pdf_files/use_case.pdf 3]
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| The extension name includes a unique identifier for the extension and a reference to the use case to which the extension applies
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| *'''Changed field'''
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| This field documents the field of the use case template which are going to be changed.
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| *'''Steps'''
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| This field mentions the steps field of the use case which require change, the changes are expressed in terms of new or altered steps which require change that apply to a use case at extension point, if some condition is true.
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| ===Use case extension example===
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| Continuing the example of the online shopping portal system use case previously explained, on extending the use case we get the following use case extension template.[[Image:Usecaseextensiontemplateexample.png]]
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| ==Use cases in UML==
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| UML represents the use cases in a diagrams called as the '''use case diagrams'''. [http://pg-server.csc.ncsu.edu/mediawiki/index.php/CSC/ECE_517_Fall_2007/wiki2_4_2q 4]
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| Lines in a UML use case between an actor and the system represent a more abstract concept of relationship of communication, acquaintance, or inheritance.
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| A use case circle can be more than a user invoking an on-demand service that passively waits until called upon.
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| A Use case circle can be event-driven, which proactively notifies one or more subscribers when specific events occur.
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| Services that run on their own without formal invocation may be better represented as an (automated) actor rather than as a use case circle.
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| The general representation of the use case environment in '''Unified Modeling Language'''(UML)is represented in the figure below
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| [[Image:Generalusecase.png]]
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| '''Example''': Consider a scenario in which a customer is visiting a online shopping portal system. In this scenario as we see the customer as the actor interacting with the online shopping portal system. [http://atlas.kennesaw.edu/~dbraun/csis4650/A&D/UML_tutorial/use_case.htm 6]
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| The use case diagram covers the basic operations which the customer would normally perform while ordering an item from the shopping portal. This use case diagram can be extended to include extra scenarios such as the multiple item order, order cancellation and so on.
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| [[Image:Usecaseexample.png]]
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| ==See Also==
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| *[http://en.wikipedia.org/wiki/List_of_UML_tools List of UML Tools]
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| *[http://alistair.cockburn.us/index.php/Pluggable_use_cases#Pluggable_Use_Case_Concept Pluggable Use Cases]
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| ==References==
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| *[1]: Wikipedia.2010.Wikipedia-Use Case. wikipedia.org
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| *[2]: Bredemeyer.2006.Functional Requirements and Use cases. Bredemeyer Consultancy
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| *[3]: Coleman,Derek.1998.A Use Case Template:draft for discussion. Hewlett Packard
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| *[4]: Mediawiki.2007.Wiki reference wiki2_4_2q.North Carolina State University
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| *[5]: Ambler,W.Scott.2009.System Use Cases.Ambysoft Inc.
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| *[6]: Braun,David.2000.UML tutorial[online].Kennesaw State University
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| *[7]: Mall,R.2004. Fundamentals of Software Engineering. Prentice Hall, New Delhi.
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| *[8]: Mar,Wilson.2010. Use cases. Wilson Mar
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| ==Links for References==
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| *[http://en.wikipedia.org/wiki/Use_case Use case]
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| *[http://www.bredemeyer.com/use_cases.htm Functional Requirements and Use cases]
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| *[http://www.bredemeyer.com/pdf_files/use_case.pdf Use case extension template]
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| *[http://pg-server.csc.ncsu.edu/mediawiki/index.php/CSC/ECE_517_Fall_2007/wiki2_4_2q Wiki reference]
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| *[http://www.agilemodeling.com/artifacts/systemUseCase.htm#Informal Use case Types]
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| *[http://atlas.kennesaw.edu/~dbraun/csis4650/A&D/UML_tutorial/use_case.htm Use cases HOW TO?]
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| *[http://www.wilsonmar.com/1usecase.htm Use cases explained (8) ]
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