Objects in OOAD

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Analysis Object Oriented Requirements, Five separate but interrelated object oriented method or diagrams are use to define the. application requirements from object oriented perspective In most cases analysts use all. five diagrams to get a complete definition of business requirements However in some. situation only three or four diagrams may be required to specify the requirements. accurately the five diagrams are,1 The class diagram. 2 The use case diagram,3 The collaboration diagram. 4 The sequence diagram,5 The state chart diagram, The purpose of class diagram is to identify classify the object that will make up new. system In the class diagram the properties or attributes of each object that need to be. recorded are also being identified Generally a single comprehensive diagram is to show. all class relationship for the entire system, The purpose of use case diagram is to identify the uses or use case of new system i e to.
identify how the system is used The use case diagrams essentially an extension of event. table The use case diagram convenient way to function that the system must support. Sometime single comprehensive use case diagram is use to describe the entire system At. other times a set of similar use case diagrams makeup the use case model. The purpose of collaboration diagram is to identify which objects collaborate to carry. out given business function For egg If one of the business uses is to record customer. order then the collaboration diagram identify the entire object involved To record the. customer order requirements a customer object some inventory objects a new order. objects so forth A single collaboration diagram use to identify these object are show. interaction messages, That is send between them to carry out this function Generally many collaboration. diagrams are needed, A sequence diagram is just another view of some information contained in a. collaboration diagram but it provides a little different perspective It is a graphical view. that emphasizes the sequence of messages rather than collaboration object A sequence. diagram is drowning to that the sequence of message is graphically depioted by their. position on the page The sequence process from top to bottom Both collaboration. diagrams the sequential diagrams are referred to as interaction diagram. State chart describe the state behavior of each individual object Each object chart has. a state chart Within the state chart are action statements that eventually become the logic. in the final system These logic components in each class are called methods. OO Requirement Event table class diagram Use case diagram Interaction. diagram collaboration and or sequence diagrams State chart diagrams. The different between traditional structured approach the object oriented approach to. system development is not the development method but in the set of methods that is. The SDLC for each approach has the same phases planning analysis design and. implementation The activity within the phases is also being same The set of method. uses is the difference Individual tasks within the activities are focused on building the. models they will be different For eg Instead of building the DFDs the analysts build. interacting diagram state chart, The description of the new system in consists of structural information and behavioral. information, The structural information is the component part of the system and behavior the logic. performed by the component The class diagram provides the definition of the. component its of the system The other diagram i e use case interaction state chart. diagram focus on the activities that the system perform i e they describe the they. behavioral aspects of the new system Thus the class diagram tells what the components. of the system are the other diagrams tell what these components do or the action they. The class diagram, The object oriented approach models classes of objects instead of data entities The.
classes of object have attributes and association Cardinality also applies among classes. The difference from traditional approach is that the object does the equal processing in. the system as well as store information Thus object have both methods attributes The. model use by this approach is call as class diagram. The two issues associated with OO approach are,1 Generalization specialization hierarchies. 2 Aggregation, Generalization specialization hierarchies are base on the idea that people classified the. things in term of similarities differences Generalization is judgement that group. similar type of things For eg there are many types of motor vehicles cars truck. tanks All other vehicle certain general characteristics so a motor vehicle is more general. class Generalization are judgment that categories different type of things For eg Special. type of cars include sport cars are similar in some ways yet different in other ways Thus. sport car is special type of car, specialization hierarchy is use to structure rank things from more. A generalization specialization, general to more special Each class of thing is hierarchy might have more general thing. above it called a super class At the same time A class might have a more specialize. class below, ow it called a super class At the same time A class has more specialize class.
below called below it called a sub class, Inheritance is the concept that allows sub class to share characteristics of super class For. eg A car is everything any other motor vehicle is but something special Thus. sometimes the A generalization,generalization specialization. specialization hierarchy called as inheritance hierarchies. Aggregation It is the relationship between an object its part for eg Learning about a. computer system might involve rrecognizing, ecognizing that the computer is composed of different. parts processor main memory keyboard disk storage A keyboard is special type of. Come to account, The class symbol is a rectangular with three section The top section contains the name of. the class the middle lists the attribute of the class Methods are not always shown in the. class symbol if they are fairly standard, A class diagram of a system maintains the blank account.
The identified class is those associated with the problem domain. Additional class such as use interfaces class are also specified in the class diagram User. identified classes include such classes as wind,ow for input screens output report. classes For e g the customer input form window is a user interface class that is designed. during development of the user interface Those type of classes are called the. implementation classes,The System Activities,Use Cases Actors. Use case is a single use or function performed by the system for those whose the system. It is an activity the system carries out in response to an event For e g consider world. processing system Various use cases could be write a letter or print a newsletter. There are two import concepts here,1 A person is involved. 2 The person uses the system, The person involve in an actor An actor is a role played by the use of the system. In the world processing example there may be a student actor who uses the world. processor to write an easy an editor actor who uses the worl. d processor to edit articles, The same person plays several rolls such as the student an editor or publisher.
The figure above shows how use case in documentation A simple stick figure use to. represent an actor The uses case is symbolized by oval w. ith name of the use case inside, Lines between actor use cases which actors participate with which use case. A use case only shows that an actor interacts with the computer system to carry out. business activity A use case is the high level el description may include whole. sequence of individual steps to accomplish the use case We describe these individual. steps with the narrative that is called as flow of activities A flow of activity describes the. internal steps or activities with a use case, For example create new order use case The steps would be record customer. information reorder order process order transaction produce confirmation. Each of this case can be further defined,The flow of activities is a general descrip. description,tion of steps with in the case In most cases we. need to extend the description to event more details. Frequently use case may have several alternative sequences of internal activities For eq. the exact sequence of tasks will probably different from the create new order use case. Depending from whether it is a customer or clerk interacting with the system It is a same. use case different sequence We describe these different sequences as scenario Scenario. is the particular sequence of activities withi,within n the use case a use case have several.
different scenarios A scenario is a identification description of a unique set of internal. activities within the use case It represent unique path through a use case For eg The. create new order could have two scenarios customer create telephone order. customer create web order,The use case diagram, A use case diagram is a graphical model that summarizes the information about the actor. use cases To do use case analysis we look at the system as the w whole. hole try to identify, all of major uses of the system These uses normally derived from the business event. identified in the event table It identifies the functions that must be supported by the new. Automation Boundary and organization,Inventory System. As indicated by the relationship lines each actor can use every use cases A boundary. line is drawn around the entire set of use cases This boundary is the automated system. boundary or the automation boundary It denotes the boundary between the environment. where the actors reside the internal function of the automated system There are. various ways to organize the use cases to depict different points of view One way is to. organize use cases by sub system, Another approach is to include all use cases that involve a specific actor. includes relationships, frequently during the development of a use case diagram in became necessary for one.
use case to use the services of another use case For eg two of the o. rder entry, subsystem use cases are create new order update order each of these use cases. may need to validate the customer account A common use case may be defined to carry. out this function,Create new,Look up item,availabilty. customer account,Customer Order,Update Order, The relation reads creates new order includes validate customer account. Sometime this relationship is referred to as a common subroutine meaning that it is. common to both use cases, The use case diagram compared to structured techniques. The objective of use case diagram is to provide an overview of the system including the. actors who use the system the functions they perform with the system As they help to. define he scope of the system a use case diagram is like a context diagram However the. individual use cases appear more like a DFD fragment in that they identify an individual. function that the system must support, One of the primary differences between structure object oriented modeling is he.
though process for developing use case diagram begins by defining the automation. boundary In the development of a DFD the automation boundary In the development of. automation boundary often is not define until the entire process as been detailed Thus in. a DFD an external agent is always the original source or destination of the information. may not necessarily be the one interacting with the system In a use case diagram an. actor is the one who actually interacts with the system Whatever that actor is the. original source of the information or not, For e g in create new order system A customer may call the clerk and make an order. The DFD would identify customer as an external entity An the clerks activity would be. embedded in a process described as enter customer order while in use case diagram the. clerk would be identified as the actor who used the system to enter or create customer. Another major difference is that the use case diagram does not initiate data flows The. information flowing i e the interacting diagrams,Development of usecase diagram. There are two possible points to developed use case diagram The most common method. is to use to even table We analyze each event in determine the way the system is used to. support that event the actor who initiate the event other use cases that may be invoked. because of the event Generally each event becomes a use case. Another method is use to start the development of a use case diagram is to identify all the. actors who use the system Build the list of actors based on the event table by looking at. the trigger source columns in the event table An analysis of those columns helps. identify who or what is using the system what its use is Sometime the actors are. sources at other time actor may be someone other than the source. Ones the actors are the use cases have been identified the next step is to develop a flow. of activities as the starting point for identifying various scenarios As the different flows. of activities are develop any common internal use cases can be identified separated. Objects in OOAD Things are objects that indirect in the system An object in object oriented approach is often similar to a data entity in the traditional approach The main difference is that object do the work in system they do not just store the information i e that is the object have behavior as well as attributes With object oriented

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