Optional Associations − Here, a link may or may not exist between the participating objects. The different aspects that are documented are as follows −. It is based upon functionality. To find the average sales, the process retrieves the sales records and computes the average. The following tasks are performed regarding operations −. One of the advantages of Object-Oriented programming language is code reuse. Additional information about the relationship could be obtained by attaching the association relationship with the association class. “PART–OF” hierarchy − It defines the hierarchical relationship in aggregation by which a class may be composed of other classes. A state machine models the behavior of an object as it passes through a number of states in its lifetime due to some events as well as the actions occurring due to the events. Connects related classes. Besides, there are notations to represent the important aspects of an element like name, scope, visibility, etc. Thus it shows the “doers” of a system. The main relationships that are addressed comprise of associations, aggregations, and inheritances. If an object is in a certain state when an event occurs, the object may perform certain activities subject to specified conditions and change the state. Model − Model is a simplified, complete, and consistent abstraction of a system, created for better understanding of the system. The process of object modelling can be visualized in the following steps −. The following figure shows the representation of the class Circle using C++. Events that trigger transitions are written alongside the arc of transition in state diagrams. An event is a specification of a significant occurrence that has a location in time and space. A class is represented by a rectangle having three sections −, The visibility of the attributes and operations can be represented in the following ways −. It preserves inherent concurrency of real objects. Terms such as superclass, subclass, or inheritance come to mind when thinking about the object-oriented approach. A link depicts the relationship between two or more objects. Each object has −. In this stage, the design model developed in the object design is translated into code in an appropriate programming language or software tool. They also include the messages passed between them. It represents the physical packaging of elements like classes and interfaces. Implementation is the concrete realization of the rules defined in the interface. It depicts the behavior of objects undergoing a specific action series. Example − The following figure shows a data store, Sales_Record, that stores the details of all sales. The relationship may be found within a group of tuples which are typed Aggregation or composition is a relationship among classes by which a class can be made up of any combination of objects of other classes. The bottom section represents the values of the attributes. The termination of the system, i.e., the closing of all running threads, cleaning up of resources, and the messages to be sent. The functional model for the Wholesale Software is given below. The object obj1 sends a message to object obj2, if obj1 wants obj2 to execute one of its methods. Dependency − This is a semantic relationship between two things such that a change in one thing brings a change in the other. Derived attributes are those attributes whose values are computed as a function of other attributes (base attributes). When an object of class Circle invokes its findArea() method, the operation finds the area of the circle without any conflict with the findArea() method of the Square class. In addition, each has its own particular characteristics. Let us assume that x-coord and y-coord are private data members, radius is a protected data member, and the member functions are public. For example, consider the one–to–one association between Employee and Project as shown in the figure below. This modeling method can run with almost all Object-Oriented Methods. If we create an object my_circle, we can assign values like x-coord : 2, y-coord : 3, and a : 4 to depict its state. Input arrows contain information to modify the contents of the data store, while output arrows contain information retrieved from the data store. Events are generally associated with some actions. The principles of encapsulation and data hiding help the developer to develop systems that cannot be tampered by other parts of the system. A relationship is an association between classes. An actor may be a person (e.g. A sub-state is a state that is nested inside another state. Aggregation may denote −. To model the requirements of a system from the outside point of view. A process may be associated with a certain Boolean value and is evaluated only if the value is true, though it is not a direct input to the process. There is only one kind of grouping thing, i.e., package. Now that we have gone through the core concepts pertaining to object orientation, it would be worthwhile to note the advantages that this model has to offer. Sometimes objects are represented using rounded rectangles. The values are explicitly defined by an enumeration within the class. To implement 1:1 associations, the primary key of any one table is assigned as the foreign key of the other table. Functional Modelling is represented through a hierarchy of DFDs. The specifications in it are written in simple English language, and hence can be more easily analyzed by non-technical personnel. represent the topologies of client/server systems. The transitions are represented by member functions that change the value of the concerned data member. An actor represents the roles that the users of the use cases play. Hiding Internal Information from Outside View − It allows a class to be viewed as a “black box” and permits class implementation to be changed without requiring any clients of the class to modify code. Consider an Employee class where age is an attribute that may have values in the range of 18 to 60. This involves testing a particular module or a subsystem and is the responsibility of the subsystem lead. The following figure shows the concept of concurrent sub-states. It can be said that a petal is a “part–of” flower. The class has methods that provide user interfaces by which the services provided by the class may be used. It can be upgraded from small to large systems at a greater ease than in systems following structured analysis. These Boolean values are called the control flows. Time Event − An event representing passage of time. Notations − These diagrams are in the form of two-dimensional charts. Now, if the operation scale() is performed on my_circle with a scaling factor of 2, the value of the variable a will become 8. The two main approaches of subsystem testing are −. State transition diagrams or state machines describe the dynamic behavior of a single object. However, a customer must not have more than one savings account or current account. State that determines the characteristic properties of an object as well as the values of the properties that the object holds. DFDs depict the boundaries of a system and hence are helpful in portraying the relationship between the external objects and the processes within the system. The following figure depicts the examples of different types of inheritance. Flexibility − Flexibility determines whether the chosen algorithm can be implemented suitably, without loss of appropriateness in various environments. External events are those events that pass from a user of the system to the objects within the system. The following C++ code incorporates it −. The designer decides whether −. The trading house has transactions with two types of customers, individual customers and corporate customers. The four major elements are −, Minor Elements − By minor, it is meant that these elements are useful, but not indispensable part of the object model. They are used to store data and retrieve the stored data. The approaches for implementation of the dynamic model are −. Collaboration Diagram − It represents the structural organization of objects that send and receive messages through vertices and arcs. Before a design is implemented, it should be optimized so as to make the implementation more efficient. They are modelled after real-world objects that the system interacts with. In state transition diagrams, the initial state is represented by a filled black circle. It is used to depict the structures and the relationships in a complex system. If an association has some attributes associated, it should be implemented using a separate class. Association is a group of links having common structure and common behavior. It can be said that the subclasses are the specialized versions of the super-class. It gives the blueprint or description of the objects that can be created from it. The attributes of this class can be identified as follows −, Some of its operations can be defined as follows −. The specifications provide a semantic backplane that contains all the parts of a system and the relationship among the different paths. System design is done according to both the system analysis model and the proposed system architecture. Relationship among objects. The operation is checked only at the time of execution, as in the programming language Smalltalk. It specifies the meaning of the operations of object modelling and the actions of dynamic modelling. Collaboration diagrams are interaction diagrams that illustrate the structure of the objects that send and receive messages. Constraints in classes restrict the range and type of values that the attributes may take. It illustrates the sequences of states that an object goes through in its lifetime, the transitions of the states, the events and conditions causing the transition and the responses due to the events. Strong Typing − Here, the operation on an object is checked at the time of compilation, as in the programming language Eiffel. 13. enumeration An enumeration is a data type that has a finite set In traditional structured analysis models, one phase should be completed before the next phase. Computational Complexity − Complexity determines the efficiency of an algorithm in terms of computation time and memory requirements. Testing is a continuous activity during software development. A state that has simpler states nested inside it is called a composite state. Public − A public member is visible from anywhere in the system. In a nutshell, a detailed description is constructed specifying how the system is to be built on concrete technologies, The stages for object–oriented design can be identified as −. The functional model shows the processes that are performed within an object and how the data changes as it moves between methods. A foreign key is an attribute that is the primary key of a related table. An operation specifies what is to be done and not how it should be done. During design optimization, it is checked if deriving new associations can reduce access costs. Each row is uniquely identified by a chosen set of minimal attributes called primary key. Once the code is in shape, it is tested using specialized techniques to identify and remove the errors in the code. 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