uml - Entity-Relationship Modeling and Object Oriented Design - Is it relevant? - Stack Overflow
After identifying objects, the various relationships among objects must be identified. This paper makes a These roles are programmed in Object-Oriented languages such as C++ and. Java. . members and a Company and its employees. This is an . The Class Diagram of the Control Command Police System. According. By giving formal models of relationships in both class- and object-based set- .. At their simplest, UML class diagrams are composed of classes and associa- .. shared with other objects — an employee may work for other companies. E-R model is a high-level conceptual model for database design; Example 1. INITIAL CONCEPTUAL DESIGN OF THE COMPANY DATABASE. First we identify . Diagram. We can use these diagrams for object-oriented database design.
You don't have to include all classes in one single class diagram, for example, include only the group of classes that participate in a use case scenarios and no others.
Company Structure Class Diagram Example
Reuse classes by use master view and auxiliary view among different class diagrams. You can also avoid cross relationship link between classes by using auxiliary view of the same class to be appeared within the same class diagram. Package related classes together to enforce software architecture and best practice such as MVC framework.
Why do we need class diagrams? Plan and model requirements ahead of time make implementation much easier in subsequently phases. Modify class diagrams quite is easy, whereas the actual code for features. Plan for a house not a simple dog house to have a blueprint, before grab a hammer and nail to get work done. Class diagram is quite easy to understand and to be used to communicate with other stakeholders for team afford. Keen to try VP Online?
No limitations, no obligations, no cancellation fees. However they are represented, the models prepared for business owners must be clear to them, in their language. In principle, any of the modeling notations could be used here, but since these models will be discussed with nontechnical people, it is desirable to use a technique whose aesthetic qualities make it attractive and easy to understand.
In Row Two, the business owner's view, the entity types classesattributes, and relationships associations represent external schemata—business objects. The notation for such a model may allow multiway relationships, many-to-many relationships, and multivalued attributes. The important thing about this model is that it represents exactly the things the people in the business see. There is no diagrammatic rigor to the model, but it is important to use language precisely and clearly.
The business owners' models are also called divergent data models, because they constitute a diverse set of entity types.
The aesthetics of the diagrams are important, since such people will have little patience for learning arcane diagraming conventions. Architect's View Row Three Models prepared for information architects information system designers are more disciplined.
In Row Three, the architect attempts to identify underlying structures. At the syntactic level, all multiway relationships are transformed into sets of binary relationships. All many-to-many relationships between entity types are transformed into intersect entity types that represent occurrences of associations between the two entity types. Following these disciplines insures that the true natures of the data are really understood.
In addition, at the semantic level, this model is expressed in terms of the most fundamental things of the business. What the business owners see may be but examples of these fundamental things. These are then related to each other, contracts, and other things, in order to show their roles as customers, vendors, employees, and so forth.
This means that entity types in architects' models may well be combinations of entity types in business owners' models. Again, in principle, any of the modeling notations could be used for this kind of model, but, since these models also will be discussed with non-technical people, they should be as aesthetically clean and easy to understand as possible. Remember, it is the clients who ultimately must ensure that any assumptions made while creating either model were in fact true.
In addition to the simple resolution of anomalies in the context of a particular area, the architect also reaches out to other spheres of interest, to create a model that extends beyond the immediate environment.
This means, for example, that what may appear to be a one-to-many relationship in the context of one department is really a many-to-many relationship when all departments are considered.
Designer's View Row Four The set of boxes and lines that constitutes a data model's notation may also be used to represent the things in the designer's view. A designer sees a data model as an expression of computer artifacts. Specifically, what you see in Row Four depends on the technology you will be using: A relational designer sees tables, columns, and foreign keys; an object-oriented designer sees classes, attributes, and associations to be navigated.
Using Entity/Relationship and Object Models | Requirements Analysis: Dealing with Data | InformIT
What is represented here are no longer things in the business but things in the computer. Aesthetics are not as important to the designer as they are to the architect or the business owner. The designer likes to see more details in the diagram than do audiences of either of the other two kinds of models. Hence, these models may be more cluttered and complex.
It is here that the data model and the object model are used quite differently. The logical schema the designer uses depends on the database management system and development technology being used.
If the implementation is to use relational technology, the boxes in the diagram represent tables, with variations on the technique representing foreign keys and other relational structures.
IDEF1X is particularly suited for this.
Class Diagram Example: Company Structure
Alternatively, the boxes can represent an object-oriented programmer's object classes, with additions to the notation for certain object-oriented constructs, such as composition and association navigation.
The UML does this well.
- DATA MODELING USING THE ENTITY-RELATIONSHIP MODEL
Note, for example, that relational developers and object-oriented programmers view relationships quite differently in the design model. A relational database relates tables by associating matching columns. That is, a relationship represents a structure that is, by definition, mutual. If A is related to B, then by definition B is related to A.
In object-oriented programming, however, a relationship represents the two navigation paths from each class to the other. Where in a relational database a relationship simply asserts that two tables could be joined together in an SQL statement.