Difference between UML and ERD

Key Difference: UML stands for Unified Modeling Language. ERD stands for Entity Relationship Diagram. UML is a popular and standardized modeling language that is primarily used for object oriented softwares. Entity-Relationship diagrams are used in structured analysis and conceptual modeling. They are often used to graphically represent the logical structure of a database.

UML stands for Unified Modeling Language. It has been released by the Object Management group in the 1997. It is a design language that is often used to develop and build computer applications. It consists of a family of graphical notations that assists in describing and designing software systems. It is mainly employed in the systems developed using an object-oriented style. The UML is independent of an implementation language. UML can be used at various stages like analysis, design and programming. There are numerous kinds of UML diagrams like object, package, sequence, state machine, timing, use case, interaction, component structure, communication, component, etc. Jim Rambaugh, Ivar Jacobson and Grady Booch are the original authors of UML.

ERD stands for Entity Relationship Diagram. It works as an important component of a conceptual data model. ERD is often used to graphically represent the logical structure of a database. The model is based on three prime components:

  • Entities: It can be any person, object, event or concept about which the data needs to be stored or maintained.
  • Attributes: Characteristics of the entities are referred to as attributes.
  • Relationships: It describes the association between the entities.

The relationships are further divided into optional and mandatory relationships. Another important term that is associated with the Entity Relationship Diagrams is the cardinality. In a relationship, it identifies the number of instances of an entity that can (or in some cases, must) be associated with another entity. Thus, Entity Relationship Diagrams consider the real world as a collection of various types of business entities. It defines the relationships between the entities and also describes the attributes related to the entities.

Comparison between UML and ERD:

 

UML

ERD

Full form

Unified Modeling Language

Entity Relationship Diagram

Definition

UML is a popular and standardized modeling language that is primarily used for object oriented softwares. 

Entity-Relationship diagrams are used in structured analysis and conceptual modeling. They are often used to graphically represent the logical structure of a database.

Advantages

  • Open Standard, Graphical notation for specifying, visualizing, constructing, and documenting software systems.
  • Independent from any specific programming language.
  • Language can be used from general initial design to very specific detailed design across the entire software development lifecycle.
  • Used for modeling of large and complex systems.
  • Increase understanding/communication of product to customers and developers.
  • Support for diverse application areas.
  • Support for UML in many software packages today (e.g. Rational, plugins for popular IDE’s like NetBeans, Eclipse).
  • Based upon experience and needs of the user community.
  • It provides the reverse engineering support
  • Though ERDs, an analyst or a designer can gain a deep insight to the information that needs to be contained in the database.
  • It serves as a documentation tool.
  • It is used to represent and communicate the logical structure of the database to the users.
  • Simple and easy to understand.
  • Very easy to transfer the construct into the relational tables.
  • Acts as a blueprint of a database.
  • Conversion from E-R diagram to a network or hierarchical data model can be easily done.

 

Conventions

  • Rectangles are classes or instances
  • Ovals are functions or use cases
  • Instances are underlined
  • Types are not underlined
  • The name of an abstract class is shown in italics.
  • An interface may be shown using a rectangle symbol with the keyword «interface» preceding the name.
  • Class with three compartments – middle compartment holds a list of attributes and bottom compartment holds a list of operations.
  • An entity is represented by a rectangle and named using singular nouns.
  • A weak entity is represented by a double rectangle.
  • Relationships are represented by diamond.
  • An attribute is represented by an eclipse
  • Ellipse with an underlying line represents a key attribute.

Key Terms

Class, object, association and attributes.

Entity, instance of an entity, relationship and attributes.

Role information

Included

Not included

Comments

Can be graphically represented and attached to any UML object

No comments in ER diagrams

Goals

  • To model systems by using concepts of object oriented approach.
  • To establish an explicit coupling to conceptual as well as executable artifacts.
  • To address the issues of scale inherent in complex and mission-critical systems.
  • To create a method that suits and used by both humans and machines.
  • Capture all the necessary or required information.
  • Ensure that information does not get duplicated or redundant.
  • Models no information that is derivable from other information already modeled.
  • Locate information in a predictable and a logical place.

Image Courtesy: orm.net, packtpub.com

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