The main difference between UML and ERD is that UML is a modeling language that represents a system or a software visually while ERD is a diagram that represents the entities and their relationships in a database.
UML is a standard modeling language that helps to get a pictorial understanding of the software. There are various diagrams in UML such as class, object, use case, activity and many more. Whereas, ERD helps to design a database. It also represents the entities and how these entities connect with each other. Overall, UML is a modeling language whereas ERD is a diagram.
Key Areas Covered
Database, ERD, OOP, UML
What is UML
UML stands for Unified Modeling Language. It is a language that helps to visualize, construct and documents software systems. It is not like other programming languages such as C, Java, and PHP because UML does not contain any programming statements. Moreover, it provides a graphical representation of the entire software. It also helps to model Object Oriented Programming concepts.
Software development is a complex process. It is more complicated than writing a usual program. Therefore, it is not possible to directly develop the code. First, it is essential to design the system. UML helps to model the system. Later, the developers can write the code according to the designed UML diagrams.
There are various UML diagrams. Some common diagrams are as follows.
Class diagram – Describes the association between classes, interfaces
Object diagram – Represents the objects and their relationships
Component diagram – Describes the components and their associations
Deploy diagram – Represents the set of nodes and their relationships
Use case diagram – Describes the use cases, actors and their associations
Sequence diagram – Represents the message flow from one object to another
State diagram – Describes the state changes of the system
Activity diagram – Represents the activity flow of the system.
Overall, UML is easier and simple to learn. Not just the developers, business analysts, and common users can also understand it due to the simplicity.
What is ERD
Most software systems have a database. ERD stands for Entity Relationship Diagram. It helps to design the database. Moreover, this diagram is based on the entity-relationship model, which is a model that represents the relationships among data.
An entity is a real-world object. In ERD, a rectangle represents an entity. Attributes are the properties that describe an entity.; an oval shape represents attributes. In a University database, the student is a table. Therefore, the student is an entity. It can have attributes such as id, name age, GPA, etc.
The relationships help to connect one entity to another. In an ERD, diamond shapes are used to represent relationships.
There are three main types of relationships as follows.
1:M relationship – One instance of an entity is associated with many instances of another entity.
1:1 relationship – One instance of an entity is associated with one instance of another entity.
M: N – Many instances of an entity is associated with many instances in another entity.
Later, an enhanced model of the ER model was developed called the Entity Relationship Diagram. It can represent advanced concepts such as generalization and specialization. In generalization, the lower level entities combine together to create a higher level entity. Specialization is the opposite of generalization.
Difference Between UML and ERD
UML is a general purpose, developmental, modeling language that provides a standard way to visualize the design of a system while ERD is a visual representation of data based on ER model that describes how entities are related to each other in the database. Thus, this is the main difference between UML and ERD.
Importantly, there are many diagrams in UML and ERD is one of those diagrams. Hence, this is another difference between UML and ERD.
Also, a difference between UML and ERD based on usage is that the UML helps to design the software system while the ERD helps to design the database.
The main difference between UML and ERD is that UML is a modeling language that represents a system or a software visually while ERD is a diagram that represents the entities and their relationships in a database. In brief, there are many diagrams in UML and, ERD itself is a UML diagram.
1.”Hierarchy of diagrams in UML 2.2″ By Derfel73; Pmerson – This file was derived from Uml diagram2.png, Public Domain via Commons Wikimedia
2.”A sample entity-relationship diagram” By TheMattrix at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia