An entity entity binding diagram is a flowchart that illustrates how “entities” (people, objects, or concepts) relate to each other in the system. An ER diagram is the model that is most often used to develop or debug relational databases in the areas of software, business information systems, and research. It uses a set of geometric symbols, such as a rectangle, rhombus, oval and lines, to display the relationship of objects, relationships and their attributes.
This ER diagram is related to the DSD data structure, which focuses on the relationships of elements within entities, rather than on the relationships between the objects themselves. ER schemes are also often used in conjunction with DFD data flow diagrams that display information for processes or systems.
History of ER models
The development of this ER chart is attributed to Peter Chen, a lecturer at Carnegie Mellon University in Pittsburgh. He began to use it for database design in the 70s of the last century. As an assistant professor at the Sloan MIT School of Management, in 1976, he published an article entitled “Model for Entities to a Single Data Representation”. In a broader historical sense, the understanding of the image of the relationship of things goes back to ancient Greece, the principles of which are found in the works of Aristotle, Socrates and Plato.
They are mentioned in the works of the logical philosophers of a later historical period - Charles Sanders Pearce and Gottloff Frege. By the 1960s and 1970s, Charles Bachmann and like-minded people worked on Chen's theoretical model. Bachmann developed a data structure diagram named after him. Brown has published work on modeling real systems. James Martin added refinements to this ER chart. The work of Chen, Bachmann, Brown, Martin and other participants led to the development of a unified modeling language (UML) used in software development.
Using Charts
This method is used to model and develop relational databases in ER diagrams. It is especially often used in a logical model and from the point of view of a specific technology that will be implemented in a physical data model. In software development, the ER diagram is often the initial step in setting requirements for the design of information systems. The relational database has an equivalent relational table and is thus expressed as necessary.
Areas of use:
- Database troubleshooting. ER charts are used to analyze existing databases to troubleshoot logic or deployment issues. The diagram should show where this happens.
- Business Information Systems. Charts are used to develop or analyze relational databases used in business processes. Any business process that uses field data that includes entities, actions, and interactions can potentially benefit from a relational database. It can streamline processes, simplify information and improve results.
- Business Process Reorganization (BPR). ER chart models help in analyzing the databases used in business process reorganization.
- Education. The database today is a method of storing relational information for educational purposes and subsequent search, so ER charts can be useful in planning these structures.
- Research. Because so much research focuses on structured facts, ERs can play a key role in creating useful databases for analyzing them.
Components and Features
ER charts are made up of entities, relationships, and attributes. They also display power, which defines relationships in terms of numbers.
An entity is a defined entity, such as a person, concept, or event. May contain data stored in it. Examples: customer, student, car, or product. Usually displayed as a rectangle. An entity type is a group of defined things, such as students or athletes, and the subject will be a specific student or athlete. Other examples are customers, cars, or products.
The set of entities is the same as their type, but defined at a given point in time, for example, students studying in class on the first day. A related term is an instance in which a particular person or vehicle will be a collection of objects.
Entities are divided into strong, weak or associative. A strong object is determined only by its characteristics, and a weak entity cannot. An associative view connects objects or elements. Entity keys point to an attribute that identifies an object in a set.
They are divided into the following categories:
Super - attributes that define objects in a set of entities. Candidate Key - has the smallest possible number of attributes. The primary key is the one chosen by the database developer to uniquely identify the set of objects.
Relations and Attribute
Relations are how subjects act on each other or are related to each other. For example, a student may register for the course. These two objects will be the student and the course, and the connection depicted is the act of enrollment connecting the two objects. Relations are usually displayed as rhombuses. Recursive relationships: the same person engages in relationships several times.
An attribute is often displayed as an oval or circle. Descriptive attribute: a property or characteristic of a relationship compared to an entity.
Attributes are divided into simple, compound, derivative, as well as single-valued or multi-valued.
Their categories:
- Simple - means that the attribute value is atomic and cannot be further separated, for example, a phone number.
- Composite or Composite - a sub-attribute that arises from an attribute.
- Derived - an attribute is calculated or otherwise determined from another attribute, for example, determining age by date of birth.
Multivalued - designation of more than one attribute value, for example, several phone numbers for a person.
Unambiguous - one attribute value.
Types are combined into simple or compound attributes.
Power performance
Power defines numerical attributes, the relationship between two objects or sets of entities. The three main cardinal relationships are one-to-one, one-to-many, and many-to-many relationships. The one-to-one example will be one student associated with one mailing address. The one-to-many or many-to-many example depends on the direction of the relationship - one student is registered to take several courses, but they all have one return line with respect to one student. Many-to-many examples: students as a group are associated with several teachers, and teachers, in turn, are associated with several students.
Power can be displayed as reverse or the same depending on where the characters are displayed. It has cardinality restrictions - minimum or maximum numbers.
ER components can be equated to parts of speech, as Peter Chen did. This example shows how an ER chart compares with a grammar:
- Common noun. Entity type. Example: student.
- Own noun. Essence. Example: Sally Smith.
- Verb, type of relationship. Example: registration.
- Adjective, attribute for the object. Example: sophomore.
- Adverb, attribute of relationships. Example: digitally.
The ERROL database query language actually mimics natural language constructs. ERROL is based on the revised relational algebra (RRA) and works with ER-models, fixing their linguistic aspects. There are several notation systems that, in general, are similar, but still differ in some features:
- Chen designation style.
- Bachmann style.
- IDEF1X style.
- Barker style.
Models of conceptual, logical, and physical data
Creating ER charts and data models are usually formed at three levels of detail:
- The conceptual data model is the highest level view that contains the least detail. Its value shows the overall scale of the model and the image of the system architecture. For a smaller system, it may not be necessary to draw. Instead, start with a logical model.
- Logical data model - contains more details than conceptual. It defines operational and transactional entities in more detail. The logical model does not depend on the technology in which it will be implemented.
- Physical data model.
It is worth noting that similar levels of detail and volume exist in other types of diagrams, for example, data streams.
Relational data
Sometimes engineers highlight ER charts with additional hierarchies to add the necessary information levels and design the database. For example, they can add groupings, expanding with superclasses and narrowing with subclasses only for relational data. ER charts show only this relational structure for unstructured data.
If the data is not clearly delineated within the field, then the rows and columns of the ER diagram will be limited. The same can be said for semi-structured data, since only some of the data will be useful.
Creating basic designs
Before you start creating ER charts, all objects are defined. An entity appears once in a specific diagram. Create rectangles for all objects and correctly name them. Determine the relationship. Connect them using lines and add a rhombus in the middle that describes their actions. Add attributes for objects. Give them meaningful names so that they can be easily distinguished.
It sounds simple, but in a complex system it can be difficult. This is something that will be improved only with practice. Inexperienced developers are better off using ready-made ER chart templates so that you can get started quickly and improve your practice.
Software development example
Entity relationship diagrams are used in software development at many stages of project planning. They help identify the various elements of the system, their relationships with each other, and are often used as the basis for data flow diagrams or DFDs.
For example, inventory software used in a retail store will have a database that controls items such as purchases, product, product type, product source, and product price. Providing this information with an ER chart would be something like this:
In the diagram, the information inside the oval shapes is an attribute of a particular object.
Flow charts
ER schemas are commonly used in conjunction with a data flow diagram to display storage contents. They help visualize how data is related in a general way. When constructing an ER diagram, you can draw entity relationships manually. However, for more complex systems and for external audiences, you need charting software such as Creately to create visually appealing and accurate ER charts.
The ER chart software offered by Creately as an online service is fairly easy to use. It is also great for development teams thanks to its strong support during the collaboration phase.
Benefits in Database Management
Database ER charts represent a very useful foundation for creating and managing data arrays. First, the ER diagram is easy to understand. This means that, for example, designers can use ER charts to easily communicate with developers, customers, and end users, regardless of their IT professionalism.
They are easily translated into relational tables, which can be used to quickly build databases. In addition, ER diagrams can be directly used by database developers as a plan for embedding data in specific software applications. They can be used in other contexts, such as describing various relationships and operations within an organization.
ER chart is very popular because it has many advantages:
- Effective communication allows readers to easily understand the relationships between different subject areas of an ER chart.
- Symbols are used to effectively represent information and also help in understanding the operation of the database.
- The visual representation of data flow diagrams together with ER diagrams can be effectively used to visually represent the layout.
- Simple understanding of design using ER diagrams.
- High flexibility. An ER diagram can be used effectively to establish relationships with existing systems. To perform this operation, mathematical formulas and relational tables can be used.
Several tools are available on the Internet related to creating and editing ER models:
- Pony ORM - Allows users to create database tables using Pony ORM and ER charts.
- Edra Soft - Helps you quickly create EM diagrams.
- Draw - Helps you efficiently draw flowcharts and ER charts.
- ERD Plus - It can be used to create star charts and relational charts along with ER charts.
- Lucidchart - allows users to import an ER chart base structure for efficient process automation.
- ERDiagrams - it can be used for free download of ready-made ER charts.
Tips for beginners
The first step in creating an ER is to identify all the objects that you plan to use. An entity is nothing more than a rectangle with a description of system information. It can be a client, manager, invoice, schedule. Draw a rectangle for each object.
Next, the relationship of the ER diagram between the two entities is determined. Draw a solid line connecting two objects. Determine the relationship. Draw a rhombus of action between two objects and write a short description of how they are connected.
After that add the attributes. They must be added using oval-shaped characters. Complete the diagram by connecting objects with lines and adding rhombuses to describe each relationship until all relationships are described. Each of the objects may have some kind of relationship, some may have several, which is quite normal.
Tips for effective ER charts:
- Before creating an ER diagram, make sure that each object in the diagram is displayed once.
- Name all entities, relationships, and attributes in the diagram.
- Learn the relationship between entities.
- Eliminate any unnecessary relationships. Do not bind them together.
- Use colors to highlight important parts of the chart.
- Show the level of detail needed for a custom purpose. You may need to draw a conceptual, logical, or physical model, depending on the necessary conditions.
- Watch for redundant relationships between entities in an ER diagram or relationship.
- If the problem with the database is fixed, they monitor for errors in relationships, the presence of missing objects or attributes.
- Be sure all items are checked. Move tables and charts back and forth if it helps to achieve your goal.
- Be sure that the ER diagram supports all the data needed for storage.
- Indicate the exact name for each element in the diagram. In object names, remember to use singular nouns. Adjectives can be used to distinguish objects belonging to the same class (for example, a part-time employee and a full-time employee). Attribute names must be meaningful, system independent, and easy to understand.
- Remove undefined, redundant, or redundant relationships among entities.
- Use color coding effectively. You can take colors to classify similar objects or to highlight key areas in charts.
As can be seen from the above, ERs are especially useful where it is required to model data in terms of different types and categories of information and their relationships with each other for database design.