--- id: kb-2026-00250 title: Entity-Relationship Model schema_type: TechArticle category: computer-science language: en confidence: medium last_verified: '2026-06-24' created_date: '2026-05-22' generation_method: ai_structured ai_models: - gpt-5-codex derived_from_human_seed: true conflict_of_interest: none_declared is_live_document: false data_period: static atomic_facts: - id: fact-entity-relationship-model-001 statement: >- Peter Chen's ACM Transactions on Database Systems article is titled "The entity-relationship model - toward a unified view of data." source_title: The entity-relationship model - toward a unified view of data source_url: https://doi.org/10.1145/320434.320440 source_doi: 10.1145/320434.320440 confidence: medium - id: fact-entity-relationship-model-002 statement: >- IBM Informix documentation summarizes the entity-relationship data-modeling method as identifying principal data objects, relationships, and attributes; diagramming the objects; translating them into relational constructs; resolving the logical data model; and normalizing the logical data model. source_title: Overview of the entity-relationship data model source_url: https://www.ibm.com/docs/en/SSGU8G_12.1.0/com.ibm.ddi.doc/ids_ddi_163.htm confidence: medium - id: fact-entity-relationship-model-003 statement: >- IBM Db2 documentation describes logical database design as the first database design task before implementation and describes logical data modeling as documenting business information requirements in an accurate and consistent format. source_title: Logical database design using entity-relationship modeling source_url: https://www.ibm.com/docs/en/db2-for-zos/12.0.0?topic=relationships-logical-database-design-using-entity-relationship-modeling confidence: medium - id: fact-entity-relationship-model-004 statement: >- IBM Db2 documentation lists one-to-many, many-to-one, one-to-one, and many-to-many as relationship types that can be expressed in a relational database design. source_title: Entities for different types of relationships source_url: https://www.ibm.com/docs/en/db2-for-zos/12.0.0?topic=modeling-entities-different-types-relationships confidence: medium - id: fact-entity-relationship-model-005 statement: >- Oracle SQL Developer Data Modeler documentation says cardinality defines how many occurrences of one entity exist for one occurrence of a related entity, including 1:1, 1:N, and N:M cases, and maps N:M relationships to a reference table in the relational model. source_title: Data Modeler Concepts and Usage source_url: https://docs.oracle.com/database/sql-developer-data-modeler-17.4/DMDUG/data-modeler-concepts-usage.htm confidence: medium completeness: 0.86 known_gaps: - >- This compact repair focuses on conceptual ER modeling and relational mapping; it does not cover every notation variant, conceptual-modeling extension, or CASE tool feature. disputed_statements: [] primary_sources: - title: The entity-relationship model - toward a unified view of data authors: - Chen, Peter P. type: academic_paper year: 1976 url: https://doi.org/10.1145/320434.320440 doi: 10.1145/320434.320440 institution: ACM Transactions on Database Systems - title: Overview of the entity-relationship data model type: documentation year: 2026 url: https://www.ibm.com/docs/en/SSGU8G_12.1.0/com.ibm.ddi.doc/ids_ddi_163.htm institution: IBM - title: Logical database design using entity-relationship modeling type: documentation year: 2026 url: https://www.ibm.com/docs/en/db2-for-zos/12.0.0?topic=relationships-logical-database-design-using-entity-relationship-modeling institution: IBM - title: Entities for different types of relationships type: documentation year: 2026 url: https://www.ibm.com/docs/en/db2-for-zos/12.0.0?topic=modeling-entities-different-types-relationships institution: IBM - title: Data Modeler Concepts and Usage type: documentation year: 2017 url: https://docs.oracle.com/database/sql-developer-data-modeler-17.4/DMDUG/data-modeler-concepts-usage.htm institution: Oracle secondary_sources: [] updated: '2026-06-24' --- ## TL;DR The Entity-Relationship (ER) model is a conceptual database modeling approach for describing entities, their attributes, and relationships before committing to physical tables. It is useful when a team needs a stable business-level data model that can later be translated into relational schema structures. ## Core Explanation ER modeling starts before database implementation. IBM frames logical design as the first database design task and describes logical data modeling as documenting business information requirements in a consistent format. In practice, that means naming the main entity types, recording their attributes, and making the relationships between them explicit. Relationship cardinality is the part of an ER model that says how many instances can participate on each side of a relationship. Oracle's Data Modeler documentation gives the common 1:1, 1:N, and N:M cases; IBM Db2 documentation also lists one-to-one, one-to-many, many-to-one, and many-to-many relationship types. A many-to-many relationship usually needs an extra relational structure, such as a reference or junction table, when translated into a relational schema. The repaired article keeps the scope deliberately narrow: ER modeling is treated as a conceptual modeling technique, not as a complete tutorial on every diagram notation or database vendor's modeling tool. ## Source-Mapped Facts - Peter Chen's ACM Transactions on Database Systems article is titled "The entity-relationship model - toward a unified view of data." ([source](https://doi.org/10.1145/320434.320440)) - IBM Informix documentation summarizes the entity-relationship data-modeling method as identifying principal data objects, relationships, and attributes; diagramming the objects; translating them into relational constructs; resolving the logical data model; and normalizing the logical data model. ([source](https://www.ibm.com/docs/en/SSGU8G_12.1.0/com.ibm.ddi.doc/ids_ddi_163.htm)) - IBM Db2 documentation describes logical database design as the first database design task before implementation and describes logical data modeling as documenting business information requirements in an accurate and consistent format. ([source](https://www.ibm.com/docs/en/db2-for-zos/12.0.0?topic=relationships-logical-database-design-using-entity-relationship-modeling)) - IBM Db2 documentation lists one-to-many, many-to-one, one-to-one, and many-to-many as relationship types that can be expressed in a relational database design. ([source](https://www.ibm.com/docs/en/db2-for-zos/12.0.0?topic=modeling-entities-different-types-relationships)) - Oracle SQL Developer Data Modeler documentation says cardinality defines how many occurrences of one entity exist for one occurrence of a related entity, including 1:1, 1:N, and N:M cases, and maps N:M relationships to a reference table in the relational model. ([source](https://docs.oracle.com/database/sql-developer-data-modeler-17.4/DMDUG/data-modeler-concepts-usage.htm)) ## Further Reading - [The entity-relationship model - toward a unified view of data](https://doi.org/10.1145/320434.320440) - [Overview of the entity-relationship data model](https://www.ibm.com/docs/en/SSGU8G_12.1.0/com.ibm.ddi.doc/ids_ddi_163.htm) - [Logical database design using entity-relationship modeling](https://www.ibm.com/docs/en/db2-for-zos/12.0.0?topic=relationships-logical-database-design-using-entity-relationship-modeling) - [Data Modeler Concepts and Usage](https://docs.oracle.com/database/sql-developer-data-modeler-17.4/DMDUG/data-modeler-concepts-usage.htm) ## Related Articles - [Database Normalization](database-normalization.md) - [SQL (Structured Query Language)](sql.md) - [Database Indexing](database-indexing.md)