Diagram notation
The shapes, lines and arrows of software, database, process and family diagrams, and what each one means.
The notation of BPMN business process diagrams: the event circles, task boxes and gateway diamonds, the flows between them, and the pools and lanes of a swimlane diagram, and what each one means.
The notation of UML class, use case, sequence and activity diagrams: the boxes, arrows and relationships, and what each one means.
The notation of entity-relationship diagrams: crow’s foot cardinality and Chen’s entities, relationships and attributes, and what each one means.
The icons of a value stream map, the lean manufacturing diagram of how material and information move from supplier to customer: process and data boxes, inventory triangles, push arrows, supermarkets, kanban, FIFO lanes, kaizen bursts and the timeline.
The four symbols of a data flow diagram (DFD), process, external entity, data store and data flow, in Yourdon/DeMarco and in Gane and Sarson notation, and what each one means.
The standard flowchart shapes, from the oval terminal and the decision diamond to the document and connector, and what each one means.
The symbols of genograms, the family diagrams of family therapy, medicine and social work: people, partnerships, children and the lines for emotional relationships.
About diagram notation
Diagram notation explains the shapes, lines and arrows of seven kinds of diagram: UML diagrams of software, ER diagrams of databases, flowcharts of processes, genograms of families, BPMN diagrams of business processes, including swimlane diagrams, value stream maps of lean manufacturing and data flow diagrams of information systems. Each has a standard behind it, or a book used in its place: the Object Management Group’s UML specification, Peter Chen’s 1976 paper on the entity-relationship model, the American flowchart standard ANSI X3.5 and its international successor ISO 5807, the symbols in Monica McGoldrick’s book Genograms, first published in 1985, the Object Management Group’s BPMN specification, Mike Rother and John Shook’s workbook Learning to See, and the structured analysis textbooks of Ed Yourdon, Tom DeMarco, and Chris Gane and Trish Sarson.
The same shape in different diagrams
The four notations share a small stock of shapes and give them different meanings. A diamond is a decision in a flowchart and in a UML activity diagram, and a relationship in Chen’s ER notation. A rectangle is a step in a flowchart, an entity in an ER diagram and, divided into compartments, a class in UML. A circle is a connector in a flowchart, a woman in a genogram, an event in BPMN and a process in a Yourdon data flow diagram. A rounded rectangle is a task in BPMN and a process in Gane and Sarson’s data flow diagrams. Each symbol’s page names the look-alikes from the other diagrams and says how to tell them apart.
Where the notations came from
Flowcharts came first. The American standard for their symbols was published in 1970, after flowcharts had spread with the use of computers in business, and ISO 5807 replaced the earlier international standards in 1985. Chen’s paper of 1976 introduced the ER diagram as a tool for database design. UML grew out of three earlier methods for describing object-oriented software, Booch, OMT and OOSE; version 2.5.1 dates from December 2017. The genogram symbols were standardized for McGoldrick’s first edition, and she writes that they have changed since.
The process notations followed. Gane and Sarson’s book of 1977 and DeMarco’s of 1978 were among the first structured analysis textbooks, the source of the data flow diagram. Learning to See, which brought Toyota’s material and information flow diagram to the rest of industry as the value stream map, came out in 1998. BPMN 1.0 was released in May 2004 by the Business Process Management Initiative; the Object Management Group’s version 2.0.2 dates from December 2013.
Sources
- OMG Unified Modeling Language (OMG UML), Version 2.5.1, OMG document formal/17-12-05, December 2017, Object Management Group, Title page; 1 Scope; 9.2.4; 11.5.4; Annex A: Diagrams
- The Entity-Relationship Model: Toward a Unified View of Data, Peter Pin-Shan Chen, ACM Transactions on Database Systems 1, no. 1 (March 1976): 9–36, Association for Computing Machinery (copy hosted by California State University, Bakersfield), Abstract; p. 9
- Flowchart Symbols and Their Usage in Information Processing, ANSI X3.5-1970, adopted for federal use as FIPS PUB 24, American National Standards Institute; National Bureau of Standards (NIST), Foreword; sections 2, 3.1 and 4.1
- Information processing: Documentation symbols and conventions for data, program and system flowcharts, program network charts and system resources charts, ISO 5807:1985, first edition (preview pages), International Organization for Standardization (iTeh Standards preview), Sections 0 and 3.3
- What's a Genogram?, Monica McGoldrick, Introduction to Genograms, 2003, The Multicultural Family Institute (Internet Archive), What's a Genogram?; About Genograms
- Business Process Model and Notation (BPMN), Version 2.0.2, OMG document formal/2013-12-09, December 2013 (also ISO/IEC 19510), Object Management Group, Title page
- Introduction to BPMN, Stephen A. White, IBM Corporation, 2004 (published on bpmn.org), IBM Corporation; Business Process Management Initiative, What Is BPMN?
- Value-Stream Mapping, Lexicon term, Lean Enterprise Institute, Definition
- Value Stream Mapping Basics, Bo Madsen and Hugh McManus, 16.660J Introduction to Lean Six Sigma Methods, IAP 2012, Massachusetts Institute of Technology (MIT OpenCourseWare), Slide 18
- Just Enough Structured Analysis, Ed Yourdon, rev. 2006 (successor to Modern Structured Analysis, 1989), Chapters 4 and 9, Ed Yourdon (yourdon.com), via Internet Archive, Chapters 7 and 9
- Approval standards and guidelines: data flow diagram, Guidance on accessing UKHSA protected data, Notation, UK Health Security Agency (GOV.UK), Notation
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research