Diagram Examples

SoftwareSectionUML sequence, class, state machine, activity, component, deployment and use case diagrams for real… DatabasesSectionEntity-relationship diagrams in crow's foot and Chen notation, logical schemas, star schemas and Data Vault… NetworkingSectionNetwork topology, data-centre leaf-spine, cloud VPC layouts, OSI layers, and TCP, TLS and DNS sequence… Data EngineeringSectionData flow diagrams, pipeline DAGs, lineage graphs, Lambda and Kappa, streaming topologies and the medallion… AI & Machine LearningSectionRAG architecture, ML training pipelines, neural-network and transformer block diagrams, and agent tool-call… CloudSectionAWS three-tier architecture, Kubernetes deployments, serverless event flows and multi-region failover. SecuritySectionSTRIDE threat-model DFDs, OAuth 2.0 / OIDC sequences, network segmentation and attack trees. Business ProcessSectionBPMN processes, swimlane flowcharts, business use cases and customer journey maps.

Worked sample diagrams, organised by the kind of system you are drawing. Each page takes one realistic scenario, draws it as a full diagram, walks through it step by step, explains the notation, and lists the pros and cons of using that diagram for the job, with the same diagram as Mermaid or PlantUML source so you can keep it in version control.

UML and the other notations. UML, the Unified Modeling Language, standardises diagrams for software: structure (class, component, deployment) and behaviour (sequence, activity, state machine, use case). Databases, networks, data pipelines and business processes are drawn with other standard notations: entity-relationship diagrams, topology diagrams, data flow diagrams and BPMN. This section keeps them together because you will use all of them on the same project. For the notation reference itself, see the Diagrams hub and the full UML diagram reference.

Which diagram for which domain

Which diagram for which domain Softwaresequence, class, state DatabasesER, schema, star Networkingtopology, VPC, protocol Data Eng.DFD, DAG, lineage AI / MLRAG, pipeline, layers Cloud3-tier, k8s, serverless Securitythreat model, OAuth BusinessBPMN, swimlane UML (gold) covers software; the other domains use the standard notations that sit alongside it.

Start with the domain closest to what you are building. A typical project uses three or four of these: a use case or BPMN diagram to agree scope, an architecture or deployment diagram for the big picture, sequence diagrams for the tricky interactions, and an ER diagram for the data.