Copyright © 2025 OGC & W3C ® (MIT, ERCIM, Keio, Beihang), W3C liability, trademark, W3C and OGC document use rules apply.

The Semantic Sensor Network ontology (SSN) describes actuators and their actuations, sensors and their observations, samplers and their samplings, the procedures implemented, the features of interest and samples changed or studied, and the actuated and observed properties. The core SSN classes and properties are defined using minimal axiomatization in a module called SOSA (Sensor, Observation, Sample, and Actuator) supplemented with additional axiomatization and terms in further modules. These allow SSN to support a wide range of applications and use cases, including satellite imagery, large-scale scientific monitoring, industrial and household infrastructures, social sensing, citizen science, observation-driven ontology engineering, and the Web of Things. Alignments to some existing ontologies and specifications are provided. Patterns for application of SSN are provided.

The namespace for the core terms is `http://www.w3.org/ns/sosa/`.

The suggested prefix for the SOSA namespace is `sosa`.

The SOSA graph containing the core definitions is available at http://www.w3.org/ns/sosa/.

The SSN graph with the full axiomatization of the core terms is available at http://www.w3.org/ns/ssn/.

General Information

For OGC this is a Public Draft of a document prepared by the Spatio-temporal Data on the Web Working Group (SDW) — a joint W3C-OGC project (see charter). The document is prepared following W3C conventions. The document is released at this time to solicit public comment.

Specification

This section introduces the specifications for the RDF implementation of the Semantic Sensor Network Ontology.

SSN Extensions

This section provides the specifications for modules that extend the scope and capabilities of SSN.

Alignments

This section provides the specifications for modules that align SOSA and SSN to a variety of related ontologies and specifications.

Common Patterns

This section discusses how to handle some common modeling questions.

Wide review

TBC

Acknowledgments

The editors recognize the major contribution of the members of the original W3C Semantic Sensor Networks Incubator Group. The editors also gratefully acknowledge the contributions made by all members of the SSN subgroup of the original Spatial Data on the Web working group.

For this new edition of SSN, in addition to the contributors listed at the top of the document, the editors acknowledge the work of the editors of ISO 19156:2023 ([[iso-19156-2023]], [[OMS]]). Ted Thibodeau Jr, Openlink Software, made many small grammatical improvements to the text.

Change History

A full change-log is available on GitHub.

Changes since W3C Recommendation 19 October 2017 (https://www.w3.org/TR/2017/REC-vocab-ssn-20171019/)

  1. Updated Abstract to reflect the revised graph and axiomatization design
  2. Updated and streamlined Introduction; moved Origins section to an Annex.
  3. Updated Chapter 2 'Modularization' to simplify and to reflect the revised graph arrangement
  4. Add conformance clause Chapter 3
  5. Updated Chapter 4 and Chapter 5.1 to explain modularization and RDF implementation
  6. Refactored SOSA and SSN into modules - sosa-common sosa-actuation sosa-observation sosa-sampling sosa (all), and matching ssn-* files (also ssn-deprecated). Refactored HTML sources to match.
  7. re-drafted all figures as SVG; added a clause on notation
  8. Mark `ssn:Input`, `ssn:Output`, `sosa:Result` deprecated
  9. Add `ExecutionCollection`, `ActuationCollection`, `ObservationCollection`, `SamplingCollection`, `SampleCollection`, `hasMember`, `isMemberOf`
  10. remove `rdfs:range` on `resultTime`
  11. Clarify meaning of `hasResult, resultTime, phenomenonTime in the context of `Actuations`
  12. Add `startTime` property
  13. Add `forProperty` links from `Procedure`, and inverse `hasProcedure`
  14. add inverses for all object-properties, add tabulation of all properties
  15. Add `madeBySystem`, `madeExecution`
  16. Remove `Sample is subclass of FeatureOfInterest` axiom
  17. Add Sample sub-classes - `MaterialSample`, `SpatialSample`, `StatisticalSample`
  18. Add `madeSamplingHasResult` and `usedForExecutionHasResult` properties
  19. Add `hasOriginalSample`, `isSampleOfUltimateFOI` from SSN-ext
  20. Deprecate `ActuatableProperty`, `ObservableProperty` in favour of generic `Property`
  21. Add `ActuatingProcedure`, `ObservingProcedure`, `SamplingProcedure` specializations of `Procedure` for each execution type
  22. Add `hasFeatureOfInterest support to Deployments
  23. Remove Functional and InverseFunctional axioms except on `hasResult
  24. Simplified the System Capabilities Module
  25. Move System Capabilities module to Appendix
  26. Add SAREF alignment
  27. Update OBOE alignment - using `ObservationCollection`, `SampleCollection`, `hasMember`
  28. Retire O&Mv2 alignment - superseded by OMS extension
  29. Retire SSNX alignment - incubator version is now two generations back
  30. Fully revise Common Modeling patterns, also with diagrams
  31. Make patterns for Location, UoM more prescriptive
  32. Move extended examples out of the document into an online repository
  33. Relaxed and simplified SOSA-DUL alignment