Signal Description Ontology
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Signal Description Ontology

Release: 2025-09-25

This version:
https://purl.org/signal-description-ontology#
Latest version:
https://purl.org/signal-description-ontology#
Revision:
0.1
Authors:
Alexander Ebner, TU Wien ✉
Download serialization:
JSON-LD RDF/XML N-Triples TTL
License:
https://creativecommons.org/licenses/by/4.0/
Cite as:
AlexanderEbner. Signal Description Ontology. Revision: 0.1.
Vocabulary maintained at:
https://github.com/lexEbner/sdo
Ontology Specification Draft

Abstract

Industrial systems generate massive streams of time series data, but differences in formats, technologies, and timing make this data hard to interpret and share. The ontology presented here provides a common language to describe such data in the form of signals. At its core, it offers a technology-neutral model that captures the essential characteristics of signals across diverse sources. On top of this, it supports specialized extension modules that adapt the model to specific technologies and provide all the details needed for actual data access. This approach makes signals easier to discover, understand, and use.

Introduction back to ToC

Modern industrial systems generate enormous amounts of data. Machines, sensors, and software exchange information at high speed, supporting everything from real-time process control to supply chain optimization. But with this growth comes a major challenge: heterogeneity. Different devices and platforms use their own formats, semantics, and access methods. The result is a patchwork of isolated data silos that are hard to integrate and even harder to interpret. To unlock the full potential of this data, we need a shared way of describing and accessing it. Semantic Web technologies already offer powerful tools for creating machine-interpretable interfaces across diverse sources, enabling true interoperability. However, when it comes to time series data, additional challenges emerge. Differences in timestamps, irregular sampling, and jitter make consistent analysis difficult. The concept of signals helps address these issues by treating time series as continuous functions of time. Signals make it possible to work with data in a consistent way, regardless of where it originates or how it is sampled. What's been missing, however, is a way to combine this concept with semantic technologies to also overcome the data access barriers. This ontology fills that gap. It provides a technology-agnostic foundation for describing signals, along with a flexible framework for building extensions that connect to specific technologies. With this ontology, signals can be described in a uniform way and linked to the mechanisms needed to access them. This makes heterogeneous time series data easier to discover, integrate, and use across different technologies and domains.

Signal Description Ontology: Overview back to ToC

This ontology has the following classes and properties.

Classes

Object Properties

Data Properties

Visualized Ontology

Signal Description Ontology: Description back to ToC

An ontology for integrating data sources providing time series data based on signal descriptions.

Cross-reference for SDO Core

Assetc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#Asset

Represents a physical or logical object that provides signals or contains other assets.
is in domain of
has asset op, has signal description op, is asset of op
is in range of
has asset op, is asset of op, is signal description of op

Cert Credentialsc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#CertCredentials

Represents authentication using certificates.
has super-classes
Credentials c
is in domain of
has certificate dp, has private key dp

Connection Infoc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#ConnectionInfo

Contains the information required to connect to a source.
has sub-classes
Influx Db Connection Info c, Opc Ua Connection Info c
is in domain of
has URL dp, has credentials op
is in range of
is credentials of op

Credentialsc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#Credentials

Serves as supertype for different authentication methods.
has sub-classes
Cert Credentials c, Token Credentials c, User Pass Credentials c
is in domain of
is credentials of op
is in range of
has credentials op

Data Accessc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#DataAccess

Serves as supertype for technology-specific types of data access, used to obtain signal values.
has sub-classes
Influx Db Access c, Opc Ua Access c
is in domain of
is historical access of op, is near real-time access of op
is in range of
has historical access op, has near real-time access op

Datatypec back to ToC or Class ToC

IRI: http://www.w3.org/2000/01/rdf-schema#Datatype

Refers to a RDFS Datatype
is in domain of
is data type of op
is in range of
has data type op

Key-Value Pairc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#KeyValuePair

Represents data the in form of a key and a value.
has sub-classes
Meta Data c, Tag c
is in domain of
has key dp, has value dp

Meta Datac back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#MetaData

A key-value pair that adds information about a signal.
has super-classes
Key-Value Pair c
is in domain of
is metadata of op
is in range of
has metadata op

Signal Descriptionc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#SignalDescription

Contains the information to enable interpretation and data access of a signal.
is in domain of
has data type op, has historical access op, has metadata op, has near real-time access op, has signal type dp, has unit op, is signal description of op
is in range of
has signal description op, is data type of op, is historical access of op, is metadata of op, is near real-time access of op, is unit of op

Token Credentialsc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#TokenCredentials

Represents authentication based on tokens.
has super-classes
Credentials c
is in domain of
has token dp

Unitc back to ToC or Class ToC

IRI: http://qudt.org/schema/qudt/Unit

Refers to a QUDT Unit
is in domain of
is unit of op
is in range of
has unit op

User Pass Credentialsc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/core#UserPassCredentials

Represents authentication based on username and password.
has super-classes
Credentials c
is in domain of
has password dp, has username dp

has assetop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasAsset

Links an Asset to another Asset it contains to.

has characteristics: transitive

has domain
Asset c
has range
Asset c
is inverse of
is asset of op

has credentialsop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasCredentials

Links Credentials to a ConnectionInfo providing it for authentication.
has domain
Connection Info c
has range
Credentials c
is inverse of
is credentials of op

has data typeop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasDataType

Links a Datatype to a SignalDescription it refers to.
has domain
Signal Description c
has range
Datatype c
is inverse of
is data type of op

has historical accessop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasHistAccess

Links historical DataAccess to a SignalDescription providing it.
has domain
Signal Description c
has range
Data Access c
is inverse of
is historical access of op

has metadataop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasMetadata

Links a metadata to a SignalDescription described by
has domain
Signal Description c
has range
Meta Data c
is inverse of
is metadata of op

has near real-time accessop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasNrtAccess

Links near real-time DataAccess to a SignalDescription providing it.
has domain
Signal Description c
has range
Data Access c
is inverse of
is near real-time access of op

has signal descriptionop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasSignalDescription

Links a SignalDescription to a Asset it contains to.
has domain
Asset c
has range
Signal Description c
is inverse of
is signal description of op

has unitop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasUnit

Links a Unit to a SignalDescription its values are measured by.
has domain
Signal Description c
has range
Unit c
is inverse of
is unit of op

is asset ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#isAssetOf

Links an Asset to another Asset contained by it.

has characteristics: transitive

has domain
Asset c
has range
Asset c
is inverse of
has asset op

is credentials ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#isCredentialsOf

Links a ConnectionInfo to Credentials provided by it for authentication.
has domain
Credentials c
has range
Connection Info c
is inverse of
has credentials op

is data type ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#isDataTypeOf

Links a SignalDescription to a Datatype referred by it.
has domain
Datatype c
has range
Signal Description c
is inverse of
has data type op

is historical access ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#isHistAccessOf

Links SignalDescription to historical DataAccess provided by it.
has domain
Data Access c
has range
Signal Description c
is inverse of
has historical access op

is metadata ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#isMetadataOf

Links a SignalDescription to a metadata describing it
has domain
Meta Data c
has range
Signal Description c
is inverse of
has metadata op

is near real-time access ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#isNrtAccessOf

Links SignalDescription to near real-time DataAccess provided by it.
has domain
Data Access c
has range
Signal Description c
is inverse of
has near real-time access op

is signal description ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#isSignalDescriptionOf

Links an Asset to a SignalDescription contained by it.
has domain
Signal Description c
has range
Asset c
is inverse of
has signal description op

is unit ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/core#isUnitOf

Links a SignalDescription to a Unit measuring it.
has domain
Unit c
has range
Signal Description c
is inverse of
has unit op

has certificatedp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasCert

The certificate used for certificate-based authentication.
has domain
Cert Credentials c
has range
any URI

has keydp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasKey

The key of a key-value pair.
has domain
Key-Value Pair c
has range
string

has passworddp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasPassword

The password used for username-password credentials.
has domain
User Pass Credentials c
has range
string

has private keydp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasPrivateKey

The private key used for certificate-based authentication.
has domain
Cert Credentials c
has range
any URI

has signal typedp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasSignalType

A enumeration that determines how values between the data samples are interpreted.
has domain
Signal Description c
has range
{ "HoldObservations" , "LinearInterpolation" , "Observations" }

has tokendp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasToken

The token used for token-based authentication.
has domain
Token Credentials c
has range
string

has URLdp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasURL

The URL of a connection.
has domain
Connection Info c
has range
any URI

has usernamedp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasUsername

The username used for username-password credentials.
has domain
User Pass Credentials c
has range
string

has valuedp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/core#hasValue

The value of a key-value pair.
has domain
Key-Value Pair c
has range
Literal
c: Classes
op: Object Properties
dp: Data Properties

Cross-reference for SDO OPC UA Extension

Message Securityc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/opcua#MessageSecurity

Contains the information required to establish a secure channel in OPC UA.
is in domain of
has client certificate dp, has client private key dp, has mode dp, has security policy dp, has server certificate dp, is message security of op
is in range of
has message security op

Opc Ua Accessc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/opcua#OpcUaAccess

Contains the information used to access OPC UA nodes.
has super-classes
Data Access c
is in domain of
has OPC UA connection information op, has identifier dp, has namespace URI dp, has namespace index dp, has server index dp
is in range of
is OPC UA connection information of op

Opc Ua Connection Infoc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/opcua#OpcUaConnectionInfo

Contains the information required to connect to an OPC UA server.
has super-classes
Connection Info c
is in domain of
has message security op, is OPC UA connection information of op
is in range of
has OPC UA connection information op, is message security of op

has message securityop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasMessageSecurity

Links MessageSecurity to OpcUaConnectionInfo requiring it for secure communication.
has domain
Opc Ua Connection Info c
has range
Message Security c
is inverse of
is message security of op

has OPC UA connection informationop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasOpcUaConnectionInfo

Links connection information to OPC UA Access requiring it.
has domain
Opc Ua Access c
has range
Opc Ua Connection Info c
is inverse of
is OPC UA connection information of op

is message security ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#isMessageSecurityOf

Links OpcUaConnectionInfo to MessageSecurity required by it for secure communication.
has domain
Message Security c
has range
Opc Ua Connection Info c
is inverse of
has message security op

is OPC UA connection information ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#isOpcUaConnectionInfoOf

Links OPC UA Access to connection information required by it.
has domain
Opc Ua Connection Info c
has range
Opc Ua Access c
is inverse of
has OPC UA connection information op

has client certificatedp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasClientCert

The client certificate used to establish an OPC UA secure channel.
has domain
Message Security c
has range
any URI

has client private keydp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasClientPrivateKey

The client's private key used to establish an OPC UA secure channel.
has domain
Message Security c
has range
any URI

has identifierdp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasIdentifier

The identifier used in node IDs.
has domain
Opc Ua Access c
has range
Literal

has modedp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasMode

A enumeration that defines the message security mode.
has domain
Message Security c
has range
{ "Sign" , "SignAndEncrypt" }

has namespace indexdp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasNamespaceIndex

The namespace index used in node IDs.
has domain
Opc Ua Access c
has range
integer

has namespace URIdp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasNamespaceURI

The URI of the namespace used in expanded node IDs.
has domain
Opc Ua Access c
has range
any URI

has security policydp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasSecurityPolicy

The name of the security policy profile defining the cryptographic algorithms for OPC UA message security.
has domain
Message Security c
has range
string

has server certificatedp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasServerCert

The server certificate used to establish an OPC UA secure channel.
has domain
Message Security c
has range
any URI

has server indexdp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/opcua#hasServerIndex

The server index used in expanded node IDs.
has domain
Opc Ua Access c
has range
integer

Cross-reference for SDO InfluxDB Extension

Influx Db Accessc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/influxdb#InfluxDbAccess

Contains the information used to query InfluxDB points.
has super-classes
Data Access c
is in domain of
has InfluxDB connection information op, has field dp, has measurement dp, has tag op
is in range of
is InfluxDB connection information of op, is tag of op

Influx Db Connection Infoc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/influxdb#InfluxDbConnectionInfo

Contains the information required to connect to an InfluxDB server.
has super-classes
Connection Info c
is in domain of
has bucket dp, has organization dp, is InfluxDB connection information of op
is in range of
has InfluxDB connection information op

Tagc back to ToC or Class ToC

IRI: https://purl.org/signal-description-ontology/influxdb#Tag

A key-value pair used to query points in InfluxDB.
has super-classes
Key-Value Pair c
is in domain of
is tag of op
is in range of
has tag op

has InfluxDB connection informationop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/influxdb#hasInfluxDbConnectionInfo

Links connection information to InfluxDB Access requiring it.
has domain
Influx Db Access c
has range
Influx Db Connection Info c
is inverse of
is InfluxDB connection information of op

has tagop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/influxdb#hasTag

Links a Tag identifying a point to InfluxDB Access.
has domain
Influx Db Access c
has range
Tag c
is inverse of
is tag of op

is InfluxDB connection information ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/influxdb#isInfluxDbConnectionInfoOf

Links InfluxDB Access to connection information required by it.
has domain
Influx Db Connection Info c
has range
Influx Db Access c
is inverse of
has InfluxDB connection information op

is tag ofop back to ToC or Object Property ToC

IRI: https://purl.org/signal-description-ontology/influxdb#isTagOf

Links InfluxDB Access to a Tag identifying a point.
has domain
Tag c
has range
Influx Db Access c
is inverse of
has tag op

has bucketdp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/influxdb#hasBucket

The bucket name in InfluxDB.
has domain
Influx Db Connection Info c
has range
string

has fielddp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/influxdb#hasField

The field key in InfluxDB.
has domain
Influx Db Access c
has range
string

has measurementdp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/influxdb#hasMeasurement

The measurement name in InfluxDB.
has domain
Influx Db Access c
has range
string

has organizationdp back to ToC or Data Property ToC

IRI: https://purl.org/signal-description-ontology/influxdb#hasOrganization

The organization name in InfluxDB.
has domain
Influx Db Connection Info c
has range
string

References back to ToC

[owl2-syntax]

OWL 2 Web Ontology Language Structural Specification and Functional-Style Syntax (Second Edition) . Boris Motik; Peter Patel-Schneider; Bijan Parsia. W3C. 11 December 2012. W3C Recommendation. URL: https://www.w3.org/TR/owl2-syntax/

[chowlk]

Chowlk: from UML-based ontology conceptualizations to OWL. Chávez-Feria, S., García-Castro, R., Poveda-Villalón, M. In: European Semantic Web Conference. pp. 338-352. Springer (2022). URL: https://chowlk.linkeddata.es/

[oops]

OOPS! (OntOlogy Pitfall Scanner!): An On-line Tool for Ontology Evaluation. Poveda-Villalón, M., Gómez-Pérez, A., Suárez-Figueroa, M.C. International Journal on Semantic Web and Information Systems (IJSWIS) 10(2), 7-34 (2014). URL: https://oops.linkeddata.es/

[widoco]

Widoco: A Wizard for Documenting Ontologies. Garijo, D., & Poveda-Villalón, M. (2019). URL: https://github.com/dgarijo/Widoco

[opcua]

OPC UA Specification Reference. OPC Foundation. (2024). URL: https://reference.opcfoundation.org/

[influxdb]

InfluxDB. InfluxData. URL: https://www.influxdata.com/

[qudt]

Quantities, Units, Dimensions and Data Types Ontologies. QUDT.org. (2020). URL: http://www.qudt.org

Acknowledgments back to ToC

The authors would like to thank Silvio Peroni for developing LODE, a Live OWL Documentation Environment, which is used for representing the Cross Referencing Section of this document and Daniel Garijo for developing Widoco, the program used to create the template used in this documentation.