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A Type

This term is in the "new" area - implementation feedback and adoption from applications and websites can help improve our definitions.
Instances of the class Observation are used to specify observations about an entity at a particular time. The principal properties of an Observation are observationAbout, measuredProperty, statType, [[value] and observationDate and measuredProperty. Some but not all Observations represent a QuantitativeValue. Quantitative observations can be about a StatisticalVariable, which is an abstract specification about which we can make observations that are grounded at a particular location and time.

Observations can also encode a subset of simple RDF-like statements (its observationAbout, a StatisticalVariable, defining the measuredPoperty; its observationAbout property indicating the entity the statement is about, and value )

In the context of a quantitative knowledge graph, typical properties could include measuredProperty, observationAbout, observationDate, value, unitCode, unitText, measurementMethod.
PropertyExpected TypeDescription
Properties from Observation
marginOfError QuantitativeValue A marginOfError for an Observation.
measuredProperty Property The measuredProperty of an Observation, typically via its StatisticalVariable. There are various kinds of applicable Property: a property, a property from other RDF-compatible systems, e.g. W3C RDF Data Cube, Data Commons, Wikidata, or extensions such as GS1's.
measurementDenominator StatisticalVariable Identifies the denominator variable when an observation represents a ratio or percentage.
measurementMethod DefinedTerm  or
MeasurementMethodEnum  or
Text  or
A subproperty of measurementTechnique that can be used for specifying specific methods, in particular via MeasurementMethodEnum.
measurementQualifier Enumeration Provides additional qualification to an observation. For example, a GDP observation measures the Nominal value.
measurementTechnique DefinedTerm  or
MeasurementMethodEnum  or
Text  or
A technique, method or technology used in an Observation, StatisticalVariable or Dataset (or DataDownload, DataCatalog), corresponding to the method used for measuring the corresponding variable(s) (for datasets, described using variableMeasured; for Observation, a StatisticalVariable). Often but not necessarily each variableMeasured will have an explicit representation as (or mapping to) an property such as those defined in, or other RDF vocabularies and "knowledge graphs". In that case the subproperty of variableMeasured called measuredProperty is applicable.

The measurementTechnique property helps when extra clarification is needed about how a measuredProperty was measured. This is oriented towards scientific and scholarly dataset publication but may have broader applicability; it is not intended as a full representation of measurement, but can often serve as a high level summary for dataset discovery.

For example, if variableMeasured is: molecule concentration, measurementTechnique could be: "mass spectrometry" or "nmr spectroscopy" or "colorimetry" or "immunofluorescence". If the variableMeasured is "depression rating", the measurementTechnique could be "Zung Scale" or "HAM-D" or "Beck Depression Inventory".

If there are several variableMeasured properties recorded for some given data object, use a PropertyValue for each variableMeasured and attach the corresponding measurementTechnique. The value can also be from an enumeration, organized as a MeasurementMetholdEnumeration.
observationAbout Place  or
The observationAbout property identifies an entity, often a Place, associated with an Observation.
observationDate DateTime The observationDate of an Observation.
observationPeriod Text The length of time an Observation took place over. The format follows P[0-9]*[Y|M|D|h|m|s]. For example, P1Y is Period 1 Year, P3M is Period 3 Months, P3h is Period 3 hours.
variableMeasured Property  or
PropertyValue  or
StatisticalVariable  or
The variableMeasured property can indicate (repeated as necessary) the variables that are measured in some dataset, either described as text or as pairs of identifier and description using PropertyValue, or more explicitly as a StatisticalVariable.
Properties from QuantitativeValue
additionalProperty PropertyValue A property-value pair representing an additional characteristic of the entity, e.g. a product feature or another characteristic for which there is no matching property in

Note: Publishers should be aware that applications designed to use specific properties (e.g.,,, ...) will typically expect such data to be provided using those properties, rather than using the generic property/value mechanism.
maxValue Number The upper value of some characteristic or property.
minValue Number The lower value of some characteristic or property.
unitCode Text  or
The unit of measurement given using the UN/CEFACT Common Code (3 characters) or a URL. Other codes than the UN/CEFACT Common Code may be used with a prefix followed by a colon.
unitText Text A string or text indicating the unit of measurement. Useful if you cannot provide a standard unit code for unitCode.
value Boolean  or
Number  or
StructuredValue  or
The value of a QuantitativeValue (including Observation) or property value node.

  • For QuantitativeValue and MonetaryAmount, the recommended type for values is 'Number'.
  • For PropertyValue, it can be 'Text', 'Number', 'Boolean', or 'StructuredValue'.
  • Use values from 0123456789 (Unicode 'DIGIT ZERO' (U+0030) to 'DIGIT NINE' (U+0039)) rather than superficially similar Unicode symbols.
  • Use '.' (Unicode 'FULL STOP' (U+002E)) rather than ',' to indicate a decimal point. Avoid using these symbols as a readability separator.
valueReference DefinedTerm  or
Enumeration  or
MeasurementTypeEnumeration  or
PropertyValue  or
QualitativeValue  or
QuantitativeValue  or
StructuredValue  or
A secondary value that provides additional information on the original value, e.g. a reference temperature or a type of measurement.
Properties from Thing
additionalType Text  or
An additional type for the item, typically used for adding more specific types from external vocabularies in microdata syntax. This is a relationship between something and a class that the thing is in. Typically the value is a URI-identified RDF class, and in this case corresponds to the use of rdf:type in RDF. Text values can be used sparingly, for cases where useful information can be added without their being an appropriate schema to reference. In the case of text values, the class label should follow the style guide
alternateName Text An alias for the item.
description Text  or
A description of the item.
disambiguatingDescription Text A sub property of description. A short description of the item used to disambiguate from other, similar items. Information from other properties (in particular, name) may be necessary for the description to be useful for disambiguation.
identifier PropertyValue  or
Text  or
The identifier property represents any kind of identifier for any kind of Thing, such as ISBNs, GTIN codes, UUIDs etc. provides dedicated properties for representing many of these, either as textual strings or as URL (URI) links. See background notes for more details.
image ImageObject  or
An image of the item. This can be a URL or a fully described ImageObject.
mainEntityOfPage CreativeWork  or
Indicates a page (or other CreativeWork) for which this thing is the main entity being described. See background notes for details.
Inverse property: mainEntity
name Text The name of the item.
potentialAction Action Indicates a potential Action, which describes an idealized action in which this thing would play an 'object' role.
sameAs URL URL of a reference Web page that unambiguously indicates the item's identity. E.g. the URL of the item's Wikipedia page, Wikidata entry, or official website.
subjectOf CreativeWork  or
A CreativeWork or Event about this Thing.
Inverse property: about
url URL URL of the item.

Instances of Observation may appear as a value for the following properties
PropertyOn TypesDescription
diseaseSpreadStatistics SpecialAnnouncement Statistical information about the spread of a disease, either as WebContent, or described directly as a Dataset, or the specific Observations in the dataset. When a WebContent URL is provided, the page indicated might also contain more such markup.



Example 1
Example notes or example HTML without markup.
As an example, the statement "According to the US Census ACS 5 Year Estimates,
the median age of women in San Antonio, Texas in 2014 was 34.4 years." can be
represented in JSON-LD.
Example encoded as JSON-LD in a HTML script tag.
<script type="application/ld+json">
  "@context": "",
  "@type": "StatisticalVariable",
  "@id": "Median_Height_Person_Female",
  "name": "Median height of women",
  "populationType": {"@id": "Person"},
  "measuredProperty": {"@id": "height"},
  "statType": {"@id": "median"},
  "gender": {"@id": "Female"},
  "numConstraints": 1,
  "constrainingProperty": {"@id": "gender"}
  "@context": "",
  "@id": "Observation_Median_Age_Person_Female_SanAntonio_TX_2014",
  "@type": "Observation",
  "name": "Median height of women in San Antonio, Texas in 2014",
  "description": "An Observation of the StatisticalVariable Median_Height_Person_Female in location: San Antonio, Texas, for time period: 2014",
  "variableMeasured": { "@id": "Median_Height_Person_Female" },
  "observationAbout": { "@id": "" },
  "observationDate": 2014,
  "value": 160,
  "unitCode": "CMT"

Structured representation of the JSON-LD example.