EntityProperty

Listing of Entity Types »

EntityProperty[type,pname]

represents a property identified by pname for use in EntityValue.

EntityProperty[class,pname]

represents a property introduced by the computed entity class class.

EntityProperty[type,pname,{qual1val1,qual2val2,}]

represents a property modified by the qualifier rules qualivali.

Details and Options

  • When referring to a property with no qualifiers, the EntityProperty wrapper is generally optional.
  • Use EntityProperties[type] to get a list of properties of the specified type.
  • Property values for an Entity object can be obtained using Entity[][EntityProperty[]] or EntityProperty[][Entity[]].
  • EntityProperty[]["prop"] can be used to look up property metadata. Metadata properties include the following:
  • "Qualifiers"the list of possible qualifiers for the property
    "QualifierValues"the list of possible values that can be given to each qualifier
    "Label"the label of the property
    "Definition"a detailed textual definition of the property
    "Source"source information for the property
    "PhysicalQuantity"the physical quantity associated with entity-property values
    "Unit"the common unit associated with entity-property values
  • A qualifier value of Automatic indicates that an applicable format of values can be used, e.g. for the "Date" qualifier; this includes a proper date or date span.
  • ExtendedEntityClass and AggregatedEntityClass can introduce new properties. For such properties, the first argument of EntityProperty will be that entity class.
  • Information of an EntityProperty expression will give different properties depending on the EntityTypeName associated with the expression.

Examples

open allclose all

Basic Examples  (3)

The property of type "Aircraft" representing the cruise speed:

Retrieve the cruise speed of the Concorde:

Find the population of the United States:

Find the population in 1980:

Make the same query using Dated:

Find the "Unit" of the "molar mass" property:

Use to query for the molecular mass of caffeine:

Scope  (2)

Get possible qualifiers for the city population property:

Get possible qualifier values for the "Age" qualifier:

Use the "Age" qualifier with the "Adult" value:

EntityProperty can have qualifiers to be more specific about a property:

Here the "Date" qualifier specifies a particular year:

Applications  (1)

Create a date range from the year 1900 to 2010 in steps of 5 years:

Get the population of China for those years:

Make a date plot using this data:

Properties & Relations  (1)

The EntityProperty wrapper is optional here. It is sufficient to use the property name:

Possible Issues  (1)

Calling entities with one property at a time is slower than calling entities with a single list of properties:

This form is faster because the entity properties are requested with a single call:

The entities and their properties are cached, so subsequent calls are much faster:

Introduced in 2014
 (10.0)
 |
Updated in 2019
 (12.0)