Property Node

Property Nodes express the constraints for a given property (identified by its IRI in sh:path). The term sh:or holds the possible ranges and their constraints for the property. If there is only 1 possible range, then it is possible to express all range constraints in the property node itself instead of using sh:or in theory, but in order to keep the same syntax for all Property Shapes sh:or should always be used.

1. Example

{
  "@type": "sh:PropertyShape",
  "sh:path": "schema:address",
  "rdfs:label": [
    {
      "@language": "en",
      "@value": "Postal address"
    },
    {
      "@language": "de",
      "@value": "Adresse"
    }
  ],
  "rdfs:comment": [
    {
      "@language": "en",
      "@value": "This Property is required. Its value must be either a String or a PostalAddress entity."
    }
  ],
  "sh:minCount": 1,
  "sh:maxCount": 1,
  "sh:or": [
    ...
  ]
}

2. Key-value table

The following table lists all possible terms that can be used by a Property Node. The order in the table reflects the recommended order of these terms within a Property Node (optional).

key

required

value type

description

related error

@type

true

sh:PropertyShape

The fixed type for a Property Node

sh:order

false

Integer

The position of this property in comparison with other properties for the same Subject (only representation purpose) - deprecated in favor of ds:propertyDisplayOrder

sh:path

true

IRI

The IRI of the property that is restricted by this node

rdfs:label

false

List of Language tagged String

The label for this Property

rdfs:comment

false

List of Language tagged String

The description/justification for this Property and/or its ranges

sh:minCount

false

Integer

The minimum cardinality (amount of values) for the property

Missing Property, Non-conform cardinality

sh:maxCount

false

Integer

The maximum cardinality (amount of values) for the property

Non-conform cardinality

sh:equals

false

List of IRI

The property must have the same values as the property specified in sh:equals

Non-conform sh:equals

sh:disjoint

false

List of IRI

The property must NOT have the same values as the property specified in sh:disjoint)

Non-conform sh:disjoint

sh:lessThan

false

List of IRI

The property must have values that are less than the values of the property specified in sh:lessThan

Non-conform sh:lessThan

sh:lessThanOrEquals

false

List of IRI

The property must have values that are less than or equal to the values of the property specified in sh:lessThanOrEquals

Non-conform sh:lessThanOrEquals

sh:or

true

List of Range Node

List of Range Nodes. Every value of this property must match at least one of the listed range nodes

Non-conform range

3. Semantics

3.1. Property match

The term sh:path specifies the IRI of the property to which this Property Node belongs.

Example:

"sh:path": "schema:name"

3.2. Property Range

The term sh:or contains all possible range specifications that the property can have. The value of the property must be compliant with at least one of the specified ranges in order to be compliant with the Property Node.

From a grammar point of view, following Node types are possible ranges (Range Nodes):

In the following example the property schema:address must have values that are either a string ("sh:datatype": "xsd:string"), or an entity with the class 'PostalAddress' ("sh:class":["schema:PostalAddress"]).

{
  "@type": "sh:PropertyShape",
  "sh:path": "schema:address",
  "sh:or": [
    {
      "sh:datatype": "xsd:string"
    },
    {
      "sh:node": {
        "@id": "https://semantify.it/ds/Oadk498#hgrdH",
        "@type": "sh:NodeShape",
        "sh:class": [
          "schema:PostalAddress"
        ],
        ...
      }
    }
  ]
}

3.3. Property-pair constraints

See SHACL specification.

The following property-pair constraints allow comparing the literal values of different properties (on the same level = properties of the same subject). It makes sense to define them at the property level, rather than at the range level. The values of the property-pair constraints terms are IRIs (multiple value possible).

In the following example the constraint sh:disjoint specifies that the property schema:name MUST NOT have the same value as the property schema:givenName.

[
  {
    "@type": "sh:PropertyShape",
    "sh:path": "schema:name",
    "rdfs:comment": [
      {
        "@language": "en",
        "@value": "The full name of a Person. It should not be the same as the 'givenName'."
      }
    ],
    "sh:disjoint": [
      "schema:givenName"
    ],
    "sh:or": [
      {
        "sh:datatype": "xsd:string"
      }
    ]
  },
  {
    "@type": "sh:PropertyShape",
    "sh:path": "schema:givenName",
    "rdfs:comment": [
      {
        "@language": "en",
        "@value": "The first name of a person."
      }
    ],
    "sh:or": [
      {
        "sh:datatype": "xsd:string"
      }
    ]
  }
]

3.3.1. sh:equals

See SHACL specification.

Specifies the condition that the set of all value nodes is equal to the set of objects of the triples that have the focus node as subject and the value of sh:equals as predicate. (The property shape having sh:equals must have the same values as the property shape with the sh:path specified with sh:equals).

3.3.2. sh:disjoint

See SHACL specification.

Specifies the condition that the set of value nodes is disjoint with the set of objects of the triples that have the focus node as subject and the value of sh:disjoint as predicate. (The property shape having sh:disjoint must NOT have the same values as the property shape with the sh:path specified with sh:disjoint).

3.3.3. sh:lessThan

See SHACL specification.

Specifies the condition that each value node is smaller than all the objects of the triples that have the focus node as subject and the value of sh:lessThan as predicate. (The property shape having sh:lessThan must have the values that are less than the property shape with the sh:path specified with sh:lessThan). The comparison should be possible for all data types except boolean and URL.

3.3.4. sh:lessThanOrEquals

See SHACL specification.

Specifies the condition that each value node is smaller than or equal to all the objects of the triples that have the focus node as subject and the value of sh:lessThanOrEquals as predicate. (like sh:lessThan, but equal values are also allowed). The comparison should be possible for all data types except boolean and URL.

Regarding the Error generation based on these property-pair constraints, tests were done trying https://shacl.org/playground/:

sh:equals produces an error if the specified property to compare does not exist.
sh:disjoint does NOT produce an error if the specified property to compare does not exist.
sh:lessThan does NOT produce an error if the specified property to compare does not exist.
sh:lessThanOrEquals does NOT produce an error if the specified property to compare does not exist.

3.4. Metadata

Following terms represent metadata about the given property. These terms do not have any effects on the verification result; They have only informational character.

3.4.1. sh:order (deprecated)

This term is deprecated in favor of ds:propertyDisplayOrder. Details can be found in DomainSpecification.md.

The term sh:order CAN be used to indicate a specific order for a list of properties. This can be used e.g. by a GUI to render the list of properties in the wished order. The value for this term must be an integer, starting with 0.

Example:

{
  "@type": "sh:PropertyShape",
  "sh:order": 0,
  "sh:path": "schema:givenName",
  ...
},
{
  "@type": "sh:PropertyShape",
  "sh:order": 1,
  "sh:path": "schema:familyName",
  ...
},

3.4.2. rdfs:comment

The term rdfs:comment CAN be used to describe and/or justify the property and its expected value types (in different languages). The value for this term is a language-tagged string. The standard description for a property term is usually provided by its vocabulary itself, rdfs:comment can be used to overwrite that standard description.

Example:

{
  "@type": "sh:PropertyShape",
  "sh:path": "schema:name",
  "rdfs:comment": [
    {
      "@language": "en",
      "@value":"Please provide only your first name and your family name, with a blank space between."
    }
  ],
  "sh:or": [
    {
      "sh:datatype": "xsd:string"
    }
  ]
}

3.4.3. rdfs:label

The term rdfs:label CAN be used to give the property a label (in different languages). The value for this term is a language-tagged string. The standard label for a property term is usually provided by its vocabulary itself, rdfs:label can be used to overwrite that standard label.

Example:

{
  "@type": "sh:PropertyShape",
  "sh:path": "schema:postalAddress",
  "rdfs:label": [
    {
      "@language": "en",
      "@value":"Postal address"
    },
    {
      "@language": "de",
      "@value": "Wohnaddresse"
    }
  ],
  ...
}

3.5. Cardinality

The terms sh:minCount and sh:maxCount CAN be used to specify the cardinality for the values of the property (the amount of values that the property can have). The value for these terms must be a positive integer. In order to avoid contradictory constraints, the value of sh:maxCount MUST NOT be smaller than the value of sh:minCount.

The following example Property Node specifies that the property schema:email must have at least two values, and at most 3 values.

{
  "@type": "sh:PropertyShape",
  "sh:path": "schema:email",
  "sh:minCount": 2,
  "sh:maxCount": 3,
  ...
}

The following example Property Node specifies that the property schema:name must have at least one value. There is no upper limit for the amount of values.

{
  "@type": "sh:PropertyShape",
  "sh:path": "schema:name",
  "sh:minCount": 1,
  ...
}

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