> For the complete documentation index, see [llms.txt](https://gitbook.semantify.it/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gitbook.semantify.it/draft/domainspecifications/ds-v7/grammar/domainspecification/class.md). # Class Node A Class Node is used as a potential range for a [Property Node](/draft/domainspecifications/ds-v7/grammar/domainspecification/property.md). It is represented by an object with `"@type": "sh:NodeShape"` that is wrapped by the term `sh:node`. This NodeShape is used to express all the characteristics and constraints of the Class Node. The most important constraint is `sh:class`, which constraints the class(es) that the target entity must have. For `sh:class` arrays are allowed, which are supposed to represent multi-typed entities (MTE). The `@id` of a Class Node is used to reference it in other parts of the Domain Specification, and so reuse already defined constraints for a specific Class. Details below. ## 1. Example ```javascript { "sh:node": { "@id": "https://semantify.it/ds/OBbzsh4_B#DpruH", "@type": "sh:NodeShape", "sh:class": [ "schema:Airport" ], "sh:closed": true, "sh:property": [ ... ] } } ``` ## 2. Key-value Table The following table lists all possible terms that can be used by a Class Node. The order in the table reflects the recommended order of these terms within a Class Node (optional). | key | required | value type | description | related error | | :-----------: | :------: | :----------------------: | ---------------------------------------------------------------- | :------------------------------------: | | `@id` | true | *IRI* | The IRI of the Class Node, which is based on the DS IRI it is in | | | `@type` | true | `"sh:NodeShape"` | The fixed type for a Class Node | | | `sh:class` | true | \[ *IRI* ] | The IRI(s) of the Class(es) that the entity must have | Non-conform range | | `sh:closed` | false | *Boolean* | Specifies if additional properties are allowed or not | Non-conform property | | `sh:property` | false | List of **PropertyNode** | A list of property nodes that apply to the entity | Missing Property, Non-conform Property | ## 3. Semantics ### 3.1. Class-Matching See [SHACL specification](https://www.w3.org/TR/shacl/#ClassConstraintComponent). A Class Node includes `sh:class` to specify the class(es) that the verified entity **MUST** match. Domain Specifications use [custom semantics for class matching](https://github.com/semantifyit/ds-specifications/tree/614b79518304b804fb01f20d98f50f853cb9839b/DomainSpecifications/DS-V7/Grammar/VerificationReport/DS-Verification.md). Examples: ```javascript "sh:class": [ "schema:LodgingBusiness", "schema:Restaurant ] ``` ```javascript "sh:class": [ "schema:Article" ] ``` ### 3.2. Properties The terms `sh:property` and `sh:closed` are used in a Class Node to give further restrictions on the properties of the corresponding entity. Such a Class Node with property restrictions is also called **Restricted Class Node**. A Class Node without further property restrictions is called a **Standard Class Node**. #### 3.2.1. sh:property See [SHACL specification](https://www.w3.org/TR/shacl/#PropertyConstraintComponent). The term `sh:property` lists the property shapes that the target entity must comply with. For every property, there is a corresponding [Property Node](/draft/domainspecifications/ds-v7/grammar/domainspecification/property.md) in this list. Example: ```javascript "sh:property": [ { "@type": "sh:PropertyShape", "sh:order": 0, "sh:path": "schema:identifier" "sh:maxCount": 1, "sh:or": [ { "sh:datatype": "xsd:string", } ] }, { "@type": "sh:PropertyShape", "sh:order": 1, "sh:path": "schema:alternateName" "sh:maxCount": 1, "sh:or": [ { "sh:datatype": "xsd:string", } ] } ] ``` #### 3.2.2. sh:closed See [SHACL specification](https://www.w3.org/TR/shacl/#ClosedConstraintComponent). The term `sh:closed` can be used to specify if additional properties (other than the properties allowed by `sh:property`) are allowed or not. In the past, Domain Specifications had `"sh:closed": true` implicitly in all NodeShapes. Now the DS creator should specify the wished behaviour. Example: ```javascript "sh:closed": true ``` ### 3.3. Use of Internal references In order to reference NodeShapes that are part of a DS, those NodeShapes need an IRI. It makes sense to give them the same BaseIRI as the DS in which they are in, with the addition of a **fragment id**, e.g. in the DS with the IRI `https://semantify.it/ds/OBbzsh4_B` there could be a NodeShape with the IRI `https://semantify.it/ds/OBbzsh4_B#DpruH`. Example Class Node (inner NodeShape): ```javascript { "sh:node": { "@id": "https://semantify.it/ds/OBbzsh4_B#DpruH", "@type": "sh:NodeShape", "sh:class": ["schema:PostalAddress"], "sh:closed": true, "sh:property": [ ... ] } } ``` Example Property node that references the previous example Class node: ```javascript { "@type": "sh:PropertyShape", "sh:path": "schema:address", "sh:or": [ { "sh:node": { "@id": "https://semantify.it/ds/OBbzsh4_B#DpruH" } } ] } ``` In order to make the use of internal references more convenient, we introduce the following rules: * Every NodeShape inside a DS receives an IRI, even if it hasn't been referenced yet. * The NodeShape that specifies the class node (the referenced NodeShape) contains `"@type": "sh:NodeShape"` and all the constraints needed. * The internal references contain only the `@id` property. They can not add additional constraints. * Only valid matches can be used as a reference for a range, for this, the `sh:class` constraint of the target NodeShape is checked. If the target class of a NodeShape is `schema:Hotel`, but the property in question can not have that class as a valid range, then that NodeShape can **not** be referenced. * It is possible to create circular Domain Specifications.