add SPARQL Constraints Tutorial

docs/explore-and-author/graph-exploration/building-a-customized-user-interface/.pages

@@ -4,4 +4,5 @@ nav:
     - Node Shapes: node-shapes
     - Property Shapes: property-shapes
     - Datatypes: datatype-reference
+    - SPARQL Constraints: sparql-constraints
 

docs/explore-and-author/graph-exploration/building-a-customized-user-interface/sparql-constraints/index.md

@@ -0,0 +1,108 @@
+---
+icon: eccenca/application-queries
+tags:
+    - SPARQL
+    - Validation
+    - AdvancedTutorial
+---
+# Using SPARQL Constraints for Custom Resource Validation
+
+## Introduction
+
+SHACL (Shapes Constraint Language) is a language for validating RDF data based on predefined shapes or constraints.
+SHACL SPARQL Constraints are a set of rules defined using SPARQL queries within SHACL shapes to express more complex validation logic that cannot be easily represented by other SHACL constructs.
+
+Key advantages:
+
+- **Complex logic**: You can implement any logic supported by SPARQL, such as aggregation, advanced pattern matching, or value ranges.
+
+- **Reusable queries**: SPARQL constraints allow the reuse of sophisticated query logic across different shapes and data types.
+
+## Setup
+
+SPARQL Constraints are resources which need to be managed in a Shape Catalog.
+This catalog graph needs to be imported (virtually, with `owl:imports`) into the main CMEM Shapes Catalog.
+Similar to property shapes, SPARQL Constraints needed to be linked from a Node Shape in order to select the set of shapes which are used for a given selection of resources.
+
+## Example
+
+In our running example, we create a Node Shape for `foaf:Person` resources.
+Then we add a SPARQL Constrain shape, which ...
+
+### Install needed Vocabularies
+
+Go to the **:eccenca-application-vocabularies: [Vocabulary catalog](../../../vocabulary-catalog)** and install the RDF Schema and FOAF Vocabulary.
+Your vocabulary catalog should look like this after installation
+
+![Vocabulary Catalog with Installed Vocabularies](vocabulary-catalog.png){ class="bordered" }
+
+### Create a Shape Catalog
+
+Go to **:eccenca-application-explore: [Knowledge graphs](../../../graph-exploration)** and create a **New Shape Catalog**.
+Name the graph e.g. *My Shapes*.
+After this step, the browser shows you a nearly empty graph which shows SHACL classes such as **SHACL Node Shape** and **SHACL SPARQL Constraint** in the navigation.
+
+![Empty Shapes Graph](empty-shapes-graph.png){ class="bordered" }
+
+### Create a SPARQL Constraint
+
+Select **SHACL SPARQL Constraint** in the Navigation component, then use the **Create a new "SHACL SPARQL Constraint"** button in the top right corner to create a new resource.
+Fill in a label and a SPARQL SELECT Query.
+
+For our example, we use the following values:
+
+- Label: `The term eccenca is not allowed in a Person label`
+- SPARQL Select:
+
+``` sparql
+PREFIX foaf: <http://xmlns.com/foaf/0.1/>
+PREFIX  rdfs: <http://www.w3.org/2000/01/rdf-schema#>
+
+SELECT $this (rdfs:label as ?path) (?label as ?value)
+WHERE {
+  $this a foaf:Person ;
+  rdfs:label ?label .
+  FILTER( REGEX(STR(?label), "eccenca" ))
+}
+```
+
+Note that the projection variables of SPARQL Constraint queries need to be named according to the [SHACL Specificaton](https://www.w3.org/TR/shacl/#sparql-constraints-example) (`$this`, `?path`, `?value`).
+After you clicked on **Create** you should see your new resource in a list.
+
+![New SPARQL Constraint](new-sparql-constraint.png){ class="bordered" }
+
+### Create a Node Shape
+
+Select **SHACL Node Shape** in the Navigation component, then use the **Create a new "SHACL Node Shape"** button in the top right corner to create a new resource.
+
+Enter the following values:
+
+- Name: `Person Shape`
+- Target class: Select `Person` from the FOAF vocabulary
+- SPARQL Constraints: Select your new constraint from the list (your have to use the **:material-plus-circle-outline: Add data** menu to extend the form with this non-default input field)
+- Property Shapes: Create a new property shape with
+    - Name: `Name`
+    - Show always: `true`
+    - Path: `rdfs:label`
+    - Node Kind: `Literal`
+
+Before you create your new Node Shape (and new Property Shape) your screen should look like this:
+
+![Create New Node Shape](create-node-shape.png){ class="bordered" }
+
+### Validate the Shape
+
+Now we can validate the shape by creating a Person with a label which contains the term `eccenca`.
+
+- Go to **:eccenca-application-explore: [Knowledge graphs](../../../graph-exploration)** and create a **New Knowledge Graph**.
+    - Name: `My Person Data`
+    - Imports: `foaf: Friend of a Friend vocabulary`
+- Select **Person** in the Navigation component, then use the **Create a new "Person"** button in the top right corner to create a new resource.
+    - Name: `The term eccenca is not allowed`
+
+The validate the resource with the validation button. You will see a screen like this:
+
+![Invalid Resource](invalid-resource.png){ class="bordered" }
+
+When you open the validation report, you will see a error message such as: **The value does not conform to SPARQL constraint**.
+