@shexjs/visitor

@shexjs/visitor

Visitor pattern for traversing ShExJ schemas

Install

npm install @shexjs/visitor

Quick start

The default behavior is to return a copy of the passed schema:

node -e 'console.log(JSON.stringify(new (require("@shexjs/visitor").ShExVisitor)()
  .visitSchema(
    {
      "type": "Schema",
      "shapes": [
        {
          "id": "http://a.example/S1",
          "type": "ShapeDecl",
          "shapeExpr": {
            "type": "Shape",
            "expression": {
              "type": "TripleConstraint",
              "predicate": "http://a.example/p1",
              "valueExpr": {
                "type": "NodeConstraint",
                "values": [
                  {
                    "value": "1",
                    "type": "http://www.w3.org/2001/XMLSchema#integer"
                  },
                  {
                    "value": "2",
                    "type": "http://www.w3.org/2001/XMLSchema#integer"
                  }
                ]
              }
            }
          }
        }
      ]
    }), null, 2))'

The result will look identical to the input schema.

Strategy

The ShExJ format is defined in JSG or Typescript. The visitor API reflects both the names of the ShExJ attributes and their types. For example, by default, the visitShapeAnd calls visitShapeExpr on each of the conjuncts. Likewise, visitTripleConstraint calls visitValueExpr on the .valueExpr attribute, which in turn calls visitShapeExpr because that is the type of .valueExpr.

Methods

• visitSchema(schema, ...args
• visitPrefixes(prefixes, ...args
• visitIRI(i, ...args
• visitImports(imports, ...args
• visitStartActs(startActs, ...args
• visitSemActs([semActs], ...args
• visitSemAct(semAct, label, ...args
• visitAnnotations([annotations], ...args
• TODO visitAnnotation(annotation, ...args
• visitShapes(shapes, ...args
• visitShapeDecl(decl, ...args
• visitShapeExpr(expr, ...args - calls one of the following
  • visitShapeOr(shapeExpr, ...args
  • visitShapeAnd(shapeExpr, ...args
  • visitShapeNot(expr, ...args
  • visitShapeRef(reference, ...args
  • visitShapeExternal(expr, ...args
  • visitNodeConstraint(shape, ...args
  • visitShape(shape, ...args
• visitExtra([extra], ...args
• visitExpression(expr, ...args - calls visitTripleExpr
• visitTripleExpr(expr, ...args - calls one of the following
  • visitOneOf(tripleExpr, ...args
  • visitEachOf(tripleExpr, ...args
  • visitTripleConstraint(expr, ...args
• visitValueExpr(shapeExpr, ...args
• visitValues(values, ...args
• visitValueExpr(shapeExpr, ...args
• visitStemRange(t, ...args
• visitExclusion(c, ...args
• visitInclusion(inclusion, ...args

simple value visitors

• visitBase
• visitStart
• visitClosed
• "visit@context"
• visitInverse
• visitPredicate
• visitName
• visitId
• visitCode
• visitMin
• visitMax
• visitType
• visitNodeKind
• visitDatatype
• visitPattern
• visitFlags
• visitLength
• visitMinlength
• visitMaxlength
• visitMininclusive
• visitMinexclusive
• visitMaxinclusive
• visitMaxexclusive
• visitTotaldigits
• visitFractiondigits
• visitInclude

index(schema)

ShExIndexVisitor.index(schema) creates a visitor and overrides visitTripleExpr and visitShapeDecl to provide an index composed of two maps:

• shapeExprs - map from shape declaration name to definition in schema,
• tripleExprs - map from triple expression name to definition in schema.

@shexjs/visitor is one of the shex.js packages; installing shex pulls in the whole suite, and its README maps them.