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Sparql

Features

  • SPARQL, the standard query language for RDF graphs, uses CWA (as do all common query languages).
  • BGP (Basic Graph Pattern) Matching refers to the process of finding matching sets of triples (subject-predicate-object) in an RDF dataset based on a basic graph pattern specified in a SPARQL query. Understanding BGP: 
    - A Basic Graph Pattern (BGP) is essentially a collection of triple patterns.
- Each triple pattern in the BGP can consist of variables, IRIs (Internationalized Resource Identifiers), or literals in the subject, predicate, and object positions.
- The task of BGP matching is to identify all sets of RDF triples in the dataset that correspond to the given patterns in the query.

Property Paths

@chatgpt (Private): Property paths in SPARQL are a powerful feature that allows you to write queries that navigate through RDF graphs in more complex ways than simple triple patterns. Property paths can be used to traverse multiple relationships, specify optional or alternative paths, and query over arbitrary lengths of paths.

Key Property Path Operators:

  1. Concatenation (/):

    • Specifies a sequence of properties.
    • Example: :parent/:child retrieves all grandchildren by following a :parent relationship and then a :child relationship.

  2. Alternatives (|):

    • Specifies a choice between properties.
    • Example: :spouse|:partner retrieves relationships where either :spouse or :partner applies.

  3. Zero or More (*):

    • Matches a property path of any length, including zero.
    • Example: :ancestor* finds any number of :ancestor relationships, including direct and indirect ancestors.

  4. One or More (+):

    • Matches a property path of at least one step.
    • Example: :ancestor+ retrieves all direct and indirect ancestors, but not the individual itself.

  5. Zero or One (?):

    • Matches a property path of zero or one step.
    • Example: :spouse? retrieves relationships where the :spouse property exists or matches no property.

  6. Inverse (^):

    • Inverts the direction of the property.
    • Example: ^:parent retrieves all entities that are children of a given individual.

Examples of SPARQL Queries Using Property Paths:

1. Find All Descendants:

PREFIX : <http://example.org/>

SELECT ?descendant WHERE {
  :John :parent+ ?descendant .
}
  • Explanation: This query finds all descendants of :John by following the :parent property one or more times.

2. Find Direct or Indirect Ancestors:

PREFIX : <http://example.org/>

SELECT ?ancestor WHERE {
  ?ancestor :parent* :John .
}
  • Explanation: This query finds all direct or indirect ancestors of :John, including :John itself.
PREFIX : <http://example.org/>

SELECT ?related WHERE {
  :John (:spouse|:partner) ?related .
}
  • Explanation: This query finds individuals related to :John by either the :spouse or :partner relationship.

4. Query for Connections through Multiple Properties:

PREFIX : <http://example.org/>

SELECT ?person WHERE {
  :John (:knows/:friendOf) ?person .
}
  • Explanation: This query finds all individuals who are friends of people that :John knows.

Resources

References

Children
  1. GeoSPARQL
  2. SPARQL Composite Datatypes (CDTS)
  3. SPARQL-MM
  4. Star
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