#4175 SPARQL Multi-Hop Queries

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#4175 SPARQL Multi-Hop Queries

#4175 Describe the various multi-hop queries possible in SPARQL

In the context of Knowledge Graphs, a multi-hop query refers to traversing multiple edges (predicates) to find a relationship between entities that are not directly connected. In SPARQL, this is primarily achieved through Property Paths.

Property paths allow you to write concise patterns for complex traversals without explicitly naming every intermediate node.

1. Sequence Paths (/)

The most fundamental multi-hop query. It connects a series of predicates in a specific order. Instead of writing multiple triple patterns, you use a forward slash to "hop" from one property to the next.

  • Logic: Find A that has property p1 leading to B, which has property p2 leading to C.

  • Syntax: ?subject :p1 / :p2 ?object .

  • Example: Finding a person's "Grand-employer" (the company that owns the company they work for):

    ?person :worksFor / :ownedBy ?parentCompany .

2. Recursive & Arbitrary Length Paths (+, *)

These are essential for traversing hierarchies (like "part-of" or "subClassOf" relationships) where you don't know the exact number of hops required.

  • One or more hops (+): Finds all connected nodes at any depth (minimum 1).

    • ?part :isPartOf+ ?product .

  • Zero or more hops (*): Includes the starting node itself in the results.

    • ?class rdfs:subClassOf* ?ancestor .

3. Alternative Paths (|)

This allows a single "hop" to be satisfied by one of several different predicates. It is useful for querying datasets where different properties might represent similar relationships.

  • Syntax: ?subject (:p1 | :p2) ?object .

  • Example: Finding a person's contact point, whether it's an email or a phone number:

    ?person (:email | :phone) ?contact .

4. Inverse Paths (^)

Multi-hop queries often require changing direction mid-stream. The caret symbol allows you to treat a triple as if it were defined in the opposite direction (Object --> Subject).

  • Syntax: ?subject :p1 / ^:p2 ?object .

  • Example: Finding "Co-workers" (People who work for the same organization):

    ?person :worksFor / ^:worksFor ?coWorker .

5. Negated Property Sets (!)

You can perform hops that specifically avoid certain predicates or look for "any property except X."

  • Syntax: ?subject !:p1 ?object .

  • Example: Find all direct relations between two entities that are not a "seeAlso" link:

    ?s !(rdfs:seeAlso) ?o .

Comparison of Multi-Hop Methods

FeatureSPARQL SyntaxBest Use Case
Fixed Chainp1/p2/p3Known, static relationships (e.g., Address --> City --> Country).
Hierarchyp1+Tree structures, taxonomies, or bill-of-materials.
Bi-directionalp1/^p2Navigating "Social Graph" style relationships (Friends of Friends).
Flexible(p1|p2)Data integration where schemas might overlap or vary.

Key Limitation: No Intermediate Data

While Property Paths are powerful for reaching a destination, they do not bind intermediate nodes to variables. If you need to know which company a person works for before reaching the parent company, you must use standard triple patterns:

?person :worksFor ?intermediateCompany . ?intermediateCompany :ownedBy ?parentCompany .

Would you like me to help you draft a specific multi-hop query for a dataset you are currently working with?


From <https://gemini.google.com/app/>  Google Gemini 3.0 (Fast)

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