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Querying in zelph

zelph provides powerful querying capabilities directly in its scripting language and interactive CLI. Queries allow you to search the semantic network for matching patterns, supporting variables, multiple conditions, and integration with inference rules. This page covers general queries first (applicable to any domain), followed by Wikidata-specific examples.

Queries are statements that contain variables (single uppercase letters) but no => (which would make them rules). They are evaluated immediately without needing .run, though inference can expand the graph beforehand to reveal more matches.

Key Features

  • Variables: Single uppercase letters (A-Z), scoped to the query. Limited to 26 per query.
  • Multi-Conditions: Separate conditions with commas (logical AND). zelph unifies across all, binding variables consistently.
  • Wildcards: Use variables for subjects, relations, or objects (e.g., X R Y matches any triple).
  • Inference Integration: Run .run first to derive new facts, then query the expanded graph.
  • Output: Matches are printed with bound values. No matches: Just the query echoed.
  • Limitations: No OR/NOT in syntax (use rules for complex logic). No multi-line queries.

General Queries

These examples use a simple geography graph. Load them in zelph (.lang zelph mode) for testing:

Berlin "is capital of" Germany
Germany "is located in" Europe
Europe "has part" Germany
X is capital of Y, Y is located in Z => X is located in Z
"is located in" ~ transitive relation
R ~ transitive relation, X R Y, Y R Z => X R Z
.run  # Infer: Berlin "is located in" Europe

Single-Condition Queries

Basic pattern matching.

  • Find capitals: X "is capital of" Y
    Output:

    X «is capital of» Y
Answer: «Berlin» «is capital of» «Germany»

  • Find locations in Europe: A "is located in" Europe
    Output (post-inference):

    A «is located in» «Europe»
Answer: «Berlin» «is located in» «Europe»
Answer: «Germany» «is located in» «Europe»

Multi-Condition Queries

Combine for intersections.

  • Capitals in Europe: X "is located in" Europe, X "is capital of" Germany
    Output:

    (X «is capital of» «Germany»), (X «is located in» «Europe»)
Answer: («Berlin» «is capital of» «Germany»), («Berlin» «is located in» «Europe»)

  • Parts with opposites: Add Europe "is opposite of" Asia, then: A "is opposite of" B, A "has part" Germany
    Output:

    (A «is opposite of» B), (A «has part» «Germany»)
Answer: («Europe» «is opposite of» «Asia»), («Europe» «has part» «Germany»)

  • No match example: X "is located in" Europe, X "has part" Germany
    Output: Just the query (no match, as nothing is both located in Europe and has Germany as part).

  • Multi-Variable: X "is located in" Y, Y "has part" Germany, X "is capital of" Z
    Output:

    (X «is located in» Y), (X «is capital of» Z), (Y «has part» «Germany»)
Answer: («Berlin» «is located in» «Europe»), («Berlin» «is capital of» «Germany»), («Europe» «has part» «Germany»)

Add symmetry for more: "is opposite of" ~ symmetric relation, R ~ symmetric relation, A R B => B R A, .run. Then: A "is opposite of" B shows bidirectional matches.

Wikidata-Specific Queries

For Wikidata, switch to .lang wikidata after loading a dump (.wikidata path/to/dump.json or .load cached.bin). Queries use Q/P IDs or names (if set). Examples from paleontology (e.g., Brontosaurus Q3222766).

Single-Condition Queries

  • Instances of fossil taxon: X P31 Q23038290
    Output: Many answers, e.g., Answer: «Q3222766» «P31» «Q23038290» (Brontosaurus).

  • Parent taxa: X P171 Q3222766
    Output: Taxa with Brontosaurus as parent (if any).

Multi-Condition Queries

Combine for targeted searches.

  • Fossil taxa in genus rank: X P31 Q23038290, X P105 Q34740
    Output: Matches like Brontosaurus/Apatosaurus.

  • Synonyms with parent taxon: X P460 Q14326, X P171 Q2544161 (Apatosaurus synonyms in Diplodocidae)
    Output:

    (X «P171» «Q2544161»), (X «P460» «Q14326»)
Answer: («Q3222766» «P171» «Q2544161»), («Q3222766» «P460» «Q14326»)

  • No-match example: Musical works with taxon: X P31 Q105543609, X P171 Q3222766
    Output: Just the query (no overlap between music and taxonomy).

Tips and Advanced Usage

  • Pre-Inference: Always .run for derived facts (e.g., transitivity).
  • Debugging: Use .node, .out, .in to inspect before querying.
  • Patterns: Fixed parts in quotes if spaces; variables anywhere.
  • For complex logic, define rules first, then query the inferred graph.

See Rules and Inference for synergy with queries.