era-mcp-query

name	era-mcp-query
description	Execute SPARQL queries against ERA ontology and railML source data using MCP servers. Use when querying ERA definitions, exploring railML structure, or analyzing source data for CONSTRUCT query development.

ERA/railML MCP SPARQL Queries

Execute SPARQL queries against two MCP server endpoints for ERA ontology exploration and railML data analysis.

Available MCP Servers

1. ERA Ontology Server

• Server: explorer-era-ontology
• Tool: mcp_explorer-era-_sparql_query
• Endpoint: http://localhost:8082/jena-fuseki/era-ontology/sparql
• Contents: ERA ontology OWL/SHACL definitions (v4.1.0)
• Use For:
  • SHACL constraint queries
  • Property domain/range lookups
  • Class hierarchy exploration
  • SKOS concept scheme browsing

⚠️ CRITICAL: Always filter out deprecated elements when querying the ERA ontology:

FILTER NOT EXISTS { ?property owl:deprecated "true"^^xsd:boolean }
FILTER NOT EXISTS { ?class owl:deprecated "true"^^xsd:boolean }

2. railML Source Data Server

• Server: explorer-one-eyed-graph
• Tool: mcp_explorer-one-_sparql_query
• Endpoint: http://localhost:8082/jena-fuseki/advanced-example-one-eyed/sparql
• Contents: Converted railML 3.2 sample data (One-Eyed infrastructure)
• Use For:
  • Exploring railML structure
  • Counting available instances
  • Extracting sample values
  • Testing CONSTRUCT query patterns

Common Query Patterns

Count railML Instances

PREFIX railml: <https://www.railml.org/schemas/3.2#>

SELECT ?type (COUNT(*) AS ?count)
WHERE {
  ?element a ?type .
  FILTER(STRSTARTS(STR(?type), STR(railml:)))
}
GROUP BY ?type
ORDER BY DESC(?count)

Explore railML Element Structure

PREFIX railml: <https://www.railml.org/schemas/3.2#>
PREFIX xyz: <http://sparql.xyz/facade-x/data/>

SELECT DISTINCT ?property ?value
WHERE {
  ?element a railml:YourElementType .
  ?element ?property ?value .
}
LIMIT 100

Find ERA Property Domain/Range

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX era: <http://data.europa.eu/949/>

SELECT ?property ?domain ?range
WHERE {
  ?property rdfs:domain ?domain ;
            rdfs:range ?range .
  FILTER(CONTAINS(STR(?property), "propertyName"))
  
  # Filter out deprecated properties
  FILTER NOT EXISTS { ?property owl:deprecated "true"^^xsd:boolean }
}

Check Class Hierarchy (InfrastructureElement)

CRITICAL: Determine if target class is a subclass of era:InfrastructureElement before using positioning patterns.

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX era: <http://data.europa.eu/949/>

SELECT ?class ?superClass
WHERE {
  era:YourClass rdfs:subClassOf* ?superClass .
  
  # Filter out deprecated classes
  FILTER NOT EXISTS { ?superClass owl:deprecated "true"^^xsd:boolean }
}

If era:InfrastructureElement appears in results:

• ✅ Class has era:netReference property
• ✅ Use NetLinearReference, NetPointReference, or NetAreaReference patterns

If era:InfrastructureElement does NOT appear:

• ❌ Class is a "functional resource" (does NOT have era:netReference)
• Find which properties reference this class:

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX era: <http://data.europa.eu/949/>

SELECT ?property ?domain
WHERE {
  ?property rdfs:range era:YourFunctionalResourceClass .
  OPTIONAL { ?property rdfs:domain ?domain . }
  
  # Filter out deprecated properties
  FILTER NOT EXISTS { ?property owl:deprecated "true"^^xsd:boolean }
}

Then check SHACL to confirm which classes have the linking property:

PREFIX sh: <http://www.w3.org/ns/shacl#>
PREFIX era: <http://data.europa.eu/949/>

SELECT ?targetClass
WHERE {
  ?shape sh:targetClass ?targetClass .
  ?shape sh:property ?propShape .
  ?propShape sh:path era:yourLinkingProperty .
}

Best Practices

1. ALWAYS Filter Deprecated: Include FILTER NOT EXISTS { ?property owl:deprecated "true"^^xsd:boolean } in all ERA ontology queries
2. Use Correct Server: ERA definitions → era-ontology, railML data → one-eyed-graph
3. Limit Results: Add LIMIT clause for exploratory queries
4. Prefix Filters: Use FILTER(STRSTARTS(STR(?var), "namespace")) to filter by namespace
5. Sample Before Construct: Query railML structure before writing CONSTRUCT queries
6. Check Availability: Verify elements exist in source data before mapping

Example Workflows

1. Implementing New Infrastructure Element

1. Query era-ontology for SHACL requirements
2. Query one-eyed-graph to count railML instances
3. Explore railML element structure
4. Draft CONSTRUCT query
5. Test pattern with sample data

2. Finding Missing Properties

1. Query era-ontology for all class properties
2. Check current SPARQL file property list
3. Identify gaps
4. Query railML data for potential source attributes

Troubleshooting

• Empty Results: Check if query sent to correct MCP server
• Syntax Errors: Verify all PREFIX declarations included
• Large Results: Use LIMIT and OFFSET for pagination
• Namespace Issues: Ensure correct namespace URIs (trailing # or /)