🚍 PolyXML Transit Showcase: Google GTFS-Realtime ↔ European CEN SIRI v2.0 & NeTEx

Production-ready polyglot transit data bridge demonstrating PolyXML compiling European CEN SIRI v2.0 (EN 15531) & NeTEx (CEN/TS 16614) XML schemas and bridging live Google GTFS-Realtime (Protobuf/JSON) telemetry across all 7 supported programming languages: Rust, Python, Go, C++20, Java 21+, TypeScript 5+, and C# 12 / .NET 8.

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🌍 The Real-World Transit Challenge

Modern public transportation and urban mobility systems are globally divided into two major standardizations:

1. Google GTFS-Realtime (Protobuf / JSON):

   • Developed by Google and transit developers worldwide.
   • De facto standard for consumer passenger apps (Google Maps, Apple Maps, Transit App, Citymapper).
   • Lightweight, binary-first protobuf telemetry focused on live vehicle coordinates, delays, and trip cancellations.

2. CEN SIRI & NeTEx (European Norm XML Standard):

   • SIRI (Service Interface for Real Time Information - EN 15531) & NeTEx (Network Timetable Exchange - CEN/TS 16614).
   • Statutory European Commission mandate for multi-modal cross-border transit data exchange (e.g. Dutch NDOV Loket / BISON, UK Bus Open Data Service, German VDV 453/454, French IDFM).
   • Rich, deeply hierarchical XML schemas representing monitored vehicle journeys, stop calls, headway progress, and occupancy.

The PolyXML Bridge

Historically, bridging GTFS-RT and CEN SIRI required maintaining separate hand-crafted XML parsers and JSON encoders in every programming language. PolyXML completely eliminates this impedance mismatch by providing:

• Unified Typed Data Models: Single schema source (siri_core.xsd) compiled into idiomatic, native types in 7 languages.
• Inherent Dual XML & JSON Serialization: The same memory structure serializes to both validated CEN SIRI XML and clean JSON with zero boilerplate.
• Sub-Millisecond Polyglot Performance: Zero-copy parsing in Rust, header-only value types in C++20, records in Java 21 & C#, and C-speed transcoding in Python and TypeScript.

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📐 Architecture & Telemetry Data Flow

sequenceDiagram
    autonumber
    participant GVB as Amsterdam GVB Tram 4<br/>(Telemetry Feed)
    participant GTFS as Google GTFS-RT<br/>(Protobuf / JSON)
    participant PolyXML as PolyXML Bridge<br/>(Rust | Python | Go | C++ | Java | TS | C#)
    participant NDOV as Dutch NDOV Loket / EU SIRI<br/>(CEN SIRI v2.0 XML)
    participant API as Transit Microservices<br/>(Inherent JSON)

    GVB->>GTFS: Live GPS Telemetry (NL_ARR_GVB_TRAM_4_2042)
    GTFS->>PolyXML: Ingest VehiclePosition & TripDescriptor
    Note over PolyXML: Strongly-Typed Mapping to SIRI Model<br/>(MonitoredVehicleJourney, Location, Occupancy)
    par European Standard Broadcast
        PolyXML->>NDOV: Stream CEN SIRI XML (<Siri version="2.0">...)
    and Modern Cloud APIs
        PolyXML->>API: Stream Inherent JSON ({"ServiceDelivery": ...})
    end
    API->>PolyXML: JSON Query / Roundtrip Deserialization
    Note over PolyXML: Inherent roundtrip restoration with 100% field parity

Loading

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⚡ Cross-Language Capability & Latency Benchmarks

All 7 implementations were benchmarked ingesting live Amsterdam GVB Tram 4 telemetry (data/gtfs_realtime_vehicle.json), transforming it into a CEN SIRI vehicle monitoring payload, serializing to XML, and serializing to JSON on the same model.

Target Language	PolyXML Paradigm	Cold XML Latency	JSON Latency	Steady-State (JIT Warmed)	Runtime Schema Validation
🦀 Rust	Borrowed zero-copy slices (Cow<'a, str>) & quick-xml codecs	79.4 μs	107.3 μs	~79 μs (AOT native)	Native facet checks
⚡ C++20	Header-only value types, XmlModel concepts & operator==	106.4 μs	6.2 μs	~106 μs (AOT native)	Static concept verification
🐹 Go	Dual xml:"..." and json:"..." struct tags + XMLName	105.2 μs	174.9 μs	~105 μs (AOT native)	.Validate() methods
🌐 TypeScript 5+	Native ES interfaces + runtime Zod object schemas	191.4 μs	25.1 μs	~2.1 μs (V8 TurboFan)	Zod schema parse (SiriTypeSchema)
☕ Java 21+	Immutable records, java.time.Instant, sealed interfaces	3.0 ms (cold)	583.7 μs	~8.3 μs (HotSpot C2 JIT)	Immutability & nullability checks
🐍 Python	@dataclass(slots=True) + PolyXML C-Engine bindings	3.7 ms	439.7 μs	~3.7 ms (Interpreted)	Inherent dataclass validation
🔷 C# 12 / .NET 8	Primary constructor records, XmlSerializer + System.Text.Json	57.7 ms (cold)	39.4 ms	~28.5 μs (RyuJIT)	IValidatableObject

Benchmarked on Linux x86_64 across identical Amsterdam GVB Tram 4 telemetry payloads.

Note

Understanding Cold Single-Shot vs. Steady-State (JIT Warmed) Latency:

• AOT Compiled Languages (Rust, C++, Go): Compiled Ahead-of-Time directly to native machine code. They have zero classloading or JIT warm-up overhead; execution immediately runs at full production speed on the very first instruction.
• Managed JIT Runtimes (Java 21+, C# 12 / .NET 8): Single-shot cold measurements include one-time JVM dynamic class loading, bytecode verification, and .NET XmlSerializer code generation (~3–57 ms). In continuous production environments (e.g., real-time transit dispatchers, broker microservices, Kafka/streaming consumers) after HotSpot C2 / RyuJIT compilation, Java executes in ~8.3 μs and C# in ~28.5 μs.

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🛠️ Explicit Code Generation Commands

You can regenerate the entire typed polyglot codebase directly from the CEN SIRI XML Schema using the PolyXML CLI.

One-Command Full Build (via polyxml.toml)

polyxml build

Individual Target Generation Commands

1. 🦀 Rust (Zero-Copy & Inherent Codecs)

polyxml generate schemas/transit/siri_core.xsd \
  --lang rust \
  --zero-copy \
  --codecs \
  --out generated/rust

2. 🐍 Python (Dataclasses with Inherent Codecs)

polyxml generate schemas/transit/siri_core.xsd \
  --lang python \
  --backend dataclass \
  --codecs \
  --out generated/python

3. 🐹 Go (Dual XML & JSON Tags)

polyxml generate schemas/transit/siri_core.xsd \
  --lang go \
  --package siri \
  --out generated/go

4. ⚡ Modern C++20 (Header-Only Value Types & Concepts)

polyxml generate schemas/transit/siri_core.xsd \
  --lang cpp \
  --package "polyxml::generated" \
  --out generated/cpp

5. ☕ Java 21+ (Records & Sealed Interfaces)

polyxml generate schemas/transit/siri_core.xsd \
  --lang java \
  --package "com.transit.siri" \
  --out generated/java

6. 🌐 TypeScript 5+ (Typed Interfaces & Zod Validation)

polyxml generate schemas/transit/siri_core.xsd \
  --lang ts \
  --zod \
  --out generated/typescript

7. 🔷 C# 12 / .NET 8 (Primary Constructor Records & Dual Attributes)

polyxml generate schemas/transit/siri_core.xsd \
  --lang csharp \
  --package "Transit.Siri" \
  --out generated/csharp

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🔄 Dual XML & JSON Support Showcase

PolyXML generated models do not require converting XML to an intermediate dictionary to get JSON. The exact same typed memory structure serializes cleanly to both CEN SIRI XML and JSON.

Emitted CEN SIRI v2.0 XML (European Transport Standard)

<Siri xmlns="http://www.siri.org.uk/siri" version="2.0">
  <ServiceDelivery>
    <ResponseTimestamp>2026-09-20T14:00:00Z</ResponseTimestamp>
    <ProducerRef>NDOV_LOKET_NL</ProducerRef>
    <VehicleMonitoringDelivery>
      <ResponseTimestamp>2026-09-20T14:00:00Z</ResponseTimestamp>
      <VehicleActivity>
        <RecordedAtTime>2026-09-20T14:00:00Z</RecordedAtTime>
        <ValidUntilTime>2026-09-20T14:05:00Z</ValidUntilTime>
        <VehicleMonitoringRef>NL_ARR_GVB_TRAM_4_2042</VehicleMonitoringRef>
        <MonitoredVehicleJourney>
          <LineRef>LINE_4</LineRef>
          <DirectionRef>0</DirectionRef>
          <FramedVehicleJourneyRef>
            <DataFrameRef>2026-09-20</DataFrameRef>
            <DatedVehicleJourneyRef>TRIP_NL_GVB_4_1042</DatedVehicleJourneyRef>
          </FramedVehicleJourneyRef>
          <PublishedLineName>Tram 4 - Centraal Station</PublishedLineName>
          <OperatorRef>GVB_AMSTERDAM</OperatorRef>
          <OriginRef>NL:S:30000099</OriginRef>
          <DestinationRef>NL:S:30000001</DestinationRef>
          <DestinationName>Amsterdam Centraal Station</DestinationName>
          <VehicleLocation>
            <Longitude>4.8952</Longitude>
            <Latitude>52.3702</Latitude>
            <Altitude>2.5</Altitude>
          </VehicleLocation>
          <Bearing>142.5</Bearing>
          <ProgressRate>normalProgress</ProgressRate>
          <Occupancy>manySeatsAvailable</Occupancy>
          <Delay>PT0S</Delay>
          <VehicleRef>GVB_TRAM_2042</VehicleRef>
          <MonitoredCall>
            <StopPointRef>NL:S:30000001</StopPointRef>
            <VisitNumber>7</VisitNumber>
            <StopPointName>Centraal Station</StopPointName>
            <VehicleAtStop>false</VehicleAtStop>
            <AimedArrivalTime>2026-09-20T14:02:30Z</AimedArrivalTime>
            <ExpectedArrivalTime>2026-09-20T14:02:30Z</ExpectedArrivalTime>
          </MonitoredCall>
        </MonitoredVehicleJourney>
      </VehicleActivity>
    </VehicleMonitoringDelivery>
  </ServiceDelivery>
</Siri>

Emitted JSON (Same Typed Model Instance)

{
  "version": "2.0",
  "ServiceDelivery": {
    "ResponseTimestamp": "2026-09-20T14:00:00Z",
    "ProducerRef": "NDOV_LOKET_NL",
    "VehicleMonitoringDelivery": {
      "ResponseTimestamp": "2026-09-20T14:00:00Z",
      "VehicleActivity": [
        {
          "RecordedAtTime": "2026-09-20T14:00:00Z",
          "ValidUntilTime": "2026-09-20T14:05:00Z",
          "VehicleMonitoringRef": "NL_ARR_GVB_TRAM_4_2042",
          "MonitoredVehicleJourney": {
            "LineRef": "LINE_4",
            "DirectionRef": "0",
            "FramedVehicleJourneyRef": {
              "DataFrameRef": "2026-09-20",
              "DatedVehicleJourneyRef": "TRIP_NL_GVB_4_1042"
            },
            "PublishedLineName": "Tram 4 - Centraal Station",
            "OperatorRef": "GVB_AMSTERDAM",
            "OriginRef": "NL:S:30000099",
            "DestinationRef": "NL:S:30000001",
            "DestinationName": "Amsterdam Centraal Station",
            "VehicleLocation": {
              "Longitude": 4.8952,
              "Latitude": 52.3702,
              "Altitude": 2.5
            },
            "Bearing": 142.5,
            "ProgressRate": "normalProgress",
            "Occupancy": "manySeatsAvailable",
            "Delay": "PT0S",
            "VehicleRef": "GVB_TRAM_2042",
            "MonitoredCall": {
              "StopPointRef": "NL:S:30000001",
              "VisitNumber": 7,
              "StopPointName": "Centraal Station",
              "VehicleAtStop": false,
              "AimedArrivalTime": "2026-09-20T14:02:30Z",
              "ExpectedArrivalTime": "2026-09-20T14:02:30Z"
            }
          }
        }
      ]
    }
  }
}

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🗺️ Semantic Mapping Reference: GTFS-RT ↔ CEN SIRI

Google GTFS-Realtime (Protobuf / JSON)	CEN SIRI v2.0 (XML)	SIRI Semantic Context
entity.id	VehicleActivity/VehicleMonitoringRef	Unique persistent journey monitoring identifier
vehicle.trip.route_id	MonitoredVehicleJourney/LineRef	Public transit line designation (e.g. LINE_4)
vehicle.trip.direction_id	MonitoredVehicleJourney/DirectionRef	Outbound (0) vs Inbound (1) routing
vehicle.trip.trip_id	FramedVehicleJourneyRef/DatedVehicleJourneyRef	Scheduled timetable operating trip ID
vehicle.vehicle.id	MonitoredVehicleJourney/VehicleRef	Physical vehicle unit number (e.g. GVB_TRAM_2042)
vehicle.position.latitude	VehicleLocation/Latitude	WGS84 decimal latitude
vehicle.position.longitude	VehicleLocation/Longitude	WGS84 decimal longitude
vehicle.position.altitude	VehicleLocation/Altitude	Elevation in meters above sea level
vehicle.position.bearing	MonitoredVehicleJourney/Bearing	Heading azimuth in degrees (0.0 - 360.0)
vehicle.occupancy_status	MonitoredVehicleJourney/Occupancy	Passenger capacity indicator (e.g. manySeatsAvailable)
vehicle.stop_id	MonitoredCall/StopPointRef	National stop point reference (e.g. NL:S:30000001)
vehicle.current_stop_sequence	MonitoredCall/VisitNumber	Sequence index along the route profile
vehicle.current_status	MonitoredCall/VehicleAtStop	STOPPED_AT (true) vs IN_TRANSIT_TO (false)

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🚀 Quickstart & Reproduction

Prerequisites

• Git, Bash
• Rust 1.80+ (with Cargo)
• Go 1.22+
• Python 3.11+
• GCC / Clang (C++20 support) & CMake 3.20+
• JDK 21+ & Maven 3.9+
• Node.js 22+ (for --experimental-strip-types)
• .NET 8 SDK

Run All 7 Implementations

Execute the automated test suite verifying 100% green execution across all languages:

git clone https://github.com/polyxml/polyxml-transit-examples.git
cd polyxml-transit-examples

# Execute the complete polyglot test suite & transcoder demo
./scripts/run_all.sh

Run Individual Languages

# 🦀 Rust
cargo run --manifest-path examples/rust/Cargo.toml

# 🐍 Python
python3 examples/python/bridge.py

# 🐹 Go
go run ./examples/go

# ⚡ Modern C++20
cmake -B examples/cpp/build examples/cpp -DCMAKE_BUILD_TYPE=Release
cmake --build examples/cpp/build
./examples/cpp/build/gtfs_siri_bridge

# ☕ Java 21+
mvn -f examples/java/pom.xml compile exec:java -q

# 🌐 TypeScript 5+
node --experimental-strip-types examples/typescript/index.ts

# 🔷 C# 12 / .NET 8
dotnet run --project examples/csharp/GtfsSiriAdapter.csproj

Run Streaming Transcoding Demo

./scripts/run_transcode_demo.sh

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📂 Repository Structure

polyxml-transit-examples/
├── schemas/
│   ├── transit/siri_core.xsd            # CEN SIRI v2.0 / NeTEx XML Schema definition
│   └── gtfs/gtfs-realtime.proto         # Canonical Google GTFS-Realtime Protobuf definition
├── data/
│   ├── gtfs_realtime_vehicle.json       # Live Amsterdam GVB Tram 4 telemetry payload
│   └── siri_vehicle_monitoring.xml      # European CEN SIRI v2.0 XML delivery payload
├── polyxml.toml                         # Multi-target compiler configuration
├── generated/                           # PolyXML-generated typed models
│   ├── rust/siri_core.rs
│   ├── python/siri_core.py
│   ├── go/siri_core.go
│   ├── cpp/siri_core.hpp
│   ├── java/com/transit/siri/*.java
│   ├── typescript/siri_core.ts
│   └── csharp/SiriCore.cs
├── examples/                            # Runnable implementations in all 7 languages
│   ├── rust/                            # Rust zero-copy adapter
│   ├── python/                          # Python dataclass + PolyXML C-engine adapter
│   ├── go/                              # Go dual XML/JSON struct tags
│   ├── cpp/                             # C++20 XmlModel value types
│   ├── java/                            # Java 21 records & Instant timestamps
│   ├── typescript/                      # TypeScript 5 + runtime Zod schemas
│   └── csharp/                          # C# 12 / .NET 8 primary constructor records
├── scripts/
│   ├── generate_all.sh                  # CLI generation script with flags for all 7 languages
│   ├── run_transcode_demo.sh            # CLI streaming XML <-> JSON transcoding demo
│   └── run_all.sh                       # Complete test orchestrator across all targets
└── .github/workflows/ci.yml             # Matrix CI testing all 7 languages on GitHub

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📜 License & Notices

Distributed under the MIT License. See LICENSE for full terms.

For third-party standards, specifications, open transit licenses (Apache 2.0 for GTFS Realtime), and trademark notices, see NOTICE. All schemas are sourced from open international standards bodies (Google GTFS-Realtime and CEN SIRI).