DEXPI XML reader

The DexpiXmlReader utility converts DEXPI XML P&ID exports into ProcessSystem models. It recognises major equipment such as pumps, heat exchangers, tanks and control valves as well as complex reactors, compressors and inline analysers. Piping segments are imported as runnable DexpiStream units tagged with the source line number.

Usage

Path xmlFile = Paths.get("/path/to/dexpi.xml");
SystemSrkEos exampleFluid = new SystemSrkEos(298.15, 50.0);
exampleFluid.addComponent("methane", 0.9);
exampleFluid.addComponent("ethane", 0.1);
exampleFluid.setMixingRule(2);
exampleFluid.init(0);

Stream template = new Stream("feed", exampleFluid);
template.setFlowRate(1.0, "MSm3/day");
template.setPressure(50.0, "bara");
template.setTemperature(30.0, "C");

ProcessSystem process = DexpiXmlReader.read(xmlFile.toFile(), template);

DexpiProcessUnit feedPump = (DexpiProcessUnit) process.getUnit("P4711");
if (feedPump.getMappedEquipment() == EquipmentEnum.Pump) {
  // handle pump metadata
}

The reader also exposes load methods if you want to populate an existing process model instance. Each imported equipment item is represented as a lightweight DexpiProcessUnit that records the original DEXPI class together with the mapped EquipmentEnum category and contextual information like line numbers or fluid codes. Piping segments become DexpiStream objects that clone the pressure, temperature and flow settings from the template stream (or a built-in methane/ethane fallback). When available, the reader honours the recommended metadata exported by NeqSim so pressure, temperature and flow values embedded in DEXPI documents override the template defaults. The resulting ProcessSystem can therefore perform full thermodynamic calculations when run() is invoked without requiring downstream tooling to remap metadata.

Metadata conventions

Both the reader and writer share the DexpiMetadata constants that describe the recommended generic attributes for DEXPI exchanges. Equipment exports include tag names, line numbers and fluid codes, while piping segments also carry segment numbers and operating pressure/temperature/flow triples (together with their units). Downstream tools can consult DexpiMetadata.recommendedStreamAttributes() and DexpiMetadata.recommendedEquipmentAttributes() to understand the minimal metadata sets guaranteed by NeqSim.

Exporting back to DEXPI

The companion DexpiXmlWriter can serialise a process system created from DEXPI data back into a lightweight DEXPI XML document. This is useful when you want to post-process the imported model with tooling such as pyDEXPI to produce graphical output.

ProcessSystem process = DexpiXmlReader.read(xmlFile.toFile(), template);
Path exportPath = Paths.get("target", "dexpi-export.xml");
DexpiXmlWriter.write(process, exportPath.toFile());

The writer groups all discovered DexpiStream segments by line number (or fluid code when a line is not available) to generate simple <PipingNetworkSystem> elements with associated <PipingNetworkSegment> children. Equipment and valves are exported as <Equipment> and <PipingComponent> elements that preserve the original tag names, line numbers and fluid codes via GenericAttribute entries. Stream metadata is enriched with operating pressure, temperature and flow values (stored in the default NeqSim units, but accompanied by explicit Unit annotations) so that downstream thermodynamic simulators can reproduce NeqSim’s state without bespoke mappings.

Each piping network is also labelled with a NeqSimGroupingKey generic attribute so that visualisation libraries—such as pyDEXPI or Graphviz exports—can easily recreate line-centric layouts without additional heuristics.

Generating PFD diagrams from DEXPI

The DexpiDiagramBridge class provides seamless integration between DEXPI imports and NeqSim’s PFD diagram generation system. This allows you to import P&ID data and immediately produce professional process flow diagrams.

// One-step: import DEXPI and create diagram exporter
ProcessDiagramExporter exporter = DexpiDiagramBridge.importAndCreateExporter(
    Paths.get("plant.xml"));
exporter.exportDOT(Paths.get("diagram.dot"));
exporter.exportSVG(Paths.get("diagram.svg"));  // Requires Graphviz

// Full round-trip: import, simulate, diagram, export
ProcessSystem system = DexpiDiagramBridge.roundTrip(
    Paths.get("input.xml"),     // Input DEXPI
    Paths.get("diagram.dot"),   // Output DOT diagram
    Paths.get("output.xml"));   // Re-exported DEXPI with simulation results

// Create optimized exporter for existing DEXPI-imported process
ProcessDiagramExporter exporter = DexpiDiagramBridge.createExporter(system);
exporter.setShowDexpiMetadata(true);  // Show line numbers and fluid codes in labels

The bridge automatically configures the diagram exporter to display DEXPI metadata (tag names, line numbers, fluid codes) alongside equipment labels, making it easy to cross-reference the generated PFD with the original P&ID source.

Round-trip profile

To codify the minimal metadata required for reliable imports/exports NeqSim exposes the DexpiRoundTripProfile utility. The minimalRunnableProfile validates that a process contains runnable DexpiStream segments (with line/fluid references and operating conditions), tagged equipment and at least one piece of equipment alongside the piping network. Regression tests enforce this profile on the reference training case and the re-imported export artefacts to guarantee round-trip fidelity.

Security considerations

Both the reader and writer configure their XML factories with hardened defaults: secure-processing is enabled, external entity resolution is disabled and ACCESS_EXTERNAL_DTD / ACCESS_EXTERNAL_SCHEMA properties are cleared. These guardrails mirror the guidance in the regression tests and should be preserved if the parsing/serialisation logic is extended.

Tested example

A regression test (DexpiXmlReaderTest) imports the C01V04-VER.EX01.xml training case provided by the DEXPI Training Test Cases repository and verifies that the expected equipment (two heat exchangers, two pumps, a tank, valves and piping segments) are discovered. The regression additionally seeds the import with an example NeqSim feed stream and confirms that the generated streams remain active after process.run(). Companion assertions enforce the DexpiRoundTripProfile and check that exported metadata (pressure, temperature, flow and units) survives a round-trip reload. A companion test exports the imported process with DexpiXmlWriter, then parses the generated XML with a hardened DOM builder to confirm that the document contains equipment, piping components and PipingNetworkSystem/ PipingNetworkSegment structures ready for downstream DEXPI tooling such as pyDEXPI.