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STEP-XML at a glance

Full name

STEP XML (ISO 10303-28)

Standard

ISO 10303-28

Family

STEP (ISO 10303) product data exchange

Extensions

.stpx, .stpxZ

Encoding

XML (classic STEP files use clear text)

Carries

Product structure, product data and references to external CAD files

3D InterOp
Read Write

.stpx read and write, .stpxZ read only

  • Building software that needs to read STEP data?

    3D InterOp is an SDK that lets your application import and export STEP alongside 30+ CAD and BIM formats.
Aspect STEP Part 21 STEP-XML

Standard

ISO 10303-21

ISO 10303-28

Encoding

Clear-text exchange syntax

XML

Extensions

.stp, .step

.stpx (.stpxZ when compressed)

Typical content

Self-contained geometry and product data

Product structure that can reference external CAD files

To read it

STEP-aware CAD software

XML tooling plus schema-aware interpretation

  • Product structure

    Complex assemblies and product structures, organized hierarchically

  • External references

    Links to CAD files that remain in their native format

  • Schema-defined data

    Product data governed by an EXPRESS schema, such as a STEP application protocol

Representation What it means

Schema-independent

A generic XML structure that works across any EXPRESS schema

Schema-specific

An XML structure tailored to one particular EXPRESS schema

Mappings

ISO 10303-28 defines how to map between the two forms

  • Spatial doesn’t provide a STEP-XML viewer or converter for end users. 3D InterOp is for software developers who want their own application to read and write STEP data.
  • Assuming STEP-XML is just a .stp file

    Both are STEP exchange methods, but they are defined by different parts of ISO 10303 and use different encodings. A Part 21 reader won’t automatically read STEP-XML, and vice versa.
  • Underestimating the EXPRESS schema

    STEP-XML changes the encoding, not the semantic complexity of the product data. Your application still needs schema-aware interpretation to make sense of the file.
  • Losing external references

    When a STEP-XML file references external CAD files, the assembly only loads completely if those files are present, at the expected location and in a supported format.
  • Mixing up compressed files

    A .stpxZ file is compressed STEP-XML, not a compressed Part 21 file (.stpZ). Check which one the receiving tool expects.
  • STEP (STP)

    ISO 10303-21 exchange files
    STEP (STP)
  • IGES

    Legacy neutral CAD exchange
    IGES
  • 3D XML

    Dassault Systèmes lightweight XML format
    3D XML
  • JT

    Lightweight 3D data (ISO 14306)
    JT
  • Semantic PMI

    Machine-readable manufacturing information
    Semantic PMI
  • Industry · CAD

    3D InterOp for CAD applications

    Read and write 30+ CAD formats, from STEP and IGES to native CATIA, NX, SOLIDWORKS and Creo files, inside your own application.
  • Add STEP import and export to your software

    Evaluate 3D InterOp on your own models with support from Spatial’s engineers.

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