The System Package Data Exchange (SPDX®) Specification

The System Package Data Exchange (SPDX®) specification is an open standard capable of representing systems with software components in as SBOMs (Software Bill of Materials) and other AI, data and security references supporting a range of risk management use cases.

The SPDX standard helps facilitate compliance with free and open source software licenses by standardizing the way license information is shared across the software supply chain. SPDX reduces redundant work by providing a common format for companies and communities to share important data about software licenses and copyrights, thereby streamlining and improving compliance.

This repository holds under active development version of the specification as:

• Markdown: development/v3.0.1 branch
• HTML: gh-pages branch, built on every commit to the development branch, see the workflow in .github/workflows/publish_v3.yml
  • Current (3.0): https://spdx.github.io/spdx-spec/v3.0/

The model itself is under active development at spdx/spdx-3-model repo (main branch).

See for the official releases of the specification or additional information also the SPDX website at https://spdx.org.

Specification structure

This repository consists of these files and directories:

• bin/ - Scripts for spec generation.
• docs/ - Specification content:
  • annexes/ - Annexes for the specification.
  • css/ - Style sheets for HTML.
  • images/ - Model diagrams. These image files are to be generated from a diagram description file model.drawio in spdx/spdx-3-model repo and manually copied here.
  • licenses/ - Licenses that used by the SPDX specifications.
  • model/ - Model files*. This subdirectory is to be created by a script from spdx/spec-parser repo, using model information from spdx/spdx-3-model repo (see the build instructions below).
• examples/ - Examples of various SPDX serializations for the current version of the spec.
• mkdocs.yml - MkDocs recipe for the spec documentation generation. The inclusion of model files and the order of chapters are defined here.

The specification consists of documents in the docs/ directory from this spdx/spdx-spec repository and a model which is generated from Markdown files in the spdx/spdx-3-model repository.

Note: The model files in the spdx/spdx-3-model repository use a constrained format of Markdown. Only a limited set of headings are allowed to be processed by the spec-parser.

Building the specification

The specification building flow looks like this:

  +-------------------+
  |[spdx-3-model]     |
  | |                 |
  | +- model/        ---- Constrained-Markdown files -+
  | |                 |                               |
  | +- model.drawio  -----------------+               |
  +-------------------+               |               |
                                      |               |
                                      |               |
  +-------------------+               v               |
  |[spdx-spec]        |            draw.io            |
  | |                 |            (manual)           |
  | +- docs/          |               |               |
  |    |              |               |               |
  |    +- annexes/    |               |               v
  |    |              |               |         spec-parser
  |    +- images/  <---- PNG images --+               |
  |    |              |                               |
  |    +- licenses/   |                               |
  |    |              |                               |
  |    +- model/   <----- Processed Markdown files ---+
  |    |              |
  |    +- index.md    |
  |    |              |
  |    +- *.md        |
  +-------------------+
          |
    mike & mkdocs
          |
          v
  +-------------------+
  |   HTML website    |
  +-------------------+

Prerequisites

Apart from Git and Python, you have to have MkDocs installed on your machine. If you don't have it yet installed please follow these installation instructions.

WeasyPrint is also required for generating PDF files. To disable PDF generation, comment out the these lines in your mkdocs.yml configuration file:

#- pdf-export:
#    combined: true

Preparing input files

Next, you have to prepare the model files, the other specification files, and the model parser, by cloning these repositoriess: spdx/spdx-3-model, spdx/spdx-spec, and spdx/spec-parser to these paths: spdx-3-model, spdx-spec, and spec-parser, respectively:

git clone https://github.com/spdx/spdx-3-model.git
git clone https://github.com/spdx/spdx-spec.git
git clone https://github.com/spdx/spec-parser.git

Install prerequisites for Python:

pip3 install -r spdx-spec/requirements.txt
pip3 install -r spec-parser/requirements.txt

Generating formatted Markdown files for MkDocs

Model files in spdx/spdx-3-model repo are written in a specific format of Markdown, with a limited set of allowed headings. The spec-parser processes these model files to generate both ontology and final Markdown files suitable for MkDocs.

The spec-parser also performs automatic formatting on the resulting Markdown files. For instance, it converts a list under the "Properties" heading into a table.

To check the model files and generate formatted files for MkDocs, run the following command:

python3 spec-parser/main.py spdx-3-model/model spdx-spec/docs/model

This will create well-formatted model files in the spdx-spec/docs/model/ directory. This directory contains two components:

• Model ontology and diagram files: These files (model.plantuml, spdx-context.jsonld, spdx-model.dot, spdx-model.json-ld, spdx-model.pretty-xml, spdx-model.ttl, spdx-model.xml) are ready for immediate use.
• Formatted Makdown files: These files (.md extension) are located in various subdirectories and are intended for processing by MkDocs in the next step.

If the output directory already exists, the spec-parser will not overwrite it. If you edited a model file and want to regenerate the formatted files, you have to delete the existing spdx-spec/docs/model directory first:

rm -rf spdx-spec/docs/model

Building HTML

With all spec and model files prepared, we will use MkDocs to assemble them into a website.

In side spdx-spec/ directory, execute a built-in dev-server that let you preview the specification:

mkdocs serve

Or building a static HTML site:

mkdocs build

To abort the build immediately when there is a warning, enables strict mode:

mkdocs build --strict

To get debug messages, enables verbose output:

mkdocs build --verbose

Configuring the website

Inside spdx-spec/ directory, there is a file mkdocs.yml. This is a configuration file for MkDocs.

Files intended for display and linking in the navigation bar should be included in the nav: section. The order of filenames in this section determines their order on the navigation bar.

Specification versions on spdx.github.io/spdx-spec/

The SPDX specifications on https://spdx.github.io/spdx-spec/ are built by using a workflow in .github/workflows/publish_v3.yml. This workflow uses mike to publish multiple versions of MkDocs-powered documentation.

The published versions, their titles, and aliases are listed in the file versions.json located in the gh-pages branch. These versions populate the version selector dropdown on the website. The line run: mike deploy in the GitHub workflow file determines the title and alias.

mike is not needed for local testing of a specific spec version.