POST: an intro to PURL

Modern software development is heavily based on open source software, and understanding and managing the components (aka. packages) we assemble to make up a codebase is both useful and hard. For instance, when a containerized app embeds 1,000 or 10,000 packages, the bulk will be free and open source software (FOSS) third-party packages bundled as dependencies. To address the difficulties to clearly identify and track software components across diverse software ecosystems like app package with Maven, npm, PyPI or systems packages like Debian, but also diverse tools, and databases, we "invented" the Package-URL (PURL) specification (or rather we discovered it).

Originally this was to fulfill a very simple and selfish need: it was way too difficult to lookup a vulnerability database using the output of a packages and dependencies scan, requiring a work intensive combination of manual expert research and guesswork, not a happy combo!

Fast forward, and PURL is today a de-facto global standard designed to reliably identify software packages and dependencies across programming languages, package managers, and software ecosystems.

It is a key part of standard like CycloneDX (an Ecma standard), OASIS CSAF (now also an ISO standard), SPDX (also an ISO standard) ,and OpenVEX, and is on the way to be integrated in the CVE schema, after its adoption in the CSAF and OSV schema.

PURL provides a consistent, human-friendly and machine-readable way to reference packages (aka. components), regardless of their origin or ecosystem. By encapsulating the key identification info like the package type, name, and version into a simple, readable and familiar URL format, PURL enables a more accurate and interoperable approach to referencing software packages, enabling all tools to talk together about software packages in this emerging software supply chain.

PURL has grown to play an important role in improving software supply chain clarity, by enabling tools and systems to more accurately trace the origin and lineage of software packages, and is facilitating better and more efficient vulnerability management, and license compliance. By having a uniform way to describe (and locate) packages, software teams can more efficiently automate tracking their FOSS package inventories, and actively manage them for currency (updates, EOL), legal (license), security (vulnerabilities) and other proactive risk assessments.

PURL supports the improved automation of software supply chain processes by serving as a base for various tools and standards, including Software Bill of Materials (SBOM), VEX, dependency tracking, and continuous integration/continuous deployment (CI/CD) pipelines. Its adoption helps bridge the gaps between these different tools and ecosystems, fostering a clearer, more secure, and efficient software development lifecycle where we can all share a common language when we talk about software packages.

Because of all this, Package-URL is a key building block for modern software supply chains. And by standardizing the way software packages are identified, PURL enables traceability, automation, and ultimately supports manageable, responsible and safer FOSS software consumption.