spdx-license-expression-tools

The SPDX specification was created to exchange licensing information along a software supply chain in a standard way. Part of this specification are license expressions which can be used to describe the licensing of a software in a formal way e.g. (LGPL-3.0 OR MIT).

Within the SPDX tools, the official specification implementation of the SPDX working group, license expressions are represented as AnyLicenseInfo composite. Interacting with this composite can be quite complicated, therefore the spdx-license-expression-tools Java library was created to provide various operations that can be performed on SPDX license expressions:

• simplification
• filtering
• merging
• splitting

Operations

Simplification

Removing of redundant terms and transforming license expressions to the distributed normal form (DNF):

AnyLicenseInfo expression = LicenseInfoFactory.parseSPDXLicenseString("(((LGPL-3.0+ OR MIT) AND GPL-2.0) OR BSD-3-Clause)");
ExpressionSimplification.simplify(expression); // -> (BSD-3-Clause OR (LGPL-3.0+ AND GPL-2.0) OR (MIT AND GPL-2.0))

Filtering

Removing of operators:

AnyLicenseInfo expression = LicenseInfoFactory.parseSPDXLicenseString("LGPL-3.0+ WITH DigiRule-FOSS-exception AND MIT");
ExpressionFiltering.filterOperators(expression, OperatorFilter.FILTER_ALL); // -> (LGPL-3.0 AND MIT)

Removing of licenses:

AnyLicenseInfo expression = LicenseInfoFactory.parseSPDXLicenseString("((LGPL-3.0+ AND MIT) AND BSD-3-Clause)");
LicenseMatcher matcher = ExpressionFiltering.createLicenseMatcher();
matcher.setLicense(LicenseInfoFactory.parseSPDXLicenseString("LGPL-3.0+"));
ExpressionFiltering.filterLicenses(expression, matcher); // -> (MIT AND BSD-3-Clause)

Merging

Joining with AND:

AnyLicenseInfo expression1 = LicenseInfoFactory.parseSPDXLicenseString("LGPL-3.0+ AND MIT");
AnyLicenseInfo expression2 = LicenseInfoFactory.parseSPDXLicenseString("BSD-3-Clause");
ExpressionMerging.andJoin(expression1, expression2); // -> ((LGPL-3.0+ AND MIT) AND BSD-3-Clause)

Joining with OR:

AnyLicenseInfo expression1 = LicenseInfoFactory.parseSPDXLicenseString("LGPL-3.0+ AND MIT");
AnyLicenseInfo expression2 = LicenseInfoFactory.parseSPDXLicenseString("BSD-3-Clause");
ExpressionMerging.orJoin(expression1, expression2); // -> ((LGPL-3.0+ AND MIT) OR BSD-3-Clause)

Splitting

Splitting to conjunctive sets (after simplification):

AnyLicenseInfo expression = LicenseInfoFactory.parseSPDXLicenseString("(((LGPL-3.0+ OR MIT) AND GPL-2.0) OR BSD-3-Clause)");
ExpressionSplitting.splitToConjunctiveSets(expression); // -> BSD-3-Clause, (LGPL-3.0+ AND GPL-2.0), (MIT AND GPL-2.0)

Splitting to licenses (list of contents):

AnyLicenseInfo expression = LicenseInfoFactory.parseSPDXLicenseString("(((LGPL-3.0+ OR MIT) AND GPL-2.0) OR BSD-3-Clause)");
ExpressionSplitting.splitToLicenses(expression); // -> BSD-3-Clause, LGPL-3.0+, GPL-2.0, MIT

Compiling and Integration

Maven is used as build system. To build from source use:

mvn package

spdx-license-expression-tools is available via the Maven Central Repository:

<dependency>
  <groupId>com.github.aschet</groupId>
  <artifactId>spdx-license-expression-tools</artifactId>
  <version>1.1.0</version>
</dependency>