Both specifications have different use cases:

• SPDX is a standard for describing the components, copyrights, and licences of a software package. The main use case is for producers of software packages to describe the licensing condintions in a machine-readable format and for consumers of software packages to more easily verify that they comply with the licensing terms of the software package. SPDX has the potential to greatly simply the "supply chain" of software (re-)distribution. Suppliers of software packages would normally include an SPDX RDF file within the software package, although this is not a requirement by the specification.
• ADMS.F/OSS v0.3 is a specification for describing software projects, software assets, and software distributions. Its main use case is to allow creating (federated) catalogues of software descriptions making it possible for consumers to explore, find, identify, select, and obtain software from a single point of access.

Both specifications also have a different conceptualisation: SPDX is not concerned with metadata about "immaterial" concepts such as the "admssw:software project" or the "admsw:software asset", but it provides detailed licensing infromation about the "spdx:Package" and "spdx:File". In my opinion, both the concepts "spdx:package" and "spdx:file" maps to the concept "admssw:software distribution", which is the physical embodiment of an asset.

There is a combined use case possible: the SPDX licensing information of software packages can also be included in software catalogues, making it possible for users to explore, find, identify, select, and obtain SPDX licensing metadata about "spdx:software packages" from a software catalogue.

Proposal: To realise this synergy the following relationships should be added to the ADMS.F/OSS conceptual model and RDF Schema:

• "admssw:SoftwareDistribution rdfs:subClass spdx:Package .". admssw:SoftwareDistribution is a SubClass of spdx:Package. This would mean that admsswSoftwareDistribution would inherit all properties and relationships of spdx:Package, including  name , versionInfo, packageFileName, supplier, originator , downloadLocation, packageVerificationCode, checksum , sourceInfo, licenseConcluded, licenseInfoFromFiles, licenseDeclared, licenseComments,  copyrightText, summary, description, hasFile. admssw:SoftwareDistribution is also a sublcass of rad:Distribution. Further alignment with properties inherited from rad:Distribution will be required. 

• New relationship "admssw: spdxDocument": " the SPDX specification allows navigating from an spdx:Document to a spdx:Package using the spdx:describesPackage relationship. It makes sense to have a reverse relationship, allowing to navigate from a admssw:SoftwareDistribution to an spdx:Document. Ideally, this relationship is provided by the SPDX vocabulary... 

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