Gathering information on many implementations has always been a chore, there exist various lists or comparisons for XMPP clients, servers and libraries, but these are often out of date, inaccurate, incomplete, or generally unmaintained.

This specification aims at solving this problem by putting the work of publishing and keeping up to date said information onto the maintainers of the software. Given many already do maintain this kind of list, the inconvenience should be minimal.

The information listed SHOULD include, but isn’t limited to, the project name, homepage, description, logo, screenshots if relevant, specifications supported (RFCs and XEPs). A full list of supported properties is described in RDF format at http://usefulinc.com/ns/doap#.

A central point should be defined to gather the list of implementations publishing their information, this specifications proposes xmpp.org for this purpose.

Creating, publishing and maintaining a project description should be as easy as possible for producers.

Fetching, parsing and using a project description should be as easy as possible for consumers.

These two requirements have oriented the choice of technologies towards being as restrictive as possible:

• The chosen RDF serialisation format MUST be RDF/XML, assuming XMPP project authors are already familiar with XML as a serialisation format.
• The resulting file should be published over HTTPS, without access restrictions.

DOAP

Description of a Project, the chosen RDF format used by this specification to describe the various properties of a project.

RDF

Resource Description Framework, a generic data model framework, supporting many serialisation formats and conversions between them. For the purpose of this specification we will only consider RDF/XML, an XML serialisation format, with the rationale that all XMPP authors are already familiar with this serialisation format.

A user might want to know which compliance suite level a given client supports before choosing it.

A sysadmin might want to know which compliance suite level a given server supports before choosing it.

An XMPP service might want to propose clients based on their advertised support of what they consider a modern client.

A specification author might want to know the list of projects implementing this specification, their support level and version.

An XMPP enthousiast website might want to automatically update their XMPP comparison page with up to date information.

A project SHOULD publish the information it deems relevant in the format defined in this specification.

A project MAY maintain this information in another serialisation (JSON-LD, Turtle…), but MUST submit it in RDF/XML serialisation.

Once satisfied with it, a project SHOULD submit their DOAP file to xmpp.org following this process.

xmpp.org SHOULD cache and host the given files on the behalf of projects, so that if their website goes down for whichever reason other consumers can keep working as usual.

Projects with an existing internationalization process are encouraged to use it to translate user-facing strings in the DOAP file.

This document introduces no additional security considerations above and beyond those defined in the documents on which it depends.

This document requires no interaction with &IANA;.

This document requires no interaction with the ®ISTRAR;.

https://schema.org/ was also considered, given the considerable overlap in features with DOAP, but it didn’t contain many properties useful for software projects. Parts of its properties are reused in this specification, where DOAP was lacking (namely for the logo, screenshot and documentation properties).

AppStream was also considered, but it lacks the extensibility and existing tooling of RDF, while being limited to being a description for software installers instead of a generic software description.