Schemas.pub is a project of the Data Transfer Initiative, built and hosted to promote interoperability and consistency especially in personal data transfer.
There are a few data types we mostly know how to exchange over the Internet. Individual calendar items, tasks and contacts can be exchanged interoperably as files or email attachments, thanks to standards written in 1998: iCalendar (RFC2445) and VCard (RFC2425). Since 1998, standards like that are not very common. While XML and JSON have both made defining structured data formats much easier, as well as schema languages like XML Schema Definition Language and JSON Schema, this has not resulted in an easier job defining any given schema as a standard. In fact, XML/JSON and Schemas have encouraged the proliferation of "unilateral" data definitions -- Web APIs withs schemas defined solely by the host of that API, Thus, pretty much every service that hosts common data (like photos in albums on the Web!) uses different schemas. Sometimes parts of these APIs use schema.org, which is great and helps a lot with consistency (and accessibility, and internationalization) of individual fields.
Is this really a problem? In practice consumers of APIs just translate API data into their own format, sometimes aided by schema definitions and sometimes not. Yet, we think this could be made somewhat better by allowing organizations to publish schemas that have some real thought behind them, alongside tools for using and applying those schemas, and reputational markers to show which data schemas have implementations, interoperability, open licenses or standards governance. We welcome your thoughts.
As of launch, schemas.pub is a fraction of the functionality and registry size that we envision eventually. We're building the site as we learn about what's most useful to publishers of schemas as well as implementers searching for solid information.
To get started, search for a schema you're interested in and see how it's defined, some examples, and how it's implemented. If you have a schema you think should be listed, create an account and add it.