FoundationEssentials is a new effort regarding the open source version of Foundation's Swift implementations. You can read more about this here if you're curious about the details, but this effort does involve breaking up the Foundation module into various smaller components to avoid the monolithic structure we currently have. Our idea is for the predicate APIs to land in the core/smaller FoundationEssentials package, but other Foundation APIs related to XML, networking, internationalization, etc. will be broken out into separate packages.