[ANN] Shape Expressions 2.1 release candidate

The ShEx Community Group would like to invite public review of three
deliverables:
 * Shape Expressions (ShEx) Primer http://shex.io/shex-primer/
 * Shape Expressions Language 2.1 http://shex.io/shex-semantics-20181122/
 * Shape Expressions Test Suite 2.1 https://github.com/shexSpec/shexTest/
including: 1088 validation tests, 99 negative syntax tests, 14 negative
structure tests and 408 schema conversion tests between ShExC, ShExJ and
ShExR.

The test suite has an Implementation Report including 4 of the 5
implementations: http://shexspec.github.io/shexTest/reports/2.1/

ShEx 2.1 is backwards compatible with ShEx 2.0. The major changes include:
 * Added IMPORT functionality (round-trips between ShExC, ShExJ and ShExR).
 * Added language support in value sets.
 * Updated definition of semantics to clarify recursion.
 * Added annotations and semantic actions to node constraints.
 * ShExC grammar allows ()s around simple TripleConstraints.
 * Added hundreds of tests of schema, validation and structure tests.
 * Multi-line comments (/* … */).

For feature requests please note the features in the 2.next milestone:
https://github.com/shexSpec/shex/issues?q=is%3Aopen+is%3Aissue+milestone%3A2.next


Comments and feedback are welcome on
 * the ShEx Community Group mailing list: public-shex@w3.org /
https://lists.w3.org/Archives/Public/public-shex/
 * the ShEx Community Group Gitter channel:
https://gitter.im/shapeExpressions/Lobby

Readers may also wish to join the ShEx Community Group:
https://www.w3.org/community/shex/join

Sincerely,
 * Andra Waagmeester
 * Dimitris Kontokostas
 * Eric Prud’hommeaux
 * Gregg Kellogg
 * Harold Solbrig
 * Iovka Boneva
 * Jérémie Dusart
 * Jose Emilio Labra Gayo
 * Katherine Thornton
 * Lucas Werkmeister
 * Michael Cochez
 * Tom Baker