Merge pull request #1430 from json-schema-org/handrews/iri-anchors

Plain name IRI fragments can use unicode (markdown version)

jsonschema-core.md

@@ -337,11 +337,24 @@ identifiers](#w3cwd-fragid-best-practices-20121025), plain name fragment
 identifiers in `application/schema+json` are reserved for referencing locally
 named schemas.
 
-Plain name fragments MUST start with a letter ([A-Za-z]) or underscore ("\_"),
-followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores
-("\_"), and periods ("."). This matches the US-ASCII part of XML's [NCName
-production](#xml-names), which allows for compatibility with the recommended
-plain name [syntax](#w3crec-xptr-framework-20030325) for XML-based media types.
+Plain name fragments MUST follow XML's [`NCName` production](#xml-names), which
+allows for compatibility with the recommended plain name
+[syntax](#w3crec-xptr-framework-20030325) for XML-based media types.  For
+convenience, the `NCName` syntax is reproduced here in ABNF form, using
+a minimal set of rules:
+
+```abnf
+NCName          = NCNameStartChar *NCNameChar
+NCNameStartChar = "_" / ALPHA
+                      / %xC0-D6 / %xD8-F6 / %xF8-2FF
+                      / %x370-37D / %x37F-1FFF
+                      / %x200C-200D / %x2070-218F
+                      / %x2C00-2FEF / %x3001-D7FF
+                      / %xF900-FDCF / %xFDF0-FFFD
+                      / %x10000-EFFFF
+NCNameChar      = NCNameStartChar / "-" / "." / DIGIT
+                      / %xB7 / %x0300-036F / %x203F-2040
+```
 
 All fragment identifiers that do not match the JSON Pointer syntax MUST be
 interpreted as plain name fragment identifiers.
@@ -3286,7 +3299,7 @@ to the document.
 
 ### draft-bhutton-json-schema-next
 - `contains` now applies to objects as well as arrays
-- Use IRIs instead of URIs
+- Use IRIs instead of URIs, including allowing unicode in plain-name fragments
 - Clarify that detecting duplicate IRIs for different schemas SHOULD raise an error
 - Consolidate and clarify the syntax and rationale for plain-name fragments
 - "$id" MUST be an absolute-IRI, without any fragment, even an empty one