Support for Unicode Grapheme Clusters.

draft-vasters-json-structure-validation.md

@@ -43,6 +43,13 @@ normative:
       ECMA Standards: ECMA-262
     target: https://www.ecma-international.org/publications-and-standards/standards/ecma-262/
     title: "ECMAScript\xAE Language Specification"
+  UNICODE_ANNEX_29:
+    author:
+    - org: The Unicode Consortium
+    date: '2025-08-17'
+    target: https://www.unicode.org/reports/tr29/
+    title: "Unicode Standard Annex #29"
+
 
 informative:
 
@@ -177,6 +184,35 @@ This section defines the validation keywords applicable to schemas with the type
 `string`. The `maxLength` keyword is not included as it is part of JSON
 Structure Core and is not redefined here.
 
+### `maxGraphemes` {#maxGraphemes}
+
+A string is valid if its number of Unicode grapheme clusters - as defined in
+Chapter 3 of Unicode Standard Annex #29 {{UNICODE_ANNEX_29}} - not exceed this
+value. The value of `maxGraphemes` MUST be a non-negative integer.
+
+The purpose of `maxGraphemes` is to specify the maximum length of perceptible
+characters in form elements that is understandable to humans.
+
+Example:
+
+~~~json
+{ "type": "string", "maxGraphemes": 3 }
+~~~
+
+### `minGraphemes` {#minGraphemes}
+
+A string is valid if its number of Unicode grapheme clusters - as defined in
+Chapter 3 of Unicode Standard Annex #29 - is at least the integer value
+specified in `minGraphemes`. The value of `minGraphemes` MUST be a
+non-negative integer.
+
+Example:
+
+~~~json
+{ "type": "string", "minGraphemes": 2 }
+~~~
+
+
 ### `minLength` {#minLength}
 
 A string is valid if its length is at least the integer value specified in