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Property Value Stability Table

This table shows the property value stability clauses from Character Encoding Stability, organized by property groups instead of by Unicode version.

Property Group Applicable Properties Constraints Applicable Unicode Versions
Bidi Bidi_Class No new Bidi_Class property values will be added, except in the case when they are introduced along with newly encoded characters such as bidirectional format controls. 3.0.0+
Bidi_Class, Bidi_Mirrored The property values for the bidirectional properties Bidi_Class and Bidi_Mirrored preserve canonical equivalence. 4.0.0+
Bidi_Paired_Bracket_Type Characters that have a Bidi_Paired_Bracket_Type property value of Open or Close also have the Bidi_Class property value Other_Neutral (ON) and the Bidi_Mirrored property value Yes. 6.3.0+
Case Case_Folding The Case_Folding property value is limited so that no string when case folded expands to more than 3× in length (measured in code units). 3.0.1+
Lowercase, Uppercase, Alphabetic All characters with the Lowercase property and all characters with the Uppercase property have the Alphabetic property. 4.1.0+
General General_Category The enumeration of General_Category property values is fixed. No new values will be added. 2.1.3+
General_Category The General_Category property value Control (Cc) is immutable: the set of code points with that value will never change. 1.1.5+
General_Category The General_Category property value Private_Use (Co) is immutable: the set of code points with that value will never change. 2.0.0+
General_Category The General_Category property value Surrogate (Cs) is immutable: the set of code points with that value will never change. 2.0.0+
Name, Jamo_Short_Name Once a character is assigned, both its Name and its Jamo_Short_Name will never change. 2.0.0+
Noncharacter_Code_Point The Noncharacter_Code_Point property is an immutable code point property, which means that its property values for all Unicode code points will never change. 3.1.0+
Identifiers ID_Continue Once a character is ID_Continue, it must continue to be so in all future versions. 3.0.1+
ID_Start If a character is ID_Start then it must also be ID_Continue. 3.0.1+
ID_Start Once a character is ID_Start, it must continue to be so in all future versions. 3.0.1+
XID_Continue Once a character is XID_Continue, it must continue to be so in all future versions. 3.0.1+
XID_Start If a character is XID_Start then it must also be XID_Continue. 3.0.1+
XID_Start Once a character is XID_Start, it must continue to be so in all future versions. 3.0.1+
Pattern_Syntax, Pattern_White_Space The Pattern_Syntax and Pattern_White_Space properties are immutable code point properties, which means that their property values for all Unicode code points will never change. 4.1.0+
Pattern_Syntax, Pattern_White_Space, ID_Continue, XID_Continue If a character has the Pattern_Syntax or Pattern_White_Space property, then it cannot have the ID_Continue or XID_Continue property. 4.1.0+
Normalization Canonical_Combining_Class The Canonical_Combining_Class property values are limited to the values 0 to 254. 1.1.5+
Canonical_Combining_Class Once a character is assigned, its Canonical_Combining_Class will never change. 3.0.0+
Canonical_Combining_Class, General_Category All characters other than those with General_Category property values Spacing_Mark (Mc) and Nonspacing_Mark (Mn) have the Canonical_Combining_Class property value 0. 1.1.5+
Decomposition_Mapping Canonical and compatibility mappings (Decomposition_Mapping property values) are always in canonical order, and the resulting recursive decomposition will also be in canonical order. 2.0.0+
Decomposition_Mapping Canonical mappings (Decomposition_Mapping property values) are always limited either to a single value or to a pair. The second character in the pair cannot itself have a canonical mapping. 3.0.0+
Decomposition_Mapping Canonical mappings (Decomposition_Mapping property values) are always limited so that no string when normalized to NFC expands to more than 3× in length (measured in code units). 2.0.0+
Decomposition_Mapping Once a character is assigned, its Decomposition_Mapping will never change. 4.0.0+
Decomposition_Mapping Canonical mappings (Decomposition_Mapping property values) to a pair of characters are limited such that the first of the pair in the mapping must have ccc=0, except for the Decomposition_Mapping of the following four characters: U+0344, U+0F73, U+0F75, U+0F81. 2.1.0+
Numeric General_Category, Numeric_Type The set of characters having General_Category=Nd will always be the same as the set of characters having Numeric_Type=de. 4.0.0+
General_Category, Numeric_Type Characters with the property value Numeric_Type=de (Decimal) only occur in contiguous ranges of 10 characters, with ascending numeric values from 0 to 9 (Numeric_Value=0..9). 6.0.0+
General_Category, Numeric_Type Characters with the General_Category property value Number (Nd | Nl | No) do not have the Numeric_Type value None. 6.2.0+
Numeric_Type No new assignment of Numeric_Type=di (Digit) will be made to any character. 6.1.0+
Script Script, Script_Extensions Whenever the Script property value of an assigned character is explicit (that is, not Common, Inherited or Unknown), that explicit value must also be contained among the set of values constituting the Script_Extensions property value for that character. 6.2.0+