Values of this type are just a sequence of character, possibly an empty sequence.
An EString is the most general metadata key type, as it places no restrictions to the character sequence.1
All printable characters are allowed.
All comparisons are done case-insensitive, i.e. “hell” will be the prefix of “Hello”.
To sort two values, the underlying encoding is used to determine which value is less than the other.
Uppercase letters are typically interpreted as less than their corresponding lowercase letters, i.e. A < a.
Comparison is done character-wise by finding the first difference in the respective character sequence. For example, abc > aBc.