Unicode Explained

placed after an otherwise identical string without them. For example, “Xmen” <

“X men” < “X‑men” < “X–men.”

Control and formatting characters, except line breaks and horizontal tabs (which count

as whitespace), are completely ignored in the default order.

We have discussed some general principles of UCA only, and you need to consult UTS

#10 for the detailed algorithm and notations. In practice, you will probably not work

with Collation Element Tables directly. Rather, you will use higher-level constructs,

such as the Collator and RuleBasedCollator classes in Java programming. These classes

let you specify your modifications of the default collating order using simple, readable

notations like “c < ch < d,” which says that “ch” is to be treated as if it were a character

between “c” and “d.”

Text Boundaries

In text processing, we often need to work with text elements larger than individual

characters. For example, we might need operations like “delete next word” or “move

one sentence forward in the text.” Therefore, we need to recognize boundaries between

elements of text, collectively called text boundaries.

Text boundary principles are defined in a separate document, Unicode Standard Annex

(UAX) #29, “Text Boundaries.” It specifies boundaries for three types of text elements:

• Grapheme cluster, which is characterized informally as “user character”

• Word, which partly corresponds to the word concept ...