4. What is a UEB Symbols Sequence? - SusanJ/UEB_back GitHub Wiki

According to the Rulebook a symbols-sequence is

an unbroken string of braille signs, whether alphabetic or non-alphabetic, preceded and followed by space (also referred to as symbols-word).

We all know that text is normally separated into words or items or tokens by certain special characters used as separators, typically spaces. It appears that the Rulebook is just using the term symbols-sequence as a synonym for the terms word, item, or token, possibly to avoid using the term word in an overly general or misleading sense.

As for what a space is, we likely take for granted that certain aspects of electronic text, such as the newline character, or the beginning and ending of an electronic file, function as spaces. Common digital text analysis methodology uses the term whitespace to refer to any of the following six characters: a space, a tab, a newline, a formfeed, a carriage return, and a vertical tab. These six characters each have a unique identifier in an elctronic file so they can be distinguished when necessary. This Wikipedia article provides additional information about the concept of whitespace along with additional characters used as whitespace.

The Rulebook doesn't focus on electronic files nor concern itself with commonly-accepted technical jargon but it seems reasonable to assume that the word space in the UEB definition of a symbols-sequence is a character that either appears to be a space to a human reader or functions as a space in an electronic file.

The Rulebook implies that the end of a line normally acts as a space since it is only possible to continue a numeric symbols-sequence from one line to the next by using an explicit numeric line continuation indicator. The practice of hyphenating a word at a syllable break at the end of a line was at one time used to save space in braille documents but the Rulebook doesn't address this issue. This practice is typically not used in modern braille documents for several reasons. For one, it can require changes in the use of contractions. For another, refreshable braille displays often allow any end-of-line indicator in an electronic braille file to be treated as a space.

An accurate understanding of the term symbols-sequence and also the term letters-sequence is essential in order to fully appreciate a number of UEB rules. A letters-sequence is

an unbroken string of alphabetic signs preceded and followed by non-alphabetic signs, including space.