SECTION 10.8
945
Accessibility Support
10.8.4 Expansion of Abbreviations and Acronyms
Abbreviations and acronyms can pose a problem for text-to-speech engines.
Sometimes the full pronunciation for an abbreviation can be divined without aid.
For example, a dictionary search will probably reveal that “Blvd.” is pronounced
“boulevard” and that “Ave.” is pronounced “avenue.” However, some abbreviations
are difficult to resolve, as in the sentence “Dr. Healwell works at 123 Industrial
Dr.” For this reason, the expansion of an abbreviation or acronym can be speci-
fied for the following items:
•
Marked-content sequences, through an
E
property
(PDF 1.4)
in a property list
attached to the sequence with a
Span
tag, as shown in Example 10.25
•
Structure elements, through an
E
entry
(PDF 1.5)
in the structure element dic-
tionary
Example 10.25
BT
/Span << /E ( Doctor ) >>
BDC
( Dr. ) Tj
EMC
( Healwell works at 123 Industrial ) Tj
/Span << /E ( Drive ) >>
BDC
( Dr. ) Tj
EMC
ET
The
E
value (a text string) is considered to be a word or phrase substitution for
the tagged text and therefore should be treated as if a word break separates it from
any surrounding text. Like other text strings, the expansion text, if encoded in
Unicode, may include an escape sequence for indicating the language of the text
(see Section , “Text String Type”).
Some abbreviations or acronyms are conventionally not expanded into words.
For the text “CBS,” for example, either no expansion should be supplied (leaving
its pronunciation up to the text-to-speech engine) or, to be safe, the expansion
“C B S” should be specified.