Specifically, we present two dozens of rules formalizing a detailed description of vowel omission in written text. In this research, we present Arabic-Unitex, an Arabic Language Resource, with emphasis on vowel representation and encoding. Although numerous studies have been published on the issue of restoring the omitted vowels in speech technologies, little attention has been given to this problem in papers dedicated to written Arabic technologies. In Arabic texts, typically more than 97 percent of written words do not explicitly show any of the vowels they contain that is to say, depending on the author, genre and field, less than 3 percent of words include any explicit vowel. Vowels in Arabic are optional orthographic symbols written as diacritics above or below letters.