In Hebrew today there are two accepted written forms, the vocalized (with nikkud), and the unvocalized, which exploits the use of the letters yod and vav (waw) as vowel markers.
There have been numerous deliberations on standardizing unvocalized Hebrew writing, beginning with the Language Committee and later in the Academy. Among the proposals was one that suggested assigning symbols for all the vowels that are used in spoken Hebrew today. This proposal was dismissed because it would have resulted in new letters being added to the Hebrew alphabet.
In the end, a more modest proposal was accepted in which the usage of the letters yodand vav is standardized: yod represents i and sometimes e, and vav represents u or o. Additional rules include the use of two vavs for the consonant v and two yods for the consonant y.