Thanks again for your inputs.The ligature features use many -> one substitutions, so e.g. f + f -> ff ligature.
Stylistic alternates (salt) can use one -> one substitutions, but they require manual input, which is inefficient, but very flexible as the user can decide which letter form to insert. One glyph has a lookup table for several other forms to substitute for that glyph — the user has to choose from a dialogue presented by the application, which Stylistic Set to use.
Your answer many ->one substitution is clear and that would still be ok.
The second answer is limited to one -> one substitution but if it requires manual input then I think it may not be as useful if such input is something like Alt+ 5 digits.
To answer WIlliam and Vanisaac question let me explain how the Atok IME pad works. The Japanese language uses a syllabic "alphabet" consisting of 228 charcacters plus some 2100 other ideograms derived from the much larger set of the Chinese ideograms. In all therefore to write in Japanese a user needs to select characters out of some 2350 glyphs. The way they have solved the problem is to use the latin alphabet, which they call Romaji, to enter the sound of the Japanese word spelt using the Romaji letters. The Atok IME pad then transliterates transparently and pops up with a dialog box which lists the corrsponding words that use that phonetic entered input. The look up glyphs that come up on the dialogue pop-up window can be few or many depending on the word that was entered. The user chooses the right one with the cursor keys and then proceeds to type the next text. There is no need to enter special code such as %%, etc. You just look up on the dialogue box and choose one of the optional glyphs that are shown, with a mouse or cursur keys or shortcuts.
The process is very user friendly and effective. It does slow down the typing speed but it works positively and is amenable to all kind of users, whether they are PC literate or not.
In the case of adopting such method for the Latin character fonts the job is much simplified as here we do not need transliteration as such but the opportunity to flag, on a pop-up dialogue box, alternative styles of letters whenever one of the basic letters is typed. For example, if I was typing the word "corrugated" then upon typing the letter "o" after the first "c" the IME pad would pop-up the dialogue box expecting that the next word to be entered could well be an r, or a v, or a w, as in such cases -provided that the font type was cursive- those letters would need to have a short leading stroke. So the user can choose the most appropriate style on the fly and continue typing undisturbed. I have been using the Atok bar for a while and I can assure you that it is painless and very user friendly.
I estimate that to make a cursive script, such as the one I am completing, truly cursive using the rule that the pen is never lifted from the paper, it essentially requires another set of 52 glyphs. Then obviously one can add some alternative styles, for example a minuscule "z" without descender if the main one was designed with a descender; and so on. Clearly if such system was available one would take advantage of this IME to add several alternative styles as well.
according to my understanding, I believe that this Romaji transliteration method is also used for the Chinese language where they have more than 50000 glyphs. I believe it may also apply to Koreaan and other similar languages.
I trust this clarifies how the Atok pad works.