Taiwanese (also called Amoy) is a phonetics-based language. A Taiwanese sentence is a Set (mathematics), a collection of well defined and distinct objects named tone group. There are two different tones for a syllable or a word in Taiwanese. In initial or medial position of a word or a tone group, the syllable or word will be given with sandhi tone while lexical tone was given for the end syllable of a word or a tone group. Therefore, if and only if a lexical tone was given at the end of a set of words, then the set of words was a tone group.
Tone sandhi is a phonological change occurring in tonal languages such as Mandarin and some languages spoken in China, in which individual word change its tone that was based on the pronunciation of adjacent words in a sentence. Tone sandhi of Taiwanese, although complex, can be followed by some rules. In addition, tones, semantics and syntactic structures are closely related in Taiwanese. A listener can distinguish exactly word meaning from its tone phase among similar sentences. For example, different tone phase of the clay oven roll represented distinct meaning in the following sentences.
Mua5-a2 (lexical tone) tua7 e5 sio-piann2. (The clay oven roll with big sesame.)
Mua5-a2 (context tone) tua7 e5 sio-piann2. (The clay oven roll as big as a sesame.)
Another example is that the tone phase of "tsit-king (the unit of a house)" depends on its context in a sentence.
Tsit-king (lexical tone) u7 tsai-hue. (There are flowers around the house.)
Tsit-king (context tone) u7 tsai-hue e5 tshu3 si7 guan2-tau. (The house with many flowers is mine.)
In general, inserting words in a Taiwanese sentence could be a lexical form, a context form or a tone group. No matter what embedding form is, the final sentence structure would be decomposed into tone groups.
The following sentences reveal the unique tone group derivative structure of Taiwanese language through variety forms of word inserting within a sentence. The original sentence consists of two tone groups: [A-bi2] [beh khi3 Tai5-pak.] (Amy is going to Taipei.)
Context word (siunn7) inserting: [A-bi2] [siunn7 beh khi3 Tai5-pak.] (Amy wants to go to Taipei.) The number of tone group doesn't change.
Lexical word (pai3-it) inserting: [A-bi2] [pai3-it] [beh khi3 Tai5-pak.] (Amy is going to Taipei on Monday.) The number of tone group was changed to three.
Tone group (tse7 gu5-tshia) inserting: [A-bi2] [beh tse7 gu5-tshia] [khi3 Tai5-pak.] (Amy is going to Taipei by an ox-cart.) The number of tone group was changed to three.
Since tone sandhi processing is so important to Taiwanese sentences that the tone group parser will surely be one of the most complicated and challenged subjects for Taiwanese text-to-speech systems. There are three major components in Taiwanese Speech notepad; a tone group parser, a speech synthesizer and a speech engine. In general, the implementation of speech synthesizer or speech engine depends on programming technique. However the tone group parser relies more on knowledge representation method and the application of artificial intelligence. Luckily we find a way to extract linguistic expertise from human experts and transfer it into an well-organized knowledge base. A symbol system that was designed to coin language expertise and heuristic knowledge was hooped to a corpus. Each symbol consist of three attributes: default tone value, part of speech and mode mark. This corpus was used to cooperate with rule based sandhi processor to pick up accuracy tone among possible tones for each word in a sentence. By means of the symbol system and rule inference homonyms or multiple-POS words such as ti7 or be2 in the following sentences can be assigned accuracy tone through tone sandhi processing.
Ti7 (chopstick, noun, lexical tone) khng3 ti7 (at/on/in, preposition, context tone) ann2-na5-a2 lai7. (The chopsticks were in a bowl basket.)
Tsit-tsiah be2 (horsae, noun, lexical tone) be2 (buy, verb, context tone) beh kah goo7-ban7. (The horse was bought for 50000 bucks.)
Through the study of Taiwanese architecture, we realize that the production system of Taiwanese is quite clear and definite. This logical and scientific natural language has been developed and inherited several thousand years without its own writing system. Tone group must be one the most important elements for Taiwanese language acquisition. Through the development of Taiwanese Speech Notepad, we found that tone group was not only the basic syntax unit of a sentence but also a unique semantic unit as well as prosodic boundary in Taiwanese. This approach may reveal that modern Mandarin that lack of the regularity of tone group is different from Taiwanese language.
Taiwanese Speech Notepad is more than a text-to-speech system. It is also a simulator for tone sandhi acquisition in Taiwanese intra-sentence. By means of the adjustment of corpus and rules, we may understand how people handle Taiwanese tone sandhi through long-term memory as well as short-term memory in our brain. In other words, the Taiwanese tone group parser based on languages learning and acquisition theory offered an experimental environment for the simulation of knowledge engineering and human thinking. The forming process and the derivative structure of Taiwanese probably is one of the keys to artificial intelligence research.
Taiwanese tone sandhi process in the brain is so marvelous that our simulator has been under construction during the last decade. A work-in-process version of artificial tone group parser that includes a knowledge base and an executable program file for Microsoft Windows system (XP/Win7) can be download for evaluation by sending a request to poirotdavid@yahoo.com.tw. or Download Taiwanese Tone Group Parser
