Abstract
Usually, it is so diffcult to record conversation that it has been diffcult to conduct communication research quantitatively. Recently, people use Internet as media for communication.The conversation through the Internet is convenient for quantitative communication study because it can be recorded easier.Especially, Internet forum is suitable for collecting a various data of conversation. In this paper, lexical analysis is applied to the log data of conversation on Internet forum. It is very famous that many regularities in a document have been found, for example, Zipf ' s law, Heaps's law, and so on. This kind analysis has been applied to documents on a various of media. However, it is little studies that this analysis was applied to a document which is temporally developed by many authors, for example, the log data of conversation on Internet forum. Moreover, it has not been examined whether Heaps' law held good in the document and there is no discussion about the relation between the document size and these known regularities. Usually, the relation between document size and these regularities is not important because the size of such a document is determined by its author which is normally only 1 person. However, the size of the communication log of Internet forum is an emergent property by people who are interested in its forum. We believe it is important for us to understand the dynamics of conversation. As a result of investigation in this paper, the following 2 trends are found;(1)law of Zipf holds well in almost all log data of Internet Forum, (2) the number of messages posted is small if the vocabulary growth parameter ! of Heaps' law is not within a particular bounds.
