Identical topic (IT henceforth) was previously known as copying topic (Xu & Liu (1998:141-157). It is fully or partially identical to a corresponding element (CE henceforth) occurring in the following part of the clause. Broadly speaking, IT is semantically empty. Being an unusual type of adding, it properly falls into the central concern of this volume.
It seems IT can be attested in all Chinese dialects, though the phenomena in question have been poorly documented and have scarcely been studied under a unified category. IT seems to be a better candidate to characterise topic prominent languages than many other topic types including the non-gap topic, which has long been called "Chinese style topic" since Chafe (1976) and has been viewed as a major characteristic of topic prominent languages (e.g., Li & Thompson, 1976, Xu & Langendoen 1985, Gasde 1999). I believe the study of IT structure is necessary to obtain a clearer and more complete picture of topic structure in general. As far as I know, Wu dialects of Chinese, including Shanghainese, are the ones which have the richest IT types and the greatest text frequency of IT. Therefore, this study will be based on both Mandarin and Shanghainese data
