Research papers is distinct from other text types owing to its components giving shape to its characteristic text structure. The property of a text is regarded as the "generic structure" to serve its distinct social purposes and the readers within the target community, according to Halliday (1978), the renowned linguist who has been exploring the nature and functions of genre. Hasan (1984a, 1984b), Halliday and Hasan (1989) further investigated the generic structure of texts proposing the "generic structure potential" (or GSP) theory, that (1) the text features could be used to predict the structure and the sequence and order of the elements in the structure; (2) every text has obligatory and optional elements determining the GSP; and (3) the obligatory elements and their sequence define the genre of the text, where the optional elements function as variations within the same genre.

Put simply, given the same genre, everyone has a different representation of such genre in his or her own text. Despite the differences, all the texts share a certain extent of similarities such as the overall framework, the necessary elements and the sequence of the elements constructing the text structure. The elements, or the generic stages or schematic structure proposed by Martin (1993), with the choice of lexical items and sentence structure at different stages thus determine the organisation of a text.

Research papers, as written text of the professional and technical field with the audience from the similar background (students, teachers and professionals), serve the functions of persuasion, evaluation, reporting research results and discussion. The following are the generic stages of a research paper:

Value & Significance ^ Review of Literature ^ Method of Research ^ Report & Analysis of Findings ^ Discussion & Conclusion

Lin and Evans (2011) conducted a corpus study compiled from a collection of published research articles, and found the general structure of the research papers being

Introduction-Literature Review-Methodology-Results and Discussion-Conclusion (ILM[RD]C)

with other optional elements merged into major stages.

For example, the Methodology section coalesced with Participants as the object of study of the research papers often involved observations based on teacher and learner activities in the classroom; Conclusion embraced other stages such as Implication, Suggestions, Limitations and Applications (Nwogu, 1997; Swales, 2004).

In the next section, we will see how each generic stage serves its rhetorical functions with the distribution and patterning of lexico-grammatical items of evaluation, persuasion and critique.

Halliday, M.A.K. (1978). Language as Social Semiotic, London: Edward Arnold.

Halliday, M.A.K. & Hasan, R. (1989). Language, context, and text: Aspects of language in a social-semiotic perspective (2nd ed.). Oxford: Oxford University Press.

Halliday, M.A.K. & Martin, J. (1993). Writing Science: Literacy and discursive power. Pittsburgh: University of Pittsburgh Press.

Hasan, R. (1984a). Coherence and cohesive harmony. In J. Flood (ed.), Understanding reading compreshension: cognition, language and the structure of prose. Newark: Internation Reading Association.

Hasan, R. (1984b). The nursery tales as a genre. Nottingham Linguistic Circular, 13, pp. 71-102.

Lin, L. & Evans, S. (2011). Structural patterns in empirical research articles: A cross-disciplinary study. English for Specific Purposes, 31(3), pp. 150-160.

Nwogu, . (1997). THe medical research paper: structures and functions. English for Specific Purposes, 16(7), pp. 119-137.

Swales, J. (2004). Research genres: Explorations and applications. Cambridge: Cambridge University Press.