4. Linguistic features and structures are not arbitrary. They are purposeful whether or not the choices are conscious or unconscious.

5. Power relations are produced, exercised, and reproduced through discourse.

6. All speakers and writers operate from specific discursive practices originating in special interests and aims, which involve inclusions and exclusions.

7. Discourse is historical in the sense that texts acquire their meanings by being situated in specific social, cultural and ideological contexts, and time and space.

8. CDA does not solely interpret texts, but also explains them.

2.3 The Present Theoretical Framework

2.3.1 Fairclough’s Three-dimensional Model

Discourse is the product of communication or discourse practice, and the process is determined by the particular social cultural practice conditions (Zuo Yanna, 2007; Li Wenmei, 2007). On this basis, Fairclough (1995) put forward the famous 3D model of Critical Discourse Analysis (Fairclough, 1995):

1. Description

Use the method of linguistics study to describe linguistic features and discourse structure features of discourse itself. This is the first step of Discourse Analysis.

2. Interpretation

Interpret the relations between discourse and its generation, transmission and accepting its communication process. Interpretation is the mediation of Discourse Analysis. It links discourse with its participants, and analyze function and results through its different goal in the process of discourse.来.自/优尔论|文-网www.youerw.com/

3. Explanation

Explain the relationship between the communication process and its social context. Contact with discourse, its participants, its related history and social context. And reproduce the interaction between social control and text results. The explanation is the last step of Discourse Analysis.

Fairclough (1995) also pointed out that there are three theses on Critical Discourse Analysis, (1) Language is one kind of social practice. It is a perpetual Intervening Forces of social orders. Language reflects reality in every angle. It operate or influence the process of society through reproduce Ideology; (2) Language, values, religions and power relations interact with each other in social cultural environment; (3) The use of language could prompt the changes of discourse and the development of society.

2.3.2 Three functions in the Domain of Systemic Functional Grammar

Critical discourse analysis requires that the language should be regarded as a multifunctional system. Therefore, Halliday's (2000) systemic functional linguistics nature has become the main source of theoretical basis and methods (Xin Bin, 2005). Systemic functional grammar is a kind of theory which is more suitable for discourse analysis than any other theory. Huang (2001) believes that we can use this theory to guide when we try to analyze Critical Discourse. Halliday (2000) summarized language which could finish its functions with full of possibilities as the three language Meta functions: Ideational Function, Interpersonal Function and Textual Function. (Xu Jun, 2005) Halliday (2000) made clear that the purpose of the construction of functional grammar is to provide a theoretical framework for discourse analysis; the framework can be used to analyze any verbal or written texts in English.