Contextual Relevance: The Basic Condition for Textual Coherence

The present paper aims to reveal what the basic condition for textual coherence is. The research method is mainly comparison and theoretical argumentation. In the first part of the paper three major theories are compared and the contributions and limitations of each are pointed out. The current situation is that the research on textual theory still lays its emphasis on the aspect of linguistic forms; the interpretations for textual coherence in the aspect of language meaning and the recognition of the essence and the condition of textual coherence are not yet deep nor comprehensive enough. Then in part two the authors reveal the different knowledge or enlightenments by the three theories about what textual coherence is, and argue that semantic relevance is the essence of textual coherence. In fact the production and understanding of language cannot be free from context. Context constrains the generation of coherent texts and the cognition of the coherence of the text. So part three of the paper elaborates the constraining effect of various contexts on the relevance of the meaning of the various linguistic items within the text. In the end the paper draws the conclusion that contextual relevance is the basic condition for textual coherence, that is to say, only relevant contexts can bring a smooth, logically coherent text.


Theoretical Orientation and Methodology of Textual Analysis
Coherence constitutes a core concept in textual linguistics (or discourse linguistics). In textual analysis, starting from different theoretical bases, different perspectives, different dimensions and levels, we have different recognitions of textual coherence, and thereby varied theoretical systems of textual analysis are formed.
ZHANG Jianli has generalized the recognitions in the linguistic world into seven types, namely: (1) textual coherence is presented as topics; (2) textual coherence is the relevance of text in terms of form, meaning and language use; (3) textual coherence is pragmatic relevance; (4) textual coherence reflects the experience/common sense of interlocutors; (5) textual coherence is embodied in unified rhetorical structures; (6) textual coherence is the result of deduction; (7) textual coherence is the result of participation, negotiation and cooperation. [1] Linked with the basic recognition of textual coherence, six theoretical paradigms are formed: Halliday [2] In terms of the basic linguistic theories, the most influential theories on textual study in China are Halliday and Hasan's Systemic-Functional Theory, Grice's and Levinson's Conversational Implicature Theories and Sperber-Wilson's Relevance Theory. All of the above are text-based linguistic theories, and thereby constitute the major theoretical foundation in textual analysis and the major source of textual theory construction. The discussion on the conditions of textual coherence in this paper will also develop primarily with reference to these three theories.
In general, different linguistic theories on text are characterized by their respective principles and methodologies. The construction of textual theory in Conversational Implicature Theory is based on logic, semantics and social psychology, and starts with the moral directions in language communication-cooperation and the social subjectivity in language communication, centers on both parties' linguistic psychological activities, their interaction and illocutionary knowledge. In textual analysis, the focus is centered on the intention of the subject in language communication. [3] The textual theory construction in Systemic-Functional Theory is based on system theory and systemic-functional linguistics, starts from a perspective of the system of linguistic forms and their social functions, centers on the communicative function of linguistic forms. In textual analysis, the focus is centered on the markedness of linguistic forms, which is one of the analytical principles of linguistics [4], functional words in the textual theory construction in Systemic-Functional Theory. [5].
The theoretical basis for the construction of textual theory in Relevance Theory is cognitive psychology and socio-linguistics. It sets off with a study into the symbolization of meaning and the meaning deduction about the linguistic symbols, and concerns more about the relevance in language communication and cognitive patterns. Implicature of language and the cognition and reasoning process of linguistic information comprise its core of research. [6] These textual theories represent the significant transformation of the research objects of contemporary linguistics at the language structure level: from words, phrases and sentences to paragraphs and texts. It should be pointed out that the appearance of the above three textual theories was an important sign that contemporary linguistic theories have achieved substantial development. For the development of linguistics, particularly for the construction and development of textual linguistics, these theories hold vital significance both in theory and in methodology, though it must be admitted that all the three theories are inherently limited to varied degrees.
Systemic-Functional Theory is limited by its research tradition of focusing on the analysis of written textual materials and by its tendency in stressing the forms in language system, thereby in textual analysis, its theoretical perspective is more often than not restricted to the linguistic forms and the formal cohesion in surface structures. On the other hand, Conversational Implicature Theory is limited as it focuses on conversational materials and social conventions, namely those supersyntactic and superlinguistic grammars. Its theoretical perspective is often confined to the social relationship among communication subjects and as a result perplexing textual analyses arise. The two textual theories share 3 defects: 1. they partially focus on the "markedness" (of linguistic symbols or social symbols); 2. they reduce language structures to a static pattern; 3. they interpret communicative behaviors and processes as fixed procedures. Relevance Theory seems to be applicable to all language communication activities, and has apparently overcome the above-mentioned three defects. But as its theoretical perspective dwells on the significance of psychological cognition, its description of communicative patterns is "more or less general and empty because of its over-brevity" [7]. When its concern on context is confined to cognitive psyche, the contextual assumptions of textual coherence and the interpretation of the relevance of cognitive reasoning are also restricted.
It is the very differences in the theoretical orientations and methodologies in textual analysis and textual theory construction that lead to the disagreements of present textual theories on the essence of textual coherence. And out of the same differences, coherence becomes "a very important and frequently-used term in the field of textual analysis, whose intension and extension are not yet fully demonstrated." [8] It should be noted, however, from such theoretical perspectives and linguistic aspects as linguistic behaviors and social psyche, language functions and linguistic forms, communicative behaviors and language cognitions, the above-mentioned three textual theories have laid essential theoretical and methodological foundations for the establishment and development of textual linguistics. All the three theories have, to some extent, identified the important role of semantic coherence in textual coherence and noticed the importance of language communication subjects and context in text production and comprehension. Therefore it is self-evident why these theoretical researches or their theoretical orientations which involve some methodological significance have exerted profound and far-reaching impact on the theoretical development of linguistics and textual linguistics.

Semantic Relevance as the Essence of Textual Coherence
In textual analysis and textual theory construction, Systemic-Functional linguists such as Halliday and Hasan have seldom used the term "coherence", instead, "cohesion", a term similar to "coherence" which is preferred by linguists from other schools, is often used. Halliday and Hasan didn't define what exactly "cohesion" is, rather they only gave it a not-so-clear theoretical description, now as the formal connection and then as the meaning connection of linguistic elements. Actually in analysis of texts, the term "cohesion" is employed as the descriptive analysis of the linguistic form of functional words. Other scholars also hold this view and think that "Cohesion constitutes a language formal aspect in a discourse." [9] It can be seen here that Halliday and Hasan's cohesion concept, while containing the two aspects of form and meaning, mainly focuses on the form. The reason for that may be Systemic-Functional linguists are concentrating on the function of forms, so their main interest falls on the functional words which tie the whole textual system and on the grammatical structures which tie the forms of the linear textual system. Language in practical use, however, tends to be something either semantically incoherent though formally cohesive, or something semantically coherent without any formal mark such as some connective words. Therefore, cohesion as well as other terms derived from it is only the individual features that represent the surface structure of texts, they fail to constitute either the sufficient or the necessary prerequisite for textual coherence. It is nothing more than the outside formal features of some normative texts. Cohesion in surface structures cannot reflect the essence of textual coherence.
The Relevance Theory by Sperber-Wilson et al explains relevance between elements of discourse from the perspective of social communication and at the level of psychological cognition. Relevance Theory, just like the Conversational Implicature Theory which shares the same theoretical origins has its theoretical orientation far from the interpretation of textual coherence. But they both take coherent discourse as their research objects. Their knowledge of discourses and their coherence helps us with our knowledge in this aspect.
The communicative patterns in which Relevance Theory finds its interest are no other than the meaningful information. Relevance Theory interprets the relevance of discourses in communication at the level of psychological cognition of meaning, namely, the coherence of discourse as texts in psychological cognition. This theory includes three aspects: 1. the speaker's encoding process and his code pattern based on cognition-reasoning; 2. the listener's decoding process and his reasoning pattern based on cognition-reasoning; 3. the mutual cognition-reasoning process based on the cognitive context, and the relevance of discourse to contextual assumptions and cognitive context. Its descriptive analysis of the psychological cognition process in successful communication is in fact an interpretation of textual coherence. The theoretical basics of Relevance Theory are mainly on the listener's assumptions and cognition-reasoning of the speaker's context, that is, the listener's reasoning-cognition of the contextual implicatures of the speaker's meaning. Since the theory concerns our cognition and psychology, it is of course the reasoning-cognition of discourse meaning on the level of meaning instead of form. It is not hard to find that Relevance Theory studies the mechanism in text production from the cognitive psychological perspective and analyzes the relevance of text from the aspect of meaning. So, the knowledge of Relevance Theory about textual coherence can be said to have been built on the level of meaning.
The disagreements in the interpretation of textual coherence are basically the disagreements in the knowledge about the essence of textual coherence, i.e. the disagreements in the knowledge about the intension and extension of textual coherence. And the knowledge about the intension of textual coherence is the theoretical foundation for the knowledge about its extension (that is, the conditions for textual coherence) and for the whole textual theory construction. Hence, in order to discuss the conditions for textual coherence, it is necessary to define what textual coherence is first.
Coherence is the basic attribute of a text. Incoherent discourse combinations and linguistic symbol collections cannot be called texts. The mutual relevance of the different aspects within and without language and linguistic units of various hierarchies is not only the mutual cohesion on the level of form, but more importantly mutual relevance on the level of meaning. This is also an intrinsic requirement in language communication. At present, the linguistic world has formed a relatively deep understanding about the significance of semantic relevance in textual coherence: "The understanding and description of coherence in the linguistic field is generally the same." [8] Coherence refers to "the relationships which link the meanings of utterances in a discourse or of the sentences in a text." [10] "A proper text should at least meet two textual standards: 1. certain informativeness, and 2. coherence in meaning." And "textual coherence is the coherence in content, while textual cohesion is the cohesion of pure forms." [11] "Coherence in texts is determined not by the specific cohesive devices themselves, but by the intrinsic intersentential semantic relationships. The intersentential semantic connection is the primary premise of textual coherence." [12] Even Halliday and Hasan who concentrate on the study of cohesion in textual forms admit that "A text is best regarded as a semantic unit: a unit not of form, but of meaning." [5] More and more researchers have realized that the root of textual coherence lies in the semantic or functional relationships in the deeper layer of texts, while cohesion remains a relationship of surface structures.
Semantic relevance among elements in a text is the essential attribute of a text. The text as a system has semantic relevance as its foundation and essential requirement. That is to say, semantic relevance among elements in a text is the essence of textual coherence, while the formal cohesion among the elements in a text is only the extrinsic representation of textual coherence. Therefore, the systematic analysis of a text should not only be based on its formal system, but more on its meaning system.
Since the theoretical interpretation of textual coherence is directed to the meaning level of a text, it is natural that the semantic analysis cannot part with the context analysis of the text. There are rarely systematic discussions on this aspect with the exception of the detailed theoretical elaboration from Li Yue'e and Han Caiying on context constraints on the semantic relevance of situational conversation discourse. [13]

Context Constraints and Semantic Relevance
"Meaning and context are naturally related." [14] No text stands alone but is interlinked with the tradition that came before it and the context in which it is produced. [15] It is a fact that semantic relevance of the sublevel linguistic units cannot be achieved within the language alone. The reason is that the form of a symbol is not the symbol itself, let alone the meaning of the symbol. The meaning of a symbol is given by man. For the individual, the meaning of a symbol is the direction of his intention; for communication, it is a convention, a convention about the symbol and its referent, a convention about the value, culture and objects of the symbol.
As conditions for language generation, development, existence and changes [16], context is a continuous system which is jointly made up of intra-language and ultra-language elements. For situational conversations, context can be analyzed into four specific levels: linguistic context, situational context, social context and cultural context. It is on the four levels or perspectives that context constrains the semantic relevance of situational conversation. [13]

Constraints of Linguistic Context on Semantic Relevance
Linguistic context refers to the context made up of certain linguistic items such as words, sentences, segments and the whole text. These contextual factors which define the exact meaning of certain linguistic items in actual use are purely linguistic, i.e., they are verbal, exclusive of para-linguistic elements, non-verbal symbols and other entities.
Language communication takes on many forms in which face to face communication is the basic form. It is generally called situational communication while other forms of language communication are the variations of this form. Situational communication also takes on different forms among which situational conversation, the casual and instant exchange, is the most basic form. So situational conversation is the most basic reality of language. In situational conversations, words cannot achieve semantic coherence by depending solely on the grammatical forms they and their context take, for even the same word may signify different referents, thereby it loses its "markedness" and no longer plays the role of cohesive words, and thus loses its function to make the discourse a coherent one. The marked words do not have markedness innately, instead the markedness is given by the context. In a specific text, linguistic context holds pragmatic constraining functions on the meaning of particular words. As the meaning of a particular word is constrained by the linguistic context, it is relevant (or in some cases even consistent) to some other linguistic units within the same context, thereby the word's function as a signifier and its signified scope are determined, and thus definiteness follows. Therefore, the markedness of cohesive words depends on the linguistic contexts. Only in certain linguistic context can words be given markedness, tie particular linguistic elements in the text, and can they maintain textual coherence.

Constraints of Situational Context on Semantic Relevance
Situational context consists of the purposes, occasions, tones, participants and their non-verbal communicative behaviors, and related objects, etc. that helps and even replaces the verbal factors. It is a state in which various communicative symbols are agglutinative with each other. Of the various elements of in situational context, what constrains the semantic relevance of text most is the cognitive state of the participant, and the para-linguistic and other non-verbal elements with the quality and value of verbal symbols, which assist and in some cases even replace the verbal communication.

Constraints of the Cognitive State of Participants on
Semantic Relevance In situational conversation, the semantic relevance of a text is the result of the deduction of textual meaning by the communicator under certain contextual conditions. The semantic relevance depends on the subject's (ie, the participant's) cognition of the meaning brought by the information carrier (ie, the communicative symbols) and his identification of its semantic relevance. The subject's cognition of the meaning and his identification of semantic relevance are reflected in three aspects: 1. the addresser's reasoning of the addressee's cognitive pattern and cognitive result in understanding his meaning; 2. the addressee's reasoning of the addresser's intentions, his expression pattern and his meaning. Both of the two can be regarded as the subjects' reasoning and cognition of the other party's pragmatic reasoning patterns; 3. the participant's identification with the relevance or continuity of the meaning of the ongoing text, and further his reasoning and cognition of the other party's code reference pattern. It is in the three aspects that the participant constrains the semantic relevance of individual linguistic items within the text, and thus constrains the coherence of the whole text.

Constraints of Participants on the Addresser's
Semantic Relevance A text can be a detailed elaboration, or a brief sketch. A certain meaning can take various forms of linguistic expression. At the beginning of a situational conversation, the addresser's beginning segments can also be either detailed or brief, and can also take various linguistic forms. Generally, the addresser always hopes the addressee can maximally understand his meaning, and he would obey the cooperative principle in his linguistic expression. In order for the addressee to understand him the addresser would have his linguistic expression constrained by the contextual factors of the addressee's linguistic proficiency, that is, in communication, the addresser makes some assumptions about the addressee's cognitive contextual factors, such as his cognitive pattern and his topic-related knowledge background, etc., and has his linguistic behavior constrained by these assumptions. In other words, the addresser's linguistic behavior is constrained by his own psychological state for linguistic behavior in response to the addressee's psychological state of language cognition. This involves the double sides of a question: from the interactive relationship in language communication, what constrains the addresser's linguistic behavior is the addressee's psychological state of language cognition; from the language communication subject, what constrains the addresser's linguistic behavior is his own psychological state in cognizing the addressee's psychological state of language cognition.
The addresser's reasoning of the addressee's cognitive contextual factors such as his linguistic cognitive patterns may also happen at the subconscious or preconscious level and under a subtle state of mind. Reasoning under whatever consciousness or state of mind will constrain the addresser's linguistic explicitness, i.e., will constrain his way of linguistic expression, number of information flows, the extent of generality or interpretation of meaning, the density or closeness of semantic relevance, which in turn constrains the semantic relevance of the addresser's segments. In this sense, the semantic relevance of the individual linguistic units in the addresser's segments is the result of the addresser's cognitive reasoning of the addressee's comprehension-cognition pattern and cognitive results in understanding his meaning.

Constraints of Participants on the Addressee's Semantic Relevance
In situational conversation, the addressee's comprehension of the addresser's meaning is constrained by such contextual factors as the addresser's intention and his purpose, that is, by his own cognitive context in which he cognizes the addresser's linguistic behavior and linguistic purpose. Similarly, the addressee's cognitive context or his cognitive psychological state has two implications: from the interactive relationship in language communication, what constrains the addressee's language cognition is the addresser's psychological state for linguistic behavior; from the language communication subject, what constrains the addressee's language cognition is his own psychological state in cognizing the addresser's linguistic behavior and psychological state.
Like the addresser's reasoning of the addressee's psyche for language cognition, the addressee's cognitive reasoning maintains various states of consciousness. But, whether the psychological state is clear or subtle, it does not alter its constraining function as a cognitive context on the addressee's comprehension and cognition of the addresser's meaning. From cognitive psychology, the semantic relevance of different linguistic units of the addresser's segments depends on the addressee's reasoning of the addresser's intention or purpose, his pattern of linguistic expression, and his meaning. This relevance is the result of the addressee's reasoning and cognition of the addresser's cognitive context on which his meaning is based.

Constraints of Participants on the Semantic
Relevance in Discourse Generation A situational conversation can be comprised of one turn or several turns. With the development of communicative process, the context of situational conversation and the participant's cognition of the context will change, and the addresser will accordingly adjust his own communicative strategies, adjust the extent of semantic relevance of individual linguistic units in his linguistic expression, hence influencing and constraining the semantic relevance of different linguistic units at different levels within the text.
In a situational conversation made up of several turns, the participant is a dynamic parameter, with the roles of the addresser and the addressee interchanging in the process of communication. This interchange of communicative roles is a dynamic process and can to some extent influence the participant's linguistic tendency and pattern, that is, can render the participant different in his attitude and his pattern of linguistic expression from when he originally was an addresser and render the participant different in his attitude and his cognitive pattern of language understanding from when he was originally was an addressee. This to some extent influences the linguistic expression pattern of the whole text, the participant's cognition of the textual meaning, and thereby the semantic relevance of the whole text.
In a situational conversation made up of several turns, the language purpose (or the theme) of the whole text is not necessarily manifested at the very beginning, but gradually appears in the process of communication. According to the general laws of formal logic, the distribution of the communicative theme and sub-themes can adopt two basic patterns: that is, sub-themes' gradual development under clear guidance of the theme and the theme's gradual clearness after sub-themes' development. But whatever the case, the participant's clarity in comprehending the theme still relies on the extent to which the whole text is developed. From the perspective of language cognition, the gradual development of language purpose is right the gradual advancement of the textual theme. In the development of the whole text, the situational context of the interacting participants constrains the participants' further reasoning-cognition of the other party's code reference pattern, constrains the participants' cognition and identification of the textual theme, and constrains the participants' cognition and identification of the constantly developing semantic relevance or continuity of the text.
Para-linguistic elements consist of tones, stresses and body languages, which are closely related to the communicative subject. In situational conversation, although not functioning as bearing specific meaning, they are used as information bearers and have relatively strong function to suggest, that is, the function to suggest the semantic structure and the relevance of the text. They can highlight the kernel words of the addresser's sentences, kernel words and kernel sentences of his segments and his text, and the topic sentence of his text, and thereby strengthen the semantic relevance of individual linguistic element to linguistic elements at various levels in the context.
In addition, the strength and frequency of para-linguistic elements also constrains the addresser's semantic relevance from his cognitive and psychological aspects, constrains the addressee's comprehension of the addresser's meaning and his cognition of the semantic relevance.
In situational conversation, the communicative function of the non-linguistic symbol is dual: on the one hand, as a relatively independent system, it exists as a context opposed to the linguistic system in situational conversation; on the other hand, it is a symbol in itself, and is a sub-system of the communicative symbol system in situational conversation. The meaning the non-linguistic symbol carries is also a component of the semantic system of the text in situational conversation.
Situational context composed of occasion, participants as well as their non-linguistic behavior, and related objects is the context of entities. In situational conversation, like verbal symbols and paralinguistic elements, the situational context of entities also plays a role in the formation of meaning. When the entities enter the scope of human's cognition, they constitute the semantic context, then the context can constrain the signification domain of specific words, give their signified object definiteness, and thus endow this word or phrase the function of markedness. It is right because of the quality of being an entity and its relevance to language communication that the situational context of entities obtains the contextual value which is equal to the linguistic context, and the same constraining function on textual semantic relevance. "Be it linguistic or paralinguistic, context plays a paramount role when meaning depends less on dictionary meaning than on speech situation." [17] So is the context of entities. As a communicative symbol, situational context of non-linguistic symbols is significant both in the formal system and in the meaning system of situational conversation. Therefore, in the cognition of textual coherence, ignorance of non-linguistic communicative symbols will certainly cause some loss of the formal system and the break of the meaning system in situational conversation, and thus deprive various linguistic units of their semantic relevance.

Constraints of Social Context on Semantic Relevance
Social context refers to the social background of communication participants and the social background factors involved in communication. It reflects such social characteristics and attributes as the participant's class, trade, and community, etc. In terms of the language characteristics of a text, social context reflects the communicative purpose or theme of the whole text and the social characteristics and attributes of linguistic symbols; in terms of participant in the development of text, social context reflects the social characteristics and attributes of the individual in the form of his linguistic expression and his language cognition and comprehension.

Constraints on Semantic Relevance of Social Context
Comprised of Individuals from Different Social Backgrounds Different individuals have different social backgrounds in the process of socialization, and their linguistic symbol sets are not the same, either. There are two respects for the differences: one is the difference in the lexical components of the social individuals, and the other is the difference in the meaning of particular words. In other words, different individuals use different words to express the same idea, and sometimes different individuals mean differently even when they use the same words. In addition, the differences in social backgrounds have also helped individuals develop their own communicative patterns, namely, the individuals' idiosyncratic linguistic expression pattern and language cognition pattern.
From the perspective of socio-linguistic psychology, language communication patterns that individuals develop in the process of their socialization are based on their psychological tendency for language. It involves two aspects: one is the tendency for their linguistic behavior, and the other is the tendency for their language cognition. In situational conversation with individuals from different social backgrounds, social differences in individuals' linguistic expression pattern and language cognition pattern lead to (lexical and structural) difference in the expression forms of individuals whose tendencies for linguistic behavior are different from each other and also lead to difference in the meaning comprehension of individuals whose tendencies for language cognition are different from each. This difference from idiosyncratic psychological tendency for language possessed by participants from different social backgrounds is essential in constraining the addresser's order and hierarchy in expressing certain meaning, and at the same time in constraining the addressee's comprehension of the meaning of particular language and his cognition of the relevance of the meaning.

Constraints on Semantic Relevance of Social Context
Comprised of Different Communicative Groups Individuals forge their personalities in different social environments, and form their own social circles. For social groups made up of individuals with similar social backgrounds, their language communication behaviors have relatively consistent social backgrounds while different social circles have different social backgrounds due to the differences of the participants. So the social contexts on which the communicative behaviors of different social circles rest are also widely different because the participants' social backgrounds such as class, trade, and community, etc. are different.
In language communication activities, social context constrains the participants and their activities and causes differences in the linguistic psyche and linguistic behaviors of different social circles, for example, similar to the case in 3.3.1, the same linguistic symbol may bear different meanings while the same meaning may have different linguistic expressions, and still the comprehension of the same linguistic symbol may be different. Right because the social contexts of different social circles are different their brevity of linguistic expressions and the extent of semantic relevance are also different in their language communication activities. Therefore, for texts derived from the communication activities of participants from different social backgrounds, the manner and extent of semantic relevance between their linguistic elements are bound to be largely different.

Constraints on Semantic Relevance of Social Context Comprised of Individuals from Similar Social Backgrounds
The same social backgrounds and recognition of them result in the same patterns of linguistic expression and language cognition, and this is the so-called register consistency. "Sameness" is only a theoretical assumption, which does not exist in actual language communication. In the analyses of actual language communication activities, only relative consistency of register can be achieved, or in other words consistency of register only exists in theory, namely in our cognition.
In situational conversation involving individuals with roughly the same or consistent social backgrounds, social contexts of individuals are similar or mostly identical. Under this condition, although the influence of social context on textual coherence is not so prominent, it does not mean that social context has lost its constraining function on textual coherence or semantic relevance of the text.
Conventional discourse analysis tends to ignore the extent to which the participant has been socialized. In the process from a biological being to a social being, an individual's social characteristics and attributes are the results of his socialization. However, different social individuals and individuals in different periods of socialization maintain different levels of socialization and different social cognitive ability, and they differ in their linguistic expressions and language cognition and comprehension. This social characteristic of individuals also constrains the individual as a language communication participant in his capabilities and ways of semantic expression, constrains his capabilities of language cognition and comprehension, constrains the semantic relevance of his expression and the semantic relevance of his cognition and comprehension, and thus constrains the semantic relevance of the whole text.
In addition, during the process of socialization, social individuals form their own language habits including the ways for textual semantic relevance. This idiosyncratic habit for textual semantic relevance is also a language tendency, that is, a psychological tendency for the linguistic behavior as an addresser and for the language cognition as an addressee. This language tendency has also to some extent influenced and constrained relevance in expression, comprehension and cognition of the textual meaning. This may well be one of the essential reasons why there are frequent ambiguities in the comprehension of textual meaning.
Social context constrains in the deep layer the linguistic psyche of participants and in the surface layer their linguistic behaviors, and constrains the patterns of the expression and comprehension of textual meaning. This is the basic psychological mechanism with which social context constrains the relevance of textual meaning.

Constraints of Cultural Context on Semantic Relevance
Cultural context refers to the cultural background of participants and the cultural background factors involved in communication. It is the foundation for the generation and comprehension of language of cultural traits. Cultural context reflects the ethnic or communal cultural characteristics and attributes of the participant. In terms of the language characteristics of a text, cultural context reflects the ethnic and communal cultural characteristics and attributes of linguistic symbols of the whole text; in terms of semantic relevance of a text, cultural context reflects the characteristics and attributes of the ethnic and communal culture of the linguistic subject in his linguistic expression and language cognition.
The constraint of cultural context on semantic relevance is also a complicated matter. Let's first discuss two extremes. On the one pole lie the utmost constraints of cultural context on the semantic relevance of the text, namely, there is no way to know whether or not a text is coherent or semantically relevant: obviously, it is hard to put up a bridge of communication and understanding for individuals with totally different cultural symbols and cultural psychology, especially individuals with totally different linguistic symbols and linguistic psychology. If there is total absence of cognition for the other party's language, then there is no way to identify whether their text is coherent or whether it is semantically relevant. This is an extreme case of constraints of cultural context on the semantic relevance of the text. On the other pole lie the zero constraints of cultural context on the semantic relevance of the text. For individuals with totally the same cultural symbols and cultural psychology, especially individuals with totally the same linguistic symbols and linguistic psychology, there are no cultural differences between them, and so, there are no barriers for them to have cultural and linguistic communication. Ethnic cultural context naturally fails to constitute overt constraints on their language communication. From the perspective of language communication then, ethnic cultural context exerts zero constraints on language communication, and hence zero constraints on the semantic relevance of texts generated from this situation.
Between the above two extreme theoretical models with the individuals having either totally the same or completely different ethnic cultural backgrounds, there in fact exist numerous types of ethnic cultural contexts, which involve the composition of different cultural elements. In the cross-cultural communications lying between the two extremes, ethnic cultural context constrains to various extents the participant's comprehension of the other party's cultural words, constrains his cognition of the other party's structural combination of cultural words and his comprehension of the meaning of word groups and sentences, constrains his cognition of the meaning of the other party's specific segments and thereof the semantic relevance of the segments. In situational conversation, the differences in ethnic cultural backgrounds of language subjects are manifested as differences in ethnic cultural contexts, and lead to differences in language generation and comprehension of participants, and accordingly constrain the participant's comprehension and cognition of the semantics and semantic relevance of the whole text.
In terms of psychological mechanism, the constraint of communal cultural context on the semantic relevance of a text is similar to the constraint of ethnic cultural context. Although the intensity and frequency of the influence and constraint communal cultural context exerts on the meaning and the semantic relevance of situational conversation texts are incomparable to those of ethnic cultural context, in an ethnic group populating in vast areas such as the Han, there are significant cultural differences among communities within the ethnic group, which are even more distinct than those in mixed ethnic groups. Under this condition, differences in participants' communal cultural context make themselves a significant factor in influencing and constraining the meaning and semantic relevance of a text.
In all, context is the underlying condition for the semantic relevance of a text. Whether for the generation of a text or the cognition and identification of a text, context makes an essential condition that influences and constrains the semantic relevance of a text.

Concluding Remarks
Finally the authors draw the following conclusions: 1. Context is the underlying condition that constrains textual coherence. It constrains the generation of coherent texts and the cognition of the coherence of the text. 2. Contextual relevance is the desired end of the interpretation of textual coherence. Interpretations of textual coherence from different perspectives and at different levels at present are meaningful to the construction of the theoretical system of textual linguistics. 3. But after all, the unilaterality in the interpretative theories that are heavily loaded with disciplinary inclinations is quite obvious, and its limitations in the explanatory power are also self-evident. But here, the authors are not to deny those theories completely, on the contrary, they believe these theories or beneficial inquires are, to a certain degree, scientific and reasonable. It is not advisable to blindly use a unilateral theory to dismiss another, which may be harmful to the development of textual linguistics and even linguistics as a whole. Besides, the scientificality and reasonableness of these theories can well get a new and better interpretation within the framework of the contextual theory. 4. Of course, only when based on contextual relevance can the reasonableness and common grounds of these textual theories be found, and then a relatively comprehensive and systematic interpretation of textual coherence can be established.