The lexical aspect focuses on sense relations and lexical repetitions, while the grammatical aspect looks at repetition of meaning shown through reference, substitution and ellipsis, as well as the role of linking adverbials. Systemic functional grammar deals with all of these areas of meaning equally within the grammatical system itself. Children’s grammar Michael Halliday (1973) outlined seven functions of language with regard to the grammar used by children: the instrumental function serves to manipulate the environment, to cause certain events to happen; the regulatory function of language is the control of events; the representational function is the use of language to make statements, convey facts and knowledge, explain, or report to represent reality as the speaker/writer sees it; the interactional function of language serves to ensure social maintenance; the personal function is to express emotions, personality, and "gut-level" reactions; the heuristic function used to acquire knowledge, to learn about the environment; the imaginative function serves to create imaginary systems or ideas. Relation to other branches of grammar Halliday's theory sets out to explain how spoken and written texts construe meanings and how the resources of language are organised in open systems and functionally bound to meanings. It is a theory of language in use, creating systematic relations between choices and forms within the less abstract strata of grammar and phonology, on the one hand, and more abstract strata such as context of situation and context of culture on the other. It is a radically different theory of language from others which explore less abstract strata as autonomous systems, the most notable being Noam Chomsky's. Since the principal aim of systemic functional grammar is to represent the grammatical system as a resource for making meaning, it addresses different concerns. For example, it does not try to address Chomsky's thesis that there is a "finite rule system which generates all and only the grammatical sentences in a language". Halliday's theory encourages a more open approach to the definition of language as a resource; rather than focus on grammaticality as such, a systemic functional grammatical treatment focuses instead on the relative frequencies of choices made in uses of language and assumes that these relative frequencies reflect the probability that particular paths through the available resources will be chosen rather than others. Thus, SFG does not describe language as a finite rule system, but rather as a system, realised by instantiations, that is continuously