a way that allowed for drawing neat tree diagrams based on the principle of 'descent with modification' and shared innovations. Dialectologists rather realized that dialect traits spread through diffusion and that social factors were decisive in how this happened. They also realized that traits spread as waves from centers and that often several competing varieties would exist in some communities. This insight prompted Gumperz to problematize the notion of the linguistic community as the community that carries a single speech variant, and instead to seek a definition that could encompass heterogeneity. This could be done by focusing on the interactive aspect of language, because interaction in speech is the path along which diffused linguistic traits travel. Gumperz defined the community of speech: Gumperz here identifies two important components of the speech community: members share both a set of linguistics forms and a set of social norms Gumperz also sought to set up a typological framework for describing how linguistic systems can be in use within a single speech community. He introduced the concept of linguistic range, the degree to which the linguistic systems of the community differ so that speech communities can be multilingual, diglossic, multidialectal (including sociolectal stratification), or homogeneous - depending on the degree of difference among the different language systems used in the community. Secondly the notion of compartmentalization described the degree to which the use of different varieties were either set off from each other as discrete systems in interaction (e.g. diglossia where varieties correspond to specific social contexts, or multilingualism where varieties correspond to discrete social groups within the community) or whether they are habitually mixed in interaction (e.g. code-switching, bilingualism, syncretic language). Noam Chomsky Gumperz's formulation was however effectively overshadowed by Noam Chomsky's redefinition of the scope of linguistics as being : William Labov Another influential conceptualization of the linguistic community was that of William Labov, which can be seen as a hybrid of the Chomskyan structural homogeneity and Gumperz' focus on shared norms informing variable practices. Labov wrote: Like that of Gumperz, Labov's formulation stressed that a speech community was defined more by shared norms than by shared linguistic forms. But like Chomsky, Labov also saw each of the formally distinguished linguistic varieties within a speech community as homogeneous, invariant and uniform. This model worked well for Labov's purpose which was to show that African American Vernacular English could not be seen as