How would I begin to discuss the following scenario where I must explain the principles of language and language use for 90 minutes?
What are the principles of language and use of language seen in this scenario: Four middle school student form a club whose members speak using a "secret code" that is understandable by only members of that club.
In order for a language to be understandable and used, such as the invented one of the four club members, it must have an established grammar and syntax and vocabulary. On the level of grammar, in an invented language inflectors that indicate relationship and possession and time would have to be decided upon. For instance, will family and personal relationship be indicated by inflecting a proper noun or by the existence of a unique vocabulary word like "Uncle"? Will there be many indicators of levels of relationship indicated in inflection or will vocabulary indicate levels, such as "my great-granduncle and my maternal cousin three times removed." Another example is whether time will be indicated by inflectors as in "whilst" or by unique vocabulary words in specific constructions such as "will have been"?
On the level of syntax, what order of construction will sentences take? For example, will the syntax follows a Subject Verb Object (SVO) order as in "You close the window" as in English syntax? Or will the syntax follow an Object Subject Verb (OSV) order as in "The window you make closed"? In addition, will vocabulary be influenced by tonal qualities in which the tone given to individual phonemes and morphemes may utterly change the meaning of the vocabulary word, for example, one tonal variation indicating "cow" and another tonal variation indicating "swim"?
These are some of the considerations you will give an overview of to begin a 90 minute discussion of language and language use in an invented language understood by only the four individuals who have invented it. You might also start out your discussion by drawing attention to pidgins that have developed into creoles and/or introducing research that reveals that when a generation is born into an environment in which a pidgin has become a native language, having been elevated by various circumstances from the status of a vehicular lingua franca, it takes only one generation for the pidgin to take on a full grammar and formalized syntax features. These topics amplify the principles of language and language use in a discussion of a "secret code" understood only by its inventors.
As a teacher who uses discussions in his teaching a lot, I feel I can respond generally on how to start a discussion and then to manage it.
My first comment would be that 90 minutes is way too long for an effective discussion. If I have a discussion it is probably maximum 15 minutes, but a discussion only works if you structure it very very carefully. To start off the discussion you need to somehow give your students a "hook" that allows them to grasp the central ideas of the topic you are referring to so that they can then discuss it. Also, I have found discussions work best if you give all students some time to think of issues that they are happy to talk about before the discussion start. Otherwise it is only the loudmouth confident ones that have anything to say! Also, if you are leading the discussion you need to have a series of extra points you can throw out to encourage people to talk more when the conversation dries up. It is always good to have a definite time limit on a discussion so people know when it is going to finish.
Hope these ideas help! The secret to good discussions is planning planning planning - you can't just expect people to start discussing!