<\body> trees> All documents or document fragments can be thought of as . For instance, the tree <\equation*> >|mode|math|>|x+y+|>|1|2>|+|>|y+z>>> typically represents the formula <\equation> x+y++ trees> Each of the internal nodes of a tree is a string symbol and each of the leafs is an ordinary string. A string symbol is different from a usual string only from the efficiency point of view: represents each symbol by a unique number, so that it is extremely fast to test weather two symbols are equal. trees> Currently, all strings are represented using the encoding>. This encoding coincides with the Cork font encoding for all characters except ``>'' and ``>''. Character sequences starting with ``>'' and ending with ``>'' are interpreted as special extension characters. For example, alpha\> stands for the letter >. The semantics of characters in the universal encoding does not depend on the context (currently, cyrillic characters are an exception, but this should change soon). In other words, the universal encoding may be seen as an analogue of Unicode. In the future, we might actually switch to Unicode. The string leafs either contain ordinary text or special data. supports the following atomic data types: <\description> Either or . Sequences of digits which may be preceded by a minus sign. Specified using the usual scientific notation. Floating point numbers followed by a , like or . When storing a document as a file on your harddisk or when copying a document fragment to the clipboard, trees have to be represented as strings. The conversion without loss of information of abstract trees into strings is called and the inverse process . provides three ways to serialize trees, which correspond to the standard format|tm-tm.en.tm>, the and the format|tm-scm.en.tm>. However, it should be emphasized that the preferred syntax for modifying documents is the screen display inside the editor. If that seems surprising to you, consider that a syntax is a way to represent information in a form suitable to understanding and modification. The on-screen typeset representation of a document, together with its interactive behaviour, is a particularly concrete syntax. Moreover, in the menu, you may find different ways to customize the way documents are viewed, such as different levels of informative flags and a for editing style files. <\initial> <\collection>