<\body> Each standard style file or package is based on a potentially finite number of subpackages. From an abstract point of view, this organization may be represented by a labeled tree. For instance, the tree which corresponds to the style is represented below: <\big-figure|||>>|>>|>>|>>|>>|>>|>>|>>|>>>>>>||>>|>>|>>|>>>>>>||>|||>>> The tree with the packages from which the style has been built up. In order to save space, we have regrouped the numerous children of and in vertical lists. Most of the style packages correspond to a (data type definition) which contains the ``abstract interface'' of the package, the exported tags. For instance, the package corresponds to the . Sometimes however, several style packages match the same . For instance, both and match the , since they merely implement different ways to render the same tags. When building your own style files or packages, you may use the primitive in order to include other packages. For instance, the style essentially consists of the line <\tm-fragment> > More precisely, the package sequentially includes the style packages corresponding to its arguments. The packages should be in , which contains , and by default. Furthermore rendering information for the source code like tags are discarded before evaluation of the files. <\remark> We strongly recommend the user to take a look at some of the standard style files and packages which can be found in <\verbatim> \ \ \ \ $TEXMACS_PATH/styles \ \ \ \ $TEXMACS_PATH/packages When loading using , these paths are in the standard load path. For instance, if you want to take a look at the package, then it suffices to type , followed by the file name and . <\remark> It is also possible to customize the presentation of the source code of the style files and packages themselves, by using other packages in addition to or by using another major style file based on . In that case, the extra markup provided by such packages may be used for presentation purposes of the source code, but it is not exported when using your package in another file.