One SBML file can have many layouts, and a layout can have many rendering styles. A RenderStyle consists of the fillStyle (For the Background of the Layout) aloong with lists for CompartmentStyles, SpeciesStyles, ReactionsStyles and TextStyles. A version attribute has been allowed for later revisions. Each of these elemens are optional. The list of CompartementStyles consists of one or more compartment style(s). Each compartment style, consists of a nonempty list of shapes, an edge style and an optional membrane style (innerStyle) The list of SpeciesStyles consists of one or more species style(s). A SpeciesStyle consists of a list of shapes. The ReferenceType is intended to be used in order to group elements, or to provide aliases (elements, with different boundingbox, but same rendering styles / glyph elements/attributes) for existing glyphs. The list of TextStyles consists of one or more text style(s). Each textStyle consists of a fontStyle. The list of ReactionStyles consists of one or more Reaction style(s). The reactionSytle specifies how arrows (at the end of product/reactants) should be rendered along with information on how the reaction should be displayed. The list of shapes consists of one or more shape(s). The fill style defines how a shape should be filled. The parameter endColor is only relevant for gradients. The parameter fillParameter allows to define how the gradient should look ... (examples are: forwarddiagonal - a diagonal linear gradient The type RenderBase is the base for all elements, it gives all elements an ID, and a reference, pointing to the corresponding element of the SBML Layout extension. This optional parameter specifies how a gradient should look. the first four types apply to linear gradients, the latter five to radial gradients. Finally "None" is allowed to specify that none of the above apply. The type ColorString represents colors in ARGB (alpha, red, green, blue) hex form. The SBase type is the base type of all main components in SBML. It supports attaching metadata, notes and annotations to components. The type SId is used throughout SBML as the type of the 'id' attributes on model elements.