The document interchange including styles can be carried out in the formats of the following three types:
a) final form (non-revisable), e.g., PDF, PostScript, or SPDL
b) editing tool's form (revisable), e.g., Word form, RTF, or etc.
NOTE: It depends upon the editing tool and is in many cases proprietary form.
c) structuring language form with a style specification by style language (revisable), e.g., [SGML + DSSSL] or [XML + XSL].
NOTE: HTML or XHTML is a simple particular case of this form, where some style specifications are fixed and implemented within a browser.
Here we focus on the case c), where the documents are revisable, complicated document styles/layouts are supported and besides their rendered image are preserved.