Leo is... * A general data management environment. Leo shows user-created relationships among any kind of data: computer programs, web sites, etc. Leo shows multiple views of data within a single outline. * An outlining editor for programmers. Leo supports optional noweb and CWEB markup. * A flexible browser for projects, programs, classes or any other data. * A project manager. * Fully scriptable using Python. * Leo's outline files are XML format.
XOXO (eXtensible Open XHTML Outlines) is an XML microformat for outlines built on top of XHTML. Developed by several authors as an attempt to reuse XHTML building blocks instead of inventing unnecessary new XML elements/attributes, XOXO is based on existing conventions for publishing outlines, lists, and blogrolls on the Web. The XOXO specification defines an outline as a hierarchical, ordered list of arbitrary elements. The specification is fairly open which makes it suitable for many types of list data. E.g. the more semantic version of the S5 presentation file format is based upon XOXO.