As a result, they base their parser on a parsing expression grammar (PEG). Sweble parses the Wikitext and produces an abstract syntax tree as output. This helps to avoid errors from incorrect markup code (e.g. having a link spanning over multiple cells of a table). A detailed description of the abstract syntax tree model can be found in a technical report about the Wikitext Object Model (WOM). The parser processes Wikitext in five stages: