Abstract: The heart of each wiki, including Wikipedia, is its content. Most machine processing starts and ends with this content. At present, such processing is limited, because most wiki engines today cannot provide a complete and precise representation of the wiki’s content. They can only generate HTML. The main reason is the lack of well-defined parsers that can handle the complexity of modern wiki markup. This applies to MediaWiki, the software running Wikipedia, and most other wiki engines. This paper shows why it has been so difficult to develop comprehensive parsers for wiki markup. It presents the design and implementation of a parser for Wikitext, the wiki markup language of MediaWiki. We use parsing expression grammars where most parsers used no grammars or grammars poorly suited to the task. Using this parser it is possible to directly and precisely query the structured data within wikis, including Wikipedia. The parser is available as open source from http://sweble.org.

Keywords: Wiki, Wikipedia, Wiki Parser, Wikitext Parser, Parsing Expression Grammar, PEG, Abstract Syntax Tree, AST, WYSIWYG, Sweble.

Reference: Hannes Dohrn and Dirk Riehle. “Design and Implementation of the Sweble Wikitext Parser: Unlocking the Structured Data of Wikipedia.” In Proceedings of the 7th International Symposium on Wikis and Open Collaboration (WikiSym 2011). ACM Press, 2011. Page 72-81.

The paper is available as a PDF file (preprint).

Abstract: Wikipedia is a rich encyclopedia that is not only of great use to its contributors and readers but also to researchers and providers of third party software around Wikipedia. However, Wikipedia’s content is only available as Wikitext, the markup language in which articles on Wikipedia are written, and whoever needs to access the content of an article has to implement their own parser or has to use one of the available parser solutions. Unfortunately, those parsers which convert Wikitext into a high-level representation like an abstract syntax tree (AST) define their own format for storing and providing access to this data structure. Further, the semantics of Wikitext are only defined implicitly in the MediaWiki software itself. This situation makes it difficult to reason about the semantic content of an article or exchange and modify articles in a standardized and machine-accessible way. To remedy this situation we propose a markup language, called XWML, in which articles can be stored and an object model, called WOM, that defines how the contents of an article can be read and modified.

Keywords: Wiki, Wikipedia, Wikitext, Wikitext Parser, Open Source, Sweble, Mediawiki, Mediawiki Parser, XWML, HTML, WOM

Reference: Hannes Dohrn and Dirk Riehle. WOM: An Object Model for Wikitext. University of Erlangen, Technical Report CS-2011-05 (July 2011).

The technical report is available as a PDF file.