XML

• A really popular KR mechanism is the extensible markup language, XML.
• It's so popular they don't even call it a KR system.
• The idea is that instead of using an existing tag set like HTML, you use a domain specific tag set.
• You define that tag set in XML, and then you use it to mark up your documents.
• You can display things, like in HTML, but the important bit is that the tags provide a formal semantics.
• This is the basis of the semantic web.
• Say you have CarML, and you've marked up documents. You can look for documents with certain tags, or certain tag value pairs. For instance, you could search for cars less that £10,000 pounds, or Red Saabs.
• We see it in spacewars, but there it's just used for providing features. (XML has now become a standard for basic data representation.)