Markup

• Stateless - does not remember between one call and the next (have to auth every time)
• HTML does not require closing tags on all tags
• XML must have all tags closed
• XML: start with version statement. Case sensitive. Follow nesting rules. Must have one root element
• schema - xml doc describing another xml doc, eg. type restrictions on variables

  
• Markup: representing how content will be represented (eg. latex)
• XML issues: often unreadable esp when autogenerated
• XML is computationally expensive. Is also DRY - (don't repeat yourself) having to open and then close at the end is kinda repeating yourself
• JSON - javascript object notation
• YAML: relies on indenting, no brackets

  
• XML does not have arrays, so have to fake a list
• Polling: periodically querying the state of something
• WebSockets: a protocol for bi-directional, real-time communication between a client and a server over a single, long-lived connection
• WS: request to switch protocol from HTTP to websocket
• Session = connection using websockets. Servers usually track all current sessions