XML 11 14 2011 Opening Discussion Minute essay comments Can you write web pages using XML Discrete and 1120 in the major minor FYs in 3194 Role of 3194 ASIMO is made by Honda not sponsored What were my influences for CS What is the wackiest programming error I ve ever seen Assignment 2 grades should be expected this week Motivation We have been using flat text files to store things Advantage it is human readable and simple Disadvantages everything else Slow Large Lacks meaning Hard to edit Hard to debug XML The eXtensible Markup Language XML is a standard for text encoding of data If you have ever done HTML XML is similar XHTML is HTML that follows the XML standard The advantage of XML is that it can encode pretty much anything and it is human readable text The downside is that it can be very verbose Composed of markup between and or and or content anything not markup Tags The primary markup used in XML is the tag A tag begins with a and ends with a There are three types of tags Start tag student End tag student Empty element tag quiz Elements The structure of XML documents comes primarily from elements An element is one of the following Everything from a start tag to the matching end tag An empty element tag Elements have to be properly nested The nesting can imply information Attributes An attribute is a name value pair They can be put in start tags or empty element tags Examples student name Jason id 0123456 quiz grade 55 XML Declaration An XML file can begin with a declaration telling information about it xml version 1 0 encoding UTF 8 We won t worry about these in this class XML in Scala The Scala language supports XML at the language level Go to the REPL and enter some XML There is a scala xml package that contains the libraries for XML The NodeSeq Node and Elem types are particularly useful I ll typically just use the word Node to describe something from the XML So is the XML object The XML Object The loadFile method can be passed a file name and it will read in the file and return a NodeSeq that allows you to get to the contents There is also a save method that takes a file name and an XML node and writes it to file Using and Use the operation on a node to search for the occurrences of something at the top level The second argument is a string Normal string searches for tags with that label If the string starts with it searches for attributes Use to search deeply Minute Essay Questions about XML Valero will be presenting at the ACM meeting starting at 4 30
View Full Document
Unlocking...