1 XML – an introduction David Nathan ELDP training March 2010

2 XML  an in-line markup system  single sequence of plain text only (but can be unicode)  equivalent to a tree structure  consists of elements and content  elements: tag syntax  entities syntax  reserved characters & " ‘

3 XML syntax  structures are defined by tags in angle brackets: eg:  tags are usually in pairs:  a start/open tag, and an end/close tag: the dog chased...  but can also be single and closed: the dog sat down

4 XML syntax  tags can have attributes with values : the dog sat down  you can name your tags, attributes or values (almost) anything  there are some restrictions:  you can have hierarchies, but not overlaps: the cat sat on the mat

5 XML is used to add knowledge...  add knowledge to content:  usually structures and labels  add the knowledge that’s relevant to your domain or task  knowledge priorities:  what’s required  what’s visually represented (eg by format/layout)  what’s implicit

6 Compare to HTML ... the man who really liked the book The Lawyer Who Lost, about habeas corpus...  in HTML:... the man who really liked the book The Lawyer Who Lost, about habeas corpus...  in XML, we can define our own elements that focus on logical structure rather than visial format

7 Compare to HTML  XML:  is flexible and extensible  must be well-formed  can be validated  is application-, platform-, and vendor- independent  is machine readable (ie parsable, or understandable by computer programs)

8 An example

9... in XML The Guardian July 1, 1997 Andrew Higgins in Hong Kong A last hurrah and an empire closes down With a clenched-jaw nod from the Prince of Wales, a last rendition of God Save the Queen, and a wind machine to keep the Union flag flying for a final 16 minutes of indoor pomp...

10 Where does XML come from?  write “raw” XML (we will do this)  XML editors  generated, eg from databases, programs

11 What is XML used for?  any symbolic data  data exchange  data transformation  structure  format  content

12 Why do I need to know about it?  you already consume a lot of XML!  many linguistic software tools (eg ELAN) use XML as data format  XML is very powerful and flexible, especially for certain tasks, and for archiving  XML is an ISO standard  XML is growing in use and support!  XML is easy!

13 XML exercise 1 1.identify times and names, code these as XML 2.draw as a tree structure THEN 1.add more information to your XML as attributes 2.draw a tree structure again James departed from Manilla on Wednesday 11 May and arrived in Boston on Thursday 12 May.

14 XML exercise 2 1.draw a simple linguistic tree structure 2.represent it as XML

15 Congratulations  you have now taken your first steps in XML