XML: A New Standard for Data

Overview of XML and its use on the web and in academic libraries.

1. XML:  A  New   Standard  for  Data Daniel  Stout University  of  Iowa  Libraries 30  May  2003
2. Find  this  presentation  Online n To  find  this  presentation  online,  visit: http://staffweb.lib.uiowa.edu/dstout/xml.htm n Or  will  be  up  on  Libraries  Intranet
3. XML:  What  is  it? n Extensible  Markup  Language (XML) n What’s  a  Markup  Language? ¨ Example:  HTML–Hypertext  Markup  Language ¨ It’s  just  a  text  file… ¨ …which  makes  it  easy  to  transfer  on  the  Web. n It  has  a  variety  of  functions,  such  as…
4. What  does  XML  do  exactly? n Standardized  method  for  encapsulating data   and  digital  objects. n It  is  a  wrapper  that  goes  around  digital   information  – text,  images,  video. n XML  can  encode  metadata… n …but  also  can  define  the  features  of  a  document   (e.g.  TOC,  formatting) n XML  is  a  way  to  describe  document  structure – like  the  structure  of  a  book,  for  example.
5. XML  is  between  the  brackets n It  uses  tags in  brackets,  just  like  HTML. ¨ HTML  example  file: <html> <head> <title>This is My Web Page</title> </head> <body background=“#FFFFFF”> <p>Hello, World! </body> </html>
6. XML  can  look  very  simple n A  very  basic  and  valid  XML  file: <?xml version="1.0"?> <oldjoke> <burns>Say <quote>goodnight</quote>, Gracie.</burns> <allen><quote>Goodnight, Gracie.</quote></allen> <applause /> </oldjoke>
7. A  MARC  Record  in  XML <fixfield id="1">" 90178038 "</fixfield> <fixfield id="3">"DLC"</fixfield> <fixfield id="5">"19900814092959.1"</fixfield> <fixfield id="8">"900724s1974 po af 000 0 fre "</fixfield> <varfield id="10" i1=" " i2=" "> <subfield label="a">90178038</subfield> </varfield> <varfield id="40" i1=" " i2=" "> <subfield label="a">DLC</subfield> <subfield label="c">DLC</subfield> </varfield>
8. But  XML  can  be  complicated n Less  readable  than  HTML… n …because  it  is  more  powerful. <xml xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:p="urn:schemas-microsoft- com:office:powerpoint" xmlns:oa="urn:schemas- microsoft-com:office:activation"> <p:presentation sizeof="screen" gridspacingx="49152" gridspacingy="49152"> <p:master id="8" slidesn="1C00DA9,3702FA30" type="main" href="master08.htm" xmlhref="master08.xml" template="Pixel" layout="title_body" slots="title,body,dateTime,footer,slideNumber"> <p:schemes>
9. Why  XML  and  not  HTML? n Unlimited  tagsets  and  definitions ¨ XML  is  a  metalanguage n HTML  describes  a  web  page ¨ XML  describes  all  manner  of  “documents” n That  is,  HTML  is  fixed,  limited  and  informal ¨ XML  is  versatile,  multifaceted  and  formal
10. Advantages  of  XML n Rigorous  Grammar  – all  tags  are  balanced n Open  Standard  – anyone  can  use  XML n Flexibility  – can  define  many  types  of  data n Relatively  Simple  – concepts  are  easy
11. XML  has  a  Rigorous  Grammar n Balanced  Tags n Tags  come  in  sets <strong>This is some bold text</strong> <ol><li>One Item</li> <li>Second Item</li></ol> n Individual  tags  must  have  a  terminator <br /> n Tags  must  be  nested  – cannot  overlap <strong><em>Invalid</strong></em>
12. XML  has  a  Rigorous  Grammar n DTD  – Document  Type  Definition ¨ DTD  defines  how  the  document  is  structured,  that  is,  allowable  tags  and   grammar ¨ Sets  rules  for  the  document,  such  as: A  <p>  is  part  of  a  <chapter>  which  is  part  of  a  <book>  -­-­ but  don’t  allow  a  <p>   in  a  <toc> n Schemas  – A  Restriction  of  DTD ¨ Can  use  multiple  schemas  with  a  given  DTD n Rigorous  Grammar  =  Machine  Readable ¨ Platform  independent…software  independent ¨ If  you  know  the  DTD,  you  can  write  software  to  read  that  type  of  XML   file. ¨ Correctly  formatted  XML  can  be  parsed.
13. XML  is  an  Open  Standard n W3C  has  control  of  the  XML  specification ¨ World  Wide  Web  Consortium-­Cambridge,  MA ¨ http://www.w3.org/XML/Core/#Publications n Anyone  can  use  the  standard  – no  fees n Only  the  W3C  can  maintain  and  update n W3C  maintains  many  web  standards… …such  as:  HTML,  XHTML,  CSS,  PNG
14. XML  is  Flexible n No  predefined  tags… n …DTD  defines  the  grammar… n …which  means  that  XML  can  contain n Text,  Graphics,  Video  …  and  so  on. n Many  new  languages  appearing  that  are   based  on  XML. ¨ Such  as….
15. Flexibility  – XML-­based  Languages n XHTML:Extensible  HyperText  Markup  Language n MetaL:  Meta  Programming  Language n MML:  Music  Markup  Language n XBRL:  Extensible  Business  Reporting  Language n MathML:  Mathematical  Markup  Language n OML:  Weather  Observation  Definition  Format n Adex:  Newspaper  Classified  Ads  Format n AML:  Astronomical  Markup  Language n rezML:  Resume  and  Job  Listing  Markup  Lang.
16. XML  as  a  concept is  simple n Designed  as  a  common  platform  for   electronic  delivery  of  data n The  Swiss  Army  Knife  of  file  formats   n Simpler  than  SGML ¨ XML  is  actually  a  simplified  subset  of  SGML ¨ Standard  Generalized  Markup  Language ¨ SGML  &  XML  were  both  initially  intended  to   facilitate  large-­scale  electronic  publishing
17. Why  XML  and  not  SGML? n Simpler  structure ¨ Easier  to  parse…  and  therefore… ¨ …easier  to  build  software ¨ SGML  systems  are  complex  &  expensive ¨ XML-­based  systems  are  much  easier  to  build n …easier  to  transmit  on  the  Internet. n Greater  degree  of  flexibility… …with  less  complicated  grammar.
18. Can  I  parse  it  and  does  it  validate? n Properly  formatted  documents  can  be   mechanically  validated  for  correctness n Validation  ensures  proper  structure… …does  not  ensure  correct  content n All  XML-­based  languages  can  be  validated n XHTML  @  http://validator.w3.org/
19. XML  and  XSL/XSLT n Extensible  Stylesheet  Language n Like  Cascading  StyleSheets  in  HTML n Defines  the  look of  an  XML  document n …that  is,  how  individual  tags  are   presented  in,  say,  a  browser  or  software n Multiple  stylesheets  for  multiple  uses         (i.e.  print,  on-­screen,  etc.)
20. RSS:  Really  Simple   Syndication A  New  Way  to  Read  and   Receive  News  on  the  Internet
21. The  RSS  Format n Really  Simple  Syndication  …  or,   n RDF  Site  Summary   n A  way  to  provide  headlines  and  content  through   a  method  of  syndication n Exciting  new  format  being  used…   n …by  the  press  and  by  individuals  (e.g.  blogs)   n You  can  “subscribe”  to  an  RSS  news  feed.
22. RSS  Readers n A  program  designed  to  read  RSS  feeds.   n SharpReader,  Syndirella,  Radio  Userland   n Common:  3-­pane  window  (like  email)   n Also:  some  use  a  web-­based  reader   n The  reader  automatically  updates  the   feeds  on  a  regular  basis.   n Full  text  messages  vs.  Summaries
23. RSS  is  another  example  of  XML n RSS  is  an  XML-­based  language n Profusion  of  versions  and  formats ¨ 7  different  versions ¨ And  2  significantly  different  formats ¨ A  problem  with  non-­proprietary  standards n RDF  – Resource  Description  Framework
24. XML  in  Libraries What  does  XML  mean  to  the   modern  library?
25. XML  in  Libraries n Uses: ¨ Digital  Collections  /  Digital  Libraries ¨ Metadata  &  Cataloging ¨ Document  delivery ¨ Archival  storage
26. XML  &  Digital  Collections/Libraries n Storage  format  for  digital  objects n Encoded  Archival  Description  (EAD) – uses  SGML  – shift  to  XML http://www.loc.gov/ead/ n XML:  the  new  standard n Interoperability  – less  likely  obsolescence
27. XML  &  Metadata/Cataloging n Metadata  Encoding  and  Description  Standard  (METS) http://www.loc.gov/standards/mets/ n Dublin  Core  XML  Schemas http://www.dublincore.org/schemas/xmls/ n Open  Archives  Initiative  Protocol  for  Metadata   Harvesting  (OAI-­PMH) -­-­ a  schema  for  MARC  records  in  XML http://www.openarchives.org/OAI/2.0/guidelines-­ oai_marc.htm n RDF – Dublin  Core,  Open  Directory  and  General   Purpose  Catalogs http://www.w3.org/RDF/#gen-­col
28. XML  &  Archival  Storage n TEI:  Text  Encoding  Initiative using  an  SGML  encoding  scheme  that  is  maximally   expressive  and  minimally  obsolescent http://www.tei-­c.org/ n HPSS:  High  Performance  Storage  System   http://www.sdsc.edu/hpss/ n ADSM n The  Question:  Is  XML  an  Archival  Format?
29. HYPERLINKS  to  RESOURCES n http://www.w3.org/XML/ n http://www.xml.com/ n http://www.xml.com/pub/a/98/10/guide0.html n http://www.tei-­c.org/ n http://www.dublincore.org/schemas/xmls/ n http://validator.w3.org/ n http://www.ucc.ie:8080/cocoon/xmlfaq
30. That’s  all  folks! nQuestions? n Find  this  presentation  at: http://staffweb.lib.uiowa.edu/dstout/xml.htm