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Parsing for XML Developers

Parsing for XML Developers. Roger L. Costello 28 September 2014. Flat XML Document. You might receive an XML document that has no structure. For example, this XML document contains a flat (linear) list of Book data:.

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Parsing for XML Developers

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  1. Parsing for XML Developers Roger L. Costello 28 September 2014

  2. Flat XML Document You might receive an XML document that has no structure. For example, this XML document contains a flat (linear) list of Book data: <Books><Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Author>Gyorgy E. Revesz</Author><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher></Books>

  3. Give it structure to facilitate processing <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher></Book><Book><Title>Introduction to Graph Theory</Title><Authors><Author>Richard J. Trudeau</Author></Authors><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher></Book><Book><Title>Introduction to Formal Languages</Title><Authors><Author>Gyorgy E. Revesz</Author></Authors><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher></Book></Books> <Books><Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Author>Gyorgy E. Revesz</Author><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher></Books>

  4. That’s parsing! Parsing is taking a flat (linear) sequence of items and adding structure so that the result conforms to a grammar.

  5. Parsing <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher></Book><Book><Title>Introduction to Graph Theory</Title><Authors><Author>Richard J. Trudeau</Author></Authors><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher></Book><Book><Title>Introduction to Formal Languages</Title><Authors><Author>Gyorgy E. Revesz</Author></Authors><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher></Book></Books> <Books><Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Author>Gyorgy E. Revesz</Author><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher></Books> parse

  6. From the book: “Parsing Techniques” • Parsing is the process of structuring a linear representation in accordance with a given grammar. • The “linear representation” may be: • A flat sequence of XML elements • a sentence • a computer program • a knitting pattern • a sequence of geological strata • a piece of music • actions of ritual behavior

  7. Grammar • A grammar is a succinct description of the structure. • Here is a grammar for Books: Books →Book+Book →Title Authors Date ISBN Publisher Authors → Author+Title →textAuthor →textDate →textISBN → text Publisher →text

  8. Parsing Grammar Books → Book+Book → Title Authors Date ISBN Publisher Authors → Author+Title → textAuthor → textDate → textISBN → text Publisher → text Linear representation <Books><Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Author>Gyorgy E. Revesz</Author><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher></Books> Structured representation <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher></Book><Book><Title>Introduction to Graph Theory</Title><Authors><Author>Richard J. Trudeau</Author></Authors><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher></Book><Book><Title>Introduction to Formal Languages</Title><Authors><Author>Gyorgy E. Revesz</Author></Authors><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher></Book></Books> parser

  9. Parsing Techniques • Over the last 50 years many parsing techniques have been created. • Some parsing techniques work from the starting grammar rule to the bottom. These are called top-down parsing techniques. • Other parsing techniques work from the bottom grammar rules to the starting grammar rule. These are called bottom-up parsing techniques. • The following slides show how to apply a powerful bottom-up parsing technique to the Books example.

  10. What does “powerful” mean? • The previous slide said, … following slides show how to apply a powerful bottom-up parsing technique … • “Powerful” means the technique can be used with lots of grammars, i.e., it can be used to generate lots of different structures.

  11. Suppose we were to structure the XML from scratch. We might follow these steps: <Books><Book><Title>Parsing Techniques</Title><Authors></Authors></Book></Books> <Books><Book></Book></Books> <Books><Book><Title>Parsing Techniques</Title></Book></Books> <Books></Books> continued on next slide

  12. Follow these steps (cont.): <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date></Book></Books> <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author></Authors></Book></Books> <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors></Book></Books> continued on next slide

  13. Follow these steps (cont.): <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN></Book></Books> <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Dover Publications</Publisher></Book><Book></Book></Books> <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Dover Publications</Publisher></Book></Books> and so forth, filling in the second Book then the third Book

  14. Last step: add the last Book’s Publisher <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher></Book><Book><Title>Introduction to Graph Theory</Title><Authors><Author>Richard J. Trudeau</Author></Authors><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher></Book><Book><Title>Introduction to Formal Languages</Title><Authors><Author>Gyorgy E. Revesz</Author></Authors><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher></Book></Books> <Books><Book><Title>Parsing Techniques</Title><Authors><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author></Authors><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher></Book><Book><Title>Introduction to Graph Theory</Title><Authors><Author>Richard J. Trudeau</Author></Authors><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher></Book><Book><Title>Introduction to Formal Languages</Title><Authors><Author>Gyorgy E. Revesz</Author></Authors><Date>2012</Date><ISBN>0-486-66697-2</ISBN> </Book></Books> last step adds this

  15. Alternate view of the steps (a tree view) continued on next slide Books Books Books Books Books Books Book Book Book Book Book Authors Title Authors Title Authors Title Title Author Author Author

  16. Alternate view (cont.) continued on next slide Books Books Books Book Book Book Publisher ISBN ISBN Authors Date Authors Date Title Title Authors Date Title Author Author Author Author Author Author

  17. Alternate view (cont.) Books and so forth, filling in the second Book then the third Book Book Book Authors Title Date ISBN Publisher Author Author

  18. Last step: add the last Book’s Publisher Books Book Book Book Authors Authors Authors Title Date Title Date Title Date ISBN ISBN ISBN Publisher Publisher Author Author Author Author last step adds this Books Book Book Book Publisher Authors Authors Authors Title Date Title Date Title Date ISBN ISBN ISBN Publisher Publisher Author Author Author Author

  19. Terminology: Production Step <Books><Book><Title>Parsing Techniques</Title><Authors></Authors></Book></Books> <Books><Book></Book></Books> <Books><Book><Title>Parsing Techniques</Title></Book></Books> <Books></Books> Each step is called a production step

  20. Top down The previous slides showed the generation of the structured XML by starting from the top (root element) down to the bottom (leaf nodes).

  21. Bottom-up parsing In bottom-up parsing we work backward: from the last step to the first step.

  22. Let’s begin … • One production step must have been the last and its result must be visible in the linear representation. • We recognize the rule Publisher →textinThis gives us the final step in the production process (and the first step in bottom-up parsing): <Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Author>Gyorgy E. Revesz</Author><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher>

  23. Next We recognize the rule ISBN → text inThis gives us the next-to-last step in the production process (and the second step in bottom-up parsing): <Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Author>Gyorgy E. Revesz</Author><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher>

  24. Next We recognize the rule Date → text inThis gives us the third step in bottom-up parsing: <Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Author>Gyorgy E. Revesz</Author><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher>

  25. Next We recognize the rule Author → text inThis gives us the fourth step in bottom-up parsing: <Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Author>Gyorgy E. Revesz</Author><Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher>

  26. Next We recognize the rule Authors →Author+inThis gives us the fifth step in bottom-up parsing: <Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Authors><Author>Gyorgy E. Revesz</Author> </Authors> <Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher>

  27. Next We recognize the rule Title →textinThis gives us the sixth step in bottom-up parsing: <Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Title>Introduction to Formal Languages</Title><Authors><Author>Gyorgy E. Revesz</Author> </Authors> <Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher>

  28. Next We recognize the rule Book → Title Authors Date ISBN Publisher inThis gives us the seventh step in bottom-up parsing: <Title>Parsing Techniques</Title><Author>Dick Grune</Author><Author> Ceriel J.H. Jacobs</Author><Date>2007</Date><ISBN>978-0-387-20248-8</ISBN><Publisher>Springer</Publisher><Title>Introduction to Graph Theory</Title><Author>Richard J. Trudeau</Author><Date>1993</Date><ISBN>0-486-67870-9</ISBN><Publisher>Dover Publications</Publisher><Book><Title>Introduction to Formal Languages</Title><Authors><Author>Gyorgy E. Revesz</Author> </Authors> <Date>2012</Date><ISBN>0-486-66697-2</ISBN><Publisher>Dover Publications</Publisher> </Book>

  29. See the algorithm? See how we are working backwards, from the bottom grammar rules up to the starting grammar rule? In the process we are adding structure to the flat (linear) XML – neat!

  30. Terminology: Reduction • In bottom-up parsing a collection of symbols are recognized as derived from a symbol. For example, Title, Authors, Date, ISBN, Publisheris derived from Book: Book Title Authors Date ISBN Publisher • Title, Authors, Date, ISBN, Publisheris reduced to Book • So the bottom-up parsing process is a reduction process.

  31. Build your own bottom up parser! You now have enough knowledge that you can go off and build your own bottom-up parser.

  32. I implemented a bottom-up parser • I used XSLT to implement a bottom-up parser. • If you would like to give my implementation a go, here is the XSLT program and a sample flat (linear) input XML document: • http://www.xfront.com/parsing-techniques/bottom-up-parser/bottom-up-parser-for-Books.xsl • http://www.xfront.com/parsing-techniques/bottom-up-parser/Books.xml

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