A1258690283CaZpc

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4/1
about XML/Xquery/RDF
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Why XML

• XML is the confluence of several factors
• The Web needed a more declarative format for
  data, trying to describe the meaning of the data
• Documents needed a mechanism for extended tags
• Database people needed a more flexible
  interchange format
• Original expectation
• The whole web would go to XML instead of HTML
• Todays reality
• Not so But XML is used all over under the
  covers

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(No Transcript)
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An XML Document Example

• ltimdbgt
• ltshow year1993gt
• lttitlegtFugitive, Thelt/titlegt
• ltreviewgt
• ltsuntimesgt
• ltreviewergtRoger
  Ebertlt/reviewergt gives ltratinggttwo thumbs
• uplt/ratinggt! A fun action
  movie, Harrison Ford at his best.
• lt/suntimesgt
• lt/reviewgt
• ltreviewgt
• ltnytgtThe standard hollywood
  summer movie strikes back.lt/nytgt
• lt/reviewgt
• ltbox_officegt183,752,965lt/box_officegt
• lt/showgt
• ltshow year1994gt
• lttitlegtX Files,Thelt/titlegt
• ltseasonsgt4lt/seasonsgt
• lt/showgt
• lt/imdbgt

Mixed Content
Attribute
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XML Terminology

• tags book, title, author,
• start tag ltbookgt, end tag lt/bookgt
• elements ltbookgtltbookgt,ltauthorgtlt/authorgt
• elements are nested
• empty element ltredgtlt/redgt abbrv. ltred/gt
• an XML document single root element

well formed XML document if it has matching tags
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More XML Attributes

• ltbook price 55 currency USDgt
• lttitlegt Foundations of Databases lt/titlegt
• ltauthorgt Abiteboul lt/authorgt
• ltyeargt 1995 lt/yeargt
• lt/bookgt

Attributes are single-valued --No
guidance on when to use them
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More XML Oids and References
Object identifiers

• ltperson ido555gt ltnamegt Jane lt/namegt lt/persongt
• ltperson ido456gt ltnamegt Mary lt/namegt
• ltchildren
  idrefo123 o555/gt
• lt/persongt
• ltperson ido123 mothero456gtltnamegtJohnlt/namegt
• lt/persongt

oids and references in XML are just syntax
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HTML vs. XML

• lth1gt Bibliography lt/h1gt
• ltpgt ltigt Foundations of Databases lt/igt
• Abiteboul, Hull, Vianu
• ltbrgt Addison Wesley, 1995
• ltpgt ltigt Data on the Web lt/igt
• Abiteoul, Buneman, Suciu
• ltbrgt Morgan Kaufmann, 1999

• ltbibliographygt
• ltbookgt lttitlegt Foundations lt/titlegt
• ltauthorgt Abiteboul lt/authorgt
• ltauthorgt Hull lt/authorgt
• ltauthorgt Vianu lt/authorgt
• ltpublishergt Addison Wesley
  lt/publishergt
• ltyeargt 1995 lt/yeargt
• lt/bookgt
• lt/bibliographygt

Self-describing -Schema info part of the
data -Good for data exchange (albeit
baroque for storage)
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lth1gt Bibliography lt/h1gt ltpgt ltigt Foundations of
Databases lt/igt Abiteboul, Hull, Vianu
ltbrgt Addison Wesley, 1995 ltpgt ltigt Data on
the Web lt/igt Abiteoul, Buneman, Suciu
ltbrgt Morgan Kaufmann, 1999
ltbibliographygt ltbookgt lttitlegt Foundations
lt/titlegt ltauthorgt Abiteboul
lt/authorgt ltauthorgt Hull
lt/authorgt ltauthorgt Vianu
lt/authorgt ltpublishergt Addison
Wesley lt/publishergt ltyeargt 1995
lt/yeargt lt/bookgt lt/bibliographygt
HTML describes presentation
XML describes content
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Why are Database folks so excited about XML?

• XML is just a syntax for (self-describing) data
• This is still exciting because
• No standard syntax for relational data
• With XML, we can
• Translate any legacy data to XML
• Can exchange data in XML format
• Ship over the web, input to any application

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XML ? machine accessible meaning
Jim Hendler
This is what a web-page in natural language
looks like for a machine
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XML ? machine accessible meaning
Jim Hendler
XML allows meaningful tags to be added toparts
of the text
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XML ? machine accessible meaning
Jim Hendler
But to your machine, the tags look like this.
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XML ? machine accessible meaning
Jim Hendler
Schemas help.
lt CV gt
by relating common termsbetween documents
private
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But other people use other schemas
Jim Hendler
Someone else has one like this.
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But other people use other schemas
Jim Hendler
lt CV gt
which dont fit in
private
Moral There is still need for
ontology mapping..
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The X-standards

• XML an on-the-wire representation for data
• Xquery a query language for XML
• Xschema a schema description language for XML
  data
• RDF a language for meta-data description
• WSDL/SOAP/UDDI languages for describing services

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lth1gt Bibliography lt/h1gt ltpgt ltigt Foundations of
Databases lt/igt Abiteboul, Hull, Vianu
ltbrgt Addison Wesley, 1995 ltpgt ltigt Data on
the Web lt/igt Abiteoul, Buneman, Suciu
ltbrgt Morgan Kaufmann, 1999
ltbibliographygt ltbookgt lttitlegt Foundations
lt/titlegt ltauthorgt Abiteboul
lt/authorgt ltauthorgt Hull
lt/authorgt ltauthorgt Vianu
lt/authorgt ltpublishergt Addison
Wesley lt/publishergt ltyeargt 1995
lt/yeargt lt/bookgt lt/bibliographygt
HTML describes presentation
XML describes content
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XML Dialect pot pourri

• Extensible Financial Reporting Markup Language
  (XFRML),
• eXtensible Business Reporting Language (XBRL),
• MusicXML,
• Spacecraft Markup Language (SML),
• Bank Internet Payment System (BIPS),
• Bioinformatic Sequence Markup Language (BSML),
• Biopolymer Markup Language (BIOML),
• Open Catalog Format (OCF),
• Chemical Markup Language (CML),
• Electronic Business XML Initiative (ebXML),
• Open Trading Protocol (OTP),
• FinXML, Financial Information eXchange protocol
  (FIX),
• RecipeML, CVML,
• XML Bookmark Exchange Language (XBEL),
• Scalable Vector Graphics (SVG),
• NewsML,
• DocBook,
• Real Estate Listing Markup Language (RELML), . . .

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XML vs. Relational Data

• XML is meant as a language that supports both
  Text and Structured Data
• Conflicting demands...
• XML supports semi-structured data
• In essence, the schema can be union of multiple
  schemas
• Easy to represent books with or without prices,
  books with any number of authors etc.
• XML supports free mixing of text and data
• using the PCDATA type
• XML is ordered (while relational data is
  unordered)

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XML Data Model
imdb
show
title
review
review
_at_year
Fugitive, The
1993
suntimes
nyt

rating
reviewer
two...
gives
Roger Ebert

• Check http//www.w3.org/XML/ for more details

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DTDs
Notice that DTD is not In XML syntax ?
lt!DOCTYPE paper lt!ELEMENT paper
(section)gt lt!ELEMENT section ((title,section)
text)gt lt!ELEMENT title (PCDATA)gt
lt!ELEMENT text (PCDATA)gt gt
Semi- structured
ltpapergt ltsectiongt lttextgt lt/textgt lt/sectiongt
ltsectiongt lttitlegt lt/titlegt ltsectiongt
lt/sectiongt
ltsectiongt lt/sectiongt
lt/sectiongt lt/papergt
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XML Schemas

• More recent proposal (with XML syntax)
• unifies previous schema proposals
• generalizes DTDs
• uses XML syntax
• two documents structure and datatypes
• http//www.w3.org/TR/xmlschema-1
• http//www.w3.org/TR/xmlschema-2

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XML Schema
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RDF Meta-data Standard for Web

• ltrdfDescription aboutwww.mypage.comgt
• ltaboutgt birds, butterflies, snakes
  lt/aboutgt
• ltauthorgt ltrdfDescriptiongt
• ltfirstnamegt John
  lt/firstnamegt
• ltlastnamegt Smith
  lt/lastnamegt
• lt/rdfDescriptiongt
• lt/authorgt
• lt/rdfDescriptiongt

Goodol semantic networks..?
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Xquery Resources

• XQuery 1.0 An XML Query Language
• W3C Working Draft 20 December 2001
• XML Query Use Cases
• W3C Working Draft 20 December 2001
• Microsoft .Net Xquery Language Demo
• http//131.107.228.20/
• http//support.x-hive.com/xquery/index.html
• Supports querying on the documents described in
  the W3C Use Cases
• Xquery Tutorial by Fankhauser Wadler
• www.research.avayalabs.com/user/wadler/papers/xque
  ry-tutorial/ xquery-tutorial.pdf

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10/24
Today Xquery discussion Semantic
Web standards

• --Exam 1 returned (both versions)
• --Project 2 due on Wednesday
• --Homework 3 started (will be closed shortly)
• --Approximate schedule of topics put up

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Exam 1 Stats

• In-class
• Avg 44 Max 62 Min 32 Stdev 12.7
• Grads 49/62/33/9.8
• UG 34/53/16/12.6

• At-home
• Avg 53Max 63 Min 32.5 Stdev 8.18
• Grads 56.8/63/49/4.75
• UG 48.4/59/32.5/9.69

All happy families are happy alike, each unhappy
family is unhappy in its own way
All correct answers are correct alike, each
incorrect answer is incorrect in its own way
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Querying XML

• Requirements
• Need to handle lack of schema.
• We may not know much about the data, so we need
  to navigate the XML.
• Need to support both information retrieval and
  SQL-style queries.
• Ordered vs. un-ordered XML
• Human readable
• like SQL? ?
• Candidates
• Many based on conflicting requirements
• XSL Makes IR folks happy
• XML-QL Makes DB folks happy
• Xquery W3Cs attempt to make everybody (un)happy

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http//support.x-hive.com/xquery/index.html
You will be asked to play with it in homework
3 qn 4
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FLoWeR Expressions

• Xquery queries are made up of FLWR expressions
  that work on paths
• For binds variables to nodes
• Let computes aggregates
• Where applies a formula to find matching elements
• Return constructs the output elements
• Path expressions are of the form
• element//element/elementattribvalue

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Comparison to SQL

• Look at the use case description on Xquery manual
• Supports all (?) SQL style queries (with
  different syntax of course) default queries in
  the demo
• Has support for
• constructionoutputting the answers in
  arbitrary XML formats (use case XMP )
• path expressions --- navigating the XML tree
  (use case seq)
• Simple text queries use case text
• Allows queries on Tag elements
• Removes the data/meta-data barrier in queries
• For each book that has at least one author, list
  the title and first two authors, and an empty
  "et-al" element if the book has additional
  authors. XMP use case 6

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DTD for http//www.bn.com/bib.xml

• lt!ELEMENT bib (book )gt
• lt!ELEMENT book (title, (author editor ),
  publisher, price )gt
• lt!ATTLIST book year CDATA REQUIRED gt
• lt!ELEMENT author (last, first )gt
• lt!ELEMENT editor (last, first, affiliation )gt
• lt!ELEMENT title (PCDATA )gt
• lt!ELEMENT last (PCDATA )gt
• lt!ELEMENT first (PCDATA )gt
• lt!ELEMENT affiliation (PCDATA )gt
• lt!ELEMENT publisher (PCDATA )gt
• lt!ELEMENT price (PCDATA )gt

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Example Query
Query
Result

• ltbibgt
• for b in /bib/book
• where b/publisher "Addison-Wesley"
• and b/_at_year gt 1991
• return ltbook year b/_at_year gt
• b/title
• lt/bookgt
• lt/bibgt
• For all books after 1991,
• return with Year changed from
• a tag to an attribute

ltbibgt ltbook year"1994"gt lttitlegtTCP/IP
Illustratedlt/titlegt lt/bookgt ltbook
year"1992"gt lttitlegtAdvanced Programming in
the Unix environmentlt/titlegt lt/bookgt lt/bibgt
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Example Query (2)

• Return the books that cost more at amazon than
  fatbrain
• Let amazon document(http//www.amazon.com/book
  s.xml),
• Let fatbrain document(http//www.fatbrain.com/
  books.xml)
• For am in amazon/books/book,
• fat in fatbrain/books/book
• Where am/isbn fat/isbn
• and am/price gt fat/price
• Return ltbookgt am/title, am/price, fat/price
  ltbookgt

Join
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XML frenzy in the DB Community

• Now that XML is there, what can we do with it?
• Convert all databases from Relational to XML?
• Or provide XML views of relational databases?
• Develop theory of native XML databases?
• Or assume that XML data will be stored in
  relational databases..
• Issues What sort of storage mechanisms? What
  sort of indices?

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XML middleware for Databases
RDBMS
On the internet, nobody needs to know that you
are a dog

• XML adapters (middle-ware) received significant
  attention in DB community
• SilkRoute (ATT)
• Xperanto (IBM)
• Issues
• Need to convert relational data into XML
• Tagging (easy)
• Need to convert Xquery queries into equivalent
  SQL queries
• Trickier as Xquery supports schema querying