ATLaS: A Complete Database Language for Streams Carlo Zaniolo, Haixun Wang Richard Luo,JanNei Law et

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ATLaSA Complete Database Language for Streams
Carlo Zaniolo, Haixun WangRichard Luo,Jan-Nei
Lawet al.Documentation and software downloads
http//wis.cs.ucla.edu/
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DB-Inspired Approach to Streams

• The Good
• Information-centered, high level Query languages,
  Data Independence, Optimization,
• isolate applications from details, amortize
  investment
• The Bad SQL lacks expressive power!
• New application domain ? ad-hoc extensions (by
  committee)
• Designed for secondary store ? blocking
  aggregates assumed
• The Ugly
• The secondary storage mantra is gone
• Can SQL designed for secondary store win over
  languages such as XQuery, XSLT or Hancock
  designed for the
• web and streamsand also claiming Turing
  completeness?

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A Brave New World

• Just extending SQL for streams will not do, if
• SQL remains crippled by its impotency in
  expressing applications
• and we will lose out against non-DB approaches
  since we lost our DB mantra and home field
  advantage

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A Brave New World

• User-Defined Aggregates (UDAs) are a path to
  salvation because they,
• Can be defined in SQL (rather than in a
  procedural language)
• Turn SQL into a Turing Complete (TC) language
• Fit the stream-oriented computation model like a
  glovee.g., non-blocking properties of queries
  can be characterized syntactically
• ATLaS does all that, and demonstrates the
  effectiveness of UDAs in expressing
  data-intensive applications, and delivers good
  performance.

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UDAs Initialize, Iterate, Terminate

• AGGREGATE myavg2(Next Int) Real
• TABLE state(sm Int, cnt Int)
• INITIALIZE INSERT INTO state VALUES (Next,
  1) 
• ITERATE UPDATE state SET smsmNext,
  cntcnt1
• INSERT INTO RETURN SELECT sm/cnt FROM state
• WHERE Cnt100
• UPDATE state SET sm0, cnt0
• WHERE Cnt100
• No TERMINATE ? Non-Blocking

• AGGREGATE myavg1(Next Int) Real
• TABLE state(sm Int, cnt Int)
• INITIALIZE INSERT INTO state VALUES
  (Next, 1) 
• ITERATE UPDATE state SET smsmNext,
  cntcnt1
• TERMINATE INSERT INTO RETURN SELECT sm/cnt
  FROM state

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Homework ProblemsSolutions in Two Flavors

• without windows (ATLaS is TC for both blocking
  and nonblocking functions), and
• with windows partitionrange construct
• ATLaS provides constructs to simplify the
  definition of UDAs on windows,
• But ATLaS does not support joins of windows,since
  
• a. Problems when windows are viewed as data
  sets,
• b. in SQL1999 windows are aggregate modifiers
  (OLAP),
• c. Simple solutions are already at hand in the TC
  ATLaS.
• The benefits of TC we add a new construct only
  when pros gtgt cons

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Interesting Times Ahead

• Language Design Issues
• Semi-structured information and XML
  documentscan they be viewed as streams?
• Ditto for references,
• Streams of Updates and Events, active databases
• Applications e.g., micro-climate monitoring,
  from UCLA Embedded Networked Sensors Center
• . Bridging the gap will not be easy.

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References

• Stephan Kepser A Proof of the Turing-completeness
  of XSLT and Xquery, SFB 441, University of
  Tubingen Technical Report, SFB 441, May 13,
  2002,kepser_at_sfs.uni-tuebingen.de