Oracle Object Interface

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Oracle Object Interface

• CMS Evaluation

Zhen Xie CERN-EP/CMC
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Object interface

• Object
• At database level, Oracle9i supports object by
  object-relational mapping.
• Support object identity, navigation,inheritance.
• Interface (our main concern)
• A generic interface that shields application from
  SQL and other database operations.
• OCCIOTT model
• Our model OCCIclass library

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Huh?Ill tell you next week. This object
includes 10 other objects and they may include
other other objects.
OCCI/OTT

OCCI
PObject (abstract )
Is a
Is a
Is a
Your data model
OTT
..
Is a
Is a
Is a
Data Base
..
Your objects here
What?! My job is to make Vincenzos object
persistent. He will kill me if I change his
original classes.
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Problems of using OTT

• Data model drives object model. But we want the
  other way around.
• Force changes in existing code which we cannt
  afford.
• Even if we could write software from scratch, we
  couldnt afford to train object-oriented
  programmers to be data-oriented programmers.

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Our current prototype

• Extract data model from object model using a C
  compiler front-end.
• Provide a template class library for common
  services.
• User implements a very simple wrapper class of
  the transient object class.

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Our current prototype

OCCI
PObject (abstract )
Middle layer
Is a
PObjectHandle ltTgt
Generic StreamIn
Generic StreamOut
C Parser library
AST
uses
uses
uses
knows
AST-SQL interpreter
Vincenzos T.h file
Data Base
Ah! I just need to write a class T that clones
Vincenzos object T and tell the generic
Streamer what to stream
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An example
Class aPoint_C public aPoint_C (aPoint
p)clone_(p) void write(OCCIAnyData
stream) StreamInltfloat,float,floatgt st
st(stream,clone_-gtx(), clone_-gty(),
clone_-gtz()) //a similar thing for
read. Private aPoint clone_
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Conclusions

• As a database, Oracle9i supports objects
• OCCI provides C language binding and basic
  services.
• A middle layer missing between OCCI and
  application
• OTT has data-oriented applications in C in
  mind, thus not suitable for our object-oriented
  system.
• Our prototype proves that building such a middle
  layer is not mission impossible.