Transcript Oracle Object Interface CMS Evaluation Zhen Xie CERN-EP/CMC

Oracle Object Interface
CMS Evaluation
Zhen Xie
CERN-EP/CMC
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.
OCCI+OTT model
Our model: OCCI+class library
Jan 29 2002
Zhen Xie, CERN-EP/CMC
2
OCCI/OTT
Huh?…I’ll tell you next
week. This object
includes 10 other
objects and they may
include other other
objects.
Your data
model
OCCI
PObject
(abstract )
Is a
Is a
OTT
.. …
Is a
Data
Base
Is a
Is a
Is a
.. …
Your objects here
What?! My job is to
make Vincenzo’s object
persistent. He will kill
me if I change his
Jan 29 2002
original classes. Zhen Xie, CERN-EP/CMC
3
Problems of using OTT
Data model drives object model.
But we want the other way around.
 Force changes in existing code which
we cann’t afford.
 Even if we could write software from
scratch, we couldn’t afford to train
object-oriented programmers to be
data-oriented programmers.

Jan 29 2002
Zhen Xie, CERN-EP/CMC
4
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.

Jan 29 2002
Zhen Xie, CERN-EP/CMC
5
Our current prototype
PObject
(abstract )
Is a
C++ Parser
library
AST
uses
AST-SQL
interpreter
Data
Base
Jan 29 2002
PObjectHandle
<T>
knows
Vincenzo’s
T’.h file
OCCI
Middle layer
Generic
StreamIn
T(T’)
Generic
StreamOut
uses
uses
StreamIn
StreamOut
Ah! I just need to write a class T
that clones Vincenzo’s object T’ and
tell the generic Streamer what to
Zhen Xie,stream
CERN-EP/CMC
6
An example
Class aPoint_C{
public:
aPoint_C (aPoint* p):clone_(p){}
void write(OCCI::AnyData& stream){
StreamIn<float,float,float> st;
st(stream,clone_->x(), clone_->y(), clone_->z());
}
//a similar thing for read.
Private:
aPoint* clone_;
};
Jan 29 2002
Zhen Xie, CERN-EP/CMC
7
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.
Jan 29 2002
Zhen Xie, CERN-EP/CMC
8