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   <TITLE>OTL 4.0, OTL classes</TITLE>
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<H1 ALIGN=CENTER>OTL 4.0, OTL classes</H1>

<H1><A NAME="otl_class"></A>OTL classes</H1>

<P>OTL 4.0 was built more like an appliance rather than just another traditional
C++ class library: more complex [than in C++ libraries] internals but a
very simple and self-contained interface on the outside. OTL 4.0 was influenced
a lot by the paradigm of generic programming promoted by the author of
the Standard Template Library (STL), Alexander Stepanov. The STL was adopted
as part of the C++ standard of 1998.</P>

<P>OTL 4.0 has a completely template framework which implements the <A HREF="otl3_str.htm">OTL
stream concept</A>. The framework is comprised of template classes and
inline functions. The template classes have ordinary classes as parameters.
The parameters of the <I>class </I>type form a set of classes that provide
the framework with an actual implementation of a database API.</P>

<P>Such an implementation is called the <I>OTL-adaptor </I>for a given
database API. In OTL 4.0, OTL-adaptors for the following database APIs
were implemented:</P>

<UL>
<LI>Oracle Call Interface for Oracle 7 (OCI7)</LI>

<LI>Oracle Call Interface for Oracle 8/8i (OCI8/8i)</LI>

<LI>Open Data Base Connectivity (ODBC)</LI>

<LI>DB2's Call Level Interface (CLI)</LI>
</UL>

<P>The adaptors are low level / thin wrappers around the database APIs.
The adaptor classes are substituted directly into the framework, so the
OTL 4.0 works <I>almost</I> at the level of the database APIs because the
OTL templates get expanded literally into the database API function calls.</P>

<P>The template framework and an OTL-adaptor substituted into the framework
generate an instance of the following concrete OTL classes:</P>

<UL>
<LI><A HREF="otl3_stream_class.htm">otl_stream</A></LI>

<LI><A HREF="otl3_connect_class.htm">otl_connect</A></LI>

<LI><A HREF="otl3_exception_class.htm">otl_exception</A></LI>
</UL>

<P>These classes, together with the <A HREF="otl3_long_string.htm">otl_long_string</A>
class, form a complete API for a given database. </P>

<P>This kind of generic approach makes the OTL 4.0 an extendable library.
Possible candidates to extend the OTL to may be Sybase (DB or CT library)
or Informix. </P>

<P>
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<P>Copyright &copy; 1996, 2008, Sergei Kuchin, email: <A HREF="mailto:skuchin@aceweb.com">skuchin@aceweb.com</A>,
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