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9.3) Odapter/OpenODB: Odapter Object Model




Description

This article is from the Object-Oriented Technology FAQ, by Bob Hathaway rjh@geodesic.com with numerous contributions by others.

9.3) Odapter/OpenODB: Odapter Object Model

The Odapter object model is based on three key
concepts - objects, types and functions.
* Objects are a combination of data and
behavior (functions). Figure 2 is an example of an
object.
* Types are dynamic templates allowing you to
group together similar components or objects.
* Functions define the attributes,
relationships and behavior of objects. Odapter
supports four types of user-defined functions:

Stored functions define attributes and
relationships that are stored in the database. In
Figure 2, flightno is a stored function. The
functions aircraft and crew are also stored
functions with user-defined results.

SQL-based functions allow you to access existing
relational tables with Odapter's object-oriented
model. In Figure 2, citypair is an SQL-based
function accessing values from an existing
relational table.

OSQL-based functions define attributes and
relationships that are derived or calculated with
OSQL statements. In Figure 2, delay and depart are
OSQL-based functions. Delay calculates changes in
arrival and departure times based upon events that
disrupt the schedule; depart handles the update of
functions related to departure and transitions the
flight from OnGround to InAir.

External functions are a reference to code or data
stored outside of Odapter. In Figure 2, cancel is
an external function that executes code outside of
Odapter to free up resources no longer assigned to
the flight.

 

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