Page 157 - DCAP308_OBJECT_ORIENTED_ANALYSIS_AND_DESIGN

Unit 12: System Design

Continuous Transformation Notes

A data transformation performed continuously as inputs change. It is a system in which the
outputs actively depend on changing inputs. It updates outputs frequently. One way to implement
continuous transformation is with a pipeline of functions. The steps in designing a pipeline for
a continuous transformation are as follows:

Break the overall transformation into stages performing one part of the transformation.
Define input, output and intermediate models between each pair of successive stages, as
for the batch transformation.

Differentiate each operation to obtain incremental changes to each stage. That is, propagate
the incremental effects of each change to an input through the pipeline as a series of
incremental updates.

Add additional intermediate objects for optimization.

Interactive Interface

A system dominated by external interactions. It is a system dominated by interactions between
the system and external agents, such as human or devices. The external agents are independent
of the system. The steps in designing an interactive interface are as follows:
Isolate interface classes from the application classes.
Use predefined classes to interact with external agents, if possible.

Use the state model as the structure of the program.
Isolate physical events from logical events. Often a logical event corresponds to multiple
physical events.

Fully specify the application functions that are invoked by the interface
Dynamic Simulation

It is a system that simulates evolving real-world objects. The steps in designing a dynamic
simulation are as follows:
Identify active real word objects from the class model. These objects have attributes that
are periodically updated.
Identify discrete events, which correspond to discrete interactions with the object.
Identify continuous dependencies. Real world attributes may be dependent on other real-
world attribute.
Generally a simulation driven by a timing loop at a fine time scale. Discrete events
between objects can often be exchanged as part of the timing loop.

Real Time System

A system dominated by strict timing constrains. It is an interactive system with tight time
constraints on actions. Transaction Manager is a system concerned with storing and updating
data, often including concurrent access from different physical locations. Most transaction
manages deal with multiple users who read and write data at the same time.

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