System Dynamics:
Systems dynamic (SD) approach is considered by its inventor Jay Forrester to represent the true representation of System Thinking. Here, this site considers SD as one of the quantitative methods of systems thinking. It differs than other methodologies as it deals with the quantitative representation of the cause of the present behavior of the system for the purpose of redesign a new or modified system to produce a desired behavior.
It uses a computer simulation packages as STELLA, iThink, Vensim, to represent the dynamic behavior of the system from its know parameters and variables. These systems of interaction may contain social, human, or physical elements. As mathematical models should be derived to get a reasonably accurate behavior a knowledge of specific system parameters should be determined. Many techniques are employed to get this kind of information, and integration with the present information technology can bring this methodology to its maximum utilization.
Now Systems thinking through SD methodology is spreading in USA hrough a systems learning project initiated in 1990 by Forrester and his students. Schools in other parts of the world as Europe, Australia, Asia and Latin America are adopting the same approach for colleges and schools education.

The methodology:
Forrester pointed out the difference between system thinking and system dynamics as it is used in United States and at the end of his comparison, Forrester suggested that the use of system thinking with Checkland method of analyzing problems or case studies can contribute and give more and deep understanding of the system which allows building a more precise model. He gave six steps methodology for system dynamics to define and build the system. As seen in the figure his 6 steps methodology has an iterative nature and suggests using soft system methodology as the first stage to define the system.
Systems Dynamics methodology
Examples and Applications:

You can review our representation for the steps of the simulation and analysis of the problem of childern overwieght presented in one of the articles of our information bulletin on this site, to have an idea on how this methodology is applied. Also, in inother issue of our information bulletin we presented a traffic accedint system dynamic model. The following figure gives a simulation for a simplified version of a recruting model at the human resource department at the Egyptian Glass factory in Egypt.

Simulation of Human resource process
System Analysis and Design:

System analysis and design is concerned with the investigation of an organization and the design and implementation of a computerized solution to that organization needs. To analyze a system is to identify its components (devices, people, rules and procedures) and their interrelationships in order to determine its objectives, requirements, and priorities. The analyst must find ways of representing organization as a whole system, taking into consideration any economic behavioral and technical constraints. To know more about systems analyst job from the internet click here. and visit the international institute of business analysis(IIBa).