What is an IT System

The purpose of this blog, as started earlier, is to “Design a Resilient Core banking IT system”.  A secondary objective is to extract the principle of IT systems resiliency.  Having defined Resilience and understood its importance let us now understand IT systems.  Understanding what makes an IT systems will help us address our main issue which is:  What set of factors taken together help build a resilient IT system.

Let us start form the fundamentals.

Let us first address as to, "What is a system?"

A system is a set of interacting elements that exhibit a specific behavior under a specific set of conditions when subjected to specific stimuli.

Extending the above definition, an IT system consists of a collection of "interacting Programs" that exhibit a specific behavior (output) when faced with a given input (i.e. when subjected to a specific stimuli).

To get a better understanding of IT systems let us delve deeper into understanding the function of a program.

Programs are instructions to machines (computers) to manipulate values.

For programs to achieve something useful the values must have some meaning to the users i.e. they must represent something that happens in the real world.  

Because these values are “representative’ of some “thing” in the real world, therefore the rules by which they are manipulated must also be the same as the rules that are applicable to the real world “thing”.

Of course you can always write programs that manipulate values in ways and means that have no linkages to real world phenomena.  But if you do so then the question to ask is, what purpose does such a program serve?

For computer programs to be useful these programs need to “model” something useful in real life.  Successful modeling requires  (1) that we identify the elements  (or “things”) whose behavior we want to study,  (2) that we identify the behaviors they exhibit under different conditions and (3) that we identify the different conditions under which we want to study the behavior of these elements.

We can now advance our definition of IT systems as not just merely collection of programs but as a collection of programs that model real world phenomena. Each "program" can be thought of as modeling a real world element.

Elaborating Further: An IT system is a collection of programs that model the behavior of real world elements under different conditions. An IT system simulates the real world system by changing the observable values of IT elements (behaviors) as the inputs (conditions) are modified.

Each Program in the IT system can then be thought of as representing and entity in the real world. In other words each IT-program can be thought of as representing a real world object. There is a special technique called the object-oriented design that provides us the necessary nomenclature and rules to represent the real world objects into IT-programs.  There are also special languages called object oriented languages that allow us to easily write programs such that each program represents an object.

This understanding of IT systems is sufficient for us to study the problem of resilience in IT systems.