System Integration

Dedicated to the dissemination of System Integration information

Software Layers

A systems software can be partitioned using the concept of software layers.

 

Software layers are where each ‘layer’ of a system deals with a certain function of a system which, usually, gets more and more detailed as you burrow down into the layer stack.

 

The diagram illustrates how an Internet Browser fits into a layer, I am not saying this is how the Internet is layered, it is merely a representation.

In the diagram above the system needed to display web pages on your P.C. has been split up into layers.  The top most layer, the application, is one layer.  From the application to the web page file system (where the web pages are actually stored) the ‘system’ is split into layers of software and hardware that perform similar functions.  Each layer has a logical function in the system.

 

Designing software this way allows functions that perform similar functions to be grouped together into a single layer.  If you align the layers with the expertise of the engineers you have available you harness the expertise of your staff.

 

You should take account of the ‘industry standard’ layers, i.e. how similar companies, and systems, define the layers.  They will be defined that way for a reason, usually for economic reasons, e.g. the hardware is constructed to support a certain layering split, off the shelf test equipment supports the testing of a certain layer.

 

If you get the layering system correct this will ensure high cohesion and low coupling, high cohesion and low coupling ensure that the System Integration process is easier as little information is crossing boundaries.

 

It also ensures that future upgrades are easier; if you upgrade part of the system you first integrate it into the appropriate layer then just slot the layer into the system, i.e. remove the old layer and slide the new layer in.