11.4 Transform Mapping (Analysis)

	A structure chart is produced by the conversion of a DFD diagram; this conversion is described as 'transform
	mapping (analysis)'.

It is applied through the 'transforming' of input data flow into output data flow.

	Transform analysis establishes the modules of the system, also known as the primary functional components,
	as well as the inputs and outputs of the identified modules in the DFD.

Transform analysis is made up of a number of steps that need to be carried out.

The first one is the dividing of the DFD into 3 parts:

Input

Logical processing

Output

	The 'input' part of the DFD covers operations that change high level input data from physical to logical form
	e.g. from a keyboard input to storing the characters typed into a database.

Each individual instance of an input s called an 'afferent branch'.

11.4 Transform Mapping (Analysis)

The 'output' part of the DFD is similar to the 'input' part in that it acts as a conversion process.

	However, the conversion is concerned with the logical output of the system into a physical one e.g. text stored
	in a database converted into a printed version through a printer.

Also, similar to the 'input', each individual instance of an output is called as 'efferent branch'.

The remaining part of a DFD is called the central transform.

	Once the above step has been conducted, transform analysis moves onto the second step; the structure chart
	is established by identifying one module for the central transform, the afferent and efferent branches.

These are controlled by a 'root module' which acts as an 'invoking' part of the DFD.

In order to establish the highest input and output conversions in the system, a 'bubble' is drawn out.

		In other words, the inputs are mapped out to their outputs until an output is found that cannot be traced
		back to its input.

	Central transforms can be classified as processes that manipulate the inputs/outputs of a system e.g. sorting
	input, prioritizing it or filtering data.

	Processes which check the inputs/outputs or attach additional information to them cannot be classified as
	central transforms.

11.4 Transform Mapping (Analysis)

	Inputs and outputs are represented as boxes in the first level structure chart and central transforms as single
	boxes.

	Moving on to the third step of transform analysis, sub-functions (formed from the breaking up of high-level
	functional components, a process called 'factoring') are added to the structure chart.

	The factoring process adds sub-functions that deal with error-handling and sub-functions that determine the
	start and end of a process.

	Transform analysis is a step by step approach that maps a DFD with transform flow characteristics into
	specific architectural style. These steps are as follows:

Step1: Review the fundamental system model

Step2: Review and refine DFD for the SW

Step3: Assess the DFD in order to decide the usage of transform or transaction flow.

Step4: Identify incoming and outgoing boundaries in order to establish the transform center.

Step5: Perform "first-level factoring".

Step6: Perform "second-level factoring".

Step7: Refine the first-iteration architecture using design heuristics for improved SW quality.