The technique known as gap analysis is widely used in the TOGAF Architecture Development Method (ADM) to validate an architecture that is being developed. The basic premise is to highlight a shortfall between the Baseline Architecture and the Target Architecture; that is, items that have been deliberately omitted, accidentally left out, or not yet defined.
A key step in validating an architecture is to consider what may have been forgotten. The architecture must support all of the essential information processing needs of the organization. The most critical source of gaps that should be considered is stakeholder concerns that have not been addressed in prior architectural work.
Potential sources of gaps include:
Business domain gaps:
People gaps (e.g., cross-training requirements)
Process gaps (e.g., process inefficiencies)
Tools gaps (e.g., duplicate or missing tool functionality)
Facilities gaps (buildings, office space, etc.)
Data domain gaps:
Data not of sufficient currency
Data not located where it is needed
Not the data that is needed
Data not available when needed
Data not created
Data not consumed
Data relationship gaps
Applications impacted, eliminated, or created
Technologies impacted, eliminated, or created
27.2 Suggested Steps
The suggested steps are as follows:
Draw up a matrix with all the Architecture Building Blocks (ABBs) of the Baseline Architecture on the vertical axis, and all the ABBs of the Target Architecture on the horizontal axis.
Add to the Baseline Architecture axis a final row labeled "New", and to the Target Architecture axis a final column labeled "Eliminated".
Where an ABB is available in both the Baseline and Target Architectures, record this with "Included" at the intersecting cell.
Where an ABB from the Baseline Architecture is missing in the Target Architecture, each must be reviewed. If it was correctly eliminated, mark it as such in the appropriate "Eliminated" cell. If it was not, an accidental omission in the Target Architecture has been uncovered that must be addressed by reinstating the ABB in the next iteration of the architecture design - mark it as such in the appropriate "Eliminated" cell.
Where an ABB from the Target Architecture cannot be found in the Baseline Architecture, mark it at the intersection with the "New" row as a gap that needs to filled, either by developing or procuring the building block.
When the exercise is complete, anything under "Eliminated" or "New" is a gap, which should either be explained as correctly eliminated, or marked as to be addressed by reinstating or developing/procuring the function.
Figure 27-1 shows an example analysis for ABBs that are services from the Network Services category of the Technical Reference Model (TRM), and shows a number of services from the Baseline Architecture missing from the Target Architecture.
Downloads of TOGAF®, an Open Group Standard, are available under license from the TOGAF information web site. The license is free to any organization wishing to use the TOGAF standard entirely for internal purposes (for example, to develop an information system architecture for use within that organization). A book is also available (in hardcopy and pdf) from The Open Group Bookstore as document G116.