Comprehensive and Detailed Explanation
Gap Analysis is an ADM technique used in Phases B, C, and D of the TOGAF ADM (Business, Information Systems, and Technology Architectures).
Its main purpose is to validate the target architecture by comparing the Baseline Architecture with the Target Architecture and identifying:
* Gaps (building blocks or capabilities present in the target but missing in the baseline).
* Overlaps (building blocks duplicated across architectures).
* Conflicts (inconsistencies between baseline and target).
The output of Gap Analysis provides:
* A validated Target Architecture.
* A set of identified gaps that must be addressed by future work packages in Phase E: Opportunities and Solutions.
Therefore, the purpose of Gap Analysis is best expressed as to validate the architecture (Answer D).
Why the other options are incorrect
* A. Establish quality metrics for the architecture: This is part of performance management and governance, not Gap Analysis.
* B. Identify non-functional requirements: Non-functional requirements are captured through requirements management and stakeholder analysis, not Gap Analysis.
* C. Determine service levels: Service levels are typically defined in SLAs and operational models, not through Gap Analysis.
References
* The Open Group, TOGAF Standard, Version 9.2, Part III: ADM Guidelines & Techniques - Gap Analysis.
* The Open Group, TOGAF 9 Certified Study Guide - explains the role of Gap Analysis in validating architectures and identifying work package inputs.