Business-IT alignment has been a top research topic for three decades now andconsistently ranks high on CIO priorities and concerns. In spite of its seemingadvantages, sustainable business-IT alignment remains elusive in practice. This canbe attributed to the language and knowledge gaps which impede mutualunderstanding between business and IT stakeholders. It can also be attributed to thelimitations imposed by approaching alignment solely from a strategic perspective.This thesis argues for an ontology-based framework that bridges the language andknowledge gaps through closer interaction between business and IT stakeholdersthroughout the software development and project management lifecycles, especiallyat the requirements engineering stage.Attempts at achieving sustainable business-IT alignment predominantly focus onstrategic alignment and have not been successful for various reasons. Firstly, drivingdown alignment initiatives to the operational and tactical levels is challenging.Secondly, it is difficult to operationalize the metrics used for evaluating alignmentmaturity at strategic levels. These limitations are less pronounced at the functionallevels of an organization. It is at these levels that business strategies are executed andinteraction between business and IT personnel is most frequent. The interactionbetween business and IT stakeholders in the execution of IT projects presents anopportunity that can be leveraged to drive alignment maturity.The proposed framework is discussed in terms of its underpinning hypotheses,workflows, tool design and implementation, its use with a third party framework andtool. Antecedents to operational and tactical alignment such as quality, reuse,communication, learning, and shared understanding, are proposed as a practicalmeans of achieving sustainable alignment maturity. The framework is applied to realworld,business-critical projects in a top global financial services organization andvalidated using descriptive statistical analysis and structural equation modellingtechniques.Contributions made through the study are highlighted. This includes the AlignmentForces Model which unifies the proposed framework and its support tool withinsoftware development and project management lifecycles. The Alignment Forcesmodel and how it can be applied in practice is presented. Results of the quantitativedata analyses indicate support for the arguments for the framework towardsimproving business-IT alignment, however with some limitations. Results alsoindicate support for the hypotheses for the antecedents to sustainable alignmentmaturity at lower organizational levels put forward. Finally, suggestions on furtheringthe study, addressing its limitations, and refining the framework and tool arearticulated.