The prevalence and advancements of existing context-aware applications are limited in their support of personalization for the user. The increase in the use of context-aware technologies has sparked growth in assistive applications and there is now a need to enable the adaptation of such technologies to reflect the changes in user behaviors. This paper describes the conceptualization and development of a personalization mechanism that can be integrated into a context-aware application for the purposes of providing an adaptable, mobile-based service to a user. We highlight the use of an ontological User Profile Model to provide a detailed representation of a user for use within adaptive applications. Special emphasis is placed on the use of rule-based reasoning using the Semantic Web Rule Language (SWRL). The paper details how these rules are created and used alongside the User Profile for the purposes of application personalization. We present a case study to illustrate the use of SWRL within the User Profile Model. Specifically, the case study focuses on providing personalized travel assistance to older users, with the use of self-service ticket machines via an 'on-demand' context-aware smart-phone.