Given the heterogeneity of healthcare software systems, data from each system is often incompatible inhibiting interoperability. To enable the sharing and exchange of healthcare information interoperability standards must be adhered to. Health Level Seven (HL7) is the international standards organisation that promotes and enforces the standardisation of electronic healthcare information to facilitate its exchange and management. Incorporating HL7 functionality into existing applications requires significant modification and intrusive extensions. Using aspect-oriented programming (AOP), we can introduce HL7 functionality into existing applications without the requirement for refactoring or modification. HL7 data formatting affects multiple parts of an application and hence is a ldquocrosscut-ting concernrdquo. These concerns which entwine with base functionality introduce complexity and reduce modularity. A second benefit of AOP is its advanced modularisation capabilities which are capable of modularising ldquocrosscut-ting concernsrdquo. We illustrate the benefits of using AOP in HL7 by example and measure the effects of the approach on healthcare applications.

Handling context is required for applications to dynamically and appropriately adapt to their changing environment. Incorporating context into applications involves the consideration of a set of concerns related to the handling of various context types and the adaptation of the application behaviour relative to the current context. These concerns are usually heavily tangled with the base code of the applications, resulting in code that is badly modularised and therefore is hard to understand, manage and modify. We propose a modularised design for the handling of different kinds of context using aspect-oriented programming techniques. We demonstrate that a context-aware application built in this manner exhibits improved modularity, with corresponding improvements in comprehensibility, manageability and maintainability. The proposed aspect-oriented modularisation is evaluated against traditional object-oriented techniques, and also against a popular context framework, using metrics indicating coupling, cohesion and complexity. The results show the positive effect of modular code on context-aware applications by quantitatively illustrating the improvements in modularisation quality factors