We are interested in the class of systems for which the satisfaction of code dependencies is a dynamic process rather than one which is determined purely at load-time. Examples include dynamic delegation, mobile code and agent systems. Such systems exhibit properties which are not well-captured by current typing models. We describe a system of ionic object types which capture these effects and allow them to be analysed within a standard object type framework. We show how ionic types improve the modeling of various forms of dynamic object completion including certain aspects of security checking, delegation and method update, contrast them with other approaches to the same problems, and sketch a possible ionic extension to Java.
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