This article, Part 4 and last in the series, describes the fifth of six strategies for grid application enablement. At this level a program becomes multiple instances of a service subroutine callable in parallel by a client through some grid middleware. The article explains characteristics of applications at this level, as well as what the program developer must, should, and can optionally do to achieve and exploit this level. A major objective is to have the application as middleware agnostic as possible.