Whenever a resource allocation fails although enough free capacity being available, fragmentation is easily spotted as cause. But how the fragmentation in a system requiring continuous allocations like time schedules or memory can be quantified is hardly analyzed. A Grid environment using advance reservation even combines two-dimensions: time and resource dimension. In this paper a new way to measure the fragmentation of a system in one dimension is proposed. This measure is then extended to incorporate also the second dimension. Extensive simulations showed that the proposed fragmentation measure is a good indicator of the state of the system. 1

This paper decomposes the callback solution proposed in [Hickey] to show all of the patterns involved in transforming a simple solution for having two separate objects talk to each other to a sophisticated callback solution. After exposing all of the patterns in Hickey's callbacks, the paper shows how the decomposition exposes a decision point where a more common pattern could be applied. By applying this pattern, the solution evolves into a different callback library that, while slightly less efficient, is simpler and more flexible than the callbacks presented in [Hickey]. INTRODUCTION Callbacks are most easily described in terms of the telephone system. A function call is analogous to calling someone on a telephone, asking her a question, getting an answer, and hanging up; adding a callback changes the analogy so that after asking her a question, you also give her your name and number so she can call you back with the answer. In this paper, the original caller is the client, and ...