The paper considers the small-world phenomenon in two contexts, ubiquitous computing and security. We argue that small-world properties emerge in ubicomp systems due to their natural occurrence in human-centered networks and their meaning as a system design principle. The relationship of small worlds and security is examined from two viewpoints. First, results on the security of small-world networks are reviewed. Second, we look into how small-world properties are obstacles to, or can be helpful in maintaining security guarantees. We then give an example of how to improve the communication security in large-scale, self-organizing networks.

A new kind of attribute grammars, called higher order attribute grammars, is defined. In higher order attribute grammars the structure tree can be expanded as a result of attribute computation. A structure tree may be stored in an attribute. The term higher order is used because of the analogy with higher order functions, where a function can be the result or parameter of another function. A relatively simple method, using OAGs, is described to derive an evaluation order on the defining attribute occurrences which comprises all possible direct and indirect attribute dependencies. As in OAGs, visit-sequences are computed from which an efficient algorithm for attribute evaluation can be derived.