Resumen
The two aspects of new-generation middleware, dynamic customizability and high-level abstractions, illustrate fundamental themes for a new generation of middleware likely to be available to programmers within this decade. Dynamic customizability provides the flexibility required to adapt the middleware for resource-aware mobile applications. High-level abstractions simplify the problem of expressing complex interaction patterns by enabling application developers to specify interactions. By dynamically composing protocols in the middleware, application developers can thus address the problem of dynamic execution environments. The result will be the seamless integration of the physical world and the computational world, where every physical object is computationally active and networked. Moreover, physical devices will be more useful because their software will be able to adapt their execution environments to improve their utility while maximizing their energy efficiency.

Resumen
This article presents certain ways to simplify the development and maintenance of complex distributed software. Software executing on distributed systems represents a unique synthesis of application code and code for managing requirements such as heterogeneity, scalability, security, and availability. Separating policies and protocols provides an abstraction boundary in the spirit of abstract data types. In particular, protocols required for interactions need not be hard-coded in application code. This allows objects and protocols to be independently developed and later composed into runnable systems. Modularity and customizability are important techniques for software development. Modularity is one attraction of toolkits for distributed programming. Although both the computational power of individual processors and their interconnectivity have increased by orders of magnitude, methods for developing and maintaining distributed software have not. The increasing complexity of distributed software systems in the absence of corresponding advances in software technology fuel a perennial crisis in software. INSETS: Object-based Middleware; Actors; Reflection.