A.1 Overview

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In this appendix, we describe the following principles applied throughout the design of the ACE wrapper facades:

• Use wrapper facades to enhance type safety.

• Simplify for the common case.

• Use hierarchies to enhance design clarity and extensibility.

• Hide platform differences whenever possible.

• Optimize for efficiency.

We document these principles here in abbreviated pattern form so you can understand the forces that shape ACE and apply them to your own frameworks and applications. The context for all these principles is developing wrapper facades for system-level IPC and concurrency mechanisms. Portability and efficiency are chief concerns in ACE, so we make tradeoffs that may not be necessary or appropriate in higher-level object-oriented application frameworks.

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