原文如下：

Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. This cloud model promotes availability and is composed of five essential characteristics, three service models, and four deployment models.

NIST Special Publication 800-145 National Institute of Standards and Technology Special Publication 800-145 (Draft) 7 pages (January. 2011)

 查了很多国内的翻译，都略显粗糙，笔者尝试翻译如下，请各位指正：