Simple answer: both. Zend Framework provides all the components required for most web applications in a single distribution. But Zend Framework components are also loosely coupled, making it easy to use just a few components in a web application- even alongside other frameworks! Using this use-at-will architecture, they are implementing features commonly found in more monolithic frameworks. In fact, they are currently working on a tooling component for the 1.8 release that will make it simpler to build applications using ZF components, yet will not sacrifice the use-at-will nature of existing ZF components. It's a testament to the use-at-will architecture of Zend Framework that the tooling component itself can be used standalone.
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