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The concept of "Dynamic Behavior" should be pretty obvious when you are building a web application; things should look different for different users/situations. But what does it mean that Tapestry has "Static Structure?" Static structure implies that when you build a page in Tapestry you are going to define all of the types of components that are used within that page. Under no circumstance during the rendering or event processing of the page will you be able to dynamically create a new type of component and place that into the component tree.

At first glance, this seems quite limiting ... other frameworks allow new elements to be created on the fly; it's also a common feature of desktop GUIs such as Swing. But static structure turns out to be not so limiting after all. You can create new elements (you're actually re-rendering existing components with different properties). And you have plenty of options for getting dynamic behavior out of your static structure; from the simple conditional and looping components to the more advanced implementations of Tapestry's BeanEditor or Grid components, Tapestry gives you the control over what renders and when, and even where it appears on the page. And starting in Tapestry 5.3 you can even use the Dynamic component, which renders whatever is in an external template file.

Why did Tapestry choose static structure as a core principle? It's really a matter of meeting the requirements of agility and scalability.

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A key feature of Tapestry 5 is its adaptive API.

In traditional Java frameworks (including Struts, JSF and even the now-ancient Tapestry 4) user code is expected to conform to the framework. You create classes that extend from framework-provided base classes, or implement framework-provided interfaces.

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