The majority of Tapestry annotations (defined in the tapestry-core and tapestry-ioc modules) are very specific to Tapestry components or Tapestry IoC services.
A small number of annotations are intended for data holding classes that are not Tapestry components; these annotations allow high-level components such as Grid and BeanEditForm to create powerful user interfaces with out any additional coding.
By separating out those annotations from the rest of Tapestry, it is reasonable to includes such annotations inside your data tier classes without having to bring all of Tapestry into your classpath. This is very useful in multi-tier applications where data objects may originate in an application tier (such as a JEE application server) and travel to the presentation tier (a Tapestry application).
The artifact id for this module has changed to tapestry5-annotations. This is necessary to support Tapestry 4 and Tapestry 5 applications co-existing within a single WAR.