(Yo provide a better defination on PRT, I quoted the following paragraph from help.sap.com - the link is provided on the left hand navigation column)
The Portal Runtime Technology (PRT) is a basic part of the SAP Enterprise Portal Environment that is integrated in the J2EE Engine environment.
The PRT provides a Java based framework that allows you to define, build, and execute applications in a portal environment by allowing the aggregation and the display of various contents such as rich text, XML, videos and so on.
The PRT provides a runtime and its corresponding services as well as a development environment for portal applications.
The design and the technical implementation of the PRT are based on the following points:
· The objective of the PRT is well identified and restricts itself to the life cycle of portal applications
· Open and extensible:
You can change or customize many of the components of the PRT and adapt them to the environment in which the PRT is executed. You can also extend the PRT to support, for example, different user interface models or different programming models.
The PRT clearly positions itself as one of the key blocks used to build and execute any kind of portal.
The PRT defines and enables you to manage two kinds of objects that define a portal application:
· Portal Components
A component that can be displayed in a portal page. From an application development perspective, a pluggable component designed to be executed in a portal environment
· Portal Services
A component that offers a globally accessible function in the portal. The PRT development model gives you a way of implementing a clear separation between a service API and its implementation.