The first PROforma-based technology for authoring and executing clinical guidelines was Arezzo . It was designed and built by the ACL and InferMed Ltd. in London, and is being used by InferMed to develop enactable clinical guidelines. Arezzo technology consists of two main modules: the Composer (knowledge authoring tool) and the Performer (application enactment engine).

The Composer is a graphical editor or knowledge authoring tool which uses PROforma notation to capture the structure of a guideline (laid out by an author) and generate an executable specification. The Arezzo Composer CASE tool is the developer's GUI. The building blocks used to construct a guideline of any level of complexity are the four PROforma task types, each type being represented by its own icon. Data items and their properties to be collected during protocol enactment are also defined using the COMPOSER. The COMPOSER also functions as a tester: guideline applications can be run, debugged and validated within this module.

The Arezzo enactment engine (the Performer) tests and executes guidelines defined in the PROforma language. The Performer interprets the guideline specification and during guideline enactment, prompting the user to perform actions, collect data, carry out procedures and make decisions as required. During enactment, the Performer also maintains a local database of patient data, which is added to by the user and queried by the Engine to evaluate specified conditions.


Tallis is a new Java implementation of PROforma-based authoring and execution tools developed by Cancer Research UK. Tallis is based on a later version of the PROforma language model. It consists of a Composer (to support creation, editing, and graphical visualisation of guidelines), Tester and Engine (to enact guidelines and allow them to be manipulated by other applications). Tallis is also designed for delivering web-based services; applications will run on any platform and integrate with other components, including 3rd party applications.

The Tallis Publisher (based on Java Servlets) forms part of the Tallis software suite. This has also been built to allow guidelines to be published and enacted over the WWW.