A new kind of Web-based application, known as Enterprise Mashups, has gained momentum in the

last years: Business users with no or limited programming skills are empowered to leverage in a

collaborative manner user friendly building blocks and to combine and reuse existing Web-based

resources within minutes to new value added applications in order to solve an individual and ad-hoc

business problem. Current discussions of the Mashup paradigm in the scientific community are limited

on technical aspects. The collaboration and the peer production management aspects of the Mashup

development have received less attention yet. In this paper, we propose a reference model for

Enterprise Mashups which provides a foundation to develop and to analyse grassroots Enterprise

Mashup environments from a managerial and collaborative perspective. By following the design

science research approach, we investigate existing reference models and leverage the St. Gallen

Media Reference Model (MRM). The development of Enterprise Mashups is structured by market

transaction phases similar to electronic markets. The user roles, the necessary processes and the

resulting services are modelled according to the views of the MRM. By means of the SAP Research

RoofTop Marketplace prototype we demonstrate the application of the designed reference model for

grassroots Enterprise Mashups environments.