With the increase in the number of sensors and actuators available to ubiquitous computing systems comes the need for architectures that can support the development of intelligent applications and expose the rich control and monitoring capabilities provided by these devices to users. In this work, we present a description of the parameters used to define services provided by sensors and actuators. Using this understanding of the devices that provide sensing and control throughout the environment, we present thedesign of Meditrina, a ubiquitous computing architecture. Meditrina provides clean interfaces for application designers to leverage devices in the environment to support the activities of users in a large variety of scenarios. To demonstrate the power and feasibility of Meditrina, we implemented a prototype, including a room lighting control application. Through the use of the prototype, we show how the architecture facilitates the quick implementation of applications that can react to and affect the environment, even in the face of device failure.