在普及運算領域裡，如何讓應用程式察覺存在環境中的資訊是一個很重要的話題；應用程式可以伴隨已取得的環境資訊來改變自己的行為或者狀態，進而為人們帶來生活上的便利。對於應用程式來說，感應器網路提供了一個有效取得環境資訊的方法。它可以隨意的擺置在環境資訊的所在地，如房間、大樓、郊區...等；雖然感應器網路是如此的便利，但它依然有先天上的限制，如電力問題、通信距離問題及感應器損壞問題...等。在本篇論文中，我們主要是研究在感應器網路上如何設計並開發能夠感知環境資訊的應用程式。我們不採用目前大多研究團體所採用的方法－Flood，而是採用Trailblazer。在Trailblazer感應器網路裡，每一個感應器都會維持一份路徑資訊以用來幫助訊息的傳送。我們以Trailblazer為基礎，發展了一套組織及架構；在這個架構下，應用程式發展人員可以輕易的開發屬於它們自己的感應器網路和感知環境資訊的應用程式；上層應用程式可以透過我們所提供的開發介面，並配以更高層次的描述，輕易地取得它們所想要的環境資訊。最後，我們並且實地示範用這套架構來開發感應器網路和感知環境資訊的應用程式，這程式是用來感知物體的所在地。

To make applications aware of the environmental contexts is an important topic in ubiquitous computing. Applications with acquired contexts can adjust their status or behavior to minimize user attention and serve people more intelligently. Sensor networks aid applications to extract contexts by connecting various sensors together for context inquiry, propagation, and aggregation. Although sensor networks provide an effective way for supplying context information to applications, their design has to cope with various restrictions, such as energy consumption, communication range, sensor failure, etc. In this thesis, we study the system software design over the sensor network to aid the development of context-aware applications. Without relying on flooding or multicasting to disseminate messages over our sensor network, a novel data-centric routing mechanism, Trailblazer, is adopted. In Trailblazer, every sensor has a set of attribute-value pairs to describe its functionalities. The description of a sensor is hashed to a hash value to identify this sensor. All the sensors maintain certain routing information to help forward messages in the sensor network. Based on Trailblazer, we have developed a framework to aid the construction of context-aware applications on top of sensor networks. The applications can publish or subscribe desired context in sensor networks easily and efficiently. The proposed framework also supports the mobility of sensors. Finally, we demonstrate an object tracking system constructed from the framework.

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