## 2 Related Works  
In the past decade, various investigations have been pursued in the fields of sensor network, linked data, and service-oriented computing.  
In the sensor network field, the works mainly focus on two aspects, network city [13, 14] and sensor Web [1, 15]. The increasing deployment of sensors and hand-held devises in recent years enhanced the capabilities to sense the environment. The way we describe and understand the environment is being revolutionary changed [16]. There are lots of projects designed to collect near real-time data, such as the weather and pollution data in cities, by wireless sensor network or pervasive computing devises. For instance, the \"LIVE Singapore!\" provides useful near real-time information about Singapore city for its citizens. It includes an open platform in order to collect, elaborate, and distribute near real-time data reflecting urban activities.  
Traditional sensors are described as tiny data detectors, receivers and transporters. They are limited in detecting range, due to restricted power supply, poor computing capacities, and narrow communication capabilities. In the Sensor Web framework, the sensors have been extended to Earth Observing sensors on a global scale. For instance, the Sensor Management for Applied Research Technologies (SMART) project, developed by National Aeronautics and Space Administration (NASA) Marshall Space Flight Center, integrates both Earth observations and forecast model output into new data acquisition and assimilation strategies.  
With the help of various sensors, huge amounts of geospatial data have been collected. There is also a remarkable number of government organizations, research institutions, and private companies providing open datasets to the general public free of charge [17]. For example, Earth Observing System (EOS) satellites are currently collecting several hundreds of terabytes of data annually, and many of those datasets can be accessed through internet in platforms such as NASA, and United States Geological Survey (USGS) [18]. OGC has published the Web Map Service (WMS) [19], Web Feature Service (WFS) [20] and Web Coverage Service (WCS) [21] specifications to encourage researchers and organizations developing standard protocols and tools to publish, interoperate, and share geospatial datasets. Web Processing Service (WPS) specifications [22] also define standardized interfaces that facilitates the publishing of geospatial processes and the discovery of and binding to those processes by user. For example, NASA developed a WMS server to manage the massive amounts of satellite data for climate and environmental monitoring. OGC WMS Server List [23] from Skylab Mobile systems shows that there were 994 WMSs and 339,254 layers available in the Internet [11] and more than 14,038 WMSs were registered [24] with the GOS by April 2011.  
To make sure the data can be exchanged and interoperated, standardization organizations have published a serial of standardizations. New database technologies coupled with emerging Web-based technologies may hold the key to lowering the cost of geospatial information service generation and allow it to become a more integral part of the scientific process [25]. Service-oriented computing focusing on service composition and services chain technology indicates a promising method to handle this problem.  
The recent developments in linked data [26], sensor network [27], wireless sensor network [28], sensor web framework (SWE) [29], and services-oriented computing [5] have shown the great potential of prompting the evolution from geospatial information systems to geospatial informationservices. However, how to link these modules has not yet been fully discussed. The proactive geospatial information services (PGIS) presented in this paper endeavors to provide a framework to link the sensor services, data services, processing services, and even human services together, and try to offer solutions for some actual applications such as disaster response.