an underlying sensor network, its communication details and various hardware components, from the applications built on top of it. OGC's SWE initiative defines the term "sensor web" as an infrastructure enabling access to sensor networks and archived sensor data that can be discovered and accessed using standard protocols and application programming interfaces. Through this abstraction from sensor details, their usage in applications is facilitated. Characteristics of Delin's sensor web architecture Delin designed a sensor web as a web of interconnected pods. All pods in a sensor web are equivalent in hardware (there are no special "gateway" or "slave" pods). Nevertheless, there are additional functions that pods can perform besides participating in the general sensor web function. Any pod of a sensor web can be a portal pod and provides users access to the sensor web (both input and output). Access can be provided by RF modem, cell phone connections, laptop connections, or even an Internet Server. In some cases, a pod will have an attached removable memory unit (such as a USB stick or a laptop) that stores collected data. The term of mother pod refers to the pod that contains the master clock of the synchronous sensor web system. The mother pod has no special hardware associated with it, its designation as a mother is merely based on the ID number associated with the pod. Often the mother pod serves as a primary portal point to the Internet, but this is done only for deployment convenience. Early papers referenced the mother pod as "a prime node" if it additionally contained special hardware for a particular type of input/output device (say an RF modem). Because of the inherent hopping of data within a sensor web, a pod with no attached sensors can be deployed as a relay with the single purpose of facilitating communication between the other pods and to expand the communication range to a particular end-point (such as a mother pod). Sensors can be attached to relay pods at a later time and relays can also serve as portal pods. Each pod usually contains: one or more sensor leading to one or more data channel, a processing unit such as a micro-controller or microprocessor, a two-way communication component such as a radio and antenna (radio ranges are typically limited by government spectrum requirements; unlicensed bands will allow for communication of a few hundred yards in unobstructed areas, although