In turn, consumers interested on that data type query that particular rendezvous node to retrieve the information.Ratnasamy et al. [9], introduced the Data Centric Storage term in 2002 as a novel mechanism that disseminates and stores data inside the WSN. This work is the cornerstone of the DCS research selleck kinase inhibitor field.Based Inhibitors,Modulators,Libraries on this research other authors have studied DCS aspects in order to improve and extend the original proposal. Some of these improvements and extensions are focused on: DCS routing, multi-replication DCS systems that employ several rendezvous nodes, combining DCS with other storage mechanisms Inhibitors,Modulators,Libraries depending on network conditions, finding the optimal location to place the rendezvous node, etc.This paper discusses the most relevant works studying DCS in the literature and presents their main contributions.

In addition, we introduce in this paper a Quadratic Adaptive Replication (QAR) scheme for multi-replication DCS that is demonstrated to perform better than previous works addressing the same problem. Finally, we discuss future research lines in the area of DCS for WSNs.Next, we introduce the scenarios where DCS can be applied as well as the terminology used Inhibitors,Modulators,Libraries in this paper.1.1. Scenarios for DCSThere are two kinds of sensor networks where DCS could be applied. On one hand, standard WSNs have a central node named sink, base station, gateway, etc, that connects the WSN with the external world. In this kind of networks, sensor nodes gather information from the environment and store it either locally, in a rendezvous node (if DCS is being applied) or push it to the sink that stores all data.

In such a network, usually the consumers of the WSN data are external users that query the network through the sink.On the Inhibitors,Modulators,Libraries other hand, nowadays not only sensors but actuators are becoming more relevant in the WSN community, and Wireless Sensor Networks are becoming Wireless Sensor and Actuator Networks (WSANs) [10, 11]. An actuator is a node that, based on the information retrieved from one or more sensors, performs some action. For instance a node controlling a water valve in a plantation Cilengitide opens it depending on the humidity and temperature conditions obtained from the sensors in the field. It must be noted that a node could perform both roles in the network, being a sensor and an actuator at the same time.

The use of WSANs opens up the possibility of autonomous WSANs that, in a distributed way, measure the environment, process the collected data and perform some actions to get a common goal without any external intervention. Therefore, in this case, DCS seems to be a suitable storage and information retrieval nearly system because there is no a clear central, powerful node as in the sink case.1.2. TerminologyThis subsection defines some common terminology to be used in the rest of the paper, since different works use different names to refer to the same thing.