# Resource Indexing and Querying in Large Connected Environments
## 2 Motivating Scenario
### Connected Environment Setup  
#### 2.1.1 Environment Description  
A connected wilderness open area has different landscape features: (i) lots of areas are highly accessible (e.g., plain fields), thus allowing easy sensor deployment and environment monitoring; (ii) a few areas are moderately accessible (like lakes and rivers), leading to challenging deployment and environment monitoring; and (iii) some areas are extremely inaccessible (e.g., rocky mountains and high surfaces) thus making deployment and monitoring highly difficult. As a result of the landscape setup, sensing device deployment is not homogeneous in the entire environment. Easily accessible areas (i.e., in open plains/fields) have a high node density, while moderately challenging areas (i.e., around water bodies) have a sparse node density. Finally, inaccessible areas contain isolated nodes in the best-case scenario or remain completely uncovered in some areas (i.e., no deployment of nodes) in the worst-case scenario. Figure 1 presents an example of a connected wilderness open area. This example shows the distribution of different temperature sensing devices in the Chiberta forest in Anglet, France. The objective of the deployment is to assess the potential for fires occurring within the forest. To distribute these sensors, a plane flew overhead and dropped the different devices, leading to a random distribution of the resources. This random distribution implies having areas with high sensor density, areas with low sensor density, and empty areas. Due to their restricted capacities, devices are unable to retain data about the entire network, which can pose significant difficulties in forwarding messages to the zone targeted by the query. We also assume that the network should handle different types of queries, based on the needs of the user (urgency levels). To send a query, users can send a query from a monitoring PC by indicating on the screen the zone desired or by specifying GPS coordinates. Then, the monitoring PC will transfer the query to the appropriate device. Furthermore, users have the choice to directly send queries to the nearest device, which will then handle the request. Let us take some examples to illustrate the sending of queries:  
* When a supervisor (user 1 in Figure 1) would like to know the temperature of a zone, she/he draws visually on the monitoring PC the zone to be requested. The PC sends the request (Q1) to the zone's head (D1) located in or near the targeted zone. The respective device will return a response with the temperature of the zone. * Another agent (user 2 in Figure 1) wants to gather the temperature of another zone (Z5). He draws visually on the monitoring PC the requested zone, and the query is forwarded to the nearest device. If the device knows from its own index that the requested zone (Z5) is uncovered, it can return an immediate response without further forwards of the request, consequently avoiding the usage of other devices' capacities. * Another interesting case is when a firefighter (user 3 in Figure 1) is trying to put out a fire but does not know its exact location inside a large and dense forest, in which fire can spread rapidly. The firefighter seeks to take out affected regions by activating the fire suppression system to extinguish the fire before it can progress further into the forest. He must predict the fire progression to activate the system in specific areas instead of activating it in the entire forest. The request is based on exceeding a certain threshold, indicating that a fire is probable. In the forest, he/she needs to urgently broadcast a request in order to quickly retrieve the fire's location. After broadcasting the request, one or several devices will be aware if a fire is detected within their zones (e.g., zone 3). The response is sent back by at least one of those devices. The response can contain the data queried, but it can also be a label indicating that no response could be received (uncovered zone due to the uneven distribution of the devices).