# Geo-DMP: A DTN-Based Mobile Prototype for Geospatial Data Retrieval
## 5 Conclusions and Outlook  
In this paper, we present Geo-DMP, a mobile prototype system supporting the sharing and exchanging of geospatial contents in an opportunistic, distributed, and collaborative way. The framework of Geo-DMP consists of a full DTN protocol stack, a \"content agent\" module, and a \"map adaptor\" module. DTN and its BPQ mechanism are employed as the foundation for their capabilities of identification, matching, and multi-hop delay-tolerant forwarding of named contents. Then we follow the \"gateway-based\" communication paradigm to develop the \"content agent\" module to break the isolation between non-DTN nodes and DTN-aware nodes. To extract the concise mobility pattern of users from their movements for the purpose of routing, we present the \"map adaptor\" module, which provides real-time regional information based on the product of our proposed multi-scale map segmentation scheme. Next, to accomplish a complete content retrieval process with the framework of Geo-DMP, we explore the design of a pure region-oriented DTN routing scheme which is tailored for real-life spatial environments. The full implementation is thoroughly verified on the emulation platform composed of VMs. Through experiments on real-world trajectories in realistic scenarios, we can conclude that with Geo-DMP, the requests of named spatial contents can be directed to and fulfilled by distant content sources via transient connectivities and cooperation of DTN nodes, and the requester can utilize the responses which are routed back across a long time period. We also find that intermediate cache resources can be efficiently exploited by Geo-DMP to lessen the reliance on content originators, reduce unsuccessful retrievals, and enhance overall delivery performance.  
Despite the achievements, we are also conscious that there is still much room for improvement. The potential directions include: large scale experiments with physical embedded devices in real environments; improving the design of routing protocol by better exploiting the knowledge of historical movements and intelligent determination of target regions; and exploring a more programmatic way to automate processing or calibrating the road network and trajectories of nodes.  
In addition to the enhancements of the system itself, we will also seek to broaden the applicability scope of Geo-DMP. Two possible ways could be suggested: First, supporting the retrieval of more manifold timely or customized geospatial contents such as emergency event warnings, safety cautions (e.g., road surface anomalies or accident prone road sections), weather updates, or POI (point-of-interest) recommendations; and second, better integration with crowd-sourcing services to assist efficient harvesting and sharing of up-to-date as well as valuable location-aware information around us.  
Conceptualization and methodology: [PERSON] and [PERSON]; software: [PERSON] and [PERSON]; validation and investigation: [PERSON]; writing--original draft preparation: [PERSON]; writing--review & editing: [PERSON], [PERSON], and [PERSON]. All authors have read and agree to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.