Abstract
The Internet of Things (IoT) has become the infrastructure to widely support ubiquitous applications. Due to the highly dynamic context setting, IoT search engines have attracted increasing attention from both industrial and academic field to crawl and search heterogeneous data sources. Today, a large amount of work on IoT search engines is devoted to finding a particular mobile object device, or a group of object devices satisfying the constraint on query terms description. However, it still lacks studies on enabling so-called spatial-temporal-keyword-aware query. Only a few research work simply applies a keyword or spatial-temporal matching to identify object devices. In this case, it is insufficient to simultaneously consider the spatial-temporal-keyword aspect in order to satisfy the user request. To address this challenge, we develop a new search mechanism over PKR-tree (denoted SMPKR), in which PKR-tree unifiedly integrates spatial-temporal-keyword proximity with the help of a coding enabled index. Efficient algorithms are developed for answering range and (enhanced) KNN queries. Extensive experimental results demonstrate that our SMPKR search engine promotes the efficiency of searching for object devices with spatial-temporal-keyword constraints in comparison with the state of arts.
Highlights
The Internet of Things (IoT) is one of the topical research disciplines nowadays, and has become the infrastructure to widely support ubiquitous applications [1]–[3]
We mainly focus on object devices and sub-index node (SIN) interaction because object devices, SIN and head nodes communicating between them are power constrained and computationally challenged devices, while primary index node (PIN) is a resource-rich device
We find that all these schemes show an increasing cost in message complexity by varying object devices number, as the number of PINs and object devices overlapping or within the same query range grows with object devices number
Summary
The Internet of Things (IoT) is one of the topical research disciplines nowadays, and has become the infrastructure to widely support ubiquitous applications [1]–[3]. There are many existing works that adopt hierarchical architectures to support construction of IoT search engine. Though current research achieves good results for simple types of query constraints, there are still limitations to be addressed for retrieving the object devices measurements with dynamically changed content in real time and fully considering spatial-temporal-keyword searching constraints simultaneously. To address this challenge, this paper develops a new search mechanism over PKR-tree (denoted SMPKR). A three-tier hierarchical search architecture is established in IoT system, where a key-based index tree is constructed for moving object devices to promote query and communication.
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