Research On Semantic-Enhanced Resource Directory For Constrained Resources

The Semantic Internet of Things combines the logical representation of the Internet of Things with the semantics of the Semantic Web,constructing ontology and semantic annotation of objects to achieve the transformation from grammatical matching to semantic matching and promote the diversity and intelligence of the Internet of Things.Constrained IoT resources and networks have the characteristics of low node processing performance,limited storage space,battery power supply and wide network range,low throughput and high packet error rate.For the constrained resources with structural differences in the Semantic Internet of Things,the traditional resource discovery method that only provides rough data is no longer applicable.Therefore,how to make resource discovery and a,cess to constrained resources in the Semantic Internet of Things becomes a key issue.In order to solve the problem of introducing semantic information to constrained resources of the Internet of Things,this thesis analyzes the application of semantic technology in the Semantic Internet of Things such as ontology construction,semantic annotation and semantic query,and introduces new attributes containing semantic information such as reference ontology,semantic description and annotation type to CoAP proposed by IETF CoRE working group.The reference ontology is the ontology URI that the semantic description refers to;the semantic description is the compressed concept expression that executes the RDF/XML syntax and describes the semantic annotation of the resource;the annotation type implies the coding standard of the ontology language,the syntax and the semantic annotation.In order to solve the problem of resource discovery and access to semantic-enhanced constrained resources,this thesis proposes a CoAP-based semantic-enhanced Resource Directory and researches the basic mechanism of resource discovery and access to constrained resources in the Semantic Internet of Things,including finding the Resource Directory,URI discovery,resource registration,operations on the registration resources such as registration resource updates,registration resource removals,reading registration resource terminal links and resource lookup through the Resource Directory.In addition,an implementation of CoAP-based semantic-enhanced Resource Directory in the open-source CoAP framework Californium which is widely used in the field of CoAP research and whose Resource Directory entities are not perfect is proposed.In this thesis,it sets the old-age care as the application scenario taking into account the semantic support of different models of old-age care applications such as nursing homes,community retirement and family supporting.In the experimental scenario providing fire warning,fire extinguishing and more functions based on piezoelectric sensors,temperature sensors,fire extinguishing equipment and so on,it uses the Firefox plug-in Copper with a graphical interface to verify the discovery and access mechanism of the CoAP-based semantic-enhanced Resource Directory to meet different function preset queries.The performance comparisons and analysis among four resource discovery and access approaches such as CoAP link "/.well-known/core",Resource Directory based on CoAP,SWoT framework proposed by Michele Ruta et al.and the CoAP-based semantic-enhanced Resource Directory clarify that the CoAP-based semantic-enhanced Resource Directory has a certain improvement of resource discovery and access among old-age care applications in terms of real-time,accuracy and throughput under high concurrency.