ONTOLOGY BASED WORKLOAD ALLOCATION PROBLEM SOLVING IN FOG COMPUTING ENVIRONMENT
Fog computing concept is quite new but applied almost everywhere. This is due to the fact of intensive processed data capacity growth, so the cloud computing architectures, which were used successfully before, become insufficient in the conditions of Internet of Things (IoT). A workload allocation problem in heterogeneous computing environment is not new and has been solved many times. However, the known problem models neglect some special aspects of fog computing such as: inequality of computation nodes; mandatory participation of cloud layer in the computing process. The current paper focuses on the problem formalizing the workload allocation problem in view of fog computing special aspects by using the device “offload” strategy. In this case the task subgraph reallocation on some computing device subsets of fog layer takes place. A constraint which is peculiar to the fog computing is added to the workload allocation problem in heterogeneous computing environment. This is a multicriteria optimization problem with multiple constraints, which are determined by the system peculiarities, so the optimization problem is NP- hard. It puts a question of quality decisions getting in the limited time conditions. In this paper an approach based on the optimization problem search space reduction through the candidate computing device set selecting is proposed. An ontological approach is used for this purpose: ontology structure that classifies the reallocated subgaph respectively to available resources has been developed. The rules, which are based on developed ontology, apply to candidate nodes choosing for task subgraph allocation. This allows to efficiently reduce the solution search space.