Efficient Top-k Matching for Publish/Subscribe Ride Hitching

Abstract

With the continued proliferation of mobile Internet and geo-locating technologies, carpooling as a green transport mode is widely accepted and becoming tremendously popular worldwide. In this paper, we focus on a popular carpooling service called <i>ride hitching</i> , which is typically implemented using a publish/subscribe approach. In a ride hitching service, drivers subscribe ride orders published by riders and continuously receive matching ride orders until one is picked. The current systems (e.g., Didi Hitch) adopt a threshold-based approach to filter ride orders. That is, a new ride order will be sent to all subscribing drivers whose planned trips can match the ride order within a pre-defined detour threshold. A limitation of this approach is that it is difficult for drivers to specify a reasonable detour threshold in practice. In addressing this problem, we propose a novel type of top- <inline-formula><tex-math notation="LaTeX">$k$</tex-math></inline-formula> subscription queries called <i><u>T</u>op-<u><inline-formula><tex-math notation="LaTeX">$k$</tex-math><alternatives><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>k</mml:mi></mml:math><inline-graphic xlink:href="li-ieq3-3124232.gif" xmlns:xlink="http://www.w3.org/1999/xlink"/></alternatives></inline-formula></u> <u>R</u>ide <u>S</u>ubscription (TkRS)</i> query, which continuously returns the best <inline-formula><tex-math notation="LaTeX">$k$</tex-math></inline-formula> ride orders that match drivers’ trip plans to them. We propose two efficient algorithms to enable the top- <inline-formula><tex-math notation="LaTeX">$k$</tex-math></inline-formula> result maintenance. We also design a novel hybrid grid index and a two-level buffer structure to efficiently track the top- <inline-formula><tex-math notation="LaTeX">$k$</tex-math></inline-formula> results for all <i>TkRS</i> queries. Finally, extensive experiments on real-life datasets suggest that our proposed algorithms are capable of achieving desirable performance in practical settings.