摘要
It is increasingly common to find graphs in which edges are of different types, indicating a variety of relation- ships. For such graphs we propose a class of reachability queries and a class of graph patterns, in which an edge is specified with a regular expression of a certain form, ex- pressing the connectivity of a data graph via edges of var- ious types. In addition, we define graph pattern matching based on a revised notion of graph simulation. On graphs in emerging applications such as social networks, we show that these queries are capable of finding more sensible informa- tion than their traditional counterparts. Better still, their in- creased expressive power does not come with extra complex- ity. Indeed, （1） we investigate their containment and mini- mization problems, and show that these fundamental prob- lems are in quadratic time for reachability queries and are in cubic time for pattern queries. （2） We develop an algorithm for answering reachability queries, in quadratic time as for their traditional counterpart. （3） We provide two cubic-time algorithms for evaluating graph pattern queries, as opposed to the NP-completeness of graph pattern matching via subgraph isomorphism. （4） The effectiveness and efficiency of these al- gorithms are experimentally verified using real-life data and synthetic data.
It is increasingly common to find graphs in which edges are of different types, indicating a variety of relation- ships. For such graphs we propose a class of reachability queries and a class of graph patterns, in which an edge is specified with a regular expression of a certain form, ex- pressing the connectivity of a data graph via edges of var- ious types. In addition, we define graph pattern matching based on a revised notion of graph simulation. On graphs in emerging applications such as social networks, we show that these queries are capable of finding more sensible informa- tion than their traditional counterparts. Better still, their in- creased expressive power does not come with extra complex- ity. Indeed, （1） we investigate their containment and mini- mization problems, and show that these fundamental prob- lems are in quadratic time for reachability queries and are in cubic time for pattern queries. （2） We develop an algorithm for answering reachability queries, in quadratic time as for their traditional counterpart. （3） We provide two cubic-time algorithms for evaluating graph pattern queries, as opposed to the NP-completeness of graph pattern matching via subgraph isomorphism. （4） The effectiveness and efficiency of these al- gorithms are experimentally verified using real-life data and synthetic data.
