1. A method for dynamically constructing a target hierarchy tree structure from profiling data of a computer system according to a predefined relational model so as to obtain profiling information of a certain selected node, wherein said predefined relational model is defined according to profiling objects of said profiling data and includes profiling information of each of nodes in the hierarchy tree structure, said method comprising steps of: (a) determining entities at each level in a path from a root node to said selected node in said target hierarchy tree structure according to said predefined relational model and definition of said target hierarchy tree structure, so as to obtain an entity array; (b) obtaining identification information of all the nodes including said selected node in each path from the root node to the selected node in said target hierarchy tree structure according to said entity array, so as to obtain one or more corresponding identification arrays; (c) selecting from said predefined relational model all the rows having corresponding values of said identification array(s) in those columns representing corresponding entities according to said obtained entity array and identification array(s), so as to determine a row set; (d) for all the rows of said row set, grouping together those rows having the same identification information in those columns in said predefined relational model, which represent entities of nodes at the next level to said selected node in said target hierarchy tree structure, according to the entity type of said nodes at the next level, so that said row set is divided into one or more groups; (e) for all the rows of each of said groups in said predefined relational model, aggregating profiling information contained in each row, so as to obtain aggregate profiling information of each group; and (f) processing the obtained aggregate profiling information of each group to obtain the profiling information of said node in said target hierarchy tree structure.