1. An operation management apparatus for performing processing when event data matches a defined condition, the event data associating a name of an attribute indicating a state of a system to be managed with an attribute value of the same, the apparatus comprising: a rule storing section that stores operation rule information that defines processing to be performed; an individual filter information storing section that stores individual filter information which is information that constitutes conditions defined for respective pieces of operation rule information and that associates attributes and attribute values, where some of the attribute values may be written as a reference value estimated from past event data and some of the attribute values may be written as a variable; a predictive event data storing section that stores predictive event data which is data in which an attribute value of event data generated by the system to be managed is substituted for an attribute value that is written as a variable in individual filter information; a predictive event index storing section that stores a predictive event index which is information that associates generated event data, predictive event data generated from individual filter information that matches the event data, and a group which is a set of individual filter information corresponding to operation rule information and to which the individual filter information matching the event data belongs; a predictive event correspondence table storing section that stores a predictive event correspondence table which is information that associates operation rule information, each piece of individual filter information that constitutes a condition defined by the operation rule information, a group to which the each piece of individual filter information belongs, and predictive event data generated from the individual filter information; a predictive event data matching decision section that decides that newly-generated event data and previously-existing predictive event data match if the attribute values of the event data match the attribute values of the predictive event data excluding a reference value or reference values, and decides that the newly-generated event data and the previously-existing predictive event data do not match if the attribute values of the event data do not match the attribute values of the predictive event data excluding a reference value or reference values; an individual filter information identification section that identifies individual filter information whose attribute values, excluding a reference value or reference values, match the attribute values of the event data if it is decided that the event data and the predictive event data do not match; a predictive event data generating section that, if the individual filter information is successfully identified, substitutes the attribute value of the event data for the variable of each piece of individual filter information that belongs to a group to which the individual filter information belongs, thereby generating predictive event data for the each piece of individual filter information, stores the predictive event data into the predictive event data storing section, stores information that shows correspondence between the event data, the predictive event data, and the group to which the individual filter information matching the event data belongs into the predictive event index storing section, and stores information that shows correspondence between the predictive event data generated, the group of the individual filter information used for generating the predictive event data, the each piece of individual filter information belonging to the group, and the operation rule information having the each piece of individual filter information as a condition into the predictive event correspondence table storing section; and a rule decision section that decides, after the predictive event data is generated by the predictive event data generating section, whether or not each piece of event data that is associated in the predictive event index with the group to which the individual filter information that matches the event data used for generating the predictive event data belongs satisfies the individual filter information of the operation rule information corresponding to the group, and if satisfies, performs the processing defined by the operation rule information.