A computer system comprising a matching platform that has the capability to examine attributes from multiple scans on multiple attributes and determine which attributes from each scan pertain to the same attribute so the attribute is not counted twice. Extensible modules of weighted attribute matching rules can be plugged into the system which define the rules for matching based upon attributes. These modules define which attributes will be examined and the weighting of each in the matching process. The modules can contain different attributes and different weighting rules for different types of machines. With regard to weighting, when a match between attributes that are returned from two different scans occurs, the amount that match contributes toward the decision that the assets the attributes were collected from are the same asset depends upon the weighting of the particular attribute. Fuzzy snapshots and time-based reporting are possible. Matching is done on devices first, then elements installed on those devices such as software. Confidence metrics can be developed based upon the weights of matches. All matching is done against a set of attributes in the persistent data warehouse which comprise the complete set of attributes collected about a device or element from all previous scans.