a method and apparatus for maintaining data consistency between a subject and an observer . in one embodiment , an observer configures an aspect with a desired update type indicator , and then instructs the aspect to attach itself to a subject . the subject sends an update to the aspect when it changes state . the aspect interrogates the update , generates a update type indication , and selectively communicates an update based on a comparison between the desired type indication and the update type indicator . some embodiments may also selectively modify and accumulate the update .