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.