It is very important to understand system behaviors in collective pattern for each knowledge domain. However, there are structural limitations to represent collective behaviors due to the size of system components and the complexity of their interactions, causing the state explosion problem. Further composition with other systems is mostly impractical due to exponential growth of their size and complexity. This paper presents an abstraction method to model the collective behaviors, based on a new concept of domain engineering: behavior ontology. Firstly, the ontology defines each collective behavior of a system from active ontology. Secondly, the behaviors are formed in a quantifiably abstract lattice, called n:2-Lattice. Thirdly, a lattice can be composed with other lattices based on quantifiably common elements. The composition can be interpreted as behavioral composition, and can reduce all the unnecessary composition not related to the behaviors in the lattices. In order to demonstrate the feasibility of the method, two examples, Emergency Medical Service and Health Care Service systems, are selected and implemented on a Behavior Ontology tool, called PRISM, which has been developed on ADOxx Meta-Modelling Platform.