Another limitation involves navigating the object model. MSAA represents the UI as a hierarchy of accessible objects in a manner similar to Windows' Window Manager. Clients navigate from one accessible object to another using the IAccessible::accNavigate method. However, servers implemented accNavigate in unpredictable ways and often not at all. Clients, however, must be able to deal with all approaches for any MSAA server. This ambiguity means extra work for client implementers, and the complexity can contribute to problems depending on the server implementations.