Client-specified schema extensions in cloud computing environments

Methods and apparatus for client-specified schema extensions in cloud computing environments are disclosed. A system includes a plurality of service managers coordinating respective multitenant network-accessible services, and one or more computer servers. In response to a schema extension request specifying a client account, a client attribute set, and a client data source, the one or more computer servers generate a composite schema customized for the client account comprising (a) attributes of a plurality of resources implementing the functionality of at least one service to which the client account has access and (b) the client attribute set. In response to an account state view request specifying the client account, the one or more computer servers provide a state representation comprising (a) at least one value of a particular client attribute and (b) at least one attribute value of a resource.