This paper formalizes three kinds of safety to be satisfied by networked appliances and services in the emerging home network system (HNS). The local safety is defined by safety instructions of individual networked appliances. The global safety is specified as required properties of HNS services, which use multiple appliances simultaneously. The environment safety is derived from residential rules in home and surrounding environments. Based on the safety defined, we propose a modeling/validation framework for the safety. Specifically, we first introduce an object-oriented modeling technique to clarify the relationships among the appliances, the services and the home (environment) objects. We then employ the technique of Design by Contract with JML (Java Modeling Language), which achieves systematic safety validation through testing.