This part of ISO/IEC 14776 defines a reference model that specifies common behaviors for SCSI devices and an abstract structure that is generic to all SCSI I/O system implementations. This standard defines generic requirements that pertain to SCSI implementation standards. It also defines implementation requirements. An implementation requirement specifies behavior in terms of measurable or observable parameters that apply to an implementation. Examples of implementation requirements defined in this standard are the status values to be returned upon command completion and the service responses to be returned upon task management function completion. Generic requirements are transformed to implementation requirements by an implementation standard. An example of a generic requirement is the hard reset behavior specified in 6.3.2.