The SCSI family of standards provides for many different types of SCSI devices (e.g., disks, tapes, printers, scanners). This standard defines a device model that is applicable to all SCSI devices. Other SCSI command standards (see 3.1.18) expand on the general SCSI device model in ways appropriate to specific types of SCSI devices. The set of SCSI standards specifies the interfaces, functions, and operations necessary to ensure interoperability between conforming SCSI implementations. This standard is a functional description. Conforming implementations may employ any design technique that does not violate interoperability. This standard defines the SCSI commands that are mandatory and optional for all SCSI devices. Support for any feature defined in this standard is optional unless otherwise stated. This standard also defines the SCSI commands that may apply to any device model. The following commands, parameter data, and features defined in previous versions of this standard are made obsolete by this standard: a) Contingent Allegiance; b) Untagged tasks; c) The RESERVE(6) and RESERVE(10) commands; d) The RELEASE(6) and RELEASE(10) commands; e) The ELEMENT_SCOPE for Persistent Reservations; f) The command support data (CmdDt) feature of the INQUIRY command; g) The relative addressing (RelAdr) bit in the standard INQUIRY data; h) The Medium Partition mode pages (2), (3), and (4); i) The Control mode page disable queueing bit; j) Discussion of the SBC REBUILD, REGENERATE and XDWRITE EXTENDED commands; and k) The ASCII Implemented Operating Definition VPD page. Figure 1 shows the relationship of this standard to the other standards and related projects in the SCSI family of standards as of the publication of this standard. Figure 1 is intended to show the general relationship of the documents to one another. Figure 1 is not intended to imply a relationship such as a hierarchy, protocol stack, or system architecture. It indicates the applicability of a standard to the implementation of a given transport. The term SCSI is used to refer to the family of standards described in this clause.