6.2.2 Format  IASA recommends the use of .wav or preferably BWF .wav files [EBU tech 3285]. The difference between the two is that the BWF contains a set of headers which can be used to organise and manage metadata. Though BWF metadata is adequate for many purposes, in some sophisticated systems and exchange situations a more comprehensive package is required, and in these circumstances Metadata Encoding and Transmission Standard (METS) is often used. The METS schema is a standard for encoding descriptive, administrative, and structural metadata regarding objects within a digital library, expressed using XML (eXtensible Markup Language). A METS package, which consists of metadata and content, is often used as an exchange standard between digital archives.  Material eXchange Format (MXF) is a container format for professional digital video and audio media defined by a set of SMPTE standards. MXF has been mostly taken up by the video archiving community, though it is capable of managing audio. Like METS, it is primarily a set of metadata which “wraps” the content, in this case, audio. Both these are very useful formats in the exchange and management of content and information between archives and repositories.  The format of the SIP will depend on the system and the size and sophistication of the enterprise. It is quite possible to establish a viable archive using .wav files and manually entering most of the necessary metadata into the system by hand, and acquiring the necessary technical metadata at the ingest stage. This however, would only be appropriate for the smallest of collections. Large collections with remote and separate digitisation processes and large quantities of material must build sophisticated ingest and data exchange systems to ensure the content is adequately ingested into the data storage systems. Production and verification software generates much of this data as standardised XML-files that may be used for preservation purposes. The National Library of New Zealand Metadata Extractor tool, for example, is a Java-based tool that extracts preservation metadata from digital objects and outputs that metadata in a standard format (XML).