DIF is the acronym for Directory Interchange Format, a de-facto standard used to create directory entries which describe a group of data. A DIF consists of a collection of fields which detail specific information about the data. Five fields are required in the DIF; the others expand upon and clarify the information. Some of the fields are text fields, others require the use of valid values.
The DIF allows users of data to understand the contents of a data set. The DIF contains those fields which are necessary for users to decide whether a particular data set would be useful for their needs.
The DIF is compatible with the U.S. federally mandated Federal Geographic Data Committee's (FGDC) Content Standard on Digital Geospatial Metadata (CSDGM), which is available at http://fgdc.er.usgs.gov/metadata/contstan.html.
The compatible content allows fields to be mapped. With the mapping, FGDC CSDGM records can be converted into DIF and vice versa. The GCMD employs software, called Docmorph, to convert records between various formats, including DIF and FGDC CSDGM. Thus, GCMD can ingest, export and display metadata of a variety of formats.
Skinny DIF is a DIF which consists of only the required DIF fields. Skinny DIFs are put into a directory to alert users of the existence of a particular data set, and may be modified at a later time to provide additional information.
This document provides information about each field of the DIF, including its syntax, specifications, recommendations, and examples. Several example DIFs are also provided. For a list of software tools which aid in the writing of DIFs, see http://gcmd.nasa.gov/software_docs/dif_tools.html.