The Elements
The FGDC Content Standard is a collection of 334 hierarchically
organized elements that define the content of the metadata record. These
elements fall into one of two categories - data elements or compound
elements. Data elements are those that can be assigned a value,
while compound elements cannot be assigned a value and exist only to
contain other elements. They simply describe the relationship among
other elements giving an overall structure to the standard. Of the 334
elements, 215 are data elements, and the remaining 119 elements are
compound elements.
The elements are organized hierarchically, with the
starting point of "metadata" (section 0). "Metadata" is considered a
compound element that is composed of 10 numbered sections, each representing
a different concept about the dataset. Sections contain both data elements
and compound elements. Compound elements are in turn defined by other
compound elements and/or data elements.
The first seven sections of the standard are
the Major, or what we refer to as the "Primary" metadata sections. They
are:
- Section 1: Identification Information
- Section 2: Data Quality Information
- Section 3: Spatial Data Organization Information
- Section 4: Spatial Reference Information
- Section 5: Entity and Attribute Information
- Section 6: Distribution Information
- Section 7: Metadata Reference Information
Of these, only Section 1: Identification Information,
and Section 7: Metadata Reference are considered mandatory, and are
absolutely required for all records. These mandatory elements are referred
to as the "core" elements.
The last three sections are the Minor, or Floating
sections. They are used by other sections and never stand alone. They
are used in conjunction with metadata elements found throughout sections
1 - 7, and are thus defined once for convenience. They are:
- Section 8: Citation Information
- Section 9: Time Period Information
- Section 10: Contact Information
Optionality
Of the 215 elements that can be assigned a value,
only a few dozen are considered "mandatory". The remainder are considered
"mandatory if applicable", or "optional". The FGDC refers to this as optionality. The optionality of a section or compound element
always takes precedence over the elements that it contains. Once
a section or compound element is recognized by the dataset producer
as applicable, then the optionality of its subordinate elements is to
be interpreted.
The standard defines these categories as follows:
- Mandatory elements must be provided. If the
information is not known for a mandatory data element, the entry "Unknown"
or a similar statement should be given.
- Mandatory-if-applicable elements must be
provided if the dataset exhibits the characteristic defined by the
element.
- Optional elements are provided at the discretion
of the metadata producer. Essentially, they provide a place for information
that might otherwise be lost if placed in a general comment field.
We highly recommended the USGS's "Image
Map of the Content Standard for Digital Geospatial Metadata" as
a complement to this guide. It is a graphical representation of the
standard with the elements color coded according to their optionality.