Differences between ArcGIS metadata and FGDC metadata

There are a few differences between the metadata content that is supported and stored in ArcGIS and the metadata content that is allowed by the FGDC CSDGM standard. By following some best practices, the metadata that you create and maintain in ArcGIS will be accurate and easier to maintain, and will transition seamlessly to the ISO metadata formats. The FGDC now recommends transitioning to the ISO metadata format as soon as it is appropriate for your organization.

Allow ArcGIS to automatically update an item's metadata

ArcGIS must be set to automatically update an item's metadata. This is required to ensure that an item's properties are included in its metadata when content is exported to the CSDGM XML format. If an item's metadata has not been automatically updated by ArcGIS 10, the item's coordinate system will not be included in the item's metadata.

Also, the feature count, feature type, raster size, and attribute field information should be exclusively derived from the item's properties to ensure they are accurate.

Some content is defined by the metadata style

ArcGIS metadata is an internal storage format that supports the FGDC CSDGM and ISO 19139 metadata standards, the INSPIRE Metadata Directive, and the North American Profile of ISO 19115. The metadata style determines how ArcGIS is configured to support a specific standard or profile. As a result, several pieces of information that are traditionally recorded within an item's metadata are now added at the time that metadata is exported based on the metadata style that is being used. They include:

• The name and version of the metadata standard that is being followed.

• If a profile of a metadata standard is being used, the appropriate metadata extension information.

• ArcGIS metadata always records time information based on the current local time. Therefore, this information is always added to exported CSDGM metadata in the Metadata Time Convention element to eliminate any ambiguity.

A few elements are not supported

There are a few CSDGM metadata elements that are not kept when metadata is upgraded or imported to ArcGIS.

• In the Distribution Information section, the information in the Online Computer and Operating System element and the information provided in the Dialup Instructions section are not transferred to ArcGIS metadata.

• Larger Work Citations are upgraded and imported for the item's primary citation. However, larger work information for secondary citations describing related resources will not be transferred to ArcGIS metadata. To learn more about a related resource, examine it or its metadata.

Some elements have standardized content

There are some metadata elements for which free-form values are supported in the CSDGM standard. Many times people write different text in these elements that are intended to have the same meaning. These values are standardized in ArcGIS.

• List elements, where the CSDGM provides a list of values, are handled as a drop-down list to eliminate ambiguity. If the text in the original FGDC element doesn't match a well-known variation of the value defined in the CSDGM, the original value will not be upgraded or imported even if the element's value has the same meaning. For example, the CSDGM Maintenance and Update Frequency element specifies a list of strings that can be used to identify the frequency with which the data changes, including the string none planned. ArcGIS stores a coded value in this element. Several string variations will be successfully mapped to the coded value, including none planned, not planned, and unplanned. However, if your metadata has a string with the same meaning that ArcGIS doesn't recognize, the upgraded or imported metadata content won't include the none planned coded value.

  

• Dates and times must be fully qualified and are stored in ArcGIS with all date and time components in the ISO 8601 Date or DateTime format for the local time zone according to the ArcGIS Desktop machine; for example, DateTimes are stored in the format YYYY-MM-DDThh:mm:ss. If only a year is provided in the original FGDC metadata, this value is transformed to January 1 of that year. If the original value is a year and month, this value is transformed to the first day of that month. If a range of time is truly needed to specify an approximate time in which the data was collected, change the single value to an appropriate time period instead. If the original date or time is provided as text, such as Spring 2002 or 2 p.m., the value won't be upgraded or imported.

  

• It is common practice to provide the value None in FGDC metadata for required elements that don't apply to an item or for which there is no value. For example, this generally occurs if there are no restrictions for accessing or using the item, and if a set of keywords was not derived from a thesaurus. The value None is not upgraded or imported into ArcGIS metadata. The best practice in ArcGIS is to leave these metadata elements empty. When metadata is exported to a standard metadata format, ArcGIS will handle mandatory elements that are empty in an appropriate manner for that standard. When metadata is exported to the CSDGM format, the value None will be included in those elements.

Some content is reorganized

Some information is organized differently in ArcGIS metadata than in the CSDGM standard. These changes were made to streamline metadata content in a manner that is consistent with how organizations generally do business today.

• In ArcGIS, when a citation is created to describe a related resource, the Originator and the Publisher of that resource are identified as full contacts. By contrast, this information is provided with simple text strings in the manner of a bibliographic entry in the original FGDC metadata. When FGDC metadata is upgraded in or imported to ArcGIS, the original Originator and Publisher values are placed in the ArcGIS Organization element for that contact. However, this information may be more appropriate in the Individual or Position elements for the contact, or the value could be split with portions of the original string stored in different elements. In general, metadata with an individual's name must be updated more frequently over time; consider providing only an organization name or specifying a position name instead.

  

  The original Publication Place value is put into the publisher contact's Address element in ArcGIS. Typically, the original value should be split and distributed among other elements associated with the publisher contact's address, for example, by putting a city name into the City element, a country name into the Country element, and so on.

• Almost every concept that exists in the CSDGM standard also exists in the ISO standard, and vice versa, but the information is arranged differently. For example, the CSDGM allows any number and combination of data formats and distribution methods to be associated with a distributor, and each distributor has its own Distribution Information section. Whereas, the ISO metadata format supports only one Distribution Information section, which can have many distributors, formats, and transfer options that can be associated with each other in different ways, or not associated with each other at all depending on the profile you choose to follow.

  Generally, the data formats and versions in which a resource is distributed, the software required to use it, the media on which it will be delivered, and so on, will change more often than the bulk of an organization's metadata is updated. From an ArcGIS perspective, it is apparent that both standards can lead to chaotic and outdated sets of distribution information. Most resources are available or described on a web page that is kept up to date even if the organization's metadata is not. A best practice for metadata is to refer people to an online location for relevant information about ordering and accessing the item. Over time, metadata created in this manner will be simpler to read and easier to maintain. Streamlining your metadata in this manner may take some effort, but it will be worth it in the long run.

  Until you streamline your distribution information, when metadata is upgraded in or imported to ArcGIS, your existing metadata content will be reorganized into a simpler structure that is compatible with both the CSDGM and ISO metadata formats. Information isn't lost, but it will be reorganized. For example:

  • There will be a separate Distributor in ArcGIS for each distributor's CSDGM Standard Order Process or Custom Order Process mechanism; this means a distributor may appear in the resulting ArcGIS metadata many times.

  • Some elements occur at the top level of the Distribution Information section in the CSDGM but at a lower level in ISO metadata. In ArcGIS metadata, this information occurs many times at the lower level. Therefore, the single CSDGM availability date or time period for all formats and delivery mechanisms is copied to each distribution method in ArcGIS; in turn, when ArcGIS metadata is exported to the CSDGM format, the first availability date is exported as the overall time period when the resource is available.

  • In the CSDGM, the distribution method is split based on whether the distribution product is digital or nondigital. In ISO, the distribution method is split based on whether the distribution product is available by URL or on media. Both digital media and hard-copy media are handled in the same manner. In ArcGIS, the offline Media Name is a standardized element, where there are coded values for different types of digital media and different types of hard-copy media. If a hard-copy media value is used, this information will be exported to the CSDGM format as nondigital distribution information.