Metadata standards and the ArcGIS metadata format |
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Release 9.3
Last modified May 9, 2012 |
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This topic was updated for 9.3.1.
Following a well-known metadata standard is a good idea because tools already exist with which you can create and validate your metadata. If you plan to publish your metadata to a large audience, following a standard will also make it easier for people from different communities, industries, and countries to understand the information you provide because the standard acts as a dictionary, defining both the terminology and the expected values.
There are a number of metadata content standards to choose from. The Federal Geographic Data Committee's (FGDC)
Content Standard for Digital Geospatial Metadata (CSDGM)
aims to provide a complete description of a data source. Because it's quite detailed, other states and regions have created their own metadata standards to try to simplify the information that should be recorded. For example, the European Committee for Standardization (CEN) and the Australia New Zealand Land Information Council (ANZLIC) created their own metadata standards and guidelines.
Learn more about FGDC CSDGM metadata.
The ISO technical committee TC211 develops standards relating to geographic information. ISO standard 19115, Geographic Information—Metadata, was designed for international use. It attempts to satisfy the requirements of all well-known metadata standards. ISO 19115 is a content standard that discusses what information should be included in metadata. It allows for detailed descriptions of geographic resources but has a small number of mandatory elements. ISO standard 19139, Geographic Information—Metadata—Implementation Specification, provides an XML schema that says how ISO 19115 metadata should be stored in XML format.
Many countries, regions, and communities are adopting profiles of ISO 19115 or ISO 19139 as their national standard. Each profile will make some modifications to the original 19115 or 19139 standard and will typically have its own XML Schema or Document Type Definition (DTD) defining how metadata following that profile should be formatted. Because many metadata standards and profiles exist, metadata in ArcGIS isn't required to meet any specific standard. However, you may be required to produce metadata that follows a standard.
The ArcGIS metadata format
ArcCatalog is the place where you create metadata content. The metadata editors provided with ArcCatalog let you create metadata content following the FGDC CSDGM or ISO 19115 standards. Use one of these metadata editors to write the documentation portion of the metadata content. The corresponding metadata synchronizer will add properties of the item to the metadata for you.
Learn more about metadata synchronization.
The metadata created by ArcCatalog is stored in an ESRI-defined XML format. This format currently combines FGDC-, ISO-, and ESRI-defined XML elements in the same XML document.
Learn about how metadata is stored.
The FGDC metadata editor, style sheets, and synchronizers work with FGDC CSDGM and ESRI XML elements as defined in the ESRI Profile of the Content Standard for Digital Geospatial Metadata. This profile adds elements to and modifies elements in the FGDC CSDGM standard. This document is available as a white paper from ESRI's Online Support Center. The esriprof80 DTD published on the ESRI Metadata Web site defines the format for the ESRI FGDC profile. This DTD is based on the FGDC CSDGM XML DTD.
ESRI-defined elements provide support for thumbnails and enclosures. They also store information used by ArcGIS Desktop and ArcIMS to manage metadata and to document information about GIS resources such as topologies, geometric networks, geodatabase relationship classes, and so on that can't be recorded using either the FGDC or ISO metadata standards. Some of the ESRI elements are integrated with the FGDC XML elements while others are not.
The ISO metadata editor, style sheets, and synchronizer work with the ISO XML elements as defined in the ESRI_ISO1 DTD published on the ESRI Metadata Web site; this is referred to as the ESRI-ISO format. The ESRI-ISO format is based on a version of the DTD that was included in a draft version of the ISO 19115 standard; that DTD was modified by ESRI to resolve technical issues and improve usability. ESRI has not created a profile of the ISO 19115 standard. The ISO metadata editor and synchronizer do not work with any ESRI-defined elements. However, the ISO style sheet shows some ESRI-defined content that may be created outside of the ISO metadata editor such as thumbnails and enclosures, if they exist.
FGDC and ISO 19115 content coexist in parallel in the metadata XML documents maintained by ArcCatalog. For example, two titles may be stored for a dataset—one in the FGDC XML element "title" and another in the ISO XML element "resTitle". If you modify the default title for a dataset using the FGDC editor, the ISO editor won't know about the new title, and vice versa. The FGDC style sheet will show the FGDC title, and the ISO style sheet will show the ISO title. View an illustration.
Learn more about viewing metadata in ArcGIS Desktop.
The esriprof80 and ESRI_ISO1 DTDs were published separately because they were designed to specify the format used by the metadata style sheets, editors, and synchronizers provided with ArcGIS that were associated with the appropriate standard. The DTDs also specify the optionality and cardinality of metadata elements used when building metadata content. These DTDs can't be used independently to validate metadata content against either the ESRI FGDC profile or ISO 19115 metadata standards. A combined DTD doesn't exist because since ArcCatalog doesn't require you to follow a metadata standard, every element would be optional.
The current format for storing metadata in ArcGIS will change. It will evolve into a standard-neutral format that is a superset of the FGDC and ISO 19115 metadata content standards. It will let you provide any FGDC or ISO 19115 metadata content and will support customization for specific profiles of those standards.
Validating metadata content
If you decided to follow a metadata standard when creating your metadata, it is a good idea to validate the content you have created against that metadata standard's rules when you are close to finishing the metadata content.
There are different types of validation that can be performed. One aspect of validation is checking metadata content against a metadata standard's rules to see if all of the appropriate information has been provided. Another aspect of validation is checking a metadata XML file's structure against the standard's rules to see if it is properly formatted.
Validating a metadata XML file against a metadata standard's DTD lets you know if the XML file has all of the required elements in the correct order in the document. Validating a metadata XML file using a standard's XML Schema gives you the same information as validating against a DTD; XML Schemas can also check if a metadata element contains a number as expected by the metadata standard instead of text, for example.
Validating metadata created with ArcCatalog against a metadata standard's DTD or XML Schema is an operation that must be performed outside ArcGIS. As-is, the ArcCatalog metadata XML files will not validate against a metadata standard's DTD or XML Schema. This is because the metadata created by ArcCatalog is stored in an ESRI-defined XML format that includes elements that are required by ArcCatalog to manage the metadata content and the identity of documents that have been published to an ArcIMS Metadata Service. These elements will not exist as-is in any metadata standard, and therefore the XML files created with ArcCatalog won't validate against a standard's DTD or XML Schema.
If you need to provide your metadata content in a specific XML format outside of ArcGIS that can be validated against an XML DTD or XML Schema, you must generate these files by exporting your metadata to the appropriate format either using the Export Metadata button in ArcCatalog or using one of the metadata geoprocessing tools. For example, to provide your content in FGDC-only format to one agency, you can use the Export Metadata button in ArcCatalog or the USGS MP Metadata Translator geoprocessing tool. And, you can provide the same content to another agency in ISO 19139 format using the ESRI Metadata Translator tool.
Learn more about exporting metadata.
XML Schemas are not perfect when it comes to validating metadata content. For example, in the ISO 19115 metadata standard, a point of contact and other responsible parties can be defined by providing the name of an individual, an organization, or a position. In an XML DTD or XML Schema, these elements must be defined as being optional, and there is no way to specify the additional constraint that the count of individual, organization, and position elements must be greater than zero. However, this validation rule can easily be handled by the ESRI Metadata Translator tool's translation engine. With the ESRI Metadata Translator, you can validate both FGDC and ESRI-ISO metadata content against the complete set of rules defined in the ISO 19115 metadata standard.
Regardless of which metadata editor you use to author your content, the metadata geoprocessing tools let you validate it against the requirements of different metadata standards. For example, suppose you author metadata in ArcCatalog using the FGDC metadata editor. You can validate this content against the FGDC CSDGM standard using the USGS MP Metadata Translator tool or against the ISO 19139 standard using the ESRI Metadata Translator.
Learn more about the metadata geoprocessing tools.
If you run the ESRI Metadata Translator by double-clicking the tool to open its dialog box, you must generate both an output XML file and a log file. However, if you run this tool from the geoprocessing command line, you can escape the Output File and Log File parameters by providing a "#" for each of these parameters instead.
ESRITranslator "C:\Data\myShapefile.shp" "C:\Program Files\ArcGIS\Metadata\Translator\FGDC2ISO19139.xml" # #
If you only escape the Output File parameter, a Log File will be created containing all of the validation warnings and errors. If you escape both the Output File and Log File parameters, the validation warnings and errors will only be shown in the results that appear on the geoprocessing command line.
With the USGS MP Metadata Translator tool, you can validate FGDC metadata content against the FGDC metadata standard using the metadata parser utility, which is known as "mp". The warnings and errors generated by mp when evaluating the metadata content will be recorded in the log file produced by this tool. To only validate your FGDC metadata with this tool, and not produce other output at the same time, choose "none" as the Conversion Type. Specify the source item or XML file, whose metadata content will be examined and a file path for the output log file. The log file produced will be a text file—if you provide the file extension .txt, the log file will automatically appear in ArcCatalog.