Draft: Best Practices Landing Page

Introduction

This wiki resource provides best practices documentation for all collection and granule metadata concepts supported by the Common Metadata Repository (CMR). It is intended to support metadata authors as well as provide general guidance to those seeking information about CMR supported metadata. 

The wiki is organized by metadata concept as specified in the Unified Metadata Model (UMM) and includes information such as: required metadata fields, definitions for each metadata concept, best practices for populating each metadata field, guidance on how to use controlled vocabularies, and the revision history of the UMM metadata schema. Also included are a detailed mapping/crosswalk between each UMM metadata field and the corresponding field in each CMR supported metadata standard. Supported standards currently include ECHO 10, DIF 10, ISO 19115-2 (in NASA specific MENDS and SMAP "flavors"), and ISO 19115-1.   

Unified Metadata Model (UMM): UMM-C, UMM-G and UMM-Common

The Unified Metadata Model (UMM) is used as a bridge to map between each of the CMR-supported metadata standards. A number of different objects require descriptive metadata that is modeled using a corresponding UMM profile. For example, a collection (or dataset level) object is modeled using the UMM-C (Collection) profile, and granule (or file level) objects are modeled using the UMM-G (Granule) profile.

While UMM-C and UMM-G are separate entities, some elements are common to each profile and are therefore modeled using UMM-Common.

Currently, this wiki resource provides documentation for elements found in the UMM-C, UMM-G and UMM-Common models. 

Other UMM models not covered here include UMM-S (Services) and UMM-Var (Variables). 

For information regarding UMM-S please refer to the CMR Documents page and the UMM-S Curator's Guide.

For information regarding UMM-Var please download the UMM-Var document from the CMR Documents page.  

Wiki Page Structure

Each wiki page has the following outline:

Element Description

• Provides a high level definition on the metadata concept

Best Practices

• Provides best practices for the metadata concept as well as sample values

Element Specification

• A table detailing each unique metadata element within the concept. For each metadata element the table specifies:
  • The UMM model it is from (UMM-Common, C or G)
  • The element name, exactly as it appears in the UMM schema
  • The element Type (string, enumeration, boolean, etc.)
  • Constraints (e.g. character length restrictions, controlled vocabularies, etc.)
  • The cardinality, which specifies how many times the element may be repeated. Please see the following for a more in depth explanation of cardinality: 
  • Notes: any additional information which may be useful about the element

Metadata Validation and QA/QC

• There are various systems in place to ensure a certain standard of metadata quality is maintained in the CMR. The Metadata Validation and QA/QC section of the wiki page provides documentation regarding these efforts and systems:
  • GCMD Metadata QA/QC: The GCMD team is responsible for stewardship of metadata records in the CMR provided by any of CMR's International Directory Network (IDN) partners. This section details both the automated and manual checks the GCMD team performs on the IDN records to help maintain a certain standard of quality.
  • CMR Validation: The CMR system itself has certain requirements. This section details any baseline CMR requirements for the metadata concept in question.
  • ARC Metadata QA/QC: The ARC team is responsible for performing quality assessments of NASA metadata records in the CMR. This section specifies what the ARC team looks for (both manually and in an automated fashion) to ensure NASA's metadata records in the CMR maintain a certain standard of quality. 

   Dialect Mappings

• The Dialect Mapping section provides detailed element-element mappings between the UMM and each CMR supported metadata standard. Current CMR supported metadata standards include:
  • DIF 10 
  • ECHO 10
  • ISO 19115-2 MENDS
  • ISO 19115-2 SMAP
• Provided for each supported standard:
  • An element specification table which includes the direct crosswalk between the UMM element path and the corresponding element path in the supported standard. This table will also indicate if an element in a supported standard does not map to the UMM, or if there are any caveats in the manner that the information gets translated.
  • An enumeration mapping table (if applicable) - sometimes there are differences in enumeration values used in a supported standard VS the UMM.
  • An example mapping showing how a snippet of metadata in the supported standard will appear in the UMM format. This might illustrate examples of how certain information can get dropped or only partially translated between the supported standard and the UMM.  

UMM Migration

• If a metadata concept undergoes significant changes between UMM version updates, this section will illustrate how the information provided in the older version of UMM will be translated over to the newer version.

Future Mapping

• Occasionally, the CMR will consider supporting a new metadata standard. For instance, work is currently under way to support the ISO 19115-1 standard in order to support a large influx of records from NOAA. ((no idea if this is true - need to confirm)). If the CMR is in the process of building support for a new metadata standard, known documentation for that standard will be provided in the 'Future Mapping' section.

History

• Provides a version history for the metadata element in question

Documentation Directory

There is a separate wiki page for each high level metadata concept in the UMM. The drop down sections below link directly to the documentation, and are categorized by UMM model:

The table below illustrates which elements in UMM-Common are shared between both Collections and Granules and their description. You will also see that while the elements are identical, some standards will include less information or different information based on the specific granule, such as that granules temporal extent. It is important to note that this is just a subset of what is in UMM-Common and the full list of elements found in UMM-Common can be from other objects (such as services and visualizations). 

Related Resources, Information, and Documentation

Here you can find further documentation about The Unified Metadata Model, UMM-C, UMM-G, UMM-Common, and other best practices regarding them. Information on this page was sourced and gathered from the following resources.

Unified Metadata Model:

• Background and Introduction
• ESO UMM Information and CMR
• CMR and UMM Schema Documentation

UMM-C and UMM-G Wiki Pages

• UMM-C Schema Representation
• UMM-G Schema Representation

Miscellaneous CMR Resources

• CMR Introduction
• Earthdata Search Engine
• Global Change Master Directory (GCMD)
• CMR API Search Introduction
• CMR API Documentation
• Analysis and Review of CMR (ARC) Introduction