Top Level Elements

An EML dataset is composed of up to three elements under the root element (<eml:eml>):

<access> More information: access
<dataset> More information: dataset <additionalMetadata>More information: additionalMetadata


The access element is found at this location (XPath):

<access> contains a list of rules defining permissions for this metadata record and its data entity. Values must be applicable by the system where data is stored. Many repositories follow the KNB system of using access control format that conforms to the LDAP “distinguishedName (dn)” for an individual, as in “uid=FLS,o=LTER,dc=ecoinformatics,dc=org.”

As of EML 2.1.0, <access> trees are allowed at two places: as the first child of the <eml:eml> root element (a sibling to <dataset>) for controlling access to the entire document, and in a physical/distribution tree for controlling access to the resource URL. With the exception of certain sensitive information, metadata should be publicly accessible. The <access> element is optional, and if omitted, the repository may presume that only the dataset submitter will be allowed access.

Example 2: access

<access authSystem="knb" order="allowFirst" scope="document">


This element is found at these locations (XPath):

Under <dataset>, the following elements are available. Some are optional, but if they appear, this order is enforced by the schema. Generally, the recommendations are presented here in this order, with the exception of elements related to people and organizations which are grouped together so that the distinctions between the uses of those elements are clear. Elements that can appear at different levels within an EML file are discussed at their first appearance, or highest level.

<purpose >

These elements are then followed by one or more elements for the data entity (or entities), designated by choosing:

[ dataTable | spatialRaster | spatialVector | storedProcedure | view | otherEntity ]


The alternateIdentifier element is found at this location (XPath):
/eml:eml/ dataset/alternateIdentifier
/eml:eml/ dataset/[entity]/alternateIdentifier

The contributing organization’s local data set identifier should be listed as the EML <alternateIdentifier>, particularly when it differs from the “packageId” attribute in the <eml:eml> element. The <alternateIdentifier> should also be used to denote that a package belongs to more than contributing organization by including each individual ID in a separate <alternateIdentifier> tag. At the entity level, the <alternateIdentifier> should contain an alternate name for the data table (or other entity) itself (see additional comments under entities, below.)

title (dataset)

The dataset title element is found at this location (XPath):
/eml:eml/ dataset/title

The dataset <title> should be descriptive and should mention the data collected, geographic context, research site, and time frame (what, where, and when).

Example 3: dataset, alternateIdentifier, shortName, title

<dataset id="FLS-1" system="FLS" scope = "system">
   <title>Long-term Ground Arthropod Monitoring Dataset at Ficity, USA
      from 1998 to 2003</title>


This element tree is found at (XPath):

<additionalMetadata> is a flexible field for including any other relevant metadata that pertains to the resource being described. Its content must be valid XML. A unit as a <customUnit> must be described in this tree.

<describes> (optional) is a pointer to an “id” attribute on an EML element (“id” described in another area). This pointer must be identical to the attribute it is pointing at, so that automated processes are able to associate <additionalMetadata> to the described attribute. If the <describes> element is omitted, it is assumed that the <additionalMetadata> content applies to the entire EML document.

<metadata> contains the additional metadata to be included in the document. The contents can be any valid XML. This element should be used for extending EML to include metadata that is not already available in another part of the EML specification, or to include site- or system-specific extensions that are needed beyond the core metadata. The additional metadata contained in this field describes the element referenced in the <describes> element preceding it. If <describes> is not used, either <metadata> must contain sufficient information to define the association between <additionalMetadata> or the <additionalMetadata> can be presumed to apply to the entire data package.

An example of “sufficient information to define the association” is the definition of a <customUnit>. The EML Parser expects to find the description of a <customUnit> in the id attribute of a <unit> element in a <unitList>, i.e., at /eml:eml/additionalMetadata/metadata/unitList/unit. For example, "stmml:unit id="siemensPerMeter" points at the <customUnit> "siemensPerMeter". The EML Parser is available from GitHub, with the EML project. For descriptions of custom units see “Other Resources.”

Example 25: additionalMetadata custom unit

         <stmml:unit id="siemensPerMeter" name="siemensPerMeter" abbreviation="S/m" 
         unitType="conductance" parentSI="siemen" multiplierToSI="1" constantToSI="0">
            <stmml:description>conductivity unit</stmml:description>