A relation element describes the relationship between its parent and the object referenced by the relation element's target attribute.
Module MEI.frbr
@analog(optional)Contains a reference to a field or element in another descriptive encoding system to which this MEI element is comparable. Value of datatype string. att.bibl
@cert(optional)Signifies the degree of certainty or precision associated with a feature. Value conforms to data.CERTAINTY. att.evidence
@evaluate(optional)Specifies the intended meaning when a participant in a relationship is itself a pointer. Allowed values are: "all" (If an element pointed to is itself a pointer, then the target of that pointer will be taken, and so on, until an element is found which is not a pointer.), "one" (If an element pointed to is itself a pointer, then its target (whether a pointer or not) is taken as the target of this pointer.), "none" (No further evaluation of targets is carried out beyond that needed to find the element(s) specified in plist or target attribute.)att.targeteval
@evidence(optional)Indicates the nature of the evidence supporting the reliability or accuracy of the intervention or interpretation. Suggested values include: 'internal', 'external', 'conjecture'. Value of datatype NMTOKEN. att.evidence
@label(optional)Provides a name or label for an element. The value may be any string. Value of datatype string. att.commonPart
@n(optional)Provides a number-like designation for an element. Value conforms to token. att.common
@rel(required)Describes the relationship between the current entity and the target entity. The values follow FRBR (see http://www.ifla.org/files/assets/cataloguing/frbr/frbr_2008.pdf). Value conforms to data.FRBRRELATIONSHIP. att.rel
@resp(optional)Captures information regarding responsibility for some aspect of the text's creation, transcription, editing, or encoding. Its value must point to one or more identifiers declared in the document header. One or more values from data.URI, separated by spaces. att.responsibility
@source(optional)Contains a list of one or more pointers indicating the sources which attest to a given reading. Each value should correspond to the ID of a <source> element located in the document header. One or more values from data.URI, separated by spaces. att.source
@target(optional)Allows the use of one or more previously-undeclared URIs to identify passive participants in a relationship; that is, the entities pointed "to". One or more values from data.URI, separated by spaces. att.pointing
@targettype(optional)Characterization of target resource(s) using any convenient classification scheme or typology. Value of datatype NMTOKEN. att.pointing
@xlink:actuate(optional)Defines whether a link occurs automatically or must be requested by the user. Allowed values are: "onLoad" (Load the target resource(s) immediately.), "onRequest" (Load the target resource(s) upon user request.), "none" (Do not permit loading of the target resource(s).), "other" (Behavior other than allowed by the other values of this attribute.)att.pointing
@xlink:role(optional)Characterization of the relationship between resources. The value of the role attribute must be a URI. Value conforms to data.URI. att.pointing
@xlink:show(optional)Defines how a remote resource is rendered. Allowed values are: "new" (Open in a new window.), "replace" (Load the referenced resource in the same window.), "embed" (Embed the referenced resource at the point of the link.), "none" (Do not permit traversal to the referenced resource.), "other" (Behavior other than permitted by the other values of this attribute.)att.pointing
@xml:base(optional)Provides a base URI reference with which applications can resolve relative URI references into absolute URI references. Value conforms to data.URI. att.commonPart
@xml:id(optional)Regularizes the naming of an element and thus facilitates building links between it and other resources. Each id attribute within a document must have a unique value. Value of datatype ID. att.id
Member of
Contained by
May contain
<memberOf key="att.common"/>
<memberOf key="att.bibl"/>
<memberOf key="att.edit"/>
<memberOf key="att.pointing"/>
<memberOf key="att.rel"/>
<memberOf key="att.targeteval"/>
<memberOf key="model.relationLike"/>

The rel attribute describes the nature of the relationship. In this triple, the parent element serves as subject, the referenced object as object. This element is used to implement FRBR-like structures in MEI.