Once an event is completely described in an ESS Document it can have relations with other ESS Event Feeds. Event relations are defined in ESS by three <item> element "type" attributes :
Event with one or more general similarities between the two events
Event with one or more specific similarities that complements the two events
Event in the same real enclosure or conceptual enclosure
ESS <relations> structure
ESS documents are composed of various main XML elements. ESS processors must consider each and every element's description as valid and applicable to each and every other XML element within the same ESS document. If it is not the case, it belong to an other <ess> feed to describe this event parameter.
Example: every <prices> items must be valid and applicable to every <dates> and <places> items within the same <ess> feed.
<relations> XML element (ess:relations) should be defined within ESS Documents, but it is not a mandatory ESS XML element.
This section describe the interaction between various events through ESS Feeds. <relations> (ess:relations) XML element, if it is defined, must be composed of at least one <item> (ess:item) XML element.
Several <item> elements can defined within <relations> XML structure to describe various event relations.
Relations <item @attibutes>
|type||The "type" attribute can take three values: "alternative", "related" or "enclosure" to represent each type of relation between one event with another. ESS Processors should consider that "related" is the default attribute if it is not specified.||String||TRUE|
|priority||The "priority" attribute refers to the order and the preference applied to each <item> XML element. ESS processors should consider the natural position as the priority if this attribute is not defined.||Number||FALSE|
Relations <item> child elements
||Unique and universal ESS feed (ess:id) identifier. Must be the same then the one defined within distant ESS Document.||IRI RFC3987||TRUE|
||Language-sensitive ESS Feed name. Should not be longer then 64 characters. Should be the same then the distant one (ess:name)||String||TRUE|
||Define distant URI where is placed ESS Feed Document.||IRI RFC2396||TRUE|
||This optional XML element contains the specific event relation description (short summary of the relation). Using HTML tags inside this XML element is possible but should be reduced to the minimum because ESS processors could use this information in an environment that can not read HTML.||String||FALSE|
ESS relations sample
DTD description http://essfeed.org/history/0.9
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE ess PUBLIC "-//ESS//DTD" "http://essfeed.org/history/0.9/index.dtd"> <ess xmlns="http://essfeed.org/history/0.9" version="0.9" lang="en"> ... <relations> <!-- 1 | Event related with current event --> <item type="related"> <id>EVENTID:AAKG64:DA848OI:Q456K2:KW8P8QT:559AAU<id> <name>Related Event</name> <uri>http://example.org/feeds/related_event.ess</uri> </item> <!-- 2 | Alternative even --> <item type="alternative"> <id>EVENTID:JKG64D5:848OIQ45:6K2KW5U8Q:T559VIU<id> <name>This is an alternative event</name> <uri>http://example.org/feeds/alternative_event.ess</uri> </item> <!-- 3 | Event in the same enclosure --> <item type="enclosure"> <id>EVENTID:JKG64D:HPO564:456K2K:W5UY55:559VIU<id> <name>Same environment event</name> <uri>http://example.org/feeds/enclosure_event.ess</uri> </item> </relations> ... </ess>
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ESS standard under RFC validation process: RFC ESS Draft