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In previous versions of the Shibboleth service provider (SP), session initiation for applications was handled using a single property, /SPConfig/Applications/Sessions/@wayfURL (which could be overridden by applications). A limited lazy session capability also existed (as of Shibboleth 1.2). The overall design led to deployers of services that span multiple Shibboleth federations artificially creating multiple applications in the ShibbolethXml file to enable multiple WAYFs to be used, based on what resources were accessed.
As of Shibboleth 1.3, this notion of initiating sessions has been generalized and expanded to prepare for additional functionality in the future, as well as to simplify the development of more advanced applications and identity provider discovery (IdPDiscovery) mechanisms. In particular, a single application can take advantage of multiple discovery services (DiscoveryServices; see also WAYF) with the same URL-based approaches but less configuration machinery.
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