Describes the "schema" for a an XML feed to "googlebase". Note that this is only an "abstract schema" in the sense that google base does not currently accept a "feed" in this format. Instead, google base accepts feeds in a wide variety of "standard" XML content feed formats (RSS2.0, Atom). The "item/entry" subelement of a "RSS/Atom" feed corresponds to the "item" element defined below. The sub elements of an item defined herein serve as the concrete definition of the "googlebase defined extensions" to the Atom/RSS schemas. Describes the "schema" for an "item" in googlebase -- the basic unit in a "feed". Since google base will also accept feeds in a wide variety of "standard" XML content feed formats (RSS2.0, Atom), some of the item's sub elements (the "baseElementGroup") are represented by their corresponding child elements of "item/entry" in "RSS/Atom". The correspondence is defined in a seperate document. The rest of the item's sub elements are represented as "extensions" (belonging to the googlebase namespace) on the "item"/"entry" elements in RSS/Atom formats. We group these extension elements into three, "google defined with complex content" ("complexExtensionElementGroup") and " google defined with "simple content" ("simpleExtensionElementGroup") and "customer defined" (customExtensionElementGroup). Since all the elements in the google defined element groups are optional, the user is free to define all extensions as "custom". However, the user is strongly encouraged to first consult the (ever-growing) list of google defined extensions to see if the information they want to provide is represented there and if so use thos extensions in favor of custom ones. Defines the collection of (sub)elements of an item that are "mappable" to (sub)elements of an "item/entry" in an existing "standard" content syndication format (RSS/Atom). Note that none of these elements (except "id") ARE top level elements in this schema. This is because we expect them to be represented using the corresponding RSS/Atom elements. "Id" is special because RSS1.0 does not have such an element defined. We will accept documents that have both id defined as a rss (sub)element and the same id defined in the gn namespace. We will use the value in the gn namespace in that case. Defines the collection of (sub)elements of an item that are "mappable" as "extension (sub) elements" of an "item/entry" in an existing "standard" content syndication format (RSS/Atom) and have "complex" content. Defines the collection of (sub)elements of an item that are "mappable" as "extension (sub) elements" of an "item/entry" in an existing "standard" content syndication format (RSS/Atom) and have "simple" content. The following wild card defines our extension mechanism. Note that while the following --> XML schema syntax is very loose, we will accept only elements with "simple content" (no sub elements). The elements can have a "optional" type attribute ("gn:elementType") associated with a value defined in the elementTypeEnumeration Defines shipping option for an item. Defines a time interval. The country that this listing is located in. The value must be a ISO 3116 uppercase 2-letter country code (http://www.iso.org/iso/en/prods-services/iso3166ma/02iso-3166-code-lists/list-en1.html). For example, United States is US and Canada is CA. ISO 4217 standard.