The Version node is required to appear once and as the first child of ITunesUResponse. And as this is the XSD for iTunes U Web Services Responses v 1.1.3, the value must be "1.1.3". Error messages may be present in the response. If the Web Services request includes a request to add an object, the "AddedObjectHandle" node will be returned in the response, if successful, and represents the handle of the newly added object. The Site node is the root node of all data returned for a ShowTree request. The File node is a representation of the actual data file of a Track. The Image node refers to an image in the associated context. Similar to a Track it has a reference to a File object and image-pertinent metadata. The Track node refers to an iTunes media file (audio or video). It can contain a reference to a File as well as metadata, associated with the File, relevant to a media file. The Group node refers to a group of tracks (denoted visually with tabs in the iTunes client), and serves as a way of grouping tracks within the same Course. The Permission node refers to the combination of a Credential and an Access for a given item. The Section node refers to a group of Courses or Divisions, and it, with Division is the key entity for developing course structure in your Site. iTunes U regularly computes and notes the top downloads within each site, using an algorithm defining track popularity. In the associated context, a LinkCollection represents a list of links to be displayed in a visual link box. Courses and divisions that are actually templates for the creation of other courses are displayed in the Templates node. The Division node refers to a group of Sections, and it, with Sections is the key entity for developing course structure in your Site. The Course node refers to a set of Groups. A Course corresponds to a page with respect to the user interface of iTunes. The CoverImage node represents artwork associated with the Site, Division, Course, or Track. The BannerImage node represents artwork associated with the Site, Division, or Course. A theme is a set of appearance attributes (text color, background colors, data formats, etc.) that may be applied to a page in your iTunes U site.