purpose of the ITU-T Rec. T.410-Series | ISO/IEC 8613 is to facilitate the interchange of documents. In the context of these Recommendations | International Standards, documents are items such as memoranda, letters, invoices, forms and reports, which may include pictures and tabular material. The content elements used within the documents may include graphic characters, raster graphics elements and geometric graphics elements, all potentially within one document. NOTE - These Recommendations | International Standards are designed to allow for extensions, including hypermedia features, spreadsheets and additional types of content such as audio and video. In addition to the content types defined in these Recommendations | International Standards, ODA also provides for arbitrary content types to be included in documents. These Recommendations | International Standards apply to the interchange of documents by means of data communications or the exchange of storage media. These Recommendations | International Standards provide for the interchange of documents for either or both of the following purposes: — to allow presentation as intended by the originator; — to allow processing, such as editing and reformatting. The composition of a document in interchange can take several forms: — formatted form, allowing presentation of the document; — processable form, allowing processing of the document; — formatted processable form, allowing both presentation and processing of the document. These Recommendations | International Standards also provide for the interchange of ODA information structures used for the processing of interchanged documents. This ITU-T Recommendation | International Standard: — defines a document architecture intended for representation of documents; — defines a document processing model; — defines the document structures, the basic constituents of the architecture and a descriptive representation of these in terms of attributes; — defines an interface which allows the use of different content architectures with the document architecture; — defines the reference model of the document layout process; — defines the reference model of the document imaging process; — defines the reference model for protecting parts of a document; — defines three document architecture classes; — defines a notation used for illustrating and describing document structures; — provides examples of document structures; — provides examples of particular document attributes.