i.e. in ASCII format and can be saved as a sequence of homogeneous elements (all presentation attributes like font, size, etc. are the same for all characters) because the page image shows the exact look of the page. In this case the UVC program of the data has two parts, one to decode the text and one to decode the image. What it entails The data contained in the bit stream is stored with an internal representation, extracted from the data stream, of logical data elements that obey a certain schema in a certain data model. A decoding algorithm (method) extracts the various data elements from the internal representation and returns them tagged according to the schema. An additional schema (schema to read schemas) with information of the schema is similarly stored with the data together with a method to decode the schema to read schemas. Logical Data View The logical data model is kept simple in order to minimize the amount of description accompanying the data and to decrease the difficulty of understanding the structure of the data. The data model chosen for the UVC-based preservation method linearizes the data elements into a hierarchy of tagged elements organized using a XML-like approach. The tagged data elements are extracted from the data stream of the digital file. A tag specifies the role that the data element plays in the data structure. The element tags hold the specific information about the content of the data in a technology-independent manner. Furthermore, the data elements tagged according to the schema are returned to the client in a Logical Data View (LDV) Example of Logical Data View <Collection> <landscape> <name> sugarloaf <category> mountains <picture> <year> 1916 <nbr_lines> 1500 <dots_per_line> 2100 <line> … The schema (format decoder) More information is needed about the various data elements in order to humanly understand what each element means, information such as the place of the tags in the hierarchy, the type of data (numeric, characters), together with some information on the semantics of the data. For example, the image has two attributes, width and heights, indicating that width times height pixels follow; but are these pixels stored line by line or column by column? Or, for colored pictures, how to interpret the RGB values in order to recreate the right color? This extra information is also called metadata. The schema is clearly application-dependent as it describes the structure