In the dLibra system, standard publications are versionized. The elements which make it possible are editions. A publication edition is a specific version of an electronic document. Let us illustrate the operating principle of the versionizing mechanism with an example. Let us assume that an author created document A. This is the first version. The author sent the document to an editor who entered it to a digital library and, in this way, created a publication (the dLibra system automatically creates the first edition of that publication). Next, the author corrected document A, so the editor received another version of it, that is, document A'. In order to make the new version, document A', available in the digital library, the editor should add a new edition of the publication (not enter a new publication). After that action, the publication has two editions: one corresponding to document A and one corresponding to document A', Thus, the reader of the digital library can see the whole ‘life history’ (subsequent editions) of the document (publication).
In the context of files, an edition is a set of particular versions of files. A file version is here defined as the file at a particular time (for example, the version from January 17, 2006, 7:32 a.m.). Coming back to our example: document A is the first version of the document, which groups the file versions sent to the editor after the document had been created. Document A' groups the file versions sent to the editor after the document had been modified. To sum up, the first edition of the publication (created automatically when the publication was being created) groups the file versions of document A, and the second edition – of document A'. It should be added that if the document had many files and the author’s modifications did not apply to all those files, the second edition would group a part of the files from document A (the unmodified files) and a part of the files from document A' (the modified files).
We could explain the versionizing mechanism in greater detail with the example illustrated below. Let us assume that a given publication only has one file at the beginning, body.html. An editor creates a publication in the dLibra system and indicates that file as its content. The dLibra system creates the first edition of the publication. The edition groups the available file version. After a time, the author modifies the body.html file and adds the title.jpg file to the document. The editor creates a second edition, which groups the title.jpg file and the modified version of the body.html file. Some time later, the author modifies the document again, changing the body.html and title.jpg files and adding a new file, logo.gif. The editor creates a third edition, which groups the new logo.gif file and the newest versions of the body.html and title.jpg files. In the end, the publication consists of three editions. Each of them groups a set of particular versions of the files. The publication contains three files. Each file groups its own versions (for example, the title.jpg file groups version 1.1 and 1.3, and the logo.gif file only groups the 1.1 version).
Another example is shown in the image below, which presents the dependencies among a publication, its editions, its files, and the file version. As we can see, the publication consists of two editions and two files. The files contain the subsequent file versions, and the editions group particular file versions across files. The web site user (reader) can see the publication and its two editions. When the reader wants to see the contents of a particular edition, the dLibra system displays the file versions relevant for that edition.