The ICAO Annex 15 requirements for AIP amendments are fully suported by the eAIP Specification. When the eAIP is presented on-screen, in HTML format, every individual change can be clearly highlighted. Further more, it is possible to compare the current (modified) content with the previous content. When an eAIP is printed, in PDF format, change bars are inserted on all affected lines within the document.
Paper AIPs are kept up-to-date by removing/inserting pages at every amendment date (AIRAC and non-AIRAC). These pages are issued in the form of an AIP Amendment (AMDT) document. The concept of 'replacement pages' does not apply to an Electronic AIP, which is re-issued in full at every amendment date. However, in order to facilitate the maintenance of a paper AIP, it is also possible to identify the pages that have been affected by the changes between two consecutive issues of the AIP in PDF format.
In order to support amendments, a dedicated set of XML elements and attributes have been included into the eAIP Document Type Definition (DTD). For example, new text is marked using an Inserted element, while deleted text is marked using a Deleted element. There is no special element for modified text. Instead, modified text is marked as a sequence of Inserted and Deleted elements.
There are also DTD elements, which do not have in-line text content, such as a references, graphics, etc.. An Updated attribute, which may take the values Inserted or Deleted is used in this case. The old element will get the value Deleted in its Updated attribute and a new element of the same type will be inserted, with the new content.
Details about how the content of each individual DTD element may be amended have been included into the DTD Documentation.
Each eAIP issue contains markup (Inserted and Deleted XML elements and attributes) only for the changes made in that issue. Eventually, if that eAIP issue corresponds to an AIRAC amendment, the changes of the previous non-AIRAC amendment can be kept (and vice-versa).
There are a few reasons behind the decision to remove the old changes in XML. If old inserted and deleted elements were kept, then:
the XML eAIP files might soon become very complex and even invalid, due to clashes between current and previous Inserted and Deleted elements; at one moment, some of the old amendment markup would need anyhow to be deleted for the content to become again understandable;
in HTML, the functionality to 'Show/Hide Amendments' would become very complex, as it should distinguish between current and previous amendments.
Before a new issue is created, a process called "fixing the amendment" has to be executed. This definitively applies the changes of an amendment into an eAIP by removing all elements marked as "deleted" (including their content) and by converting all elements marked as "inserted" so that they are seen as not amended.
It should be noted that this approach does not have a direct impact on the paper format. It is still possible to keep the old changes, by printing the PDF and inserting into the paper version only the updated pages. Naturally, the old pages are not affected.
The eAIP Specification allows for publishing changes in advance by 2 or more AIRAC cycles. However, the fact that a full eAIP is issued, requires special consideration. When an amended eAIP is issued with an effective date earlier than that of a previously issued eAIP which is not yet in force, the previous issue needs to be updated.
The full eAIP Amendment process is described in the eAIP Editors Manual. This includes the procedure for advanced changes publication, by two or more AIRAC cycles.
Users will benefit from receiving a full eAIP, in which all changes are clearly marked. They are no longer required to do the page replacement, which, estimated at the scale of the whole aviation community, every AIRAC cycle, is a costly effort. However, the benefit of not having to do yourself the updates comes at a price in terms of complexity/flexibility for the eAIP editor.
Amendment production can be partially automated. For example, provided a content management and versioning software is available, the amendment creation, validation and publication procedure can be completely embedded in the tool.
Similarly, if automation is available within the XML editor software, then the actual creation and manipulation of changes can be made a lot simpler. It is highly recommended that especially the XML to PDF production process is automated, as the manual process is quite fastidious.
Another approach is a fully automated text amendment editing. In this approach, editors simply amend their eAIP without worrying at all about amendment mark-up. They just replace text where needed, add and remove paragraphs where necessary. When the edition process is finished, a software program compares the new (modified) eAIP with the previous issue and inserts amendment mark-up as appropriate. After that, the editors can check the result on screen and on paper.