Executive summary

This requirement presented an opportunity to use new technology to implement a longestablished, internationally controlled specification in an electronic format. Our combination of expertise in XML and experience in producing documents to aviation specifications was ideal for this complex analysis and implementation project.

Benefits

About EUROCONTROL

The EUROCONTROL Agency was founded to oversee air traffic control in member states. Its most important goal today is to develop a coherent and coordinated air traffic control system in Europe.

All countries (states) involved in international flights must provide aeronautical information in a standard format, defined by the ICAO in Annex 15, Aeronautical Information Services. Different interpretations of the standard can impede information sharing. The Agency is managing the EAD Programme, which will compile a database of quality assured aeronautical information.

Objective

The aim was to create an electronic equivalent of the Annex 15 standard. Electronic AIPs are more flexible, since they can be viewed on screen and printed as required. Implementing the standard through a DTD produces more consistent data than when individual states interpret a paper standard.

Our extensive experience in electronic publishing enabled us to analyse the existing standard and propose optimal technologies for the electronic equivalent. The XML approach is well proven and appropriate for non-aviation environments.

Challenges

Solution

Our analysis suggested an XML DTD as the basis for an electronic AIP to meet the Annex 15 requirements. To demonstrate compliance, once we had developed the DTD, we created a test document using all the structural elements in it.

The need to display the AIP on screen and print it on paper meant we had to develop two style sheets. One enables Microsoft Internet Explorer to display the XML document and the other is used in generating PDF files.

The last stage of the project was to create a sample electronic AIP.

DTD

We designed the DTD to make life as simple as possible for authors. For example, meaningful element names are easier to recognise. For sections and sub-sections of Annex 15, the DTD uses logical names already familiar in the industry, such as ENR- 3.5. These are supplemented by a range of descriptive elements to address state-specific requirements. AIPs are frequently produced in more than one language.

For tracking changes, the DTD uses in-line elements. Attributes identify a change and show basic information about it. Pointers lead to more detailed information.

Paragraph numbering in AIPs is complex and the DTD uses two mechanisms to provide the required flexibility. Standard ICAO sections use enumerated attributes. Other numbering is done automatically by the stylesheet application.

To support future integration with the EAD Programme, Mekon based some elements on the electronic Aeronautical Information Conceptual Model. For example, the En-Route tables required a complex model and new presentation style for data; these were reflected in both browser and print style sheets.

Our expertise in XML and SGML enabled us to design a DTD that supports both specifications. This provides the option to use established SGML tools as well as newer XML offerings.

Solution

Style sheets

The browser style sheet implements the Microsoft XML parser and uses XSLT to transform the XML source into XHTML for rendering on screen. A table of contents is created to help readers to navigate the document.

For the print style sheet, Mekon customised its own filter for importing XML into FrameMaker+SGML. The customisation involved fitting graphics into their respective columns and creating customised tables for En- Route routes, navigation aids and designated points. Tables of contents are created automatically for each of the three main sections of an AIP.

Sample AIP

Our sample AIP is closely based on the ICAO sample document. It demonstrates the formatting and structure of an electronic AIP.

An ongoing relationship

EUROCONTROL will run pilot implementation schemes in conjunction with a group of European states. Aeronautical information also includes circulars and supplements. These may later be integrated into the electronic standard.

Glossary

AIP: Aeronautical Information Publication
AIS: Aeronautical Information Services
DTD: Document Type Definition
EAD: European AIS Database
ICAO: International Civil Aviation Organisation
PDF: Portable Document Format
SGML: Standard Generalised Markup Language
XHTML: eXtensible HyperText Markup Language
XML: eXtensible Markup Language
XSLT: eXtensible Stylesheet Language Transformations
AIC: Electronic Aeronautical Information Circular
SUP: Electronic Aeronautical Information Publication Supplement

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