Back to SITA ATI Messaging Journal Q1 2009

Messaging technology

What's inside the message?

Maximum efficiency

ATI messaging pre-dates open messaging standards such as those used on the worldwide web by some four decades1, and even email systems by around 15 years2. So when it came to defining what would go into the ATI's first electronic messages, there was very little to go on - other than a clear desire to keep the messages as short as possible.

What keeps Type B messages so short - still a worthwhile goal, even in an era of more abundant bandwidth - is the IATA standards which efficiently encode ATI data as short strings of ASCII characters (American Standard Code for Information Interchange). These include the well-known IATA city codes (ATL, GVA, HKG etc) as well as codes for every operation carried out by ATI applications.

The Type B message codes and format rules were defined by IATA working groups (one for each process, such as reservations, cargo, flight ops etc), which agreed that messages would start with a 3-letter Standard Message Identifier (SMI) identifying the business message type, and would contain certain application data in specific places within the message. Other definitions included 2-letter Text Element Identifiers for use inside the user data, and punctuation marks to separate the data elements.

The standards defined by IATA are so incredibly efficient that the global daily Type B message volume - around 20 million messages a day - would fit comfortably onto an 8-GB memory stick or a couple of DVDs3. There are clear benefits to having dense, structured, data, of course, but the true value lies not just in the message size, but in the messaging ability - in terms of functionality, reliability, security, and automation through machine-readable format etc.

Bringing XML on board

It would take a decade and billions of dollars to completely move away from these standards and formats, but there is increasing ATI interest in beginning to introduce alternatives as well, particularly with the widespread adoption of Web technologies.

With the rise of the Internet, a number of Web 'languages' have evolved (notably HTML, HyperText Markup Language), culminating in the definition of XML (eXtensible Markup Language) by the World Wide Web Consortium (W3C).

The W3C XML standard defines rules for encoding application data in computer files or messages. It specifies how to define a header that identifies how to interpret the content for each data element. So while one XML header might specify that the content is ASCII-encoded text, others may specify different types of content - such as the images, or barcodes, for example, which will increasingly be used in ATI security applications.

In theory, if XML had existed at the time, the IATA working groups could have used XML as a sort of 'grammar' for Type B, though in practice they wouldn't have done, as XML data element headers greatly increase the length of messages. The formats and standards were developed decades before bandwidth started becoming cheaper, and so keeping messages as short as possible was vital.

Moving from the very short IATA text-based application data encoding to XML-based encoding will depend on the need to send information that does not fit within standard text messages, or on the need to develop new generation applications on platforms that have generic XML technology built-in.

At a higher level, the emerging architecture is Service Oriented Architecture (SOA), using Web Services technology (mainly specified by OASIS) in which applications expose functions and information as services encoded using XML. This SOA/Web Services concept defines a new logic for decoupled and reusable services. Business processes make use of appropriate services that can then invoke services across a network with some level of orchestration for the business process. The most popular infrastructure for SOA is provided by an Enterprise Service Bus (ESB).

SITA is actively working with ATI partners to define how these various new technologies can be accommodated and utilized to improve operations, while ensuring that traditional, growth-efficient ATI messaging services are retained where they remain pertinent, as the ATI will continue to rely on it for many years to come. SITA initiated the creation of the new industry standard Type X now part of IATA PADIS (Passenger and Airport Data Interchange Standards). The Type X core standard is under the last review to be sent to the PADIS board for voting during the second quarter of 2009. SITA has been key in chairing this working group and driving the standard and prototypes to ensure it meets the defined requirements. Additionally the Type X data dictionary and implementation guidelines have been created to facilitate its use and implementation.

Click on image for an enlargement.

SITA Air Transport Industry Messaging

Note 1: Source: http://en.wikipedia.org/wiki/History_of_the_World_Wide_Web
Note 2: The first e-mail systems were developed in 1965/66 - see http://en.wikipedia.org/wiki/E-mail for more information
Note 3: Total daily messaging volume = approx 20,000,000 x an average of 274 characters per message = 5.48 GBs of data

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