The significance of services in TITAN

As you may have heard, TITAN is an EU 7Th Framework project working on improving the predictability and efficiency of the aircraft turnaround. Its name says it all: turnaround integration in trajectory and network. Building on the baseline to be provided by Airport CDM (A-CDM), TITAN will make the details of the turnaround process more visible on a scale much wider than anything in the past. By providing context sensitive information to the various stakeholders enabling them to anticipate problems and take remedial action not only on a timely basis but also commensurate with the problem to be solved.
You can find more information on TITAN here. This article is about a very important characteristic of TITAN, namely its service oriented architecture (SOA). You can read more about SOA here, but to recap briefly, let me say that in this approach the business aspects and the IT aspects of a system are decoupled from each other, with the business aspects driving the IT aspects and not the other way round. This is a major step in the right direction already as in the past the blessings of modern IT were often negated by the limitations they placed on what the business side was able to achieve. The S in SOA stands for “service” and these are traditionally defined for the IT part of course but even more importantly, the business level also gets its set of services. Where do we get those business services from? Usually they are puzzled out from process models but this can result in an unmanageably complex result. By using domain models to deduce a “what do we actually do” model, things are much simplified and the result is actually usable.
But what does this all have to do with TITAN?

Originally Airport CDM was defined in the legacy way with the key element being the Milestones Approach. In brief this means that you identify a number of monitoring points or milestones along the turnaround process and you allocate times to each one of them. When the turnaround is in progress, you compare the time of actual achievement of a milestone with the planned time and deduce the degree to which the turnaround is on-time. If you fall too far behind, there is a problem and you will never make the off-block on time with all the dire consequences this entails.
While effective, the degree of possible anticipation and the granularity of the picture leave much to be desired when everything is predicated on watching completion of the milestones only.
Enter the services. Once more, it must be noted that we are talking about business services, i.e. something the system does to improve the ability to achieve the business aims as opposed to the IT services which constitute the underlying enablers one needs to achieve the business aims.

If you recall what we said about the best way to identify the business services needed (i.e. creating a “what do we actually do” model), it will be easy to see how the TITAN services were identified. So, what do we actually want to do above and beyond basic A-CDM that will improve the turnaround process beyond what A-CDM can do?
The complete picture of the turnaround can be described in a process oriented way, where the turnaround itself is the main process with the various activities (like fuelling, aircraft cleaning, boarding, etc.) being sub-processes, each of which needs to be completed on time in order for the main process to be itself successful (i.e. aircraft off-blocks on time).
The sub-processes give us a good appreciation of “what do we actually do” and hence they are a good basis for defining the services we need.
Knowing that passengers late at the gate constitute a major problem for the turnaround, we can say that we will want to closely monitor the flow of passengers towards their aircraft. Hence Passenger Flow Information Service – PFIS is one of the obvious TITAN services. With baggage being another potential source of problems, the BFIS or Baggage Flow Information Service is a natural second.
Keeping a close tab on the situation of the aircraft concerned as well as the airports involved through its trajectory is also important and so specific services have been created to cater for those needs.
Now we have the services, good, but what do they do?
To understand this, let’s take a look at an extract from a hypothetical scenario where TITAN is helping all partners in their decision making. We will take the case of a missing passenger as an example. PFIS is the Passenger Flow Information Service, BFIS is the Baggage Flow Information Service and ASRS stands for Aircraft Status Report Service. When we say a service “publishes” something, this means that the information is made available to all others (services or people) who have access privileges to the information.
“The PFIS notes that although the closing time of the boarding sub-process is approaching, three passengers travelling as a group have still not passed by the gate. They are known to have passed baggage drop off (they had checked in at home) and also security and one of the group members has also presented his boarding pass at one the concession stores.
PFIS publishes the Passenger Name Records (PNR) of the missing passengers.
BFIS notes that there are missing passengers at the gate. Based on the PNR and the associated baggage tag information, it publishes a “Possible flow disruption” message.
PFIS triggers the PA system which starts calling the missing passengers’ names asking them to come to the gate immediately.
PFIS extends the “occupied status” of the second bus used to take passengers to the remote stand where the aircraft is parked in expectation of needing it to rush the missing passengers to the aircraft.
ASRS publishes a “maximum time to find” message which means that it will change the aircraft status to “delayed” if the passengers are not found within the time limit given.”

Even this short extract from the scenario shows clearly how the various services collect information from the sub-processes they are responsible for, interpret them and then publish the results in a way that enables awareness of the situation and anticipation of the future to a much higher degree of detail and reliability than was the case before. Whether this higher detail is used to drive a more powerful graphical user interface or influence another service, the end result will be better decision making in a more predictable environment. As we all know, improved predictability is one of the keys to benefits for all partners involved in the turnaround process.
So, are milestones passé? No, they are not. Monitoring points and milestones can co-exist with the services and they will simply be one of the “sensors” that send information to be used by the services. The enhancements brought by the TITAN services manifest themselves in the fact that there are many more “sensors” that feed the services than just the milestones and hence a much finer picture of the turnaround can be generated for improved predictability and responsiveness.
When you look at the evolution of an aircraft’s trajectory from a CDM perspective, monitoring most of the trajectory as a whole or a part like the turnaround, with milestones alone is in many cases sufficient. It is when you want to really optimize the turnaround that you need something like TITAN that is able to work efficiently to the desired degree of granularity.
One of the benefits of a service oriented architecture is the reusability of the services. Although it is often said that no two airports are alike, the fact remains that certain elements are invariably identical or very similar irrespective of the differences. Passenger flow is a good example of this. While the physical characteristics of the different airports show a lot of variation, people must always get from the point of entry onto the airport premises to their aircraft. A well defined service able to monitor such a flow is reusable over and over across the “enterprise” with only the proper “sensors” having to be deployed taking local specifics into account.
It is not by accident that SESAR is also aiming to define the future ATM system in a service oriented approach. The potential for re-use of the services and other benefits service orientation offers are even more significant on the scale of a project like that.
TITAN, in its own modest way, will fit right into that big picture bringing added value to basic airport CDM.