TECHNICAL MESSAGE SPECIFICATION .1 ASM Message Specification

5.7 SSM SUB-MESSAGE DEFINITION

5.7.1 NEW – Insertion of New Flight Information 5.7.2 CNL – Cancellation

5.7.3 RIN – Reinstatement

5.7.4 RPL – Replacement of Existing Flight Information 5.7.5 ACK – Acknowledgement

5.7.6 ADM – Change of Existing Information Expressed by the Use of Data Element Identifier Only 5.7.7 CON – Change of Aircraft Configuration/Version

5.7.10 NAC – Not Actioned 5.7.11 RRT – Change of Routing

5.7.12 TIM – Change of Time Information 5.8 ADDITIONAL MESSAGE EXAMPLES

5.8.1 NEW – Insertion of New Flight Information 5.8.2 CNL – Cancellation

5.8.3 EQT – Change of Equipment Information 5.8.4 TIM – Change of Time Information

5.1 Introduction

In order to allow all airlines to electronically exchange information on a deviation from their basic schedule, standard message formats have been agreed. These formats also allow the airlines to submit these amendments to schedule aggregators.

The message formats have been designed to provide as much clarity as possible for the message users and the received message details can be processed either by computer or by manual methods.

Deviations from the basic schedules, such as an addition of a supplementary or an extra flight, change to a single operation of an existing flight in routing, timing, equipment or other data and cancellation of a flight are transmitted using the Ad-Hoc Schedules Message (ASM).

A message may consist of one or more Action sub-messages. Each sub-message will have its own Action Identifier to identify a specific change being made to the basic schedule.

The rules for the use and composition of this message, together with detailed specifications and examples, are explained in the following Sections of this Chapter.

Amendments to the basic schedule may be transmitted in the Standard Schedule Message (SSM).

The rules for the use and composition of this message, together with detailed specifications and examples, are explained in Chapter 4.

The Ad-Hoc Schedules Message (ASM) forms part of a complex system of timetable information exchange. The design of the message is based on the philosophy that a flight is recognised by the Flight Identifier, i.e. the combination of the Flight Designator and the Flight Identifier Date.

The ASM applies to long term ad-hoc modifications of schedules (generally resulting from schedules or operational planning) as well as short-term operational decisions that affect flight schedules.

For reporting of operational events, such as delays and actual movements not affecting schedules, reference should be made to the procedures defined in the IATA Airport Handling Manual (AHM).

In order to facilitate industry-wide acceptance of these standards, a range of optional features is included to ensure complete compatibility with the standards set in Chapter 7 for the exchange of computerized schedules and with the Standard Schedules Message set in Chapter 4.

These optional features include such items as the use of local dates and times, leg and segment oriented traffic and sales information.

5.2 Principles and Rules

In order to ensure full interline exchangeability, it is strongly recommended that airlines adhere to the rules for the construction of the standard messages as described in this Chapter.

The common rules for the data elements as described in Chapter 2 of this Manual should also be followed.

• The ASM exchange usually takes place on the basis of bilateral understanding.

• The ASM may be issued at any time prior to the actual departure from the station concerned. It shall be regarded as a firm amendment to the basic schedules except for punctuality rules that may vary from airline to airline.

• The addressees of the ASM are selected at the originator's discretion and will normally be limited to the parties directly concerned.

• Any schedules or changes advised by ASM cannot be modified by subsequent computerized schedule data sets or SSM (unless the ASM Withdrawal Indicator has been used).

A facility exists, however, to withdraw an ASM modification by re-establishing the original flight

• Any bilaterally agreed use of local dates and times must be based on the current information in SSIM Appendix F and any updates to it by message.

If the relation used is different or doubtful, it should be stated using Data Element Identifier 97 (UTC/Local Time Variation Specification).

• If a Flight Leg(s) Change Identifier in a sub-message does not match the routing of the flight(s) being changed, that sub-message may be ignored by the recipient.

• If a Segment on a line of a sub-message does not match a Segment of the flight(s) being changed, that line of the sub-message may be ignored by the recipient.

If a change or cancellation is received where the period and/or days of operation to be changed/cancelled do not match those stored, or a new flight is added that is already stored, it is recommended that the correct schedule information should be requested from the sender, e.g. by use of SSM/RSD.

• The ACK/NAC exchange takes place on the basis of bilateral agreement.

• It is assumed that it is the responsibility of the ASM sender to ensure that they receive an ACK or a NAC and take the appropriate action if not.

5.3 Message Standards

5.3.1 Introduction

The technical specifications for message construction are based on the guidelines of the ATA/IATA Systems and Communications Reference Manuals (SCR).

The standard message is enclosed within the standard communications “envelope”, i.e. signal identifiers, serial number, priority, address, originator and date/time of transmission.

The message will then read line by line by always starting at the left, i.e. left justified. For Type B messages, the maximum line length of the message must not exceed 69 printable characters including spaces. Some systems may restrict line length limits to less than 69 characters.

Although the Systems and Communications Reference Manual defines the maximum number of characters for one telegragh (Type B) message as 3,840, some service providers have the capability to increase this limit to 64,000 characters.

Type B users are, however, cautioned that some systems may not be able to receive or process messages with more than 3,840 characters.

This maximum length limitation takes into account all printed and non-printed characters, such as letter shifts, figure shifts and new line.

In the extreme case of a Flight, Aircraft or Leg Information line overflow, the excess elements should be stated on an additional line immediately following and must start with a Data Element Identifier.

When the message limit is exceeded, messages must be broken into separate parts with a Break between two sub-messages. Use can be made of the Message Sequence Reference to connect the related parts of the total message.

5.3.2 Security of Message Exchanges

To secure the exchange of ASMs between computers, it is recommended that the following techniques be used:

• Sequence all ASMs using the Message Sequence Reference;

• Process all ASMs in the same order as they are produced, according to the Message Sequence Reference;

• Request the re-transmission of a missing ASM using a “REPEAT” message:

ASM REP

‹Message Sequence Reference›

An “REP” message is sent by the receiver to inform the sender that a message has not been received. The ASM originator will identify the missing message by its Message Sequence Reference and will re-transmit the original message identified with original Message Sequence Reference and with the same data content.

• Inform the receiver of the last message sent within the current date of issue using an “END”

message:

ASM REP

‹Message Sequence Reference›

The “END” message is designed to close the current sequence of messages before opening another one. It will allow recovery with an “REP” of the last message of the current sequence if this message has not been received. The Message Group Serial Number of the “END” message will be the previous Message Group Serial Number incremented by 1. The “END” message is unique for each date of issue.

5.3.3 ASM Composition

Each ASM message consists of consists of 5 major components:

• Message address/originator in accordance with communications instructions;

• Message Header including the Ad-Hoc Schedules Message Identifier (ASM), the Time Mode and an optional Creator Reference;

• One or more Action Sub-Messages that always include one or two the Action Identifiers, the flight identification and appropriate data elements, and always ends with a Sub-Message separator;

• An optional Supplementary Information Sub-Message applicable to the whole message;

• Message End in accordance with communications instructions.

The ASM Action Sub-messages are defined in Section 5.4.

The general technical specifications for ASM message construction are defined in Section 5.5.

The ASM Action Sub-Message composition and examples are defined in Section 5.6.