72 information becomes available to the DMS, and is transmitted by the DMS to the aircraft
client. The DMS logs the time of message transmission to the aircraft client. Upon message reception, the aircraft client sends a reliable messaging acknowledgement to the
DMS. This client acknowledgement contains a timestamp describing message reception time. The DMS compares the acknowledgement timestamp to the DMS transmission
timestamp to determine the total latency from issuance to delivery. If the transmission latency is greater than the limit set by the client, the latency is logged as “Exceeds
timeliness”. If the transmission latency is less than the limit set by the client, the latency is logged as “Meets timeliness”. This metric is tracked and calculated by the DMS using
the following formula percent per 1,000 messages:
of messages sent to client minus of msgs exceeding timeliness factor of messages sent to client
13.1.3 Subscription Interval Validation
The purpose of the Subscription Interval Validation feature is to monitor subscription based ground services i.e. Event Service notification intervals to ensure they are
occurring within a client specified frequency. To configure this module, the aircraft client defines an acceptable range or variance from subscribed update intervals during
client validity policy creation. The DMS compares the actual reception interval of notification messages against the update interval configured by the client in the ground
service. Published notification messages received by the DMS within the subscribed update interval defined in the client’s Validation Profile are recorded as “Meets
subscribed interval” in a log. Published notification messages received by the DMS outside of the subscribed interval defined in the client’s Validation Profile, are recorded
as “Exceeds subscribed interval” in a log. The log is stored for future analysis by stakeholders.
13.1.3.1 Recommended Approach
During session negotiation, a client configuring the Validity Policy in the DMS will specify:
1. Whether or not the DMS is to perform “Subscription Interval Validation”. ONOFF
a. The update message interval the client configured for a subscription based service. String
b. The tolerated variance from client’s configured subscription based service. String
During the client Validity Policy creation, the client defines the acceptable range of variance from subscribed Event Service notification message intervals. Once the client
has configured its policy, the DMS compares received update message interval against the interval defined in the client’s profile. When the DMS receives an update messages
within the interval defined in the client’s profile, the DMS logs the update message
73 reception as “Meets subscribed interval”. When the DMS receives an update messages
outside of the interval defined in the client’s profile, the DMS logs the update message reception as “Exceeds subscribed interval”. The DMS tracks the ground services
compliance with notification message intervals by the following formula:
of messages sent to client minus of msgs subscriptions intervals missed by more than n seconds of messages sent to client
13.2 Implementation
During session negotiation, the client contacts the DMS with a GetSessionOptions request. The DMS responds to the client with a list of the available DMS modules and
their configuration options. To configure the Data Validation Module, the client configures a session profile, invoking specific DMS modules. The Data Currency
Validation feature configuration options are listed below: note: only one option can be selected by the client
1. Data Currency Validation a. OnOff Flag
b. OnOff Drop
13.2.1 Currency Validation
Messages sent to a client with “Data Currency Validation” configured as “On” in their Validity Policy will have all messages evaluated for the existence of currency metadata
e.g. AIXM TimeSlice. The currency metadata defines a time range in which the message is considered valid. To determine the validity of the message, the currency
metadata is compared to the time of message reception by the DMS. The DMS uses AIXM TimeSlice XML elements found in the AIXM standard to determine the validity
of a message. Messages received by the DMS with a TimeSlice element specifying a time range that is inclusive of the DMS message reception time, are considered to be
“valid”. Message received by the DMS with a TimeSlice element specifying a time range is non-inclusive of the DMS message reception time, are considered to be “non-valid”.
Valid messages are transmitted to the client unaltered. Invalid messages are either dropped or tag as “non-valid” and forwarded to the client, depend on the how the client
configured its Validity Policy.
If the client Validity Policy specifies the DMS shall drop non-valid messages, the DMS then blocks the transmission of non-valid to the client. If the client Validity Policy
specifies the DMS shall tag non-valid messages with metadata before transmission have a “validityfalsevalidity” tag inserted into their SOAP message header before
transmission to the client. The evaluation of timestamps by the Data Validation Module is aided through the use of standardized XML exchange models such as AIXM and
WXXM. Schemas defining the format of these exchange models are publicly available
