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Inc. All Rights Reserved.
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The framework has been modified to process raw Deflate instead of GZIP, with the possibility to use a pre-loaded dictionary and specify the compression level from 1 to 9.
CWXML C library is now supported through the JNI adapter of Japex. Japex was modified to be able to generate graph including maximum memory
consumption.
7.9.1.2 Test cases
Four families of AIXM files were identified and populated: A first family composed of small files 10kB : tree Digital Notice To AirMen
DNOTAMs A second family composed of medium sized files between 10kB and 1MB, each
made from a single AIXM feature, bringing its own characteristic for instance airspaces, geo borders, runways and taxiways elements contains much more
coordinates than other features, routes have simple structure only 28 different elements taking 65 of the file compared to airspaces 60 different elements
taking 30 of the file
A third family made of bigger files 1MB, alternating both mixed features like the whole Estonian database or the sum of all features from family 2 or single
features to see how the performance of compression algorithms evolve along with volume
A fourth family made of technical files, useful to check a specific aspect against all algorithms influence of order, handling of autoclosing tags, dropping
comments, formatting ….
7.9.1.3 Results
To sum up the results of the AIXM Compression ER see OGC 11-097, we can conclude saying:
EXI, using both schema knowledge and deflate post compression reduces a D- NOTAM to 13 of the size of the original file with no more indenting and
comments. This compression level provides DNOTAMs under 1KB, which allows their transmission using Very High Frequency VHF datalink 4 messages
in Plain Old ACARS POA, 1 single Aviation VHF Link Control AVLC default frame for Aeronautical Telecommunication Network ATN or ACARS
over AVLC AOA.
The building of the grammar is slow seconds and consumes memory MBs, but is done only once at startup.
The deflate post-compression implemented in java in Exificient is slow and can be improved.
When the file size grows, EXI performance decays compared to other algorithms. Depending on the structure of the file complexity, presence of free text,
coordinates it performs better than deflate only in a 20-50 range. This poor
