1. The European Organisation for the Safety of Air Navigation AIXM 5.1 – use of CRC Draft proposal

2. DNM/COO/NOM/ADM ADQ CRC Workshop 2 ADQ Context – pragmatic solution Regulator group to acknowledge formally that CRC32 is not mandatory; more constraining algorithms (MD5, SHA-1, SHA-2, etc.) would be a sufficient means of compliance AIXM CRC Guidelines Provide a ‘basic’ CRC solution (extension), for those who are imposed by their regulator to strictly comply with the Regulation

3. DNM/COO/NOM/ADM ADQ CRC Workshop 3 CRC - guidelines operational principles AIXM 5.1 support extension

4. DNM/COO/NOM/ADM ADQ CRC Workshop 4 The VERY IMPORTANT question 1.Do we need to allocate a CRC value when the data is originated and preserve (store/transmit) that same CRC value along the whole data chain, up to the end user? Or 2.Is it OK if CRC are used just for data in transit, meaning that they are calculated 'on the fly' when the data is packed for transmission, checked at the other end and then dropped?

5. DNM/COO/NOM/ADM ADQ CRC Workshop 5 CRC recalculation allowed when merging data sub-sets Data merging – re-calculate CRCV! DATA SUB-SET 1 IdentifierHeightCRCV Point A123.45 AAAA123 Point B110.65 AAAA456 DATA SUB-SET 2 IdentifierLatitudeLongitudeCRCV Point A532432.15N0342355.49E BBBB123 Point B533000.00N0342355.49EBBBB456 DATA SET A IdentifierLatitudeLongitudeHeightCRCV Point A532432.15N0342355.49E123.45 XXXX123 Point B533000.00N0342355.49E123.45XXXX456

6. DNM/COO/NOM/ADM ADQ CRC Workshop 6 CRC in AIXM 5.1 Nothing included in the core model Unclear requirements at the time when model was finalised Original thought – use Metadata (ISO 19139) schema, already embedded in AIXM 5.1 Current proposal AIXM 5.1 extension Main principle = flexibility CRC on whole features and/or selected attributes Use xpath to indicate which elements are included

7. DNM/COO/NOM/ADM ADQ CRC Workshop 7 CRC Extension

8. DNM/COO/NOM/ADM ADQ CRC Workshop 8 CRC extension

9. DNM/COO/NOM/ADM ADQ CRC Workshop 9 AIXM 5.1 – resulting XML encoding AIXM Extensions Each AIXM Feature CRC “subjects” - xPath expression … //aixm:ARP//gml:pos | //aixm:ARP//aixm:elevation | //aixm:ARP//aixm:elevation/@uom 582C2727 …

10. DNM/COO/NOM/ADM ADQ CRC Workshop 10 CRC in AIXM 5.1 Open questions Need to specify CRC algorithm? Probably not, also allow MD5, SHA-1, SHA-2, etc. Doe we need a predefined list? CRC calculated on values only? Same CRC value remains valid during non-XML storage Or also including tags? Unusable for non-XML storage

11. DNM/COO/NOM/ADM ADQ CRC Workshop 11 Questions