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Updated dataconsistency (markdown)

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Christopher Ronnewinkel committed 2013-12-05 10:38:53 +00:00
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wiki/planning/businesscases/dataconsistency.md
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# Data Consistency
## Description
### Rationale
The SAP sailing solutions are a set of software applications that process data - live and recorded - about sailing regattas, in order to visualize sailing races, various linked measures, as well as, regatta results. In order to capture sailing races, information about the race course, the competitors, the boat positions, the weather conditions (especially wind and water current), mark passing times and race times are transmitted using various kinds of wireless communication and collected on servers as raw data. In further processing steps, this raw data is linked by data structures to allow for visualization, live ranking estimation, scoring calculation and calculation of aggregate measures like boat speed, velocity-made-good, distance-to-leader, and more.
Linkage of raw data for example includes mapping of GPS-tracker-IDs to mark-IDs and competitor-IDs, joining time-dependent data along UTC time line and handling differing sampling rates, as well as, transmission delays for different kinds of raw data.
In an ideal world, this linkage would always work correctly and result in an all-time consistent representation of the race in terms of visualization and derived measures. However, in the real world of public events, a complex mixture of causes typically leads to intermittent faulty, misaligned or even missing raw data which in turn influences derived measures negatively with regards to accuracy, consistency, or even their well-definedness.
The experience from previous sailing events has shown that the SAP sailing solutions are currently quite sensitive to such intermittent faults in raw data. This results for example in misleading live ranking estimation, wrong visualization of the advantage line, non-availability of live play or replay of races, obvious out-of-range values of derived aggregate measures.
One approach to tackle these problems is to work and improve on the data measurement units (e.g. GPS trackers, wind measurement unit), improve the data transmission infrastructure (e.g. wide-range Wifi vs mobile network GPRS), increase the stability of required WAN network connections to remote servers (e.g. reserve DSL-lines for sailing IT) and extend education & discipline of involved people (e.g. sailors should not accidentally power-off GPS-trackers, race committee officers should not rearrange GPS-trackers across race course marks). But even on events were all these requirements were seemingly fulfilled, intermittent faults in raw data and hence faults of SAP sailing solutions have occurred in the past.
Another approach to gain higher stability of SAP sailing solutions is to introduce robustness against raw data faults right into the heart of data processing: data structures should be able to represent raw data faults and aggregate calculations should react moderately ensuring well-definedness and consistency of visualization and all data displayed.
### Purpose
### Features