[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Round 2: Identifying Data for Interchange
Hi Don, Don Bate wrote: > > You've got this backward. Position is always derived from distance, > azimuth, or elevation measurements and there may not be enough > measurements to calculate position. Thanks for your observations. I am sure that you are correct, but I'd rather not go on a tangent about peculiarities of my example. Let's make it simpler: Let's take a sheet of graph paper. Put a dot on the paper. That's the ground station. Now put another dot somewhere else. That's the aircraft. Now calculate (derive) the distance using Pythagorean's theorem. Now move the aircraft to another x, y location. Calculate (derive) the distance. If a client were to receive a sequence of these x,y coordinate values then he/she could: - calculate the distance - calculate the heading - calculate the relative location of another aircraft - plot this onto a map etc. Let me call the position data fundamental, and the distance data derived. ... Now let's get back to the hard issues: - should there be 2 schemas, one for fundamental data and one for derived data? I will argue that there should only be one schema - the fundamental data schema. Derived data is transient and should not have its own schema. What do you think? - at what point does sharing of fundamental data become a Service of derived data? /Roger
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