[Kstars-devel] Some thoughts on catalogs

[Khudyakov Alexey]

Hello.


I believe that there is a problem with current data model. Stellar objects can 
(and they do) appear in different catalogs. But there is no way to express 
such relation. DeepSkyObject has ugc() and pgc() methods[1] which return UGC 
and PGC number respectively. This isn't best way to add multiple catalog 
support. And of course i does not provide way to get data from that catalogs. 

Second there is no way to extract arbitrary data from catalog. Star catalogs 
can contain very diverse kind of data. Data which is present in one catalog 
may be absent in another. Currently there is no way get arbitrary data 
present in catalog. Creating all possible virtual functions is infeasible in 
my opinion. Just too many of them. 

So what is catalog? I'm going abstract from that point. Catalog is just set of 
pair: { (k,v) } where `k' is record type (magnitude, RA, B-V, etc.), and `v' 
is some value. Problem is that it could easily be of any type: number, 
string, couple of numbers. So it's difficult to implement this properly. 
I haven't much idea about it. It's kind of heterogenous map.

Another problem I mentioned already - creating one object <-> many catalogs 
relation. It's only become more difficult with need to utilize HTM and 
requirement that catalogs must be pluggable. 

This is attempt to formulate problem. No solutions or even proposal yet.
Comments, suggestions, crytitism are welcome. 

[1] kstars/deepskyobject.h : 152,157
--
  Khudyakov Alexey