[Smwg] Two more issues coming from development front
Marcin.Gnat at dlr.de
Marcin.Gnat at dlr.de
Fri Jan 26 14:01:28 UTC 2018
I just wanted to provide two more observations/issues from the "development front" while implementing CCSDS Service Management.
1. Xrefs and ID's in our documents are mostly of type xsd:string, which is as such unlimited in the length. I do not remember if we did had enough thoughts on that already, but in principle the issue is, that most of the databases (like MySQL) support the length of indexed references up to 256 characters (or even less). Only the Oracle (which belongs to rather expensive ones) supports indices of 1024 characters. Especially if we imagine in future users generating ID's based on some uri's (like iso:ccsds:blah:blah:blah... ;-) ) it can quickly exceed the limit for the most of databases. Now, it is possible to use internally in the database separate indexed references, and map them to the external ones, but this makes the actual database advantage (indexed references -> quick references) to be inherited. Effectively, to find anything in database based on such long reference, causes the search mechanism to walk through all records. Maybe this is not an issue, because we may imagine not have such large databases it will be something to care about. I do not know. Limiting the ID's and Refs to let's say 128 characters would overcome this issue, but I'm not sure this good in terms of uri's. Anyway, just to have an awareness of that.
2. Usage of CDATA in datatype for Trajectory (SMURF). As such the CDATA for trajectory would be okay. However, as soon there will be some entity, which will include the trajectory data from us, and will be than also provided as CDATA itself, this will cause XML parser to crash with error, as nesting of CDATA inside other CDATA is not allowed. So other words, as long we guarantee the CDATA is used only in case of trajectory submission and InfoRequest, than it's fine. The references to trajectory are also okay. But as soon we come to the idea of having this embedded (like verbose version of Service Package) and combined with other CDATA extensions, we may get into issues. So, again, just to wave a flag about it.
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