I know that OpenJUMP uses a FID to uniquely track features during a "session" or period of time when the program is executing. I believe from earlier discussions on this list and in my work with the code that this FID is generated when a data source is loaded into a FeatureCollection.
I'm working on a very simple spatial relationship plug-in that I can use as a demo for an OSGeo article. The plug-in will allow the user to query information about the spatial relationships in features on the same layer or in different layers. I'm going to try storing this information persistently in an HSQL database. Here is the challenge I am facing. I need a way to uniquely identify features between sessions of OpenJUMP, or it does me no good to store the spatial relationship information. Since OpenJUMP supports a number of different file formats for the storage of features, the only sensible way (it seems to me) to do this is with a "special" attribute of the Feature. The attrubute would be named something like "persistent_id" and could store an int or long value. Here are some of my questions for the other OpenJUMP programmers: [1] I can't imagine that I will be the only plug-in developer that will want to identify features between sessions of OpenJUMP. Could we decide on a standard attribute name and data type to do this? I'll use just about anything that makes sense. [2] Is there a more elegant solution that I am missing? The solution I describe could have some problems. For example, what happens when you copy features and their attributes to a new layer? The persistent ID would be duplicated. (One way around this obstacle would be to use the layer name as part of the identification mechanism.) There could be other problems. For example, I think I would need to include a simple plug-in that could add this attribute to a Feature Collection's schema if it did not exist and generate values for this attribute on each of the features. I appreciate any thoughts or suggestions on this. Perhaps OpenJUMP already has the ability to persistently identify features and I am overlooking it. The Sunburned Surveyor ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
