[GRASS5] How to write to a vector coverage?

[Cedric Shock]

To whomever may be of assistance,

I am working on a vector import method for Trimble .ssf files. I have 
most of the file format worked out. Now I need to find a way to put the 
information into grass. My target version is 5.3.

I took a look at the grass 5 programming manual, and did not find what 
I'm looking for.

How can I open an existing vector coverage and add features to it. The 
documentation indicates that we have a read only interface for existing 
data and a write only interface for new data. How can we add new data to 
an existing coverage? Can you provide an example of code that does this?

Alternatively, is there a high level file format that is easy to 
generate with which I could use an existing import utility to bring the 
data into grass?

I did not find structs for point, line, area, etc. How much information 
can be encoded with vector information? I understand that we can do 
diferent map layers, and can assign category numbers in those layers. So 
we could have a database like:

Layer	Category
Roads
	1. US 95
	2. SW 48th st
	...

Waterways	
	1. Porcupine Creek
	2. Octopus River
	...


Can we encode any of the following information with a vector:

Error / variance for points?

Elevation of points?

Other observations like regions with continous (non - categorical) 
measurements like density associated with each region.

Can the vector implementation handle features which are single points of 
data, or will I need to make site coverages for these?

Thank you in advance for your time and input,

Cedric Shock