John,
You may wish to try h5ls tool to find the address of the object 
header for that dataset and then use h5debug tool to see header 
messages.
I believe commands will be like in the following examples
h5ls -var file.h5
You will see addresses of the datasets (say the address of the 
dataset you are interested in is XXXX).
Then use h5debug
h5debug file.h5 XXXX
to see the messages at address XXXX.
May be it is not exactly the correct syntax but it is easy to figure 
out when you know what you are looking for in the file.
Elena
At 5:50 PM -0600 7/24/07, John Caron wrote:
    Hmm, looks like the docs are out of date and/or wrong for 
region references.  Because region references are variable in 
length, the actual reference information is stored in the global 
heap and a (fixed length) heap ID is stored in the dataset's raw 
data - that part is right, although too briefly described.
the data storage layout messaage seems to imply the HeapID is 12 
bytes long. Usually they are 16 bytes long.
   type = Layout(8); contiguous storageSize = (2,12) dataAddress=13352
I dont see enough detail in h5dump:
        DATASET "VIIRS-NCC-EDR_Gran_0" {
           DATATYPE  H5T_REFERENCE
           DATASPACE  SIMPLE { ( 2 ) / ( 2 ) }
is there another option that would verify that?
in any case is 12 bytes correct? if so, what does a 12-byte HeapId look like?
The format of the data in the
heap is wrong however.  The information actually stored in the heap 
is as follows:
    - The offset of the object header of the object (ie. dataset) 
pointed to (yes, an object ID)
    - A serialized form of a dataspace _selection_ of elements (in 
the dataset pointed to).  I don't have a formal description of this 
information now, but it's encoded in the H5S_<foo>_serialize() 
routines in src/H5S<foo>.c, where foo = {all, hyper, point, none}.
    There is _no_ datatype information stored for these sort of 
selections currently.
    I'll file a bug report in our bugzilla to make certain this 
description gets fixed in the file format spec.
    Quincey
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