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Suggestions for
Checking Intelligibility This is usually easily
checked, but sometimes it requires a bit of simple
programming. Also, while it is true that many formats
both common and arcane are ultimately intelligible,
reviewers should keep in mind that PDS requires these
files to be readable on the timescale of decades. Thus,
the preferred formats are those that are essentially
simple and logically consistent with the type of data
being archived.
ASCII Data
Most often this is in the form of a table. Reviewers
have repeatedly demonstrated a preference for ASCII
format for tabular data, even when the data were
delivered in a binary format, because it is so easy to
visually inspect the data and determine that it is
intact. Thus, human-readability is usually a large
factor in determining the intelligibility of ASCII data
sets. The best test of intelligibility is to print out a
section of the file and examine it.
- If the data are intended to be used primarily
via visual inspection (a cross-identification list
or small catalog, for example), is the record size
small enough that the file may be easily printed or
viewed with an editor?
- Was the file printable? Displayable on a
computer screen?
- Are data values appropriately aligned (i.e.,
decimal points aligned, character values
left-justified, etc.)?
- Is there a blank column or other delimiter
separating fields?
- Are the data values appropriately formatted,
especially fields with exponent values?
Binary Data
There are essentially two types of binary data: image
and tabular. Image data is 2-dimensional and should be
displayable with suitable software; tabular data is
either a simple vector or an inhomogeneous array,
yielding either a plot or an equivalent ASCII table of
values, respectively. Given that ASCII is so often
preferred for tables, some nodes routinely convert this
last form into an ASCII table prior to ingest. However,
some data sets are so large or so clearly intended to be
used as input to a display or reduction routine that
they are left as binary tables in order to conserve disk
space.
Either way, checking the intelligibility of binary
data will almost always involve some programming.
- For binary tables: is it possible to generate an
ASCII equivalent?
- For linear data: is it possible to produce a
graph or plot of the primary datum?
- For image data: is it possible to display the
image?
- In all cases, do the data values look real, or
do they look like noise?
Problems?
Problems encountered reading the data should be
relayed to the discipline node as soon as possible
so that they can be resolved immediately. (Clearly, an
inability to read the data precludes the possibility of
determining its fitness for archiving.)
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