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						Checking IntelligibilityThis 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.)  Back to What We Need 
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