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Second, contamination can happen in method 1) above if a pen or paper is moved from one
location to another. Similarly to the previous contamination example, if there exists a document
in the Capture Database where the "wrong" data is processed, it will update a document where
it does not belong. Again, neither the pen nor PlanetPress Workflow have any idea that this
causes an error until it's too late.
Third, contamination (the most common one) can happen if pattern sequences get mixed up, if
pens or paper gets swapped between users, etc. For example, again using a shipping
company (with example 2-A), if two of the drivers were to meet for a coffee and exchange their
pens inadvertently (we hope, anyways), the pens would be signing the "wrong" documents all
day and, when docked, would update the wrong documents in the database.
In all of these cases, the errors often do not appear when the wrong document is updated - it
actually occurs when the "right" data is processed. This happens precisely because the Pen
and Production have no idea that the wrong data is received and will generally close the
document after that "wrong" data has been processed - this often works with no error. However,
when the "right" data is processed, then it tries to update a document that has already been
closed by the "wrong" data, and thus fails.
Safeguards
There are certain safeguards against contamination:
l PlanetPress Capture checks for pattern size and placement. If the data contains ink for a
specific pattern but the ink location does not correspond to the Capture Fields of the
document it's updating, it will fail.
l Errors can be set to stop and revert the whole current batch. If a single error occurs during
the pen data processing, it is possible for this processing to be stopped and all changes
the Capture Database reverted. In implementations where the pen signs high number of
documents, this can especially be an easy way to do this, as chances are the data will not
match in at least one case.
Conclusion
l PlanetPress Workflow can only generate 20,000 unique patterns
l One pattern is used (locked) for each page containing a pattern.
l Processing the ink data from a pen and closing the document releases the pattern
l Most implementations will not need more than 20,000 patterns
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