A standard system for encoding and transmitting bar
code data where data message bytes are output from the decoder
but no control information about the message is transmitted.. A
decoder, complying to this model, operates in Basic Channel Mode
One of three subsets of ‘PDF417' symbol characters,
all of which are mutually exclusive. The symbol characters in a
given cluster conform to particular structural rules which are
used in decoding the symbology.
A single group of bars and spaces (or "elements")
representing one or more numbers, letters, or other symbols (i.e.,
codeword values for the data to be encoded). Each PDF417 codeword
contains four bars and four spaces, for a total of 17 module
widths. Each codeword starts with a bar and ends with a space.
The name given to one of three data compaction
algorithms in ‘PDF417': Text, Numeric and Byte Compaction modes.
These modes efficiently map 8-bit data bytes into ‘PDF417'
codewords.
Mathematical calculations used to reconstruct
undecoded or corrupted portions of a PDF417 symbol.
A codeword in a symbol which encodes a value derived from the
error correction codeword algorithm to enable decode errors to be
detected and, depending on the error correction level, to be
corrected.
A procedure within some symbologies, including ‘PDF417',
to replace the default interpretation with another interpretation
in a reliable manner. The interpretation intended prior to
producing the symbol can be retrieved after decoding the scanned
symbol to recreate the data message in its original format.
A system for encoding and transmitting both data
message bytes and control information about the message. A
decoder, complying to this model, operates in Extended Channel
Mode. The control information is communicated using Extended
Channel Interpretation (ECI) escape sequences.
A codeword in a symbology which initiates a particular
operation within the symbology, for example to switch between
data encoding sets, to invoke a compaction scheme, to program the
reader, to invoke Extended Channel Interpretations.
A procedure in the ‘PDF417' symbology, which
behaves in a similar manner to Extended Channel Interpretation.
The GLI system was the symbology-dependent precursor to the
symbology-independent ECI system.
A latch character causes a mode switch to another
mode. That mode stays active until another latch or shift character occurs and activates a new mode.
A procedure within the ‘PDF417' symbology to
logically distribute data from a computer file across a number of
related ‘PDF417' symbols. The procedure considerably extends
the data capacity beyond that of a single symbol.
Compaction schemes used to reduce the overall size
of the PDF417 symbol.
A codeword in ‘PDF417' which is used to switch from one mode
to another mode, which stays in effect until another latch or
shift codeword is implicitly or explicitly brought into use, or
until the end of the label is reached.
A codeword in ‘PDF417' that is used to switch from one mode
to another for only one codeword.
The nominal unit of measure that is the narrowest
width of a bar or space in a bar code. In a PDF417 bar code, all
bars or spaces are multiples (up to six times) of this width.
A lateral set of elements made up of a start pattern,
codewords, and a stop pattern. Each PDF417 symbol must have at
least 3 rows. In each row, between left and right row indicators,
there may be from 1 to 30 data codewords. Collectively, among all
rows, these codewords form data columns.
A ‘PDF417' codeword adjacent to
the start or stop character in a row, which encodes information
about the structure of the ‘PDF417' symbol in terms of the row
identification, total number of rows and columns, and the error
correction level.
The level of error correction used in the PDF417
symbol.
A shift character causes a mode switch for only one
character or codeword, returning immediately afterward to the previous
mode.
A unique pattern of light and dark elements that
indicates the leftmost part of a bar code label.
A unique pattern of light and dark elements that
indicates the rightmost part of a bar code label.
The ratio of the height and width of a PDF417 symbol.
The codeword in a ‘PDF417' symbol that encodes the total
number of data codewords in the symbol. The symbol length
descriptor is always the first codeword in a ‘PDF417' symbol.
The width of the narrowest bar or space in a bar
code symbol.
The sequence that represents the module widths of
the elements of a symbol character.
The height of a row in PDF417.