--- /dev/null
+Barcodes module documentation
+==============================
+
+The Barcodes module defines barcode nomenclatures whose rules identify specific type
+of items e.g. products, locations. It contains the following features:
+
+- Barcode patterns to identify barcodes containing a numerical value (e.g. weight, price)
+- Definitin of barcode aliases that allow to identify the same product with different barcodes
+- Unlimited barcode patterns and definitions,
+- Barcode EAN13 encoding supported.
+
+Barcode encodings
+-----------------
+
+A barcode is an arbitrary long sequence of ASCII characters. An EAN-13 barcode is a 13 digit
+barcode, whose 13th digit is the checksum.
+
+Simple barcodes and rules
+-------------------------
+
+The default nomenclature assumes an EAN-13 encoding for product barcodes. It defines a rule
+for Unit Products whose encoding is EAN-13, and whose pattern is '.', i.e. any barcode
+matches this pattern. Scanning the barcode of a product, say '5410013101703', matches this rule.
+The scanned item is thus identified as a Unit Product, and is retrieved from the product table.
+
+Note: the special character '.' in patterns is matched by any character. To explicitely specify
+the '.' character in a pattern, escape it with '\'. The '\' character has to be escaped as well
+('\\') to be explicitely specified.
+
+Let us now suppose that we identify other items with barcodes, say stock locations. We define a
+new rule in the nomenclature with the corresponding type (in our example, the type is 'Location'),
+and whose pattern is e.g. '414.', that is, any location barcode starts with '414'. Scanning a barcode
+location, say '41401', matches this Location rule, and the corresponding location is retrieved from
+the location table.
+
+Note: Rules have a sequence field which indicates the order the rules are evaluated (ASC). In our
+previous examples, the Unit Product rule should have a larger sequence that then Location rule,
+because we want the latter one to be evaluated first.
+
+Barcodes with numerical content
+--------------------------------
+
+Barcodes may encode numerical content, which is decoded by the barcodes module. To that purpose,
+one have to define a new rule for barcodes with numerical content (e.g. barcodes for Weighted
+Products). The numerical content in a pattern is specified between braces (special characters '{' and
+'}'). The content of the braces must be a sequence of 'N's (representing the whole part of the numerical
+content) followed by a sequence of 'D's (representing the decimal part of the numerical content).
+For instance, let us define a new rule for Weighted Products whose pattern is '21.....{NNDDD}.'. Since
+we assume EAN-13 encoding for product barcodes, the encoding of this rule should be EAN-13 as well.
+
+Let us now assume that we want to write a barcode for a given Weighted Product, say oranges. We first
+have to define in product oranges a barcode that will match the Weighted Product rule. This barcode
+must start with '21' and be a correct EAN-13 barcode (i.e. the 13th digit must be a correct checksum).
+Moreover, all the numerical content must be set to a '0'. For instance, let us set the barcode to
+'2100001000004'.
+
+We now want to write a barcode for 2.75kg of oranges. This barcode should be '2100001027506' (the
+numerical content of this barcode is '02750', and the correct checksum is '6'). When scanned, this
+barcode matches the Weighted Product rule (since is starts with '21'). The numerical content is extracted,
+and replaced by a sequence of '0's. The correct checksum is then computed for the obtained barcode
+('2100001000004') and the corresponding product (oranges) qgit is retrieved from product table.
+
+Note: the special characters '{' and '}' in patterns are used to identify numerical content. To
+explicitely specify '{' or '}' in a pattern, they must be escaped.
+
+
+Strict EAN-13 field of barcode nomenclatures
+--------------------------------------------
+
+Many barcode scanners strip the leading zero when scanning EAN-13 barcodes. Barcode nomenclatures
+have a boolean field "Use strict EAN13". If False, when trying to match a scanned barcode with
+a rule whose encoding is EAN-13, if the barcode is of length 12 and, by prepending it by a 0,
+the last digit is the correct checksum, we automatically prepend the barcode by 0 and try to
+find a match with this new barcode. If "Use strict EAN13" is set to True, we look for a pattern
+matching the original, 12-digit long, barcode.
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