Barcodes

Barcodes are an efficient mechanism to retrieve documents with minimal user input. BHIMA generates barcodes for every receipt produced. This document describes how barcodes work in BHIMA.

Record Naming Conventions

Note: this might be best put somewhere else

Internally, BHIMA uses version 4 universally unique identifiers (UUIDs) as the primary key for most records. While they have many advantages, being humanly readable is not one of them. In order to easily and meaningfully refer to documents, we developed a human-readable “reference” composed with the following syntax:

${type}.${project}.${integer}

where ${type} is the two letter document type, ${project} is the abbreviation of the project which created the document, and ${integer} is monotonically increasing integer identifier. Some examples of these references may be IV.TPA.123, VO.XYZ.333, and so on.

The following types are hard-coded into the system:

1. IV -> Invoice
2. VO -> Voucher
3. CP -> Cash Payment
4. SM -> Stock Movement
5. PA -> Patient Card

Thus, the reference PA.NXR.3 is read as “the third patient of project NXR”. Similarly, VO.UOU.39410 is the “39410th voucher of project UOU”.

Barcode Generation

Similar to the human readable references, the barcodes generated by the system have a specific syntax. It is:

${type}${first 8 chars of UUID}

For example, a barcode might be IVBBA182AF which denotes the invoice with the first 8 characters of the uuid as BBA182AF. The code is found in server/lib/barcode.js.

Why use 8 characters? Because barcodes are wide and we needed a format to fit on an 80mm thermal receipt while still being readable. Despite their obfuscation, barcodes are an alphabet, read left to right. More characters create a longer barcode “word”. Interestingly, QR codes do not have this problem - instead they increase the complexity of the QR code pattern. But QR code readers are expensive whilst barcode readers are cheap.

How barcodes are read in BHIMA

A barcode reader behaves like a keyboard. BHIMA uses a barcode reading component (found in client/src/modules/templates/bhBarcodeScanner.html) to do all the work of reading the barcode. The barcode reader will return the uuid of the record scanned. It is up to the module’s controller to determine what needs to happen next (render a receipt, attach to an object, load the record from the database, etc).

Because a barcode reader behaves like a keyboard, you don’t need a barcode reader to fake a barcode read. Simply copying a string, opening the barcode reading component and pasting (C-V) will trigger the read with the content that you pasted. This is quite useful during development when barcode readers are not handy.