Advanced calculations
Raw data entry is only the start of your digital quality management. Based on this data, you want to make decisions and steer your operation. These decisions rely on predefined business rules and logic. Imagine how effective and powerful your quality system would be if it could apply these rules and logic automatically. Well, that is exactly what AlisQI is capable of with the expression engine.
The calculations that you can add to analysis sets are powered by our expression engine. This versatile engine enables you to implement rich logic in your analysis sets. Combined with the workflows, this enables you to create business logic within AlisQI.
This article presents an overview of how to create and use advanced expressions in AlisQI. Due to the vast possibilities, this guide is necessarily incomprehensive. Please refer to the resources on the bottom of this page for full documentation of the underlying syntax and available features.
In this article
Introduction
Let's start with a short introduction video on the power of the AlisQI expression engine.
Syntax and features
The expression engine is based on Twig, an opensource templating engine.
The expression engine supports a rich syntax with many features, including functions, filters, tests, and operators.
Since the expressions run in a sandboxed environment there is no security risk. Users can never get to the core application code by means of the expressions engine.
Variables
{fieldname_}
During the evaluation of the expression, the variable contains the value of that particular field. Calculated values are available as well. This enables you to create complex, nested expressions.
Operators
Twig provides a variety of operators for math, logic, comparisons, and other means.
Here are two examples to show you a few possibilities of operators.
1. if the user is known, display the username, display 'unknown user' otherwise
'Hello, ' ~ ({user_} ? {user_} : 'unknown user')
2. if the remainder of a divded by b is nonzero, return b, else 1
{a_} // ({b_} != 0 ? {b_} : 1)
Filters
Variables can be modified by filters. Filters are separated from the variable by a pipe symbol ( 
). Multiple filters can be chained. The output of one filter is applied to the next.
The 'upper' filter would convert 'diana' into 'DIANA'
{name_}upper
The 'capitalize' filter would convert 'diana' into 'Diana'
{name_}capitalize
Functions
Functions can be called to generate content. Functions are called by their name followed by parentheses () and may have arguments.
For instance, the date function can convert date(time)s. The following function call returns the current date minus 2 days:
date('2days')
See Twig documentation on functions
Tests
Tests can be used to test a variable against a common expression.
{numericfield_} is odd 'pass' in {status_}
See Twig documentation on tests
Greater than and less then operators
Values with a <
or >
sign are inaccurate by nature. Calculating these values can be risky, as the outcome can be inaccurate. AlisQI aims to keep the data accurate. This can lead to not performing a calculation that cannot be resolved to an accurate value.
Learn all about AlisQI's behavior with these operators here
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Beyond result values

The value for a particular field in your analysis set. Can be null .For selection fields, this is the string value of the chosen option (e.g., "Pass"). 
{fieldname_}.id For selection fields only 
The option's static id, as integer numeric value. Use this to prevent changes to the option value (e.g., from "Pass" to "OK") from impacting the calculation. 
{fieldname_}.option For selection fields only 
This syntax allows you to retrieve all field values from a selection list option. See example #7 below. (Technically speaking, the .option is a hash of the selected option's values.) 
{field_}.spec 
The current specification values for this field. For numeric fields (including calculations), this is a hash with keys min, innermin, goal, innermax, max . Access any boundary using {field_}.spec.min .For selection fields, this is a list (array) of inspec options (e.g., ['White', 'Transparent'] ). 
{field_}.offspec and {field_}.offspec_internal For selection and numeric fields only 
Boolean value which indicates whether the value is outside of (internal) specification. 
{fieldname_}.label and {fieldname_}.unit 
The field's label and unit (if any, can be null ). 
{fieldname_}.decimals and {fieldname_}.default For numeric fields (including calculations) only 
The field's number of decimals and default (if any, can be null ). 
{fieldname_}.visibility 
The current field visibility state for this field. 
{fieldname_}.operator For numeric fields (including calculations) only 
The operator (< or >) set for this field (if any, can be null ). 
attachments 
The list (array) of filenames, e.g., ['CoA.pdf', 'Delivery by pallet.jpeg'] . 
Examples
Calculate the expiry date by adding 3 months to the production date
DATE_ADD_MONTH({productiondate_}, 3)
({productiondate_}date('U') + 3 * 30 * 24 * 60 * 60)date('Ymd')
Logical expressions
If (condition) then (A) else (B)
Can be defined as:
condition ? A : B
Read here about how to use logical operators in your expressions.
Use the inputted value, or fall back to the goal spec if no value was inputted. (Uses the ternary operator)
{ph_} ?: {ph_}.spec.goal
Test if an attachment was uploaded
attachments is empty ? "No attachments" : ("Number of attachments: " ~ attachmentslength)
List all pdf attachments
attachmentsfilter(att => att ends with '.pdf')join("\n")
Find the lower of two dates
Convert date1 and date2 to timestamps, determine the minimum value, are transformed back to yyyymmdd.
MIN({date1_}date('U'), {date2_}date('U'))date('Ymd')
Actually, thanks to the formatting of date strings (yyyymmdd), we can compare the date strings directly.
MIN({date1_}, {date2_})
Suppose the field
assignee_
is a selection field based on the user list. The following will evaluate the chosen user's address.
{assignee_}.option.email
Test if a result has offspec values
You might want to trigger or deviation process in case a result has an offspec value. The following expression tells you whether the result has an offspec value:
offspecfilter(s => s) is not empty ? "Has offspec values" : "No offspec values"
Blog alert!
Custom calculations from Excel to LIMS
One of our customers, a mediumsized food factory, had a hard time replacing their Excel QC sheets with a standard solution. Not because they did not have a budget or time, but because of the complexity of their Excel sheets. They had many, many calculations in their sheets. The AlisQI expression engine provided the solution.
Errors and warnings
The enormous flexibility offered by the expression engine does come with a price. It's possible to create calculations that will run into problems.
AlisQI will try to validate the calculation by evaluating it using dummy values, but it cannot possibly catch all errors. Therefore, a list of errors and warnings is displayed while creating the calculation, as well as in the result entry screen. Use the preview in the analysisset management to test the calculation with different input without needing to actually store results.
Examples
Consider the following example for a numeric calculation: {$batch_}
, where Batch is a text field. The syntax of this calculation is fine, but whether a batch number can be interpreted as a number depends on its value. "1234AB" will be interpreted as the number 1234, but "AB1234" cannot be interpreted as a number. AlisQI cannot predict what values will be used, so it can only warn that using a text field in a numeric calculation can cause issues.
Here's a more devious example, using a numeric field a : 1 + ({a} ?: {})
. As long as the value for a
is truthy (not empty and not 0), this calculation will evaluate to 1 + a
, which will always be a number. However, if the value for a
is empty, the engine will try to add a number and a hash, which isn't defined and causes an error.
Caveats and technical details
If you read Twig's documentation, you may have noticed a couple of discrepancies with the syntax of calculations. To understand the differences, let's dive into how calculations are evaluated.
First of all, calculation is enclosed in output delimiters: {{ calculation }}
. Therefore, you cannot use Twig tags.
Next, the field variables (e.g., {field_}
) are actually invalid syntax. AlisQI transforms these to values['field_']
. Likewise, {field_}.spec.min
is transformed to spec['field_'].min
, etc. The sandbox context actually contains (only) the following variables: attachments, values, id, operator, decimals, default, label, unit
. You can use these if you wish.
Useful resources
Here are some suggestions for more information on the technology behind our expression engine.
 Twig reference
 Twig Math operators
 Twig logic operators
see also this article on logical expressions in AlisQI  PHP date formattingthe format parameters can be used in Twig date filters