Subscribe

UiPath Document Understanding

UiPath Document Understanding

RegEx Based Extractor

What is RegEx Based Extractor

The Regex Based Extractor is the perfect tool for simple use cases, in which, for certain fields, data is always found in a strict, predictable format and context. In other words, if you have a field for which you can define a Regular Expression that is consistently good when matched, then the Regex Based Extractor is a good choice.

The activity comes with a configuration wizard that assists you in defining the regular expressions for the fields you want to target for data extraction in this way.

The activity supports both simple fields as well as table field extraction.

It is recommended to look into other extraction methods, in case there is a high variability of the context and format of the expected values. In such cases, either a Form Extractor or a Machine Learning Extractor may be better suited.

This extractor does not have learning (training) capabilities and requires up-front configuration.

Special Requirements

There are no special requirements for using the Regex Based Extractor.

How to configure

Activity Configuration


The Regex Based Extractor has two major configurations to be considered:

  • the Configure Regular Expressions wizard - which allows you to define regular expressions for certain fields. This wizard also makes available the Regex Editor wizard, which assists you in building your regular expressions.
  • the UseVisualAlignment setting - which allows you to control whether the regular expressions configured for an extractor should be applied to the text output of the digitization component, or to a text version in which text lines are organized visually, and words are rearranged on lines based on their visual alignment.

The Configure Regular Expressions Wizard


The Configure Regular Expressions Wizard can be used for defining regular expressions to be used to capture data for both simple as well as table fields.

  1. Add a RegEx Based Extractor activity to your workflow, within a Data Extraction Scope activity.
  2. Configure your regular expressions by clicking on the Configure Expressions button.
    • The Wizard window opens.
  1. Expand a document type entry in order to see all defined fields, and to start configuring your regular expressions. Document types and their respective fields are automatically read from the project's Taxonomy. The Regex configuration option is available for every field in the taxonomy.
    • expanded document type showing a single regular field:
  • Expanded document type and table field, showing configuration options for a table:

For a simple field, only a single regular expression can be defined using the RegEx wizard that opens when you click the "Edit" option next to that field.

For a table field, there are multiple settings and options available for configuration:

  • The Table Value RegEx can be used for capturing an entire table area. If no value is added on the Table field line, the entire text content of the document is considered onward for table processing.
  • The Rows Value RegEx can be used for capturing an entire row from a given table capture. If no value is added on the Rows field line, the table area is split by end-of-line. Each captured value is considered from this point forward as a row on which the column extraction is to be applied.
  • The Column Value RegEx can be used for capturing the value of a particular column, from each captured row.

Scenarios of using the Table, Rows and Column Regex:

  • If you leave the Table RegEx and the Rows RegEx fields empty, all lines in the text version of the document are used to apply the Column Level Regexes for cell value identification.
  • If you define a RegEx to capture the table area, but leave the Rows RegEx empty, all lines in the table capture are individually processed using each Column RegEx to capture the cell values.
  • If you leave the Table RegEx empty but define a Rows RegEx, then all text captured with the Rows RegEx is used and the Column RegExes are applied to capture cell values for each row.
  • If you fill in both Table and Rows RegEx, the activity applies the Table RegEx to identify the table string, then apply the Rows RegEx to identify each line, followed by the Column Level RegEx for capturing cell values.
  1. Add your Regular Expression in the Expression field.

📘

Provide a Regex, or Build One

You have the option of either writing the whole RegEx in the Expression field or to build it by using the Edit button.

🚧

Specify Your Capture Groups!

For any of the regular expressions you define, make sure you have at least one capture group! Only the captured parts of an expression are used for value reporting.

  1. Click on the drop-down list from the Regex Options column. You can set Regex Options from this multi-select option.
  1. There are multiple options you can choose from:
    • CultureInvariant - Specifies that the linguistic cultural differences are ignored.
    • ECMAScript - Enables ECMA Script compliant behavior for the expression. This value can be used only in conjunction with the IgnoreCase and Multiline options.
    • ExplicitCapture - Specifies that the only valid captures are the ones of groups that are explicitly named or numbered and are defined as (?<name> subexpression). Any unnamed parentheses are to be ignored.
    • IgnoreCase - Specifies that the search is not case sensitive.
    • IgnorePatternWhitespace - Eliminates the unescaped white space from the defined pattern and enables the comments marked with #. This option does not apply to character classes, numeric quantifiers, or tokens marking the beginning of an individual RegEx language element.
    • Singleline - Specifies that the search is initiated in a single line. The dot (.) matches all characters, including the exception \n.
    • Multiline - Specifies that the search is initiated in multiple lines. For this option, the special characters ^ and $ match the beginning and the ending of any line.
    • RightToLeft - Specifies that the search is performed from right to left.

📘

More on Regex Options

More information about the Regular Expression Options can be found here.

The Regex Editor Wizard


  1. Click on the Edit button for editing the options of that field and the format of the regular expression.
  1. Add text in the Test Text field for testing the search criteria you choose against the text that you want to apply RegEx on.
  1. Select one of the RegEx formula types from the drop-down list. This sets the Regular expression to match one of the following characteristics:
    • Literal - Matches the exact characters specified by you. This option is case sensitive.
    • Digit - Matches a digit.
    • One of - Matches a single character present in the set.
    • Not one of - Matches a single character not present in the set.
    • Anything - Matches any character, except for \n.
    • Any word character - Matches any letters and numbers.
    • Whitespace - Matches one white space.
    • Starts with - Initiates the search where the line starts.
    • Ends with - Initiates the search where the line ends.
    • Advanced - Requires a custom expression.
    • Email - Matches an email address.
    • URL - Matches an URL.
    • US date - Matches the US date format.
    • US phone number - Matches the US phone number format.

📘

More on Regex Expression Building and Quantifiers

More information about the Regular Expressions in .NET can be found here.

  1. Use the Value field for writing the value of the regular expression.
  2. Select a quantifier from the Quantifiers drop-down list.
  • Exactly - Matches the preceding element exactly how many times it is specified. By default, it is set to 1.
  • Any (0 or more) - Matches the preceding element for zero or more times, but as few times as possible.
  • At least one (1 or more) - Matches the preceding element for one or more times.
  • Zero or one - Matches the preceding element for zero or one time but for as few times as possible.
  • Between x and y times - Matches the preceding element between x and y times, where x and y are integers, but as few times as possible.
  1. Use the plusplus button for adding an extra RegEx field. Move fields up and down in the hierarchy by using the upup and downdown buttons. Use the deletedelete button for deleting the field.
  2. Select the check box for the Capture option if you want to extract that specific field.
  3. The Full Expression field shows the entire expression exactly how it was customized by you.
  4. Select one or multiple options from the Regex Options drop-down list.
  1. Click the Save button once all your configurations are done to exit the Edit mode and then click the Save once again for closing the wizard.

Updated about a month ago


RegEx Based Extractor


Suggested Edits are limited on API Reference Pages

You can only suggest edits to Markdown body content, but not to the API spec.