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Adding a new regular expression-based semantic type

You can create a semantic type based on a regular expression in Talend Dictionary Service and add it to the list of recognized data types in Talend Data Preparation

In Talend Data Preparation, not every type of data can currently be matched with one of the predefined semantic types. Italian social security numbers, also known as codice fiscale, are currently not recognized for example.

Let's say that you work for an Italian company, only dealing with Italian customers. In this example, you need to clean some customer data, such as their names, email address, or their social security number. The semantic type for the column containing the social security number data will be set by default to text. This is not specific enough and you would like to create a new category in order to match this type of data: a codice fiscale semantic type in this case.

Codice Fiscale column menu opened with Column is a text option highlighted.

You will create this new semantic type in Talend Dictionary Service, and it will be automatically available in Talend Data Preparation so that your data can be matched with a proper type.

Information noteImportant: For security reasons, a few regular expressions cannot be used, especially the backreferences. For more information, see the RE2/J documentation.

Procedure

  1. Open the Semantic types view from the left panel of the Talend Data Preparation homepage and click Add semantic type.
  2. In the Name field, enter codice fiscale.
  3. In the Description field, enter Italian social security number.
  4. In the Type drop-down list, select Regular expression.
  5. Keep the Use for validation switch activated.

    Using a regular expression, a dictionary or a compound type for validation means that it will be used to define which values are considered right or wrong in a given column. The result of this validation process can be seen in the quality bar of each column in your datasets.

    In any case, regular expressions or dictionary of values are used for data discovery, that calculates the matching percentage between the reference values and your data to define the semantic type of each column.

    In this example, if you were to deactivate the switch, the regular expression would only be used for data discovery, and no value would be considered invalid.

  6. In the Content drop-down list, select the type of content that you want to validate, Any character in this case.

    This option helps optimizing performances. Only the data that matches the selected type will be validated. You can choose to only validate Alphabetic or Numeric values against a regular expression, but because Italian social security numbers contain both, you have to select Any character.

  7. In the Validation pattern field, enter ^[A-Z]{6}[0-9]{2}[A-Z][0-9]{2}[A-Z][0-9]{3}[A-Z]$.

    This regular expression is designed to match the Italian codice fiscale, which is an alphanumeric code of 16 characters. Data that matches that pattern in Talend Data Preparation will be identified as codice fiscale.

  8. Click Save and publish to send the new semantic type to the Talend Dictionary Service server and make it available to the Talend Data Preparation users.

    Clicking Save as draft means that the semantic type will be stored in Talend Dictionary Service, but will not be broadcast to the Talend Web applications. This allows you to chose the moment when you want to make your semantic types public.

    The codice fiscale type is now available in the list of semantic types with the status set as Published.

    Codice Fiscale type published.

    The change in semantic types is instantly effective in Talend Data Preparation for every new dataset that you import. For existing datasets, you need to manually change the column type or reimport your dataset.

  9. Go back to your dataset containing the Italian social security numbers.
  10. Click the menu icon in the codice_fiscale column header and select this columns is a... > codice fiscale.

    The column type now matches the newly created category.

    Codice Fiscale type highlighted with 100%.

Results

Your data is now matched with the codice_fiscale semantic type, that you manually created in Talend Dictionary Service. From now on, when importing new datasets containing Italian social security numbers, they will automatically be matched with the proper type.

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