Lexical Expression Qualifiers

Lexical expression qualifiers enable you to scan content for items which match specific entries in a source file. For example, you might want to construct a lexical expression which detects only a particular set of account passwords or credit card numbers, stored in an external file.

You can import lexical data safely into the Gateway and construct user-defined expressions which use lexical expression qualifiers to search for matching content.

Data sets can be imported from an upload server either manually or automatically, using a user-defined schedule.

Tell me about...

• How lexical expression qualifiers work

  Lexical expression qualifiers are applied to lexical expressions in order to restrict the matching values to specific entries. Each qualifier looks up information in a Data Set that has been imported to the Gateway. Any match with an identical value in the data set will be detected.

  You must ensure your lexical data has been imported to the Gateway as a Data Set before you can create a lexical expression qualifier which uses the relevant information. See Import Lexical Data to find out how to do this.

• Data Sets

  Lexical expression qualifiers use an external data source as a reference. This data can be converted from a tab-separated file and imported as a Data set.

  The Gateway reads the data set when looking for a matching expression.

  Input data sets are imported securely using the Import Lexical Data feature.

• Lexical Data

  Lexical Data is the information used by a qualifier to match a detected expression. The data is prepared and imported onto the Gateway using the Import Lexical Data process.

  For more information, see Import Lexical Data.

• Key Fields

  You can configure a qualifier to reference a particular data set and a unique Key field. Key fields are specified when you convert your tab-separated file into a data set.

  If a key field is removed from a Data Set, the key will no longer be selectable and the qualifier will be ignored by the policy.

  For more information on how to configure Data Sets and Keys, see Import Lexical Data

How do I...

• Create a lexical expression qualifier?

  1. From the Policy Center Home page, click Lexical Expressions. Select the Lexical Expression Qualifiers tab.

     Existing qualifiers are displayed in the list.

  2. Click New.

  3. Use the Overview section to change the Name of your qualifier, or add any relevant Notes.

  4. Use the Manage Lexical Expression Qualifier panel to configure:

     • Data set: the *.leq file containing your data.

     • Key field: the column (key) in the data set which you want the qualifier to use.

       The Key field and Data set must contain ASCII characters only.

     • Additional fields: the other fields from the .leq file that must also be present. These additional fields must come from the same row as the key field, but do not need to be key fields themselves. Note that the case-sensitivity of qualifier matching is controlled by ffcreate, and does not depend on whether the lexical expression that uses the qualifier is not flagged as being case-sensitive.
     Why am I unable to find the Data set or Key Field I am looking for?

     • Check the Lexical Data Import server settings and verify that the import is correctly configured using the file path. The infrastructure log also displays which files have been successfully imported.
     • If the Key you are expecting is no longer available from the drop-down menu, it may have been removed from the most recently uploaded Data set. The qualifier will be ignored by the policy unless provided with a valid key.
     • The Key field and the Data set must be composed of ASCII characters.
  5. Click Save.
  6. Apply the configuration.
• Add a qualifier to an expression?

  You can only use lexical expression qualifiers with user-defined expressions.

  1. From the Policy Center Home page, click Lexical Expressions. Select the Lexical Expressions tab and locate the expression list you want to use.

  2. Click Edit.

     Click New to create a new expression list. See Working with Lexical Expression Lists for more information.

  3. If you are creating a new lexical expression, click New.

     If you are adding a qualifier to an existing expression, select it from the list and click Edit.

  4. Enter your lexical expression, using a User defined text entity.

     See Create a Lexical Expression to find out more about using expressions.

  5. Move the cursor to the position preceding the closing period character. The qualifier must be inserted after the PATTERN and before the closing period.

     .PATTERN=Names|.

  6. Use the Qualifiers tab to select your qualifier. Add it to the expression.

     The qualified expression must be contained within opening and closing period characters.

  7. When you have configured the expression, click Add.
• Change the data source used by a qualifier?

  1. From the Policy Center Home page, click Lexical Expressions. Select the Lexical Expression Qualifers tab.

  2. Select the qualifier and click Edit.

  3. Use the Manage Lexical Expression Qualifier panel to configure:

     • Data set: the imported file containing your data.
     • Key field: the column (key) in the data set which you want the qualifier to use.
     • Additional fields: the other fields from the .leq file that must also be present. These additional fields must come from the same row as the key field, but do not need to be key fields themselves. Note that the case-sensitivity of qualifier matching is controlled by ffcreate, and does not depend on whether the lexical expression that uses the qualifier is not flagged as being case-sensitive.
  4. Click Save.
  5. Apply the configuration.
• Import data?

  You can import lexical Data sets to the Gateway either according to a schedule, or instantly. If you have a large amount of reference data for your qualifiers, you might want to configure the import at an off-peak time.

  If you remove an active Data Set from the Gateway, any content rules which use this data will be ignored by the policy.

  See Lexical Data Import for more information.

Show me...

• Example: Matching credit card numbers

  I want to configure a lexical expression that only looks for the credit card numbers of my customers.

  1. Ensure your Data set has been correctly imported. Show me

     The columns containing the relevant information must have been configured with Key fields in a Data set (*.leq file). The relevant information is the information you want the Gateway to access: Credit Card Numbers.

     1. Prepare your input file as tab-separated data.
     2. Save the file in a suitable directory.

     3. Run ffcreate in the directory.

     4. Configure the key fields and the structure of your output file using the command line:

        ffcreate -k <key_name The reference the lexical expression will look for. Each key must be composed of alphanumeric characters a-z, A-Z, 0-9 and must match one reference from the schema.> -s <schema reference,type;reference,type... index of the columns available in your input file. Type must be 'Simple' or 'Credit Card'. If you are using Linux, enclose the schema in quotation marks (").> -i <input_file The name of the file containing your source data> -o <output_file The required name of the output file (.leq)>

        You must include the file extension of the input file, and append the output file with the extension .leq to ensure it can be accessed by the Gateway.

     5. Import the data set using the Lexical Data Import page.

     See Import Lexical Data to find out more about importing lexical data.

  2. Create a Lexical Expression Qualifier (In this example, CustomerCC). Configure CustomerCC to use the ClientInfo Data set (leq) to look up data from the column referenced by the CCNum Key field. If you want to specify Additional fields that must be present, you can select those fields from the .leq file. Show me

     

     

  3. Create an expression list.

     See Working with lexical expressions to find out how to do this.

  4. Create a Lexical Expression and add a Predefined entity (Credit Card). This scans content for all credit card numbers.

     See Create a Lexical Expression to find out more about how to create an expression.

  5. Position the cursor inside the expression, immediately preceding the final period character.
  6. Use the Qualifiers tab to add the CustomerCC qualifier to the custom expression to qualify credit card numbers. Show me

     

  7. When you have configured the expression as required, click Add.

     This example scans content for credit card numbers (using the lexical expression) and restricts the search to values found in the appropriate column of the ClientInfo data set using the lexical expression qualifier. Only these values will be detected.

See also...

• Import Lexical Data
• More about using Regular Expressions
• Working with content rules
• About Lexical Expressions