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Learn how to use Verifiers

How to use verifiers to filter out false positive results

 

Verifiers are one of the rule-based validation approaches, which filter out the false-positives. These let the user narrow down extraction results by applying some additional logic and checks to the extraction results. One can for example say that a specific type of information will always occur on the first page of the document, or that it must be on the lower half of the page, etc.
The verifiers will be processed after the transformers.
The verifiers with a star symbol * follow in the next release.
Verifier
Description
coords: Is Close To*
Definition of keywords, which should be found in the near of the candidate
coords: Position Range
Rejects candidates which are not with the rectangle made of `left`, `right`, `top`, `bottom` coordinates, e.g. at the top half page.
coords: Position Range Center
Rejects candidates whose centers are not with the rectangle made of `left`, `right`, `top`, `bottom` coordinates, e.g. at the top half page.
key-value: Pair Orientation*
Defintion of keywords, which should be found in the near (horizontaly or verticaly) of the candidate
number: Page Number
Checks whether a candidate is on the specified page. Candidates found on other pages are ignored.
number: Value Range
Can only be used if the `output_data_type` is numeric (integer or float). Candidates with a value that is smaller than `minimum value` or larger than `maximum_value` are rejected.
string: Ends With
Candidates that do not end with the specific string are rejected.
string: Has Not Pattern
Candidates containing the specified `pattern` are rejected.
string: Has Pattern
Candidates that do not contain the specified `pattern` are rejected. In this case only Swiss vat numbers are allowed
string: Starts Not With
Skips candidates whose prediction value start with a specific string.
string: Starts With
Candidates that do not start with the specific string are rejected.
string: String Length
Rejects candidates that do not have the right number of "characters"
pick_nth
This verifier picks the n-th element of the sorted candidate list

 

Verifier "coords: Is Close To"

Definition of keywords, which should be found in the near of the candidate.
Parameter
Description
Pattern (string)
Search string (regex)

 

Verifier "coords: Position Range"

Definition of coordinates, where the candidate have to be found. The verifier can restrict the result horizontally (left coordinate [0..1] (float) - right coordinate [0..1] (float)) and vertically (top coordinate [0..1] (float) - bottom coordinate [0..1] (float)). All values are defined in percent between 0 and 1, using a point as decimal.
Parameter
Description
Left coordinate
Left coordinate of the rectangle (related to page width)
0 <= value <= 1
Right coordinate
Right coordinate of the rectangle
(related to page width)
0 <= value <= 1
Top coordinate
Top coordinate of the rectangle
(related to page height)
0 <= value <= 1
Bottom coordinate
Bottom coordinate of the rectangle
(related to page height)
0 <= value <= 1

 

Verifier "coords: Position Range Center"

Definition of coordinates, where the center of the candidate have to be found. The verifier can restrict the result horizontally (left coordinate [0..1] (float) - right coordinate [0..1] (float)) and vertically (top coordinate [0..1] (float) - bottom coordinate [0..1] (float)). All values are defined in percent between 0 and 1, using a point as decimal.
 
Parameter
Description
Left coordinate
Left coordinate of the rectangle (related to page width)
0 <= value <= 1
Right coordinate
Right coordinate of the rectangle
(related to page width)
0 <= value <= 1
Top coordinate
Top coordinate of the rectangle
(related to page height)
0 <= value <= 1
Bottom coordinate
Bottom coordinate of the rectangle
(related to page height)
0 <= value <= 1

 

Verifier "key-value: Pair Orientation"

Definition of keywords, which should be found in the near (horizontaly or verticaly) of the candidate.
Parameter
Description
Orientation (string)
Search string (regex)

 

Verifier "number: Page Number"

Checks whether a candidate is on the specified page. Candidates found on other pages are ignored. Here an example to extract the invoice date, which is normaly placed on the first page of an invoice.
Parameter
Description
Page number
Page number 1 = first page

 

Verifier "number: Value Range"

Can only be used if the output_data_type is numeric (integer or float). Candidates with a value that is smaller than minimum value or larger than maximum_value are rejected. Here an example to determine percentage values ( 0<= value <= 100).
Parameter
Description
Minimum value
Minimal value
Maximum value
Maximal value

 

Verifier "string: Ends With"

Candidates that do not end with the specific string are rejected. As example to restrict candidates to amounts with to decimal places.
Parameter
Description
Pattern (string)
Search string (regex)

 

Verifier "string: Has Not Pattern"

Candidates containing the specified pattern are rejected. As example that the result is no German IBAN number.
Parameter
Description
Pattern (string)
Search string (regex)

 

Verifier "string: Has Pattern"

Candidates that do not contain the specified pattern are rejected. In this case only Swiss vat numbers are allowed.
Parameter
Description
Pattern (string)
Search string (regex)
 

 

Verifier "string: Starts Not With"

Skips candidates whose prediction value start with a specific string. In this case remove all tax identification number candidates with German identifier.
Parameter
Description
Pattern (string)
Search string (regex)

 

Verifier "string: Starts With"

Skips candidates whose prediction value not start with a specific string. In this case remove all tax identification number candidates, except Austrian ids.
Parameter
Description
Pattern (string)
Search string (regex)

 

Verifier "string: String Length"

Rejects candidates that do not have the right number of "characters".
Parameter
Description
Minimum length
minimal length of the value
Maximum length
maximal length of the value

 

Verifier "pick_nth"

This verifier picks the n-th element of the sorted candidate list, in this example the second element (zero-based index).
Parameter
Description
Index number
Index of the value
0 = first value
Result before restriction:
Result after restriction: