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+=================
+Model Constraints
+=================
+
+
+-------------------------
+ComparedToFieldConstraint
+-------------------------
+
+The CoparedToFieldConstraint copares the value of the current field to the value of a referenced field
+on the same level (for example in the same ArrayField).
+It is for example used for the rspamd_ plugin, to ensure that some values are in the correct order.
+This constraint can be used to compare numeric values.
+
+.. _rspamd: https://github.com/opnsense/plugins/blob/master/mail/rspamd/src/opnsense/mvc/app/models/OPNsense/Rspamd/RSpamd.xml
+
+Example:
+
+::
+
+    <check003>
+      <ValidationMessage>This field must be bigger than the greylist score.</ValidationMessage>
+      <type>ComparedToFieldConstraint</type>
+      <field>greylistscore</field>
+      <operator>gt</operator>
+    </check003>
+
+In this example, the valueof the current field must be greater than the value of the field "greylistscore".
+
+Field values:
+
+================= ====================================================================================
+ValidationMessage Validation message (translateable) which will be shown in case the validation fails.
+type              ComparedToFieldConstraint
+field             the other field which we reference
+operator          The operator to check the value. Valid operators are gt, gte, lt, lte, eq, neq
+================= ====================================================================================
+
+Operators:
+
+=== =====================
+gt  greater than
+gte greater than or equal
+lt  lesser than
+lte lesser than or ewual
+eq  equal
+neq not equal
+=== =====================
+
+
+
+---------------
+SetIfConstraint
+---------------
+
+The SetIfConstraint is used to make some fields conditionally mandatory. It is mainly used in the nginx_
+plugin for example to choose an implementation type. In general the other field should be an OptionField,
+but does not need to. In general it is a good idea to hide or show fields which are (not)
+required by an implementation in the frontend as well to simplify the web interface.
+Please note: the checked field is intended to be on the same level (for example ArrayField).
+
+.. _nginx: https://github.com/opnsense/plugins/blob/master/www/nginx/src/opnsense/mvc/app/models/OPNsense/Nginx/Nginx.xml
+
+Example:
+
+::
+
+    <check001>
+      <ValidationMessage>This field must be set.</ValidationMessage>
+      <type>SetIfConstraint</type>
+      <field>match_type</field>
+      <check>id</check>
+    </check001>
+
+In this example, the value will be mandatory, if the field "match_type" has the value "id".
+
+Field Values:
+
+================= ====================================================================================
+ValidationMessage Validation message (translateable) which will be shown in case the validation fails.
+type              SetIfConstraint
+field             the other field which we reference
+check             The value of the other field which makes this field required
+================= ====================================================================================
+