WorkWithPlus for Web provides the possibility to add Dynamic Validations to the transactions. These validations can be defined at runtime with the attributes you previously added in the references. 

Dynamic validations are used as an alternative to some validations added in the transaction rules since they are responsible for performing the validations in these. The main difference is that they are defined at runtime, so a system administrator could change them at runtime.

In GeneXus you will enable the Dynamic Validations for a certain Transaction, and define which Attributes of the Transaction you will need to reference in the Dynamic Validation:

Then, at runtime, you will define all the Dynamic Validations, mentioning the Attributes defined as Referenced Attributes:

In order to use it, you must have the Dynamic Forms Module activated.

If you have dynamic sections and you have validations done on these sections, it is not necessary to use dynamic validations, but it is useful in cases where you do not have dynamic sections.