A text field considering space as an data .

In Appian we typically use validations on text fields to make sure the entered text is valid.

Example: docs.appian.com/.../recipe-add-multiple-validation-rules-to-one-component.html

I assume you've made your text field "required" but that someone is entering a space which is being considered to be data and thus allowing the user to submit the form? The easiest way to think about this is to think about what would the content of your field be if all the spaces were removed. If the length of the resulting value is 0 (i.e it only contains spaces) then you can use this information to throw a validation error, which will then prevent the user form submitting the form.