How to use ko.validation.group function

This worked well for me. Rather than grouping on this, create a proxy object that holds the properties you want validated.

this.errors = ko.validation.group({
    P1: this.P1,
    P2: this.P2,
    P3: this.P3
});

If you do this, consider using validatedObservable instead of group. Not only do you get the errors, but you can collectively check if all the properties are valid using the isValid property.

this.validationModel = ko.validatedObservable({
    P1: this.P1,
    P2: this.P2,
    P3: this.P3
});

// is the validationModel valid?
this.validationModel.isValid();
// what are the error messages?
this.validationModel.errors();