Error during the validating of XML Schema

Sorry,

I have too much doubts for this arguments, but i don't know other person
that can help me. So, I installed and configurated Jakarta-Tomcat, and now I
think my parser is working because in the console of my program I have a lot
of mistake about XML Schema. Obviously, I can't write you all of mistake,
but some errors are very strange. For example:

 

[Error] InvoiceXML.xml:21:60: cvc-attribute.3: The value '' of attribute
'CAB' on element 'BankingEnds' is not valid with respect to its type,
'integer'.

 

What does error mean? In my XML Schema this attribute is declared like:

 

            <!-- ID CAB -->

            <xsd:attribute name="CAB" type="xsd:integer" use="required"/>

 

What is the problem? I found that the simpletype that I can put in my XML
SCHEMA are integer, decimal, string, etc.... If I put string, I don't have
problems, but if I put date, integer, DateTime, float, decimal, I have this
error. Please, someone can help me? Thank you so much.

Regards

              Gianni

 

P.S. Oh I was forgotting to say you that during the validation across DTD I
didn't have this error.