在声明xs:integer数据类型时允许空值的选项

My problem (or question) centers around empty elements which are typed as xs:integer. I need to allow for empty elements so I used a union to allow an empty element or a valid integer as the value as shown in the schema below. However, my schema serves a dual role and also needs to be imported into 3rd party software which expects data types of String, Float, Integer or Date. If I code the schema using the union method for all integers they will not be typed as integers in the software. Is there another way other than the union method of allowing an empty element for integer data types? I'd like to just have the one XSD but can have two if that is what needs to happen.My problem (or question) centers around empty e