When it comes to creating an XML schema, one of the most important considerations is how to handle string values. In particular, how should case sensitivity be handled when enumerating simple type strings? In this article, we will explore the concept of case insensitive enumeration of simple type strings in XML schema and how it can be achieved.
First, let's define what we mean by case insensitive enumeration. Essentially, it means that when defining a simple type string in an XML schema, the values within the enumeration are not case sensitive. This means that the values "apple", "Apple" and "APPLE" would all be considered the same value. This can be important when ensuring consistency and avoiding errors in data processing.
So, how can we achieve case insensitive enumeration in an XML schema? The answer lies in the use of regular expressions. Regular expressions allow for the specification of a pattern that a value must match in order to be considered valid. In this case, we can use a regular expression to ignore the case of the values within the enumeration.
Let's take a look at an example. Say we have a simple type string called "fruit" and we want to define an enumeration of valid values. Traditionally, we would do so like this:
<xs:simpleType name="fruit">
<xs:restriction base="xs:string">
<xs:enumeration value="apple"/>
<xs:enumeration value="orange"/>
<xs:enumeration value="banana"/>
</xs:restriction>
</xs:simpleType>
In this case, the values "apple", "orange" and "banana" are case sensitive. However, by adding a regular expression to the restriction, we can achieve case insensitive enumeration.
<xs:simpleType name="fruit">
<xs:restriction base="xs:string">
<xs:pattern value="[a-zA-Z]+"/>
<xs:enumeration value="apple"/>
<xs:enumeration value="orange"/>
<xs:enumeration value="banana"/>
</xs:restriction>
</xs:simpleType>
By using the [a-zA-Z]+ pattern, we are essentially saying that any combination of letters (upper and lower case) is a valid value. This means that "apple", "Apple" and "APPLE" would all be considered valid values for the "fruit" simple type string.
It's important to note that this regular expression should only be used for case insensitive enumeration. If a more specific pattern is needed, it should be used instead.
In addition to allowing for case insensitive enumeration, this approach also allows for more flexibility. For example, if we wanted to add a new value to the enumeration, we can simply add it without worrying about case sensitivity.
<xs:simpleType name="fruit">
<xs:restriction base="xs:string">
<xs:pattern value="[a-zA-Z]+"/>
<xs:enumeration value="apple"/>
<xs:enumeration value="orange"/>
<xs:enumeration value="banana"/>
<xs:enumeration value="strawberry"/>
</xs:restriction>
</xs:simpleType>
In conclusion, when working with simple type strings in an XML schema, it is important to consider case sensitivity and how it should be handled when enumerating values. By using regular expressions, we can achieve case insensitive enumeration and ensure consistency and accuracy in our data processing. So the next time you are defining
