The xml-combine attribute provides a fine level of control over how two tags are combined. However, frequent use of this attribute can quickly prove unwieldy. For this reason, the xml-combine attribute takes on a default value that makes the most intuitive sense, according to the following rules:
If either of the combined tags contains only a PCDATA section (i.e., a text block without any embedded tags), then the
xml-combineattribute takes on the default value ofreplace.Otherwise, the
xml-combineattribute takes on the default value ofappend.
This means that most XML files will combine naturally without the use of any xml-combine attributes. The xml-combine attributes can then be used to fine-tune any special behaviors.
Remember that the values of XML elements may be set in the DTD. If an XML element has a default setting specified in the DTD, that default setting will be applied in any XML file that does not explicitly set the element. For example, the SQL Repository DTD specifies the expert attribute of the property element like this:
expert%flag;"false"
If your base SQL repository definition file sets the expert attribute of a property to true, and if supplemental SQL repository definition files modify that property, you must also explicitly set the expert attribute of a property to true in the supplemental SQL repository definition files; otherwise the attribute’s value will revert to the default specified in the DTD.
