Conversion to XML

Conversion to XML takes an array with the format described above and generates XML text from it. There are some simplifications to the array which are accepted:

• The fifth column is not needed for XML generation and is effectively ignored. Any numeric values are accepted, or the column may be omitted altogether.
• If there are no attributes in a particular row then the (0 2⍴⊂'') may be abbreviated as ⍬ (zilde). If the fifth column is omitted then the fourth column may also be omitted altogether.
• Data in the third column and attribute values in the fourth column (if present) may be provided as either character vectors or numeric values. Numeric values are implicitly formatted as if ⎕PP was set to 17.

The following validations are performed on the data in the array:

• All elements within the array are checked for type.
• Values in column 1 must be non-negative and start from level 0, and the increment from one row to the next must be ≤ +1. 
• Tag names in column 2 and attribute names in column 4 (if present) must conform to the XML name definition.

Then, character references and entity references are emitted in place of characters where necessary, to ensure that valid XML is generated. However, markup, if present, is not validated and it is possible to generate invalid XML if care in not taken with markup constructs.