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After parsing XML DTDs with four different software packages in our last installment, we will look at the resulting data structures in Java, Perl, and PHP, respectively. This will be step two out of four in our creation of dtddoc:
We used the following parsers:
As demonstrated before, these parsers have a straightforward way of calling them on an input stream, creating an internal data structure in return. Let's examine those internal data structures in turn.
Using DTDParser's parseXMLDocument() or parseExternalSubset()
functions returns a DTD object for further inspection. The DTD object holds
hashtables of entities and element types of the parsed DTD. An ElementType has various members
that carry interesting information:
| member | value |
|---|---|
| attributes | A Hashtable of attributes for the respective element type. |
| children | A Hashtable of child ElementTypes. |
| content | A Group representing the content model of the element type. |
| contentType | The type of content, one of: CONTENT_ANY: Any content type. CONTENT_ELEMENT: Element content type. CONTENT_EMPTY: Empty content type. CONTENT_MIXED: "Mixed" content type. CONTENT_PCDATA: PCDATA-only content type. CONTENT_UNKNOWN: Unknown content type. |
| name | The XMLName of the element type. |
| parents | A Hashtable of parent ElementTypes. |
With this information, enumerating all element types and outputting the above information in HTML should
be a snap. The content model's hierarchy can be easily navigated through the parents and
children members of each element type.
on to inspecting the other tools' data structures...
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Created: Oct 14, 2002
Revised: Oct 14, 2002
