Purpose

A shelf used to store compiled SGML DTDs as items. These items are created and used as follows:

• Compiling an sgml-dtds item (document or subdocument with creating) sets an item of the shelf to be the compiled DTD. It creates the item if it did not previously exist.
• Parsing an instance or instance part (instance or element-content) uses an item of the sgml-dtds shelf. An item of this shelf can be used any number of times. Items can even be used simultaneously for nested do sgml-parse actions.

You can perform the following on the sgml-dtds shelf:

• Items can be accessed using their key by using {...}, but not by their item number (you cannot use [...]). An sgml-dtds item can only be used in a do sgml-parse action.
• Items cannot be removed from the shelf using remove.
• clear sgml-dtds permanently removes all compiled DTDs from the shelf.

The action new can't be applied to the sgml-dtds shelf. The creating option of do sgml-parse adds items to the sgml-dtds shelf.

None of the other shelf modification actions are allowed with the sgml-dtds shelf. You cannot use the following keywords with these shelves:

• new
• remove
• using
• lastmost
• item of
• repeat over
• key of
• number of

sgml-dtds can be thought of as a shelf, except that item values can't be created or used except by do sgml-parse (for example, you can't output a compiled DTD). dtds is a deprecated synonym for sgml-dtds.

Related Syntax    clear    creating    new    remove    do sgml-parse

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