Equations are parsed in Arbortext Editor like any other markup. Prior to release 6.0, equations were parsed by the Equation Editor and required that the <?Pub Eqn> processing instruction be present before the equation markup. Beginning in release 6.0, that processing instruction is no longer required. Arbortext Editor continues to write the processing instruction before equations for backwards compatibility.

If your DTD includes the ati-eqn fragment, the container element should not require content. Otherwise, you will get parser errors about missing equation markup in a document containing PIs.