1. A computer program product, tangibly embodied on computer-readable storage media, the computer program product causing being operable to cause a data processing apparatus to: retrieve a design document from a markup language repository, the design document comprising markup language defining a design for rendering a report to present data from a data repository, the design defining a plurality of sections of the report, each section comprising a list of at least one associated conditions that are also defined in the markup language, each associated condition comprising both a logical expression pertaining to the data to be presented in the section and a description in the markup language of a visual representation to be used in rendering the section to which the associated condition applies; retrieve a schema definition from a grammar repository, the schema definition corresponding to the design document and comprising a pre-defined grammar that defines a correct markup language syntax for the design and the associated conditions; render the report, the rendering comprising evaluating in a report renderer each associated condition for each section to determine if the logical expression is true, and, if the logical expression is true, applying the visual representation described by the condition; apply the predefined grammar to the design and the at least one condition using a validating parser to determine whether the design and the at least one condition are syntactically correct; report any determined deviation from syntactical correctness of the design and the at least one condition; and render the report according to the design and the at least one condition using the data; and write a description of a visual representation specified in each section.