Abstract: The present invention relates to a system 10 for generating a content hierarchy 12 for use in laying out content from a source 14 for display. The system comprises a content gatherer 16 co-operable with a source for gathering content from the source into content sub-groups dependent on the content type of the content; a design fragment populater 24 for populating at least one design fragment 19 using the gathered source content, the plurality of design fragments each comprising design parameters specifying how the source content can be laid out; and a content hierarchy assembler 32 for attaching the populated design fragment to a selected parent fragment 19 permitted for the populated design fragment, the parent fragment containing design parameters specifying how each design fragment can be laid out for display.

Abstract: A densitometer providing simultaneous sensing of the density in precisely adjacent portions of plural adjacent tracks. The densitometer preferably operates with stellar a pattern in which two reference tracks have been photographically recorded either side of a central specimen track of a star. The simultaneous detection of the three tracks insures a high degree of alignment between the reference and star tracks so that the correlation of their relative positions is a more accurate indication of the shift between the reference and star tracks. Alignment controls and the ability to microscopically view the radiation path through the densitometer facilitates set-up of the system to the high accuracy of results that it can achieve.