The Specdre Extension

The NDF data access routines - together with the lower-level HDS routines - allow the construction of extensions to the data format. Extensions unknown to an application package are propagated, and extensions known to an application enable it to provide more functionality.

The Specdre applications use a set of extensions to the basic NDF format to communicate information between themselves. This extension is known (not unreasonably) as the Specdre Extension. It is recognised and understood by all the Specdre applications. Other Figaro applications, and applications in other Starlink packages such as KAPPA, simply propagate the Specdre extension unchanged without modifying (or understanding) it. This behaviour is not always correct, but in general it is the best that can be done. If the dataset is not processed with another Specdre application it does not matter if the Specdre extension and the basic NDF become inconsistent (because other applications will ignore the extension). If a Specdre application is presented with a dataset in which the Specdre extension is obviously inconsistent with the basic NDF it will notice and report an error.

Specdre contains a number of subroutines for easy and consistent access to the Extension. Programmers are advised to contact the Figaro support username (e-mail figaro@star.rl.ac.uk) if they want to make use of the Specdre Extension in their programs.

All Specdre applications support version 0.7 of the Specdre Extension, which was introduced in version 0.7 of Specdre. Some applications support an advanced version 1.1 of the Extension, as introduced in version 1.1 of the package.