Description

The MDL is a FITS file that stores (or restores) the results a user has created during an analysis session with Sherpa. This means the following information is available in an MDL file:

• All data files in use
• Instrument responses
• Background data
• All Sherpa "sources" (Models for individual regions of the data)
• Line/Feature Identifications

Sherpa can write an MDL file based on the current data and models using the command write mdl "mdl_filename.fits". Restoring from an MDL file is done using the read mdl "mdl_filename.fits" command (the "'s are required for both read and write), the previous sessions data files, instrument responses, and source models are restored.

MDL files can serve a purpose similar to the JOURNAL command, since a journal file can be used to write all Sherpa commands to a file. For some uses, a JOURNAL file may be more useful, as not all relevent information is currently stored in the MDL file; for example, data filters are not stored. However, an MDL file is a structured version of the data, which means it is easier to analyze a collection of MDL files, especially using S-lang.

The "Accessing MDLs from S-Lang" section of "ahelp sherpa" describes how you can create a MDL structure within a Sherpa session, without having to use an external file.