org.lcsim Conditions Database

Overview

The conditions database is designed to allow a running analysis or reconstruction module to access information about the run "conditions". In our current environment, conditions include the entire detector description.

The org.lcsim conditions framework is designed to be very flexible, both in use and in implementation. Our current implementation looks up conditions based on the detector name.

Conditions Formats

The recommended format for storing conditions information is in a zip file. The conditions database includes facilities for downloading zip files from the web and caching them, so no web connection is required when running analysis or reconstruction jobs, as long as the required conditions have been previously accessed.

The conditions themselves are stored as an arbitrary collection of files, either stored in a filesystem or in a zip file. The most common files used are property files (name, value pairs) or XML files (e.g. for geometry). However, there are no constraints as to which file formats can be used for conditions information.

Properties Files

Properties files contain line-delimited key, value pairs with the 'equals' as a '=', ':' or ' ' (space). The file extension should be '.properties'.

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The value of the key 'charm' will be 'beauty, truth, strange'. These strings can be read as individual values using the method String.split() .

Accessing Conditions

For the following sections, we will use as an example the SDJan03 detector with corresponding tag of sdjan03 for conditions lookup.

Detector Alias Files

Alias files are properties files, named alias.properties, that list the location of conditions information for specific detector tags.

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Multiple detector tags can be used used in the same alias.properties file, but each detector tag should eventually resolve to a single location.

Recursive Name Translation

If the value is not a URL, then it is assumed to be an alias. This is resolved recursively until the "base" value is obtained for that key.

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The d name will be resolved using the conditions lookup algorithm.

Alias File Locations

Alias files are stored at one or more of the following locations.

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as this is likely the only place to which you'll have write access, and your own aliases should be kept separate from the common ones.

Conditions Lookup

Conditions information for a detector tag is retrieved as follows.

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If the lookup process does not result in a valid set of conditions, the program will terminate with an error. (In Java, this is a ConditionsNotFoundException).

Java Example

Here is an example of accessing conditions of the sdjan03 detector from Java code.

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