File Metadata Schema

File Metadata Schema is a description of what excerpted, summary information we store about each file and outside each file.

Documents

• {{DocDB|8093|A Proposal for LBNE Metadata in SAM}
• LBNE File Metadata Schema Evolution Policy and Procedure
• Review of Initial LBNE File Metadata Schema Proposal
• t.b.d. "Proposed change to file metadata in support of 35t raw data"

Drivers

The metadata schema is something that multiple systems rely on

• detector DAQ systems must ultimtely produce it
• end-user analyses rely on datasets defined in terms of it
• production data processing systems need to query it

Currently, the schema to describe data from the the verticle slice test and 35t prototype test run are paramount.

SAM

The de'facto choice for a file metadata system is "SAM" from Fermilab. It has a required/default schema. The table in this Redmine page gives a summary. It is up to the experiment to extend and for some elements, interpret, this schema. This extension and interpretation needs to be carefully nailed down and allowed to evolve in a well controlled manner.

File numbers

See below for issues on this topic related to 35t.

SAM supports both subrun and file numbers. It has two fields that pertain on a per-file basis:

runs = [ [<runnumber>, <subrunnumber>, <runtype>], ]
file_partition = <filenumber>

The "runs" variable is a list of 2-tuples or 3-tuples. In the former case, the subrunnumber is dropped. This means that a single file may be recorded as spaning runs and/or subruns. The file_partition is open to interpretation by the experiment (as are the other numbers).

35 ton

This section collects info specific to metadat for 35t raw data file production

File numbering

Some email ca. July 2014 between online and offline people discussed this. The summary:

• artDAQ writes files to disk and enstore and is the initial source of metadata (Kurt Biery, John Freeman)
• Monotonically increasing "run number" (likely not starting at zero/one, and tracked/asserted by run control. Subrun and/or file numbers generated by artDAQ (Erik Blaufus)
• artDAQ will set subrun number and will keep one file per subrun (Kurt Biery)

In terms of SAM, this means either dropping subrunnumber and using the 2-tuple form of runs and using file_partition to count the subrun OR keeping the 3-tuple form and either ignoring file_partition or filling it with a redundant count. My (bv) recomendation is to adopt the latter.

Desire metadata schema

This section collects the metadata schema desired for the 35t, parameter names, types, etc. This will become the fodder for a formal change proposal.

Parameter types:

extenum 

an extensible enumeration. This type takes values from a fixed but extensible set of strings. The set is not allowed to grow unrestricted or via one individuals action. Some consensus among a larger group is required to add to the set.

verstr 

a string left up to the experts who determine the version of something. The values such a type may take should governed by some pattern. See DocDB #9888 section 3.2 for a recommended interpretation of version numbers.

list(type) 

an ordered sequence of elements of type type

N-tuple 

an ordered sequence of exactly N elements of unspecified types.

name	type	example	comment
Basic Parameters (types pre-defined by SAM schema)
file_type	extenum	raw35t,log	indicates category of use, any application that can read files of a given file_type should be able to read all such files. file_type is different than file_format
file_format	extenum	rawdaq, dk2nu, detsim	defines the lowevel format (eg, ASCII, ROOT) and the general schema which the content follows
runs	list(3-tuple)	[(100,2,"label"),]	Following SAM requirements the 3-tuple holds: (run-number, subrun-number, "label"). TBD: specify expectation for label. Note, this is a list; a given file may have multiple run/subrun numbers associated.
...
Schema Extensions (parameters not directly defined by SAM)
file_format_version	verstr	1.0, 1.1	See DocDB #9888 section 3.2 for a recommended interpretation of version numbers
...