Values are obtained by either overlaid replacement or appending if the
append attribute is set. value is the last attribute to be calculated.
Values are calculated from files in order of directory tree traversal from root to working
directory and in order of appearance in a file. Multiple entries will result in
a warning being issued and the last value
being used. Empty value strings will result in the value becoming undefined, if
previously defined.
Values are encoded as a Unicode strings. The default encoding used is UTF-8, unless
overridden by an .encoding.txt file or an encoding attribute.
Input is checked to see if it passes type, bounds, allowed value, and path existence checking. Failure of any of these checks produces a fatal error.
For metadata of type path, values inherited from directories above
the working directory will be replaced with the correct number of up-referenced values
(e.g., the path README.txt inherited from a directory one level above will become
../README.txt).
Values for sequence types must be interpretable as python literals. This means that strings must be in quotes.
If the evaluate attribute is set, the value string will be evaluated using
python syntax as defined by asteval <http://newville.github.io/asteval/>.
The symbol table will be taken from the metadata values that
have been defined up to that point, plus additional internal values:
| Symbol | Value |
|---|---|
| date | The date in ISO 8601 format. |
| time | The date and time (Zulu) in ISO 8601 format. |
| node | Name of the computer on which meta_iron was run. |
| root | Relative path to the root directory. |
| depth | Integer depth of the current working directory from the root working directory. |
| bindir | Additional directory that will be prepended to path
from environment before executing commands via
execute attribute. Set to root+'/bin' by
default if that directory exists, but can be overridden
by global switch if necessary. |
| user | Username associated with the meta_iron process. |
| meta_iron | Version string from meta_iron. |
| self | Current metadata item name. |
| self.attribute | Every attribute that is defined, including
self.value are available for evaluation. |
| prefix | Global prefix for the data store. |
| last_accession | An integer value stored in the root metadata file. This will
be incremented to guarantee a unique value. The mint_accession
command will cause this value to be stored in the accession
value in the current directory and the last_accession number
will be incremented. |
| accession | The accession number of the most recent metadata. |
| version | A value of type version set by the set_version command. This is
specific to the directory and stored there. |
| OID | A value of type OID that is the current Object ID, obtained by
concatenating [prefix, accession, 'v', version], e.g.,
LegFed000124v2.2. The OID is used by the prefix_OID
update_OID. and register_directory commands. |
| parent_OID | OID of parent, may be more than one directory level up. |
| child_OIDs | List of OID's of registered children. Not all subdirectories may be registered. |
Note that evaluated values must quote literals in either single or double quotes or else the string will be interpreted as a symbol.
Values which are undefined at the level of the current working directory are not output.