marc21-skosify(1)

NAME

marc21-skosify — Convert records to SKOS/RDF

DESCRIPTION

This command converts a set of arbitrary MARC21 records into a SKOS/RDF graph. The specifications for how the conversion should be performed are defined in a configuration file.

Note

If you’re interested in converting MARC21 to SKOS/RDF, you should also take a look at mc2skos as an alternative.

CONFIGURATION

Parameterization is performed using a configuration file in TOML format, which must be specified using the -c or --config option.

Scope

If only a subset of the input records is to be processed, a filter criterion can be specified using the scope option. Only records that meet this criterion are included in the SKOS graph.

Note

In addition to this option, the set of records to be processed can also be limited using the command-line option --where. If both methods are used, a record must meet both criteria.

In the following example, the scope is defined as follows: Only authority records (leader type z) with an authentication code gnd1 (field 042 $a) and an authority data code s in field 079 $q are processed.

scope = 'ldr.type == "z" && 042.a == "gnd1" && 079.q == "s"'

Concept URI

There are two ways to specify the URI of a concept: Either by directly specifying it using a path expression (only the first value of the expression is used). In the following example, the URI from the field 024/7# $0 is used if the subfield $2 in the same field contains the value gnd:

uri = { path = '024/7#{ 0 | 2 == "gnd" }' }

Alternatively, the URI can be created by concatenating a base URI and a value determined by a path expression (only the first value is used). In the following example, the URI is formed from the base URI https://d-nb.info and the control number of the record (field 001):

uri = { base-uri = 'https://d-nb.info/', path = '001' }

Groups

The properties of a concept are specified within a group. The group defines which SKOS property is derived from which MARC21 values. This type of specification takes into account the fact that the values are often located in other fields, depending on a property of the record. A group can therefore (optionally) be restricted to a subset of records by specifying a scope. The groups are processed in order. Processing of the groups stops when at least one triple has been generated for a record.

In the following example, a subject-heading group is created that refers only to GND subject headings (scope). The prefLabel (preferred) is derived from field 150 $a, and the altLabel (alternative) from field 450 $a. No hiddenLabels (hidden) are defined.

[group.subject-heading]
scope = '075{ b == "s" && 2 == "gndgen" }'
labels = [
  { kind = 'preferred', path = '150.a' },
  { kind = 'alternative', path = '450.a' },
]

Miscellaneous

pretty = true | false: The pretty flag can be used to specify whether extra effort should be made to format the output nicely. This flag should be used with caution, as grouping related triples can be very time- and resource-intensive. If the flag is not set (default), output occurs in streaming mode, meaning subject and predicate “factorization” will only occur based on the previous triple(s) in the stream.

OPTIONS

-c, --config: Specifies the configuration file that defines the parameters rules for the SKOS/RDF graph.
-o <filename>, --output <filename>: Write output to <filename> instead of stdout. The output is automatically Gzip-compressed if the file ends with the suffix .gz.

-l, --limit <n>: Limit the result to first <n> records (a limit value 0 means no limit)
-s, --skip-invalid: Skip invalid records that can’t be decoded
--strsim-threshold <value>: The minimum score for string similarity comparisons. The value must be between 0 and 100.
--where: An filter expression for filtering records
--filter-normalization <form>: Transliterate the given filter or query expression into the specified Unicode normal form. Possible values: nfd, nfkd, nfc, nfkc. This option can also be specified by setting the environment variable MARC21_FILTER_NORMALIZATION.

Common Options

-p, --progress: If set, show a progress bar
--compression: Specify compression level (0..=9)

EXIT STATUS

0 — Command succeeded.
1 — Command failed.

EXAMPLES

In the following example, an SKOS graph is created that consists solely of GND entities of type saf (“Formangabe”). The literals for prefLabel and altLabel are taken from fields 150 $a and 450 $a.

scope = '''
  ldr.type == "z"
    && 075{ b == "saf" && b == "saz" && 2 == "gndspec" }
    && 042.a == "gnd1" && 079.q == "s"
'''

uri = {
  base-uri = "https://explore.gnd.network/gnd/",
  path = '001'
}

[group.entity-type-saf]
labels = [
  { kind = 'preferred', path = '150.a' },
  { kind = 'alternative', path = '450.a' },
]

The graph can be generated using the following command (for the sake of brevity, the output has been limited to the Rezension (review/recension) entity):

$ marc21 skosify -c saf.toml authorities-gnd-sachbegriff_dnbmarc.mrc.gz \
    --where '001 == "040497127"'
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
<https://explore.gnd.network/gnd/040497127> a <http://www.w3.org/2004/02/skos/core#Concept>;
        <http://www.w3.org/2004/02/skos/core#prefLabel> "Rezension";
        <http://www.w3.org/2004/02/skos/core#altLabel> "Buchbesprechung",
                "Buchrezension",
                "Buchkritik".

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