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pkiraly / metadata-qa-api

Metadata Quality Assessment Framework API
http://pkiraly.github.io/
GNU General Public License v3.0
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code4lib csv json xml

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Metadata Quality Assessment Framework API

This project is the central piece of the Metadata Quality Assurance Framework, every other project is built on top of it. It provides a general framework for measuring metadata quality in different digital collections.

Quality dimensions

The framework measures the following features:

above these there are some helper calculators:

Running as command-line application

usage:

./mqa -i <file> -s <file> -m <file>
      [-f <format>] [-h <arg>] [-o <file>] [-r <path>] [-v <format>] [-w <format>] [-z]

Using the library

If you want to implement it to your collection you have to define a schema, which presentats an existing metadata schema, and configure the basic facade, which will run the calculation.

First, add the library into your project's pom.xml file:

<dependencies>
  ...
  <dependency>
    <groupId>de.gwdg.metadata</groupId>
    <artifactId>metadata-qa-api</artifactId>
    <version>0.9.4</version>
  </dependency>
</dependencies>

Define a configuration:

MeasurementConfiguration config = new MeasurementConfiguration()
  // we will measure completeness now
  .enableCompletenessMeasurement();

You can create a configuration file.

Define a schema:

Schema schema = new BaseSchema()
  // this schema will be used for a CSV file
  .setFormat(Format.CSV)
  // DataELement represents a data element, which might have 
  // a number of properties
  .addField(
    new DataELement("url", Category.MANDATORY)
        .setExtractable()
  )
  .addField(new DataELement("name"))
  .addField(new DataELement("alternateName"))
  ...
  .addField(new DataELement("temporalCoverage"));

Build a CalculatorFacade object:

CalculatorFacade calculator = new CalculatorFacade(config) // use configuration
  .setSchema(schema)   // set the schema which describes the source
  .configure();        // finalize the configuration

If you have a CSV source and you would like to reuse the headers use setCsvReader():

CalculatorFacade calculator = new CalculatorFacade(config) // use configuration
  .setSchema(schema)   // set the schema which describes the source
  .setCsvReader(       // optional, if it is a CSV source
    new CsvReader()
      .setHeader(((CsvAwareSchema) schema).getHeader()))
  .configure();        // finalize the configuration

These are the two important requirements for the start of the measuring. The measuring is simple:

String csv = calculator.measure(input)

The input should be a string formatted as JSON, XML or CSV. The output is a comma separated line. The calculator.getHeader() returns the list of the column names.

There are a couple of alternatives, if you would like to receive a List or a Map:

"0.352941,1.0,1,1,0,1,0,0,0,0,1,0,0,1,1,0,0,0,0,1,1,0,1,0,0,0,0,1,0,0,1,1,0,0,0,0"
List.of("0.352941", "1.0", "1", "1", "0", "1", "0", "0", "0", "0", "1", "0", "0", "1", "1",
        "0", "0", "0", "0", "1", "1", "0", "1", "0", "0", "0", "0", "1", "0", "0", "1", "1",
        "0", "0", "0", "0");
List.of(0.35294117647058826, 1.0, true, true, false, true, false, false, false, false, true,
        false, false, true, true, false, false, false, false, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0,
        0, 1, 1, 0, 0, 0, 0);
Map.of(
  "completeness:TOTAL", 0.35294117647058826,
  "completeness:MANDATORY", 1.0,
  "existence:url", true,
  "existence:name", true,
  "existence:alternateName", false,
  "existence:description", true,
  "existence:variablesMeasured", false,
  "existence:measurementTechnique", false,
  "existence:sameAs", false,
  "existence:doi", false,
  "existence:identifier", true,
  "existence:author", false,
  "existence:isAccessibleForFree", false,
  "existence:dateModified", true,
  "existence:distribution", true,
  "existence:spatialCoverage", false,
  "existence:provider", false,
  "existence:funder", false,
  "existence:temporalCoverage", false,
  "cardinality:url", 1.
  "cardinality:name", 1,
  "cardinality:alternateName", 0,
  "cardinality:description", 1,
  "cardinality:variablesMeasured", 0,
  "cardinality:measurementTechnique", 0,
  "cardinality:sameAs", 0,
  "cardinality:doi", 0,
  "cardinality:identifier", 1,
  "cardinality:author", 0,
  "cardinality:isAccessibleForFree", 0,
  "cardinality:dateModified", 1,
  "cardinality:distribution", 1,
  "cardinality:spatialCoverage", 0,
  "cardinality:provider", 0,
  "cardinality:funder", 0,
  "cardinality:temporalCoverage", 0
)
{
  "completeness":{
    "completeness":{
      "TOTAL":0.35294117647058826,
      "MANDATORY":1.0
    },
    "existence":{
      "url":true,
      "name":true,
      "alternateName":false,
      "description":true,
      "variablesMeasured":false,
      "measurementTechnique":false,
      "sameAs":false,
      "doi":false,
      "identifier":true,
      "author":false,
      "isAccessibleForFree":false,
      "dateModified":true,
      "distribution":true,
      "spatialCoverage":false,
      "provider":false,
      "funder":false,
      "temporalCoverage":false
    },
    "cardinality":{
      "url":1,
      "name":1,
      "alternateName":0,
      "description":1,
      "variablesMeasured":0,
      "measurementTechnique":0,
      "sameAs":0,
      "doi":0,
      "identifier":1,
      "author":0,
      "isAccessibleForFree":0,
      "dateModified":1,
      "distribution":1,
      "spatialCoverage":0,
      "provider":0,
      "funder":0,
      "temporalCoverage":0
    }
  }
}
assertTrue(metrics instanceof Map);
assertEquals(1, metrics.size());
assertEquals("completeness", metrics.keySet().iterator().next());
// the calculator produced three metrics
assertEquals(3, metrics.get("completeness").size());

// first: completeness
assertEquals("completeness", metrics.get("completeness").get(0).getName());
assertEquals(
  Map.of("TOTAL", 0.35294117647058826, "MANDATORY", 1.0),
  metrics.get("completeness").get(0).getResultMap());

// second: existence
assertEquals("existence", metrics.get("completeness").get(1).getName());
assertEquals(
  Set.of("url", "name", "alternateName", "description", "variablesMeasured", "measurementTechnique",
        "sameAs", "doi", "identifier", "author", "isAccessibleForFree", "dateModified",
        "distribution", "spatialCoverage", "provider", "funder", "temporalCoverage"),
  metrics.get("completeness").get(1).getResultMap().keySet());
assertEquals(
  List.of(true, true, false, true, false, false, false, false, true, false, false, true, true,
          false, false, false, false),
  new ArrayList(metrics.get("completeness").get(1).getResultMap().values()));

// third: cardinality
assertEquals("cardinality", metrics.get("completeness").get(2).getName());
assertEquals(
  Set.of("url", "name", "alternateName", "description", "variablesMeasured", "measurementTechnique",
        "sameAs", "doi", "identifier", "author", "isAccessibleForFree", "dateModified",
        "distribution", "spatialCoverage", "provider", "funder", "temporalCoverage"),
  metrics.get("completeness").get(2).getResultMap().keySet());
assertEquals(
  List.of(1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0),
  new ArrayList(metrics.get("completeness").get(2).getResultMap().values()));

If your input is a CSV file, and you already processed the lines into list of cells, you could use the same methods:

An example which collects output into a StringBuffer (you can persist lines into a CSV file or into a database):

// collect the output into a container. The output is a CSV file
StringBuffer output = new StringBuffer();

// get the header of the output CSV
output.append(calculator.getHeader())

// The input could be JSON, XML or CSV. 
// You can set any kind of datasource, as long it returns a String
Iterator iterator = ...;
while (iterator.hasNext()) {
  try {
    // measure the input
    String csv = calculator.measure(iterator.next());
    // save csv
    output.append(csv);
  } catch (InvalidJsonException e) {
    // handle exception
  }
}

// get the output
String metrics = output.toString();

Defining schema with a configuration file

It is possible to define the schema with a YAML or JSON configuration file.

Schema schema = ConfigurationReader
  .readSchemaYaml("path/to/some/configuration.yaml")
  .asSchema();

A YAML example:

format: json
fields:
  - name: edm:ProvidedCHO/@about
    path:  $.['providedCHOs'][0]['about']
    indexField: id
    extractable: true
    rules:
      - and:
        - minCount: 1 
        - maxCount: 1
        failureScore: -10
      - pattern: ^https?://.*$
        successScore: 3
    categories:
      - MANDATORY
  - name: Proxy/dc:title
    path: $.['proxies'][?(@['europeanaProxy'] == false)]['dcTitle']
    categories:
      - DESCRIPTIVENESS
      - SEARCHABILITY
      - IDENTIFICATION
      - MULTILINGUALITY
      - CUSTOM
  - name: Proxy/dcterms:alternative
    path: $.['proxies'][?(@['europeanaProxy'] == false)]['dctermsAlternative']
    categories:
      - DESCRIPTIVENESS
      - SEARCHABILITY
      - IDENTIFICATION
      - MULTILINGUALITY
groups:
  - fields:
      - Proxy/dc:title
      - Proxy/dc:description
    categories:
      - MANDATORY

The same in JSON:

{
  "format": "json",
  "fields": [
    {
      "name": "edm:ProvidedCHO/@about",
      "path":  "$.['providedCHOs'][0]['about']",
      "indexField": "id",
      "extractable": true,
      "rules": [
        {
          "and": [
            {"minCount": 1},
            {"maxCount": 1}
          ],
          "failureScore": -10
        },
        {
          "pattern": "^https?://.*$",
          "successScore": 3
        }
      ],
      "categories": ["MANDATORY"]
    },
    {
      "name": "Proxy/dc:title",
      "path": "$.['proxies'][?(@['europeanaProxy'] == false)]['dcTitle']",
      "categories": [
        "DESCRIPTIVENESS",
        "SEARCHABILITY",
        "IDENTIFICATION",
        "MULTILINGUALITY"
      ]
    },
    {
      "name": "Proxy/dcterms:alternative",
      "path": "$.['proxies'][?(@['europeanaProxy'] == false)]['dctermsAlternative']",
      "categories": [
        "DESCRIPTIVENESS",
        "SEARCHABILITY",
        "IDENTIFICATION",
        "MULTILINGUALITY"
      ]
    }
  ],
  "groups": [
    {
      "fields": [
        "Proxy/dc:title",
        "Proxy/dc:description"
      ],
      "categories": [
        "MANDATORY"
      ]
    }
  ]
}

The central piece is the fields array. Each item represents the properties of a single data elements (a DataELement in the API). Its properties are:

Optionaly you can set the "canonical list" of categories. It provides two additional functionalities

Here is an example (in YAML):

format: json
...
categories:
  - MANDATORY
  - DESCRIPTIVENESS
  - SEARCHABILITY
  - IDENTIFICATION
  - CUSTOM
  - MULTILINGUALITY

Rules

One can add constraints to the fields. There are content rules, which the tool will check. In this version the tool mimin SHACL constraints.

Cardinality

One can specify with these constraints how many occurrences of a data element a record can have.

minCount <number>

Specifies the minimum number of field occurence (API: setMinCount() or withMinCount())

Example: the field should have at least one occurrence

- name: about
  path:  $.['about']
  rules:
  - minCount: 1
maxCount <number>

Specifies the maximum number of field occurence (API: setMaxCount() or withMaxCount())

Example: the field might have maximum one occurrence

- name: about
  path:  $.['about']
  rules:
  - maxCount: 1

Value Range

You can set a range of value within which the field's value should remain. You can set a lower and higher bound with boolean operators. You can specify either integers or floating point numbers.

minExclusive <number>

The minimum exclusive value ([field value] > limit, API: setMinExclusive(Double) or withMinExclusive(Double))

minInclusive <number>

The minimum inclusive value ([field value] >= limit, API: setMinInclusive(Double) or withMinExclusive(Double))

maxExclusive <number>

The maximum exclusive value ([field value] < limit, API: setMaxExclusive(Double) or withMaxExclusive(Double))

maxInclusive <number>

The maximum inclusive value ([field value] <= limit, API: setMaxInclusive(Double) or withMaxInclusive(Double))

Example: 1.0 <= price <= 2.0

- name: price
  path:  $.['price']
  rules:
    - and:
      - minInclusive: 1.0
      - maxInclusive: 2.0

Example: 1.0 < price < 2.0

- name: price
  path:  $.['price']
  rules:
    - and:
      - minExclusive: 1
      - maxExclusive: 2

Note: integers will be interpreted as floating point numbers.

String constraints

minLength <number>

The minimum string length of each field value (API: setMinLength(Integer) or withMinLength(Integer))

Example: the field value should not be empty

- name: about
  path:  $.['about']
  rules:
    - minLength: 1
maxLength <number>

The maximum string length of each field value (API: setMaxLength(Integer) or withMaxLength(Integer))

Example: the value should be 3, 4, or 5 characters long.

- name: about
  path:  $.['about']
  rules:
    - and:
      - minLength: 3
      - maxLength: 5
hasValue <String>

The value should be equal to the provided value (API: setHasValue(String) or withHasValue(String))

Example: the status should be "published".

- name: status
  path:  $.['status']
  rules:
    - hasValue: published
in [String1, ..., StringN]

The string value should be one of the listed values (API: setIn(List<String>) or withIn(List<String>))

Example: the value should be either "dataverse", "dataset" or "file".

- name: type
  path:  $.['type']
  rules:
    - in: [dataverse, dataset, file]
pattern <regular expression>

A regular expression that each field value matches to satisfy the condition. The expression can match a a part of the whole string (see the Java Matcher object's find method). (API: setPattern(String) or withPattern(String))

Example: the field value should start with http:// or https:// and end with .jpg, .jpeg, .jpe, .jfif, .png, .tiff, .tif, .gif, .svg, .svgz, or .pdf.

- name: thumbnail
  path: oai:record/dc:identifier[@type='binary']
  rules:
    - pattern: ^https?://.*\.(jpg|jpeg|jpe|jfif|png|tiff|tif|gif|svg|svgz|pdf)$
minWords <number>

The minimum word count of each field value (API: setMinWords(Integer) or withMinWord(Integer))

Example: the field value should have at least one words

- name: about
  path:  $.['about']
  rules:
    - minWords: 1
maxWords <number>

The maximum string length of each field value (API: setMaxWords(Integer) or withMaxWords(Integer))

Example: the value should be at least 3 character long, but should not contain more than 2 words.

- name: about
  path:  $.['about']
  rules:
    - and:
      - minLength: 3
      - maxWords: 2

Comparision of properties

equals <field label>

The set of all values of a field is equal to the set of all values of another field (API: setEquals(String) or withEquals(String))

Example: The ID should be equal to the ISBN number.

fields:
  - name: id
    path:  $.['id']
    rules:
      - equals: isbn
  - name: isbn
    path:  $.['isbn']
disjoint <field label>

The set of values of a field is disjoint (not equal) with the set of all values of another field (API: setDisjoint(String) or withDisjoint(String))

Example: The title should be different from description.

fields:
  - name: title
    path:  $.['title']
    rules:
      - equals: description
  - name: description
    path:  $.['description']
lessThan <field label>

Each values of a field is smaller than each values of another field (API: setLessThan(String) or withLessThan(String))

Example: the date of birth is less than the date of death

- name: birthDate
  path: oai:record/dc:date[@type='birth']
  rules:
    - lessThan: deathDate
lessThanOrEquals <field label>

Each values of a field is smaller than or equals to each values of another field (API: setLessThanOrEquals(String) or withLessThanOrEquals(String))

Example: the starting page of the article should be less than or equal to the ending page:

- name: startingPage
  path: startingPage
  rules:
    - lessThan: endingPage

Logical operators

With logical operators you can build complex rules. Each component should fit to its own rules.

and [<rule1>, ..., <ruleN>]

Passes if all the rules in the set passed. (API: setAnd(List<Rule>) or withAnd(List<Rule>))

Example: The ID should have one and only one occurrence, and is should not be an empty string.

- name: id
  path: oai:record/dc:identifier[@type='providerItemId']
  rules:
    - and:
      - minCount: 1
      - maxCount: 1
      - minLength: 1
or [<rule1>, ..., <ruleN>]

Passes if at least one of the rules in the set passed. (API: setOr(List<Rule>) or withOr(List<Rule>))

Example: The thumbnail should either end with a known image extension or its content type should be one of the provided MIME image types.

- name: thumbnail
  path: oai:record/dc:identifier[@type='binary']
  rules:
    - or:
      - pattern: ^.*\.(jpg|jpeg|jpe|jfif|png|tiff|tif|gif|svg|svgz)$
      - contentType: [image/jpeg, image/png, image/tiff, image/tiff-fx, image/gif, image/svg+xml]
not [<rule1>, ..., <ruleN>]

Passes if none of the rules in the set passed. (API: setNot(List<Rule>) or withNot(List<Rule>))

Example: make sure that the title and the description is different.

- name: title
  path:  $.['title']
  rules:
    - not:
      - equals: description

Other constraints

These rules don't have parallel in SHACL.

contentType [type1, ..., typeN]

This rule interprets the value as a URL, fetches it and extracts the HTTP header's content type, then checks if it is one of those allowed.

Example: The HTTP content type should be image/jpeg, image/png, image/tiff, image/tiff-fx, image/gif, or image/svg+xml.

- name: thumbnail
  path: oai:record/dc:identifier[@type='binary']
  rules:
    - contentType: [image/jpeg, image/png, image/tiff, image/tiff-fx, image/gif, image/svg+xml]
unique <boolean>

(since v0.9.0)

This rule checks if the value of the field is unique. Prerequisite: the field should have indexField property, and the content should be indexed with Apache Solr.

dependencies [id1, id2, ..., idN]

(since v0.9.0)

This rule checks if other rules has already checked and passed. It passes if all dependent rules has passed or resulted NA, otherwise fail. The ids should be valid, and the dependent rule should take place after the ones from which it depends.

dimension [criteria1, criteria2, ..., criteriaN]

(since v0.9.0)

This checks if a linked image fits to some dimension constraints (unit in pixel) - if the value is an URL for an image. One can check the minimum and maximum size of width, height and shorter or longer sides (in case it is not important if width or height is the shorter). The criteria:

example:

format: csv
fields:
- name: thumbnail
  path: oai:record/dc:identifier[@type='binary']
  rules:
  - id: 3.1
    failureScore: -9
    dimension:
      minWidth: 200
      minHeight: 200
hasLanguageTag <anyOf|oneOf|allOf>

(since v0.9.6)

It checks if the data element value has language tag. In XML the language tag is found in @xml:lang attribute. In JSON it might be encoded differently. Right now MQAF suppoert the following encoding:

"description": {
  "de": ["Porträt"]
}

Since this kind of structure might be applied not only for the language annotation, at the field level we should set that the field is expected to have language annotation:

format: json
fields:
  - name: description
    path: $.['description']
    asLanguageTagged: true

The parameters defines if any, one or all instances should have language annottation:

A full example:

format: json
fields:
- name: description
  path: $.['description']
  asLanguageTagged: true
  rules:
  - hasLanguageTag: allOf
isMultilingual <boolean>

(since v0.9.6)

It checks if the data element is multilingual, so it has at least two instances with different language annotations.

{
  "description":{
    "de":["Portr\u00e4t"],
    "zh":["\u8096\u50cf"]
  }
}

an example schema

format: json
fields:
  - name: description
    path: $.['description']
    asLanguageTagged: true
    rules:
      - isMultilingual: true

General properties

id <String>

You can define an identifier to the rule, which will be reflected in the output. If you miss it, the system will assign a count number. ID might also help if you transform a human readable document such as cataloguing rules into a configuration file, and you want to keep linkage between them. (API setId(String) or withId(String))

description <String>

Provide a description to document what the particular rule is doing. It can be anything reasonable, it does not play a role in the calculation.

failureScore <integer>

A score which will be calculated if the validation fails. The score should be a negative or positive integer (including zero). (API setFailureScore(Integer) or withFailureScore(Integer))

successScore <integer>

A score which will be calculated if the validation passes. The score should be a negative or positive integer (including zero). (API setSuccessScore(Integer) or withSuccessScore(Integer))

naScore <integer>

A score which will be calculated if the value is missing (there is no such data element). The score should be a negative or positive integer (including zero). (API setNaScore(Integer) or withNaScore(Integer))

Example: set of rules with IDs and scores.

- name: providerid
  path: oai:record/dc:identifier[@type='providerid']
  rules:
  - and:
    - minCount: 1
    - minLength: 1
      failureScore: -6
      id: 2.1
  - pattern: ^(DE-\d+|DE-MUS-\d+|http://id.zdb-services.de\w+|\d{8}|oai\d{13})$
    failureScore: -3
    naScore: 0
    id: 2.2
  - pattern: ^(DE-\d+|DE-MUS-\d+|http://id.zdb-services.de\w+)$
    successScore: 6
    naScore: 0
    id: 2.4
  - pattern: ^http://id.zdb-services.de\w+$
    successScore: 3
    naScore: 0
    id: 2.5
  - pattern: ^http://d-nb.info/gnd/\w+$
    successScore: 3
    naScore: 0
    id: 2.6
hidden <boolean>

(since v0.9.0)

If the rule is hidden it will be calculated, but its output will not be present in the overall output. It can be used together width dependencies to set up compound conditions.

skip <boolean>

(since v0.9.0)

This rule prevents a particular rule to be part of calculation. This could be useful in development phase when you started to create a complex rule but haven't yet finished, or when the execution of the rule takes long time (e.g. checking content type or image dimension), and temporary you would like to turn it off.

debug <boolean>:

(since v0.9.0)

If set, the tool logs the rule identifier, its value and the rule's result.

Set rules via Java API

Schema schema = new BaseSchema()
  .setFormat(Format.CSV)
  .addField(
    new DataELement("title", "title")
      .setRule(
        new Rule()
          .withDisjoint("description")
      )
  )
  .addField(
    new DataELement("url", "url")
      .setRule(
        new Rule()
          .withMinCount(1)
          .withMaxCount(1)
          .withPattern("^https?://.*$")
      )
  )
  ;

Via configuration file (a YAML example):

format: csv
fields:
  - name: title
    categories: [MANDATORY]
    rules:
      disjoint: description
  - name: url
    categories: [MANDATORY]
    extractable: true
    rules:
      minCount: 1
      maxCount: 1
      pattern: ^https?://.*$

In both cases we defined two fields. title has one constraints: it should not be equal to the value of description field (which is masked out from the example). Note: if this hypothetical description field is not available the API drops an error message into the log. url should have one and only one instance, and its value should start with "http://" or "https://".

As you can see there are two types of setters in the API: setSomething and withSomething. The difference is that setSomething returs with void, but withSomething returns with the Rule object, so you can use it in a chain such as new Rule().withMinCount(1).withMaxCount(3) (while new Rule().setMinCount(1).setMaxCount(3) doesn't work, because setMinCount() does returns nothing, and one can not apply setMaxCount(3) on that nothing).

Defining MeasurementConfiguration with a configuration file

MeasurementConfiguration can be created from JSON or YAML configuration files with the following methods:

an example:

MeasurementConfiguration configuration = ConfigurationReader
  .readMeasurementJson("path/to/some/configuration.json");

An example JSON file:

{
  "fieldExtractorEnabled": false,
  "fieldExistenceMeasurementEnabled": true,
  "fieldCardinalityMeasurementEnabled": true,
  "completenessMeasurementEnabled": true,
  "tfIdfMeasurementEnabled": false,
  "problemCatalogMeasurementEnabled": false,
  "ruleCatalogMeasurementEnabled": false,
  "languageMeasurementEnabled": false,
  "multilingualSaturationMeasurementEnabled": false,
  "collectTfIdfTerms": false,
  "uniquenessMeasurementEnabled": false,
  "completenessCollectFields": false,
  "saturationExtendedResult": false,
  "checkSkippableCollections": false
}

Using an experimental version

If you want to try an experimental version (which has SNAPSHOT in its version name), you have to enable the retrieval of those versions in the pom.xml file:

<repositories>
  <repository>
    <id>sonatypeSnapshots</id>
    <name>Sonatype Snapshots</name>
    <url>https://oss.sonatype.org/content/repositories/snapshots</url>
    <releases>
     <enabled>false</enabled>
    </releases>
    <snapshots>
      <enabled>true</enabled>
    </snapshots>
  </repository>
</repositories>

<dependencies>
  ...
  <dependency>
    <grroupId>de.gwdg.metadata</grroupId>
    <artifactId>metadata-qa-api</artifactId>
    <version>0.9-SNAPSHOT</version>
  </dependency>
</dependencies>

Thanks to Miel Vander Sande (@mielvds) for the hint!

More info

Since version 0.8-SNAPSHOT the project requires Java 11.

For the usage and implementation of the API see https://github.com/pkiraly/europeana-qa-api.

Java doc for the actual development version of the API: https://pkiraly.github.io/metadata-qa-api.

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