Use JSON files for stand-off annotations.

.gitlab-ci.yml

@@ -1,8 +1,5 @@
 image: docker:19.03.13
 
-variables:
-  DOCKER_TLS_CERTDIR: "/certs"
-
 services:
   - docker:19.03.13-dind
 
@@ -10,6 +7,10 @@ stages:
   - build
   - push
 
+variables:
+  DOCKER_TLS_CERTDIR: "/certs"
+  INTERMEDIATE_IMAGE_TAG: $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME-$CI_COMMIT_SHA
+
 .reg_setup:
   before_script:
     - apk add --no-cache curl
@@ -28,8 +29,6 @@ build_image:
   stage: build
   tags:
     - docker
-  variables:
-    INTERMEDIATE_IMAGE_TAG: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
 
 push_master:
   extends:
@@ -47,7 +46,6 @@ push_master:
     - docker
   variables:
     IMAGE_TAG: $CI_REGISTRY_IMAGE:latest
-    INTERMEDIATE_IMAGE_TAG: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
 
 push_other:
   extends:
@@ -68,4 +66,3 @@ push_other:
     - docker
   variables:
     IMAGE_TAG: $CI_REGISTRY_IMAGE:$CI_COMMIT_REF_NAME
-    INTERMEDIATE_IMAGE_TAG: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA

Dockerfile

@@ -7,28 +7,29 @@ LABEL authors="Patrick Jentsch <p.jentsch@uni-bielefeld.de>, Stephan Porada <por
 ENV LANG=C.UTF-8
 
 
-RUN apt-get update
+RUN apt-get update \
+ && apt-get install --no-install-recommends --yes \
+     wget
 
-
-# Install pipeline dependencies #
+# Install the NLP pipeline and it's dependencies #
 ## Install pyFlow ##
-ENV PYFLOW_RELEASE=1.1.20
-ADD "https://github.com/Illumina/pyflow/releases/download/v${PYFLOW_RELEASE}/pyflow-${PYFLOW_RELEASE}.tar.gz" .
-RUN tar -xzf "pyflow-${PYFLOW_RELEASE}.tar.gz" \
- && cd "pyflow-${PYFLOW_RELEASE}" \
+ENV PYFLOW_VERSION=1.1.20
+RUN wget --no-check-certificate --quiet \
+      "https://github.com/Illumina/pyflow/releases/download/v${PYFLOW_VERSION}/pyflow-${PYFLOW_VERSION}.tar.gz" \
+ && tar -xzf "pyflow-${PYFLOW_VERSION}.tar.gz" \
+ && cd "pyflow-${PYFLOW_VERSION}" \
  && apt-get install --no-install-recommends --yes \
       python2.7 \
  && python2.7 setup.py build install \
  && cd .. \
- && rm -r "pyflow-${PYFLOW_RELEASE}" "pyflow-${PYFLOW_RELEASE}.tar.gz"
+ && rm -r "pyflow-${PYFLOW_VERSION}" "pyflow-${PYFLOW_VERSION}.tar.gz"
 
 
 ## Install spaCy ##
-ENV SPACY_VERSION=3.0.3
+ENV SPACY_VERSION=3.0.5
 RUN apt-get install --no-install-recommends --yes \
       python3.7 \
       python3-pip \
-      zip \
  && pip3 install \
       chardet \
       setuptools \
@@ -36,22 +37,22 @@ RUN apt-get install --no-install-recommends --yes \
  && pip3 install --upgrade pip \
  && pip3 install "spacy==${SPACY_VERSION}"
 
+
+# Only models that include the following components are compatibel: 
+# lemmatizer, ner, parser, senter, tagger,
+ENV SPACY_MODELS="de_core_news_md,en_core_web_md,it_core_news_md,nl_core_news_md,pl_core_news_md,zh_core_web_md"
 ENV SPACY_MODELS_VERSION=3.0.0
-RUN python3 -m spacy download "da_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "de_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "el_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "en_core_web_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "es_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "fr_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "it_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "nl_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "pt_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "ru_core_news_md-${SPACY_MODELS_VERSION}" --direct \
- && python3 -m spacy download "zh_core_web_md-${SPACY_MODELS_VERSION}" --direct
+RUN for spacy_model in $(echo ${SPACY_MODELS} | tr "," "\n"); do python3 -m spacy download "${spacy_model}-${SPACY_MODELS_VERSION}" --direct; done
+
+
+## Further dependencies ##
+RUN apt-get install --no-install-recommends --yes \
+      procps \
+      zip
 
 
 ## Install Pipeline ##
-COPY nlp spacy-nlp /usr/local/bin/
+COPY nlp spacy-nlp vrt-creator /usr/local/bin/
 
 
 RUN rm -r /var/lib/apt/lists/*

nlp

@@ -14,39 +14,14 @@ import os
 import sys
 
 
-SPACY_MODELS = {'da': 'da_core_news_md',
-                'de': 'de_core_news_md',
-                'el': 'el_core_news_md',
+SPACY_MODELS = {'de': 'de_core_news_md',
                 'en': 'en_core_web_md',
-                'es': 'es_core_news_md',
-                'fr': 'fr_core_news_md',
                 'it': 'it_core_news_md',
                 'nl': 'nl_core_news_md',
-                'pt': 'pt_core_news_md',
-                'ru': 'ru_core_news_md',
+                'pl': 'pl_core_news_md',
                 'zh': 'zh_core_web_md'}
 
 
-def parse_args():
-    parser = ArgumentParser(description='NLP Pipeline utilizing spaCy.')
-    parser.add_argument('-i', '--input-directory',
-                        help='Input directory (only txt files get processed)',
-                        required=True)
-    parser.add_argument('-o', '--output-directory',
-                        help='Output directory',
-                        required=True)
-    parser.add_argument('-l', '--language',
-                        choices=SPACY_MODELS.keys(),
-                        required=True)
-    parser.add_argument('--check-encoding', action='store_true')
-    parser.add_argument('--log-dir')
-    parser.add_argument('--n-cores',
-                        default=min(4, multiprocessing.cpu_count()),
-                        help='total number of cores available', type=int)
-    parser.add_argument('--zip', help='Zips everything into one archive.')
-    return parser.parse_args()
-
-
 class NLPPipelineJob:
     """An NLP pipeline job class
 
@@ -56,8 +31,6 @@ class NLPPipelineJob:
     Arguments:
     file -- Path to the file
     output_dir -- Path to a directory, where job results a stored
-    intermediate_dir -- Path to a directory, where intermediate files are
-                        stored.
     """
 
     def __init__(self, file, output_dir):
@@ -67,21 +40,11 @@ class NLPPipelineJob:
 
 
 class NLPPipeline(WorkflowRunner):
-    def __init__(self, input_dir, lang, output_dir, check_encoding, n_cores, zip):
+    def __init__(self, input_dir, output_dir, check_encoding, lang, zip):
         self.input_dir = input_dir
-        self.lang = lang
         self.output_dir = output_dir
         self.check_encoding = check_encoding
-        self.n_cores = n_cores
-        self.output_dir = output_dir
-        if zip is None:
-            self.zip = zip
-        else:
-            if zip.lower().endswith('.zip'):
-                # Remove .zip file extension if provided
-                self.zip = zip[:-4]
-                self.zip = self.zip if self.zip else 'output'
-            else:
+        self.lang = lang
         self.zip = zip
         self.jobs = collect_jobs(self.input_dir, self.output_dir)
 
@@ -96,9 +59,7 @@ class NLPPipeline(WorkflowRunner):
         '''
         setup_output_directory_tasks = []
         for i, job in enumerate(self.jobs):
-            cmd = 'mkdir'
-            cmd += ' -p'
-            cmd += ' "{}"'.format(job.output_dir)
+            cmd = 'mkdir -p "{}"'.format(job.output_dir)
             lbl = 'setup_output_directory_-_{}'.format(i)
             task = self.addTask(command=cmd, label=lbl)
             setup_output_directory_tasks.append(task)
@@ -109,20 +70,36 @@ class NLPPipeline(WorkflowRunner):
         ' ##################################################
         '''
         nlp_tasks = []
-        n_cores = min(self.n_cores, max(1, int(self.n_cores / len(self.jobs))))
+        n_cores = max(1, int(self.getNCores() / len(self.jobs)))
         for i, job in enumerate(self.jobs):
-            output_file = os.path.join(job.output_dir, '{}.vrt'.format(job.name))  # noqa
+            output_file = os.path.join(job.output_dir, '{}.nopaque-stand-off.json'.format(job.name))  # noqa
             cmd = 'spacy-nlp'
-            cmd += ' -i "{}"'.format(job.file)
             cmd += ' -l "{}"'.format(self.lang)
-            cmd += ' -o "{}"'.format(output_file)
-            if self.check_encoding:
-                cmd += ' --check-encoding'
+            cmd += ' --check-encoding' if self.check_encoding else ''
+            cmd += ' "{}"'.format(job.file)
+            cmd += ' "{}"'.format(output_file)
             deps = 'setup_output_directory_-_{}'.format(i)
             lbl = 'nlp_-_{}'.format(i)
-            task = self.addTask(command=cmd, dependencies=deps, label=lbl, nCores=n_cores)  # noqa
+            task = self.addTask(command=cmd, dependencies=deps, label=lbl,
+                                nCores=n_cores)
             nlp_tasks.append(task)
 
+        '''
+        ' ##################################################
+        ' # vrt creation                                   #
+        ' ##################################################
+        '''
+        for i, job in enumerate(self.jobs):
+            output_file = os.path.join(job.output_dir, '{}.vrt'.format(job.name))  # noqa
+            nlp_file = os.path.join(job.output_dir, '{}.nopaque-stand-off.json'.format(job.name))  # noqa
+            cmd = 'vrt-creator'
+            cmd += ' "{}"'.format(job.file)
+            cmd += ' "{}"'.format(nlp_file)
+            cmd += ' "{}"'.format(output_file)
+            deps = 'nlp_-_{}'.format(i)
+            lbl = 'vrt_creation_-_{}'.format(i)
+            task = self.addTask(command=cmd, dependencies=deps, label=lbl)
+
         '''
         ' ##################################################
         ' # zip creation                                   #
@@ -136,7 +113,7 @@ class NLPPipeline(WorkflowRunner):
             cmd += ' -r'
             cmd += ' "{}.zip" .'.format(self.zip)
             cmd += ' -x "pyflow.data*"'
-            cmd += ' -i "*.vrt"'
+            cmd += ' -i "*.vrt" "*.json"'
             cmd += ' && '
             cmd += 'cd -'
             deps = nlp_tasks
@@ -152,20 +129,64 @@ def collect_jobs(input_dir, output_dir):
             jobs += collect_jobs(os.path.join(input_dir, file),
                                  os.path.join(output_dir, file))
         elif file.lower().endswith('.txt'):
-            jobs.append(NLPPipelineJob(os.path.join(input_dir, file),
-                                       os.path.join(output_dir, file)))
+            job = NLPPipelineJob(os.path.join(input_dir, file),
+                                 os.path.join(output_dir, file))
+            jobs.append(job)
     return jobs
 
 
+def parse_args():
+    parser = ArgumentParser(description='NLP pipeline for TXT file processing',
+                            prog='NLP pipeline')
+    parser.add_argument('-i', '--input-dir',
+                        help='Input directory',
+                        required=True)
+    parser.add_argument('-o', '--output-dir',
+                        help='Output directory',
+                        required=True)
+    parser.add_argument('-l', '--language',
+                        choices=SPACY_MODELS.keys(),
+                        required=True)
+    parser.add_argument('--check-encoding',
+                        action='store_true')
+    parser.add_argument('--log-dir',
+                        help='Logging directory')
+    parser.add_argument('--mem-mb',
+                        help='Amount of system memory to be used (Default: min(--n-cores * 2048, available system memory))',  # noqa
+                        type=int)
+    parser.add_argument('--n-cores',
+                        default=min(4, multiprocessing.cpu_count()),
+                        help='Number of CPU threads to be used',
+                        type=int)
+    parser.add_argument('--zip',
+                        help='Create one zip file per filetype')
+    parser.add_argument('-v', '--version',
+                        action='version',
+                        help='Returns the current version of the NLP pipeline',
+                        version='%(prog)s {}'.format(__version__))
+    args = parser.parse_args()
+
+    # Set some tricky default values and check for insufficient input
+    if args.log_dir is None:
+        args.log_dir = args.output_dir
+    if args.n_cores < 1:
+        raise Exception('--n-cores must be greater or equal 1')
+    if args.mem_mb is None:
+        max_mem_mb = int(os.popen('free -t -m').readlines()[-1].split()[1:][0])
+        args.mem_mb = min(args.n_cores * 2048, max_mem_mb)
+    if args.mem_mb < 2048:
+        raise Exception('--mem-mb must be greater or equal 2048')
+    if args.zip is not None and args.zip.lower().endswith('.zip'):
+        # Remove .zip file extension if provided
+        args.zip = args.zip[:-4]
+        args.zip = args.zip if args.zip else 'output'
+    return args
+
+
 def main():
     args = parse_args()
-    nlp_pipeline = NLPPipeline(args.input_directory, args.language,
-                               args.output_directory, args.check_encoding,
-                               args.n_cores, args.zip)
-    retval = nlp_pipeline.run(
-        dataDirRoot=(args.log_dir or args.output_directory),
-        nCores=args.n_cores
-    )
+    nlp_pipeline = NLPPipeline(args.input_dir, args.output_dir, args.check_encoding, args.language, args.zip)  # noqa
+    retval = nlp_pipeline.run(dataDirRoot=args.log_dir, memMb=args.mem_mb, nCores=args.n_cores)  # noqa
     sys.exit(retval)
 
 

spacy-nlp

@@ -2,56 +2,39 @@
 # coding=utf-8
 
 from argparse import ArgumentParser
-from xml.sax.saxutils import escape
 import chardet
 import hashlib
+import json
 import os
 import spacy
 import textwrap
 
 
-SPACY_MODELS = {'da': 'da_core_news_md',
-                'de': 'de_core_news_md',
-                'el': 'el_core_news_md',
-                'en': 'en_core_web_md',
-                'es': 'es_core_news_md',
-                'fr': 'fr_core_news_md',
-                'it': 'it_core_news_md',
-                'nl': 'nl_core_news_md',
-                'pt': 'pt_core_news_md',
-                'ru': 'ru_core_news_md',
-                'zh': 'zh_core_web_md'}
+spacy_models = {spacy.info(pipeline)['lang']: pipeline
+                for pipeline in spacy.info()['pipelines']}
 
 
-SPACY_MODELS_VERSION = os.environ.get('SPACY_MODELS_VERSION')
-SPACY_VERSION = os.environ.get('SPACY_VERSION')
-
 # Parse the given arguments
-parser = ArgumentParser(description=('Tag a text file with spaCy and save it '
-                                     'as a verticalized text file.'))
-parser.add_argument('-i', '--input', metavar='txt-sourcefile', required=True)
-parser.add_argument('-o', '--output', metavar='vrt-destfile', required=True)
-parser.add_argument('-l', '--language', choices=SPACY_MODELS.keys(), required=True)  # noqa
-parser.add_argument('--check-encoding', action='store_true')
+parser = ArgumentParser(description='Create annotations for a given txt file')
+parser.add_argument('input', metavar='Path to txt input file')
+parser.add_argument('output', metavar='Path to JSON output file')
+parser.add_argument('-l', '--language',
+                    choices=spacy_models.keys(),
+                    required=True)
+parser.add_argument('-c', '--check-encoding', action='store_true')
 args = parser.parse_args()
 
 
 # If requested: Check the encoding of the text contents from the input file
 # Else: Use utf-8
-if args.check_encoding:
-    with open(args.input, "rb") as input_file:
-        bytes = input_file.read()
-        encoding = chardet.detect(bytes)['encoding']
-else:
+with open(args.input, "rb") as input_file:
+    if args.check_encoding:
+        encoding = chardet.detect(input_file.read())['encoding']
+    else:
         encoding = 'utf-8'
-
-
-# hashing in chunks to avoid full RAM with huge files.
-with open(args.input, 'rb') as input_file:
-    source_md5 = hashlib.md5()
-    for chunk in iter(lambda: input_file.read(128 * source_md5.block_size), b''):
-        source_md5.update(chunk)
-    source_md5 = source_md5.hexdigest()
+    text_md5 = hashlib.md5()
+    for chunk in iter(lambda: input_file.read(128 * text_md5.block_size), b''):
+        text_md5.update(chunk)
 
 # Load the text contents from the input file
 with open(args.input, encoding=encoding) as input_file:
@@ -63,57 +46,119 @@ with open(args.input, encoding=encoding) as input_file:
     # longer needed...
     del text
 
-
-# Setup the spaCy toolkit by loading the chosen language model
-model = SPACY_MODELS[args.language]
+model = spacy_models[args.language]
 nlp = spacy.load(model)
 
+meta = {
+    'generator': {
+        'name': 'nopaque NLP service',
+        'version': '1.0.0',
+        'arguments': {
+            'check_encoding': args.check_encoding,
+            'language': args.language
+        }
+    },
+    'file': {
+        'md5': text_md5.hexdigest(),
+        'name': os.path.basename(args.input)
+    }
+}
 
-# Create the output file in verticalized text format
-# See: http://cwb.sourceforge.net/files/CWB_Encoding_Tutorial/node3.html
-output_file_original_filename = args.output
-output_file_stand_off_filename = args.output.replace('.vrt', '.stand-off.vrt')
-common_xml = ('<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n'
-              + '<corpus>\n'
-              + '<text>\n'
-              + '<nlp name="spaCy:{}"\n'.format(SPACY_VERSION)
-              + '     model="{}:{}"\n'.format(model, SPACY_MODELS_VERSION)
-              + '     source-md5="{}" />\n'.format(source_md5))
 
-with open(output_file_original_filename, 'w+') as output_file_original, \
-     open(output_file_stand_off_filename, 'w+') as output_file_stand_off:
+tags = {
+    'token': {
+        'description': '',
+        'properties': {
+            'lemma': {
+                'description': 'The base form of the word',
+                'flags': ['required'],
+                'tagset': None
+            },
+            'pos': {
+                'description': 'The detailed part-of-speech tag',
+                'flags': ['required'],
+                'tagset': {label: spacy.explain(label) for label in spacy.info(model)['labels']['tagger']}  # noqa
+            },
+            'simple_pos': {
+                'description': 'The simple UPOS part-of-speech tag',
+                'flags': ['required'],
+                'tagset': {
+                    'ADJ': 'adjective',
+                    'ADP': 'adposition',
+                    'ADV': 'adverb',
+                    'AUX': 'auxiliary verb',
+                    'CONJ': 'coordinating conjunction',
+                    'DET': 'determiner',
+                    'INTJ': 'interjection',
+                    'NOUN': 'noun',
+                    'NUM': 'numeral',
+                    'PART': 'particle',
+                    'PRON': 'pronoun',
+                    'PROPN': 'proper noun',
+                    'PUNCT': 'punctuation',
+                    'SCONJ': 'subordinating conjunction',
+                    'SYM': 'symbol',
+                    'VERB': 'verb',
+                    'X': 'other'
+                }
+            },
+            'ner': {
+                'description': 'Label indicating the type of the entity',
+                'tagset': {label: spacy.explain(label) for label in spacy.info(model)['labels']['ner']}  # noqa
+            }
+        }
+    },
+    's': {
+        'description': 'Encodes the start and end of a sentence',
+        'properties': None
+    },
+    'ent': {
+        'description': 'Encodes the start and end of a named entity',
+        'properties': {
+            'type': {
+                'description': 'Label indicating the type of the entity',
+                'flags': ['required'],
+                'tagset': {label: spacy.explain(label) for label in spacy.info(model)['labels']['ner']}  # noqa
+            }
+        }
+    }
+}
 
-    output_file_original.write(common_xml)
-    output_file_stand_off.write(common_xml)
-    text_offset = 0
-    for text_chunk in text_chunks:
+annotations = []
+
+chunk_offset = 0
+for text_chunk in text_chunks:
     doc = nlp(text_chunk)
-        for sent in doc.sents:
-            output_file_original.write('<s>\n')
-            output_file_stand_off.write('<s>\n')
-            space_flag = False
-            # Skip whitespace tokens
-            sent_no_space = [token for token in sent
-                             if not token.text.isspace()]
-            # No space variant for cwb original .vrt file input.
-            for token in sent_no_space:
-                output_file_original.write('{}'.format(escape(token.text))
-                                           + '\t{}'.format(escape(token.lemma_))
-                                           + '\t{}'.format(token.pos_)
-                                           + '\t{}'.format(token.tag_)
-                                           + '\t{}\n'.format(token.ent_type_ or 'NULL'))
-            # Stand off variant with spaces.
-            for token in sent:
-                token_start = token.idx + text_offset
-                token_end = token.idx + len(token.text) + text_offset
-                output_file_stand_off.write('{}:{}'.format(token_start,
-                                                           token_end)
-                                            + '\t{}'.format(escape(token.lemma_))
-                                            + '\t{}'.format(token.pos_)
-                                            + '\t{}'.format(token.tag_)
-                                            + '\t{}\n'.format(token.ent_type_ or 'NULL'))
-            output_file_original.write('</s>\n')
-            output_file_stand_off.write('</s>\n')
-        text_offset = token_end + 1
-    output_file_original.write('</text>\n</corpus>')
-    output_file_stand_off.write('</text>\n</corpus>')
+    for token in doc:
+        if token.is_space:
+            continue
+        if token.is_sent_start:
+            annotation = {'start': token.sent.start_char + chunk_offset,
+                          'end': token.sent.end_char + chunk_offset,
+                          'tag': 's'}
+            annotations.append(annotation)
+        # Check if the token is the start of an entity
+        if token.ent_iob == 3:
+            for ent_candidate in token.sent.ents:
+                if ent_candidate.start_char == token.idx:
+                    ent = ent_candidate
+                    break
+            annotation = {'start': ent.start_char + chunk_offset,
+                          'end': ent.end_char + chunk_offset,
+                          'tag': 'ent',
+                          'properties': {'type': token.ent_type_}}
+            annotations.append(annotation)
+        annotation = {'start': token.idx + chunk_offset,
+                      'end': token.idx + len(token.text) + chunk_offset,
+                      'tag': 'token',
+                      'properties': {'pos': token.tag_,
+                                     'lemma': token.lemma_,
+                                     'simple_pos': token.pos_}}
+        if token.ent_type_:
+            annotation['properties']['ner'] = token.ent_type_
+        annotations.append(annotation)
+    chunk_offset = len(text_chunk)
+
+with open(args.output, 'w') as output_file:
+    json.dump({'meta': meta, 'tags': tags, 'annotations': annotations},
+              output_file, indent=4)

vrt-creator

@@ -0,0 +1,107 @@
+#!/usr/bin/env python3.7
+# coding=utf-8
+
+from argparse import ArgumentParser
+from xml.sax.saxutils import escape
+import json
+
+# Parse the given arguments
+parser = ArgumentParser(description='Create annotations for a given txt file')
+parser.add_argument('input', metavar='Path to txt input file')
+parser.add_argument('annotations', metavar='Path to JSON annotation file')
+parser.add_argument('output', metavar='Path to vrt output file')
+args = parser.parse_args()
+
+with open(args.input) as text_file, \
+     open(args.annotations) as data_file:
+    text = text_file.read()
+    stand_off_data = json.load(data_file)
+
+
+def meta_to_string():
+    string = ''
+    string += '<generator software="{} ({})" arguments="check_encoding: {}; language: {}"/>\n'.format(  # noqa
+        stand_off_data['meta']['generator']['name'],
+        stand_off_data['meta']['generator']['version'],
+        stand_off_data['meta']['generator']['arguments']['check_encoding'],
+        stand_off_data['meta']['generator']['arguments']['language']
+    )
+    string += '<file name="{}" md5="{}"/>\n'.format(
+        stand_off_data['meta']['file']['name'],
+        stand_off_data['meta']['file']['md5']
+    )
+    return string
+
+
+def tags_to_string():
+    return ''
+
+
+def annotations_to_string(end=float('inf')):
+    string = ''
+    while stand_off_data['annotations']:
+        if stand_off_data['annotations'][0]['start'] >= end:
+            break
+        annotation = stand_off_data['annotations'].pop(0)
+        #######################################################################
+        # Check for malformed annotations                                     #
+        #######################################################################
+        if 'tag' not in annotation:
+            raise Exception('Annotation tag is missing')
+
+        if annotation['tag'] not in stand_off_data['tags']:
+            raise Exception('Unknown annotation tag: ' + annotation['tag'])
+
+        tag_model = stand_off_data['tags'][annotation['tag']]
+        if 'properties' in tag_model:
+            properties_model = tag_model['properties']
+            if properties_model is not None:
+                required_properties = filter(lambda x: 'flags' in x and 'required' in x['flags'], properties_model)  # noqa
+                if required_properties and annotation['properties'] is None:
+                    raise Exception('There are required properties but the "Properties" attribute is missing')  # noqa
+                for property in required_properties:
+                    if property not in annotation['properties']:
+                        raise Exception('Required property is missing: ' + property)  # noqa
+        #######################################################################
+        # Process tokens ~ cwb's positional attributes                        #
+        #######################################################################
+        if annotation['tag'] == 'token':
+            string += '{}\t{}\t{}\t{}\t{}\n'.format(
+                escape(text[annotation['start']:annotation['end']]),
+                escape(annotation['properties']['pos']),
+                escape(annotation['properties']['lemma']),
+                escape(annotation['properties']['simple_pos']),
+                escape(annotation['properties']['ner'] if 'ner' in annotation['properties'] else 'None')  # noqa
+            )
+        #######################################################################
+        # Process other tags ~ cwb's structural attributes                    #
+        #######################################################################
+        else:
+            properties = ''
+            if 'properties' in annotation and annotation['properties'] is not None:  # noqa
+                for property, value in annotation['properties'].items():
+                    if not value:
+                        continue
+                    if properties_model and property in properties_model:
+                        if 'flags' in properties_model and 'multiple' in properties_model['flags']:  # noqa
+                            properties += ' {}="|{}|"'.format(property, '|'.join(value))  # noqa
+                        else:
+                            properties += ' {}="{}"'.format(property, value)
+            string += '<' + annotation['tag'] + properties + '>\n'
+            string += annotations_to_string(end=min(annotation['end'], end))
+            string += '</' + annotation['tag'] + '>\n'
+    return string
+
+
+vrt = ''
+vrt += '<?xml version="1.0" encoding="UTF-8" standalone="yes"?>\n'
+vrt += '<corpus>\n'
+vrt += '<text>\n'
+vrt += meta_to_string()
+vrt += tags_to_string()
+vrt += annotations_to_string()
+vrt += '</text>\n'
+vrt += '</corpus>'
+
+with open(args.output, 'w') as vrt_file:
+    vrt_file.write(vrt)