diff --git a/src/doc/converters.rst b/src/doc/converters.rst
index 28b81947587f68381d52a380cc54748e58b9c794..99c0bbffe0d312faae3f10c1f832f08eaac82144 100644
--- a/src/doc/converters.rst
+++ b/src/doc/converters.rst
@@ -43,7 +43,7 @@ JSONFileConverter
TextElementConverter
TableConverter
-=================
+==============
A generic converter (abstract) for files containing tables.
Currently, there are two specialized implementations for xlsx-files and csv-files.
@@ -80,7 +80,7 @@ Example:
XLSXTableConverter
-=================
+==================
CSVTableConverter
=================
@@ -88,3 +88,162 @@ CSVTableConverter
Custom Converters
+++++++++++++++++
+It was previously mentioned that it is possible to create custom converters.
+These custom converters can be used to integrate arbitrary data extraction and ETL capabilities
+into the caosdb-crawler and make these extensions available to any yaml specification.
+
+The basic syntax for adding a custom converter to a yaml cfood definition file is:
+
+.. code-block:: yaml
+
+ Converters:
+ <NameOfTheConverterInYamlFile>:
+ package: <python>.<module>.<name>
+ converter: <PythonClassName>
+
+The Converters-section can be either put into the first or second document of the cfood yaml file.
+It can be also part of a single-document yaml cfood file. Please refer to :doc:`the cfood documentation<cfood>` for more details.
+
+Details:
+
+- **<NameOfTheConverterInYamlFile>**: This is the name of the converter as it is going to be used in the present yaml file.
+- **<python>.<module>.<name>**: The name of the module where the converter class resides.
+- **<PythonClassName>**: Within this specified module there must be a class inheriting from base class :py:class:`caoscrawler.converters.Converter`.
+
+The following methods are abstract and need to be overwritten by your custom converter to make it work:
+
+- :py:meth:`~caoscrawler.converters.Converter.create_children`
+- :py:meth:`~caoscrawler.converters.Converter.match`
+- :py:meth:`~caoscrawler.converters.Converter.typecheck`
+
+
+Example
+=======
+
+In the following, we will explain the process of adding a custom converter to a yaml file using
+a SourceResolver that is able to attach a source element to another entity.
+
+**Note**: This example might become a standard crawler soon, as part of the scifolder specification. See https://doi.org/10.3390/data5020043 for details. In this documentation example we will, therefore, add it to a package called "scifolder".
+
+First we will create our package and module structure, which might be:
+.. code-block::
+
+ scifolder_package/
+ README.md
+ setup.cfg
+ setup.py
+ Makefile
+ tox.ini
+ src/
+ scifolder/
+ __init__.py
+ converters/
+ __init__.py
+ sources.py # <- the actual file containing
+ # the converter class
+ doc/
+ unittests/
+
+Now we need to create a class called "SourceResolver" in the file "sources.py". In this - more advanced - example, we will not inherit our converter directly from :py:class:`~caoscrawler.converters.Converter`, but use :py:class:`~caoscrawler.converters.TextElementConverter`. The latter already implements :py:meth:`~caoscrawler.converters.Converter.match` and :py:meth:`~caoscrawler.converters.Converter.typecheck`, so only an implementation for :py:meth:`~caoscrawler.converters.Converter.create_children` has to be provided by us.
+Furthermore we will customize the method :py:meth:`~caoscrawler.converters.Converter.create_records` that allows us to specify a more complex record generation procedure than provided in the standard implementation. One specific limitation of the standard implementation is, that only a fixed
+number of records can be generated by the yaml definition. So for any applications - like here - that require an arbitrary number of records to be created, a customized implementation of :py:meth:`~caoscrawler.converters.Converter.create_records` is recommended.
+In this context it is recommended to make use of the function :func:`caoscrawler.converters.create_records` that implements creation of record objects from python dictionaries of the same structure
+that would be given using a yaml definition.
+
+.. code-block:: python
+
+ import re
+ from caoscrawler.stores import GeneralStore, RecordStore
+ from caoscrawler.converters import TextElementConverter, create_records
+ from caoscrawler.structure_elements import StructureElement, TextElement
+
+
+ class SourceResolver(TextElementConverter):
+ """
+ This resolver uses a source list element (e.g. from the markdown readme file)
+ to link sources correctly.
+ """
+
+ def __init__(self, definition: dict, name: str,
+ converter_registry: dict):
+ """
+ Initialize a new directory converter.
+ """
+ super().__init__(definition, name, converter_registry)
+
+ def create_children(self, generalStore: GeneralStore,
+ element: StructureElement):
+
+ # The source resolver does not create children:
+
+ return []
+
+ def create_records(self, values: GeneralStore,
+ records: RecordStore,
+ element: StructureElement,
+ file_path_prefix):
+ if not isinstance(element, TextElement):
+ raise RuntimeError()
+
+ # This function must return a list containing tuples, each one for a modified
+ # property: (name_of_entity, name_of_property)
+ keys_modified = []
+
+ # This is the name of the entity where the source is going to be attached:
+ attach_to_scientific_activity = self.definition["scientific_activity"]
+ rec = records[attach_to_scientific_activity]
+
+ # The "source" is a path to a source project, so it should have the form:
+ # /<Category>/<project>/<scientific_activity>/
+ # obtain these information from the structure element:
+ val = element.value
+ regexp = (r'/(?P<category>(SimulationData)|(ExperimentalData)|(DataAnalysis))'
+ '/(?P<project_date>.*?)_(?P<project_identifier>.*)'
+ '/(?P<date>[0-9]{4,4}-[0-9]{2,2}-[0-9]{2,2})(_(?P<identifier>.*))?/')
+
+ res = re.match(regexp, val)
+ if res is None:
+ raise RuntimeError("Source cannot be parsed correctly.")
+
+ # Mapping of categories on the file system to corresponding record types in CaosDB:
+ cat_map = {
+ "SimulationData": "Simulation",
+ "ExperimentalData": "Experiment",
+ "DataAnalysis": "DataAnalysis"}
+ linkrt = cat_map[res.group("category")]
+
+ keys_modified.extend(create_records(values, records, {
+ "Project": {
+ "date": res.group("project_date"),
+ "identifier": res.group("project_identifier"),
+ },
+ linkrt: {
+ "date": res.group("date"),
+ "identifier": res.group("identifier"),
+ "project": "$Project"
+ },
+ attach_to_scientific_activity: {
+ "sources": "+$" + linkrt
+ }}, file_path_prefix))
+
+ # Process the records section of the yaml definition:
+ keys_modified.extend(
+ super().create_records(values, records, element, file_path_prefix))
+
+ # The create_records function must return the modified keys to make it compatible
+ # to the crawler functions:
+ return keys_modified
+
+
+If the recommended (python) package structure is used, the package containing the converter
+definition can just be installed using `pip install .` or `pip install -e .` from the
+`scifolder_package` directory.
+
+The following yaml block will register the converter in a yaml file:
+
+.. code-block:: yaml
+
+ Converters:
+ SourceResolver:
+ package: scifolder.converters.sources
+ converter: SourceResolver
diff --git a/src/doc/macros.rst b/src/doc/macros.rst
index d8e819464b6af55cf6ea4e133b9b4110406f98dc..3d995c1fbc67b155a6df606ac2f84a0cec26d1a5 100644
--- a/src/doc/macros.rst
+++ b/src/doc/macros.rst
@@ -1,7 +1,7 @@
Macros
------
-Macros highly facilitate the writing of complex :doc:`CFoods<cfoods>`. Consider the following prevalent example:
+Macros highly facilitate the writing of complex :doc:`CFoods<cfood>`. Consider the following prevalent example:
.. _example_files:
.. code-block:: yaml