ERC specification

An Executable Research Compendium (ERC) is a packaging convention for computational research. It provides a well-defined structure for data, code, text, documentation, and user interface controls for a piece of research and is suitable for long-term archival. As such it can also be perceived as a digital object or asset.


This is a draft specification. If you have comments or suggestions please file them in the issue tracker. If you have explicit changes please fork the git repo and submit a pull request.



Specification version: 1


This version is under development!

Notational conventions

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” are to be interpreted as described in RFC 2119.

The key words “unspecified”, “undefined”, and “implementation-defined” are to be interpreted as described in the rationale for the C99 standard.

Purpose, target audience, and context

This specification defines a structure to transport and execute a computational scientific analyses (cf. computational science). It carries technical and conceptual details on how to implement the reproducibility specifications and is as such most suitable for developers. Authors may feel more comfortable with the user guides.

These analyses typically comprise a workspace on a researcher’s computer, that contains data, code, third party software or libraries, and outputs research results such as plots. Code and libraries are required in executable form to re-do a specific analysis. Research is only put into a context by a textual publication, a research paper, which is published in scholarly communication. The text comes in two forms: one that is machine readable, and another one that is suitable for being read by humans. The latter is often derived, or “rendered” from the former and can be static, visual, or even interactive following a trend towards more interactivity between reader and scientific publication.

Putting all of these elements in a self-contained bundle allows examining, reproducing, transferring, archiving, and formal validation of computational research results. The ERC specification also defines metadata and file structures to support these actions.

Major constituents and design goals

Three major constituents classify user interaction with ERC:

  • Create means transforming a workspace with data, code and text into an ERC.
  • Examine means looking at depths of an ERC, scrutinizing its contents.
  • Discover means searching for content powered by ERC properties, such as text, content metadata, code metadata et cetera.

A core design goal is simplicity. This specification should not re-do something which already exists (if it is an open specification or tool). It must be possible to create a valid and working ERC manually, while supporting tools should be able to cover typical use cases with minimal required input by a creating user.

The final important notion is the one of nested containers. We acknowledge well defined standards for packaging a set of files, and different approaches to create an executable code package. Therefore an ERC comprises one or more containers but is itself subject to being put into a container. We distinguish these containers into the inner or “runtime” container and the outer container, which is used for transfer of complete ERC and not content-aware validation.

How to use an ERC

The steps to (re-)run the analysis contained in an ERC as part of an examination are as follows:

  • (if compressed first extract then) unpack the ERC’s outer container
  • execute the runtime container
  • compare the output files contained in the outer container with the output files just created by the runtime container

This way an ERC allows computational reproducibility based on the original code and data.

ERC structure

Base directory

An ERC MUST has a base directory. All paths within this document are relative to this base directory.

The base directory MUST contain an ERC configuration file.

Besides the files mentioned in this specification, the base directory MAY contain any other files and directories.

Main & display file

An ERC MUST have a main file, i.e. the file which contains the text and instructions being the basis for the scientific publication describing the packaged analysis. An ERC MUST have a _display file, i.e. the file which is shown to the user first when he opens an ERC in a supporting platform or tool.

Main file and display file MUST NOT be the same file.

The main file MUST be executable in the sense that a software reads it as the input of a process to create the display file. The main file‘s name SHOULD be main with an appropriate file extension and media type.


The main file thus follows the literate programming paradigm.


If the main file is an R Markdown document, then the file extension should be .Rmd and the media type text/markdown. A file main.Rmd will consequently be automatically identified by an implementation as the ERC’s main file.

The display file’s name SHOULD be display with an appropriate file extension and media type.


If the display file is an Hypertext Markup Language (HTML) document, then the file extension should be .htm or .html and the media type text/html. A file display.html will consequently be automatically identified by an implementation as the ERC’s display file.

The ERC MAY use an interactive document with interactive figures and control elements for the packaged computations as the display file. The interactive display file MUST have HTML format and SHOULD be valid HTML5.


Typical examples for the two core documents are R Markdown with HTML output (i.e. main.Rmd and display.html), or an R script creating a PNG file (i.e. main.R and display.png).

Nested runtime

The embedding of a representation of the original runtime environment, in which an analysis was conducted, is crucial for supporting reproducible computations. Every ERC MUST include two such such representations:

  1. an executable runtime image of the original analysis environment for re-running the packaged analysis, and
  2. a runtime manifest documenting the image’s contents as a complete, self-consistent recipe of the runtime image’s contents which is a machine-readable format that allows a respective tool to create the runtime image.

The image MUST be stored as a file, e.g. a “binary”, in the ERC base directory. The name of the archive file MUST be configured in the ERC configuration file in the node image under the root-level node execution.

The manifest MUST be stored as a text file in the ERC base directory. The name of the manifest file MUST be configured in the ERC configuration file in the node manifest under the root-level node execution.

ERC configuration file

The ERC configuration file is the reproducibility manifest for an ERC. It defines the main entry points for actions performed on an ERC and core metadata elements.

Name, format, and encoding

The filename MUST be erc.yml and it MUST be located in the base directory. The contents MUST be valid YAML 1.2. The file MUST be encoded in UTF-8 and MUST NOT contain a byte-order mark (BOM).

Basic fields

The first document content of this file MUST contain the following string nodes at the root level.

  • spec_version: a text string noting the version of the used ERC specification. The appropriate version for an ERC conforming to this version of the specification is 1.
  • id: globally unique identifier for a specific ERC. This SHOULD be a URI (see rfc3986) or a UUID, Version 4.

The main and display file MAY be defined in root-level nodes named main and display respectively, if they differ from the default file names. If they are not defined and multiple documents use the name main.[ext] or display.[ext], an implementation SHOULD use the first file in alphabetical order.

Example of ERC configuration file with user-defined main and display files

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1
main: the_paper_document.rmd
display: paper.html

Additionally, related resources such as a related publication can be stated with the relatedIdentifier element field. A related identifier SHOULD be a globally unique persistent identifier and SHOULD be a URI.

Control statements

The configuration file MUST contain statements to control the runtime container.

These statements MUST be in an array under the root-level node execution in the ERC configuration file in the order in which they must be executed.

Implementations SHOULD support a list of bash commands as control statements. These commands are given as a list under the node cmd under the root-level node execution. If extensions use non-bash commands, they MUST define own nodes under the execution node and SHOULD define defaults.

The execution statements MAY ensure the re-computation being independent from the environment, which may be different depending on the host of the execution environment. For example, the time zone could be fixed via an environment variable TZ=CET, so output formatting of timestamps does not break checking. This is in addition to ERC authors handling such parameters at a script level.

Example for control statements

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1
    - `./ --input my_data`
    - `./ --output results --iterations 3`

License metadata

The file erc.yml MUST contain a first level node licenses with licensing information for the code, data, and text contained. Each of these three have distinct requirements, hence different licenses need to be applied.

The node licenses MUST have five child nodes: text, data, code, ui_bindings, and metadata.


There is currently no mechanism to define the licenses of the used libraries, as manual creation would be tedious. Tools for automatic creation of ERC may add such detailed licensing information and define an extension to the ERC

The content of each of these child nodes MUST have one of the following values:

  • text string with license identifier or license text. This SHOULD be a standardized identifier of an existing license as defined by the Open Definition Licenses Service, or
  • a dictionary of all files or directories and their respective license, each of the values following the previous statement. The node values are the file paths relative to the base directory.

Example for global licenses

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1
  code: Apache-2.0
  data: ODbL-1.0
  text: CC0-1.0
      ui_bindings: CC0-1.0
      metadata: CC0-1.0

Example using specific licenses for files

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1
    others_lib.bin: MIT
    my_code.c: GPL-3.0
    facts.csv: ODbL-1.0
  text: CC0-1.0
        paper.Rmd: CC-BY-4.0
      ui_bindings: CC0-1.0
      metadata: CC0-1.0


It IS NOT possible to assign one license to a directory and override that assignment or a single file within that directory, NOR IS it possible to use globs or regular expressions.

Comprehensive example of erc.yml

The following example shows all possible fields of the ERC specification with example values.

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1
main: paper.rmd
display: paper.html
  cmd: "Rscript -e 'rmarkdown::render(input = \"paper.Rmd\", output_format = \"html\")'"
    others_lib.bin: MIT
    my_code.c: GPL-3.0
    facts.csv: ODbL-1.0
  text: CC0-1.0
    paper.Rmd: CC-BY-4.0
  ui_bindings: CC0-1.0
  metadata: CC0-1.0
  interactive: true
    - purpose: http://.../data-inspection
      widget: http://.../tabular-browser
      code: [...]
      data: [...]
      text: [...]
    - purpose: http://.../parameter-manipulation
      widget: http://.../dropdown

The path to the ERC configuration file subsequently MUST be <path-to-bag>/data/erc.yml.

Docker runtime

The ERC uses Docker to define, build, and store the nested runtime environment, i.e. the inner container.

Runtime image

The runtime environment or image MUST be represented by a Docker image v1.2.0.


A concrete implementation of ERC may choose to rely on constructing the runtime environment from the manifest when needed, e.g. for export to a repository, while the ERC is constructed.

The base directory MUST contain a tarball, i.e. an archive file, of a Docker image as created be the command docker save, see Docker CLI save command documentation, as defined in version 1.12.x.

The image MUST have a label of the name erc with the ERC’s id as value, e.g. erc=b9b0099e-9f8d-4a33-8acf-cb0c062efaec.

The image file MAY be compressed.

The tar archive file names SHOULD be image.tar, or image.tar.gz if a gzip compression is used for the archive with an appropriate file extension, such as .tar, tar.gz or .bin, and have an appropriate mime type, e.g. application/vnd.oci.image.layer.tar+gzip.


Before exporting the Docker image, first build it from the Dockerfile, including the label which can be used to extract the image identifier, for example:

docker build --label erc=b9b0099e-9f8d-4a33-8acf-cb0c062efaec .
docker images --filter "label=erc=b9b0099e-9f8d-4a33-8acf-cb0c062efaec"
docker save $(docker images --filter "label=erc=1234" -q) > image.tar
# save with compression:
docker save $(docker images --filter "label=erc=1234" -q) | gzip -c >     image.tar.gz

Do not use docker export, because it is used to create a snapshot of a container, which must not match the Dockerfile anymore as it may have been manipulated during a run.

The output of the image execution can be shown to the user to convey detailed information on progress or errors.

Runtime manifest

The runtime manifest MUST be represented by a valid Dockerfile, see Docker builder reference, as defined in version 1.12.x.

The file MUST be named Dockerfile.

The Dockerfile MUST contain the build instructions for the runtime environment and MUST have been used to create the image saved to the runtime image using docker build, see Docker CLI build command documentation, as defined in version 1.12.x. The build SHOULD be done with the option --no-cache=true.

The Dockerfile MUST NOT use the latest tag in the instruction FROM.


The “latest” tag is merely a convention to denote the latest available image, so any tag can have undesired results. Nevertheless, using an image tagged “latest” makes it much more likely to change over time. Although there is no guarantee that images tagged differently, e.g. “v1.2.3” might not change as well, using such tags shall be enforced here.

The Dockerfile SHOULD contain the label maintainer to provide authorship information.

The Dockerfile MUST have an active instruction CMD, or a combination of the instructions ENTRYPOINT and CMD, which executes the packaged analysis.

The Dockerfile SHOULD NOT contain EXPOSE instructions.

Docker control statements

The control statements for Docker executions comprise load, for importing an image from the archive, and run for starting a container of the loaded image. Both control statements MUST be configured by using nodes of the same name under the root-level node execution in the ERC configuration file. Based on the configuration, an implementation can construct the respective run-time commands, i.e. docker load and docker run, using the correct image file name and further parameters (e.g. performance control options).


The following example shows default values for image and manifest and typical values for run.

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
version: 1
  image: image.tar.gz
  manifest: Dockerfile
      - TZ=CET


The Docker CLI commands constructed based on this configuration by an implementing service could be as follows:

docker load --input image.tar
IMAGE_ID=$(docker images --filter "label=erc=b9b0099e-9f8d-4a33-8acf-cb0c062efaec" -q)
docker run -it --name run_abc123 -e TZ=CET -v /storage/erc/abc123:/erc --label user:o2r $IMAGE_ID

In this case the implementation uses -it to pass stdout streams to the user and adds some metadata using --name and --label`.

The only option for load is quiet, which may be set to Boolean true or false.

The only option for run is environment to set environment variables inside containers as defined in docker-compose. Environment variables are defined as a list separated by =.

Example for load and run properties

    quiet: true
      - DEBUG=1
      - TZ=CET

The environment variables SHOULD be used to fix settings out of control of the contained code that can hinder successful ERC checking, e.g. by setting a time zone to avoid issues during checking.

The output of the container during execution MAY be shown to the user to convey detailed information to users.

Making data, code, and text available within container

The runtime environment image contains all dependencies and libraries needed by the code in an ERC. Especially for large datasets, it in unfeasible to replicate the complete dataset contained within the ERC in the image. For archival, it can also be confusing to replicate code and text, albeit them being relatively small in size, within the container.

Therefore a host directory is mounted into a container at runtime using a data volume.

The Dockerfile SHOULD NOT contain a COPY or ADD command to include data, code or text from the ERC into the image.

The Dockerfile MUST contain a VOLUME instruction to define the mount point of the ERC base directory within the container. This mountpoint SHOULD be /erc. Implementations MUST use this value as the default. If the mountpoint is different from /erc, the value MUST be defined in erc.yml in a node execution.mount_point.

Example for mountpoint configuration

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1
  mount_point: "/erc"

Example Dockerfile

In this example we use a Rocker base image to reproduce computations made in R.

FROM rocker/r-ver:3.3.3

RUN apt-get update -qq \
    && apt-get install -y --no-install-recommends \
    ## Packages required by R extension packages
    # required by rmarkdown:
    lmodern \
    pandoc \
    # for devtools (requires git2r, httr):
    libcurl4-openssl-dev \
    libssl-dev \
    git \
    # for udunits:
    libudunits2-0 \
    libudunits2-dev \
    # required when knitting the document
    pandoc-citeproc \
    && apt-get clean \
    && rm -rf /var/lib/apt/lists/*

# install R extension packages
RUN install2.r -r "" \
      rmarkdown \
      ggplot2 \
      devtools \
      && rm -rf /tmp/downloaded_packages/ /tmp/*.rd

# Save installed packages to file
RUN dpkg -l > /dpkg-list.txt

LABEL maintainer=o2r \
  description="This is an ERC image." \"123456"

VOLUME ["/erc"]

ENTRYPOINT ["sh", "-c"]
CMD ["R --vanilla -e \"rmarkdown::render(input = '/erc/myPaper.rmd', output_dir = '/erc', output_format = rmarkdown::html_document())\""]

See also: Best practices for writing Dockerfiles.

R workspaces


The structure within the ERC contents directory are intentionally unspecified. However, the contents structure MAY follow conventions or be based on templates for organizing research artifacts.

If a convention is followed then it SHOULD be referenced in the ERC configuration file as a node convention within the structure section. The node’s value can be any text string which uniquely identifies a convention, but a URI or URL to either a human-readable description or formal specification is RECOMMENDED.

A non-exhaustive list of potential conventions and guidelines for R is as follows:

Example for using the ROPenSci rrrpkg convention

The convention is identified using the public link on GitHub.

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1

R Markdown main file

The ERC’s main file for R-based analyses SHOULD be R Markdown.

The main document SHOULD NOT contain code that loads pre-computed results from files, but conduct all analyses, even costly ones, during document weaving.

The document MUST NOT use cache=TRUE on any of the code chunks (see knitr options. While the previously cached files (.rdb and .rdx) MAY be included, they SHOULD NOT be used during the rendering of the document.


A popular alternative solution is Sweave with the .Rnw extension, which is still widely used for vignettes. R Markdown was chosen of LaTex for its simplicity for users who are unfamiliar with LaTeX.

Fixing the environment in code

The time zone MUST be fixed to UTC Coordinated Universal Time) to allow validation of output times (potentially broken by different output formats) by using the following code within the RMarkdown document, or other code to that effect.

Sys.setenv("TZ" = "UTC")

The manifest file (i.e. Dockerfile) MUST run a plain R session without loading .RData files or profiles at startup, i.e. use R --vanilla.

Interactive ERC

Enabling interaction with the contents of an ERC is a crucial goal of this specification (see Preface). Therefore this section defines metadata to support two goals:

  • aide inspecting users to identify core functions and parameters of an analysis, and
  • allow supporting software tools to create interactive renderings of ERC contents for manipulation.

These goals are manifested in the UI bindings as part of the ERC configuration file under the root level property ui_bindings.

An ERC MUST denote if UI bindings are present using the boolean property interactive. If the property is missing it defaults to false. An implementation MAY use the indicator interactive: true to provide other means of displaying the display file.

Example for minimal interaction configuration

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1
  interactive: true

An ERC MAY embed multiple concrete UI bindings. Each UI binding is represented by a YAML dictionary.

It MUST comprise a purpose and a widget using the fields purpose respectively widget (both of type string). The values of these fields SHOULD use a concept of an ontology to clearly identify their meaning.

A purpose defines the user’s intention, for example manipulating a variable or inspecting dataset or code. A widget realizes the purpose with a concrete interaction paradigm chosen by the author, for example an input slider, a form field, or a button.

For each widget, implementations MAY use the properties code, data, and text to further describe how a specific UI binding acts upon the respective part of the ERC.

Example of two UI bindings

id: b9b0099e-9f8d-4a33-8acf-cb0c062efaec
spec_version: 1
  interactive: true
    - purpose: http://.../data-inspection
      widget: http://.../tabular-browser
      code: [...]
      data: [...]
      text: [...]
    - purpose: http://.../parameter-manipulation
      widget: http://.../dropdown

Preservation of ERC

This section places the ERC in the context of preservation workflows by defining structural information and other metadata that guarantee interpretability and enable the bundling of the complete ERC as a self-contained, archivable digital object.

Archival bundle

For the purpose of transferring and storing a complete ERC, it MUST be packaged using the BagIt File Packaging Format (V0.97) (BagIt) as the outer container. BagIt allows to store and transfer arbitrary content along with minimal metadata as well as checksum based payload validation.

The remainder of this section comprises

  • a description of the outer container,
  • a BagIt profile,
  • a package leaflet, and
  • secondary metadata files.

BagIt outer container

The ERC base directory MUST be the BagIt payload directory data/. The path to the ERC configuration file subsequently MUST be <path-to-bag>/data/erc.yml.

The bag metadata file bagit.txt MUST contain the case-sensitive label Is-Executable-Research-Compendium with the case-insensitive value true to mark the bag as the outer container of an ERC.

Implementations SHOULD use this field to identify an ERC.

Example bagit.txt

Payload-Oxum: 2172457623.43
Bagging-Date: 2016-02-01
Bag-Size: 2 GB
Is-Executable-Research-Compendium: true

Example file tree for a bagged ERC

├── bag-info.txt
├── bagit.txt
├── data
│   ├── 2016-07-17-sf2.Rmd
│   ├── erc.yml
│   ├── metadata.json
│   ├── Dockerfile
│   └── image.tar
├── manifest-md5.txt
└── tagmanifest-md5.txt

BagIt profile


The elements of the o2r Bagit Profile is yet to be specified. This section is under development. Current BagIt tools do not include an option to add a BagIt Profile automatically.

A BagIt Profile as outlined below could make the requirements of this extension more explicit. The BagIt Profiles Specification Draft allows users of BagIt bags to coordinate additional information, attached to bags.

  "Contact-Name":"o2r Team",
  "External-Description":"BagIt profile for packaging executable research compendia.",

Package leaflet

Each ERC MUST contain a package leaflet, describing the schemas and standards used. Available schema files are supposed to be included with the ERC, if available (licenses for these schemas may apply).

Example package leaflet

    "standards_used": [{
        "name": "DataCite Metadata Schema 4.0",
        "name-short": "datacite40",
        "description": "The DataCite Metadata Schema is a list of core metadata properties chosen for an accurate and consistent identification of a resource for citation and retrieval purposes, along with recommended use instructions.",
        "schema-version": "4.0",
        "schema-path-local": "erc/schema/datacite40.json ",
        "schema-url": "",
        "schema-identifier": "doi:10.5438/0013"
    }, {
        "name": "Zenodo Metadata Schema",
        "name-short": "zenodo",
        "description": "The metadata schema applicable for zenodo 2017.",
        "schema-version": null,
        "schema-path-local": "erc/schema/zenodo.json ",
        "schema-url": null,
        "schema-identifier": null

Elements used for each schema / standard used:

  • name: The name of the schema.
  • name-short: The abbreviated name.
  • description: The description of the schema.
  • schema-version: The version of the schema as stated in the corresponding official schema file.
  • schema-path-local: The path to the local version of the schema. It may point to a translated version of the original schema, e.g. json file from xml file.
  • schema-url: The official URL of the schema file
  • schema-identifier: The persistent identifier for the schema/standard.

Secondary metadata files

The ERC as an object can be used in a broad range of cases. For example, it can be an item under review during a journal publication, it can be the actual publication at a workshop or conference or it can be a preserved item in a digital archive. All of these have their own standards and requirements to apply, when it comes to metadata.

These metadata requirements are not part of this specification, but the following conventions are made to simplify and coordinate the variety.

Metadata specific to a particular domain or use case MUST replicate the information required for the specific case in an independent file. Domain metadata SHOULD follow domain conventions and standards regarding format and encoding of metadata. Duplicate information is accepted, because it lowers the entry barrier for domain experts and systems, who can simply pick up a metadata copy in a format known to them.

Metadata documents of specific use cases MUST be stored in a directory .erc, which is a child-directory of the ERC base directory.

Metadata documents SHOULD be named according to the used standard or platform, and the used format respectively encoding, e.g. datacite40.xml or zenodo_sandbox10.json, and SHOULD use a suitable mime type.

Requirements of secondary metadata

In order to comply to their governing schemas, secondary metadata must include the mandatory information as set by 3rd party services. While the documentation of this quality is a perpetual task, we have gathered the information most relevant our selection of connected services.


  • Accepts metadata as JSON.
  • Mandatory elements:
    • Upload Type (e.g. Publication)
    • Publication Type
    • Title
    • Creators
    • Description
    • Publication Date
    • Access Right
    • License

DataCite (4.0)

  • Accepts metadata as XML.
  • Mandatory elements:
    • Identifier
    • Creator
    • Title
    • Publisher
    • Publication Year
    • Resource Type

Other third party standards that will be considered comprise: CodeMeta, EuDat, mets/mods.

Development bundle

While complete ERCs are focus of this specification, for collaboration and offline inspection it is useful to provide access to parts of the ERC. To support such use cases, a development bundle MAY be provided by implementations. This bundle most importantly would not include the runtime image, which is potentially a large file.

The development bundle SHOULD always include the main file and (e.g. by choice of the user, or by an implementing platform) MAY include other relevant files for reproduction or editing purposes outside of the runtime environment, such as input data or the runtime manifest for manual environment recreation.

Content metadata under development

Current JSON dummy to visualise the properties. It SHOULD be filled out as good as possible.

    "access_right": "open",
    "author": [{
        "name": null,
        "affiliation": [],
        "orcid": null
    "codefiles": [],
    "community": "o2r",
    "depends": [{
        "identifier": null,
        "version": null,
        "packageSystem": null
    "description": null,
    "ercIdentifier": null,
    "file": {
        "filename": null,
        "filepath": null,
        "mimetype": null
    "generatedBy": null,
    "identifier": {
        "doi": null,
        "doiurl": null,
        "reserveddoi": null
  "inputfiles": [],
    "keywords": [],
    "license": {"text": None,
            "data": None,
            "code": None,
            "uibindings": None,
            "md": None
    "paperLanguage": [],
    "paperSource": null,
    "publicationDate": null,
    "recordDateCreated": null,
    "softwarePaperCitation": null,
    "spatial": {
        "files": [],
        "union": []
    "temporal": {
        "begin": null,
        "end": null
    "title": null,
    "upload_type": "publication",
    "viewfiles": []

The path to the o2r metadata file MUST be <path-to-bag>/data/metadata.json.

Description of metadata properties

Defining explanations on the concept of each metadata element in use.

  • access_right Modify embargo status, default is open.
  • author Contains a list of authors, each containing author related information.
  • author.affiliation A list of institutions, organizations or other groups that the creator of the asset is associated with.
  • The name of the human individual, institution, organization, machine or other entity that acts as creator of the asset.
  • author.orcid The ORCid of the creator of the asset.
  • codefiles A list of files, containing programm code (i.e. script files, e.g. .R files) retrieved during the extraction.
  • community Indicates belonging to a scientific community, e.g. on a repositoy platform.
  • depends A block for each entity that the software is directly dependent on for execution. The dependency information is designed for the identification of dependent packages within packaging systems. A depends block may describe a transitive dependency.
  • depends.identifier An identifying name for the depending package.
  • depends.version The computer software and hardware required to run the software.
  • depends.packageSystem The package manager system that makes the dependency entity available.
  • description A text representation conveying the purpose and scope of the asset (the abstract).
  • ercIdentifier A universally unique character string associated with the asset as executable research compendium, provided by the o2r service.
  • file A block for the main source file for the metadata (e.g. rmd file), generated and used by the o2r service.
  • file.filename See above
  • file.filepath See above
  • file.mimetype See above
  • generatedBy The entity, person or tool, that created the software.
  • identifier Contains information related to persitent identifiers for the asset.
  • identifier.doi The DOI for the asset.
  • identifier.doiurl The resolving URL for the asset.
  • identifier.reserveddoi The assigned but inactive DOI for the asset. Might be minted by a repository during publication.
  • inputfiles A list of files that are loaded as resources by the main or code files of a workspace.
  • interaction Information on interactive elements in the asset.
  • interaction.interactive ‘TRUE’ if interactive elements are already included, otherwise ‘FALSE’.
  • interaction.ui_binding A block for each UI binding - extends a figure by a UI widget, e.g. for manipulation. Final structure depends on purpose.
  • interaction.ui_binding.purpose What the UI binding is supposed to do.
  • interaction.ui_binding.widget Which UI widget realizes the purpose.
  • interaction.ui_binding.code A block containing source-code-specific information required to realize the UI binding.
  • interaction.ui_binding.code.filename Name of the file including the plot function that creates the figure.
  • interaction.ui_binding.code.function Name of the function that plots the figure.
  • interaction.ui_binding.code.functionParameter Parameters required by the shinyInputFunction. Final set of parameters depends on UI widget.
  • interaction.ui_binding.variable Variable that should be controlled by the UI widget.
  • interaction.ui_binding.code.shinyInputFunction Function that incorporates the UI widgets, provided by Shiny.
  • interaction.ui_binding.code.shinyRenderFunction Function that renders the plot after each change, provided by Shiny.
  • keywords Tags associated with the asset.
  • license License information for each part of the ERC.
  • license.code License for the code part of the ERC
  • license.text License for the text part of the ERC
  • License for the data part of the ERC
  • license.uibindings License for the user interface bindings of the ERC
  • License for the metadata of the ERC
  • paperLanguage A list of language codes that indicate the language of the asset, e.g. en.
  • paperSource The text document file of the paper.
  • publicationDate The publication date of the paper publication as ISO8601 string.
  • publication_type The type of the publication. Default is other since the ERC may contain text, data, code and interaction widgets not depictable by other categories.
  • recordDateCreated The date that this metadata record was created as ISO8601 string.
  • softwarePaperCitation Related citation information for the asset, e.g. a citation of the related journal article.
  • spatial Information about the geometric bounding box of the underlying data/software.
  • spatial.files A Geojson object of the file-wise bounding boxes of the underlying data/software.
  • spatial.union A Geojson object displaying the spatial properties, e.g. a bounding box of the whole data.
  • temporal Aggregated information about the relevant time period of the underlying data sets.
  • temporal.begin The starting point of the relevant time period.
  • temporal.end The end point of the relevant time period.
  • title The distinguishing name of the paper publication.
  • upload_type The zenodo upload type, default is publication. This element will be removed, once the target repository is completely configurabe within the o2r shipper micro service.
  • view_file The main display file.

ERC checking


A core feature ERCs are intended to support is comparing the output of an ERC executions with the original outputs. Therefore checking an ERC always comprises two steps: the execution and the comparison.

The files included in the comparison are the comparison set. An implementation MUST communicate the comparison set to the user as part of a check.

Previous to the check, an implementation SHOULD conduct a basic validation of the outer container’s integrity, i.e. check the file hashes.

Comparison set file

The ERC MAY contain a file named .ercignore in the base directory to define the comparison set.

Its purpose is to provide a way to efficiently exclude files and directories from checking. If this file is present, any files and directories within the outer container which match the patterns within the file .ercignore will be excluded from the checking process. The check MUST NOT fail when files listed in .ercignore are failing comparison.

The file MUST be UTF-8 (without BOM) encoded. The newline-separated patterns in the file MUST be Unix shell globs. For the purposes of matching, the root of the context is the ERC’s base directory.

Lines starting with # are treated as comments and MUST be ignored by implementations.

Example .ercignore file

# comment


If using md5 file hashes for comparison, the set could include plain text files, for example the text/* media types (see IANA’s full list of media types. Of course the comparison set should include files which contain results of an analysis.

Comparing plain text documents

Comparing graphics and binary output

This section outlines possibilities beyond simple comparison and incorporates “harder” to compare files and what to do with them, e.g. plots/figures, PDFs, …

Security considerations

Why are ERC not a security risk?

  • the spec prohibits use of EXPOSE
  • the containers are only executed without external network access using Network: none, see Docker CLI run documentation