The openMINDS umbrella

In summary, openMINDS is the overall umbrella for a set of distributed GitHub repositories, each defining a particular metadata model for neuroscience research products.

The main (or central) openMINDS GitHub repository ingests all these GitHub repositories as git-submodules. Furthermore it stores the openMINDS vocabulary (vocab), providing general definitions and references for types and properties used in schemas across all openMINDS repositories (cf. below). And last but not least, it holds the schema representations for all supported metadata formats created by the openMINDS integration pipeline (cf. below).

For this to work smoothly for the existing, but also for all new openMINDS metadata models, the corresponding openMINDS submodules (GitHub repositories) have to meet the following requirements:

(1) The openMINDS metadata model has to be located on a public GitHub repository and published under an MIT license.

(2) The GitHub repository should have at least one version branch (e.g., "v1").

(3) The version branch should have the following main directory folders: schemas (required), tests (recommended),  examples (recommended), and img (optional).

(4) The schemas folder should contain the schemas of that metadata model implemented in the openMINDS schema template syntax (cf. below). The directory of the schemas can be further structured or flat.

(5) The tests folder should contain test-instances (JSON-LDs) for the schemas in a flat directory. The file names for these test-instances should follow the convention of

<<XXX>>-<<YYY>>.jsonld

for files that should pass the tests, and

<<XXX>>-<<YYY>>-nok.jsonld

for files that should fail the test. In both cases, <<XXX>> should be replaced with the label of the schema that is tested, and <<YYY>> with a user defined label for what aspect is tested (e.g., person-withoutCI.jsonld).

(6) The examples folder should contain examples for valid instance collections for that metadata model. Each example should receive its own directory (folder) with a README.md describing the example, and an metadataCollection subfolder containing the openMINDS instances (JSON-LDs). This subfolder can be further structured or flat.

(7) The img folder should contain image files used on that GitHub repository (e.g., the logo of the new openMINDS metadata model). The directory of the images can be further structured or flat.

The openMINDS vocabulary

Located under the folder vocab in the main openMINDS GitHub directory, the openMINDS vocabulary is semi-automatically gathered and stored in dedicated JSON files (types.json and properties.json). The openMINDS integration pipeline makes sure that both files are updated with each commit to any of the GitHub repositories for the openMINDS metadata models. With that, the openMINDS vocab reflects always an up-to-date status of the general attributes of existing schemas and properties across all openMINDS metadata models, while providing the opportunity to centrally review and maintain their consistency. In addition, this design allows us to centrally define and maintain multiple references to related schemas and matching schema properties of other metadata initiatives. How this works in detail is explained in the following.

The types.json file is an associative array listing all existing openMINDS schemas (via their type). For each openMINDS schema, a small list of general attributes are provided in a nested associative array. Currently, the following attributes are captured:

With each new schema committed to one of the openMINDS metadata models, a new entry is appended to the types.json file, with the display label automatically derived from the respective schema type and the remaining attributes predefined with a null value. Once an entry for a schema is made in the types.json file, the values of all attributes ("name", "description", and "translatableTo") can be manually edited. All manual editions will be preserved and not overwritten when the file is updated again with a new commit. In case a schema is deleted from the openMINDS metadata models, the corresponding entry in the types.json file is marked as being deprecated (additional attribute-value pair; "deprecated": true). It only can be permanently removed from the types.json file, if the entry is manually deleted.

Similar to the types.json file, the properties.json file is an associative array listing all properties across all existing openMINDS schemas (via the property name). For each openMINDS property, a small list of general attributes are provided in a nested associative array. Currently, the following attributes are captured:

With each new property committed to a schema of one of the openMINDS metadata models, a new entry is appended to the properties.json file, with the display label and list of schemas in which this property occurs automatically derived. The remaining attributes are initially provided with a null value. Once an entry for a property is made in the properties.json file, the values of all attributes ("name", "description", "nameForReversedLink", and "sameAs") can be manually edited, except for "schemas" which will be always automatically updated. All those manual editions will be preserved and not overwritten when the file is updated again with a new commit. In case a property is not used anymore in any of the schemas from the openMINDS metadata models, the corresponding entry in the properties.json file is marked as being deprecated (additional attribute-value pair; "deprecated": true). It only can be permanently removed from the properties.json file, if the entry is manually deleted.

The openMINDS schema template syntax

All openMINDS metadata models are defined using a light-weighted schema template syntax. Although this schema template syntax is inspired by JSON-Schema, it outsources most schema technicalities to be handled by the openMINDS integration pipeline, making the openMINDS schemas more human-readable, especially for untrained eyes. 

The few remaining customized technical properties which need additional interpretation or translation to a formal schema languages (e.g. JSON-Schema) have an underscore as prefix (e.g., "_type"). Within the openMINDS integration pipeline (cf. below), the schema template syntax is interpreted, extended and flexibly translated to various formal schema languages. All further specifications of the openMINDS schema template syntax are described below.

Basic openMINDS schema structure

All openMINDS schemas need to have the extension .schema.tpl.json and each schema is defined as a nested associative array (dictionary) with the following conceptual structure:

"_type" defines the schema type (or namespace) with the depicted naming convention, where the label of the respective openMINDS metadata model (e.g., "core") and the schema name (format: UpperCamelCase; e.g. "ContactInformation") have to be specified. Obviously, the schema name should be meaningful and provide some insides into what metadata content the schema covers. 

Under "properties" a nested associative array is defined, where each key defines the property name (format: lowerCamelCase; e.g. "givenName"). The corresponding value is again a nested associative array defining the expected data "type" (cf. below) and the "_instructions" for entering the correct metadata for the respective property. 

Under "required" a list of property names can be provided that are obligatory to be present in a correctly instantiated metadata instance of the respective schema. If none of the properties are required, this key-value pair does not have to be specified.

Schemas extending a context-schema

In the case that several schemas are highly related and contain a common set of properties, it is possible to define a non-type context-schema with these common properties that can be extended and modified by the group of related schemas.

All properties and constraints (e.g. required properties, expected data types) defined in the context-schema are passed on to the schemas extending this context-schema. Each of these schemas can define additional properties, or (if necessary) can overwrite the constraints of the context-schema (incl. "_instructions"). In order to state that a schema is extending a context-schema, the following additional key-value pair has to be added to the schema template above:

"_extends": "RELATIVE_PATH_TO_OPENMINDS-CONTEXT-SCHEMA"

This design not only makes it easier to identify highly related schemas, but also facilitates the maintenance of the commonly used properties. A good hands-on example, is the context-schema ResearchProduct which is extended by the following schema set: Dataset, MetaDataModel, Model, and Software.

Data type depending constraints

Depending on the expected data "type" additional constraints can be made for the metadata entry of a respective property. Currently, the openMINDS schema template syntax supports the following data types: "string", "integer", "float", "boolean", "array" and "object".

If the expected data "type" is a "string" the expected number of characters, the format or a regular expression pattern of the string can be further defined.

The openMINDS integration pipeline

(coming soon) If you'd like to learn more about the openMINDS integration pipeline, especially if you'd like to contribute to it, please get in touch with us (the openMINDS development team) via the issues on the openMINDS or openMINDS_generator GitHub or the support email: openminds@ebrains.eu