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  === The openMINDS umbrella ===
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--openMINDS is the overall umbrella for a set of integrated metadata models for describing neuroscience research products in graph databases. The correct integration of these metadata models as well as the provision of a central access point is handled by an integration pipeline. All metadata models are developed on separate GitHub repositories, in order to facilitate extensions and maintenance of existing, as well as development and integration of new openMINDS metadata models and schemas. The integration pipeline ensures that the central openMINDS GitHub repository ingests all these GitHub repositories as [[git-submodules>>https://git-scm.com/docs/git-submodule||rel="noopener noreferrer" target="_blank"]], integrates the respective metadata models and builds the openMINDS GitHub pages, as well as ZIP files containing the respective openMINDS schemas in the supported formats, such as the openMINDS syntax (cf. below), JSON-Schema, or HTML. In the following we will summarize the contents and requirements for the central openMINDS GitHub repository as well as all metadata model git-submodules. The openMINDS integration pipeline will be handled in a separate chapter (cf. below).
++In summary, openMINDS is the overall umbrella for a set of distributed GitHub repositories, each defining a particular metadata model for neuroscience research products.
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--Let us start with the [[central openMINDS GitHub repository>>https://github.com/HumanBrainProject/openMINDS||rel="noopener noreferrer" target="_blank"]] which has a **main branch**, a **documentation branch**, and **version branches** (naming convention: vX; e.g., v1). Official releases (naming convention: vX.Y; e.g., v1.0) are tagged and provided as release packages.
++The main (or central) [[openMINDS GitHub repository>>https://github.com/HumanBrainProject/openMINDS||rel="noopener noreferrer" target="_blank"]] ingests all these GitHub repositories as [[git-submodules>>https://git-scm.com/docs/git-submodule||rel="noopener noreferrer" target="_blank"]]. 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).
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--The **main branch** hosts the general README, the LICENSE document, the CONTRIBUTING document, and the general openMINDS logo. In addition, it maintains the openMINDS vocabulary (vocab; cf. below) which provides general definitions and references for schema types and properties used across all openMINDS metadata models and their versions, as well as the bash script that builds the content of the documentation and version branches.
++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:
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--The **documentation** branch hosts the HTML files that build the [[openMINDS GitHub pages>>https://humanbrainproject.github.io/openMINDS/||rel="noopener noreferrer" target="_blank"]], as well as a ZIP file for each version branch and official release containing the respective openMINDS schemas in the currently supported formats, such as the openMINDS syntax (`.schema.tpl.json`; cf. below), JSON-Schema (`.schema.json`), or HTML (`.html`).
++**(1)** The openMINDS metadata model has to be located on a **public GitHub repository** and published under an **MIT license**.
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--The **version** branches host the respective openMINDS schemas of a major version by ingesting the corresponding metadata models as git-submodules. Note that these version branches can have official release tags. If a version branch has an official release tag, only backwards compatible changes can be merged on this branch. This can include corrections of typos in instructions, introduction of additional properties to schemas, loosening constraints on expected value numbers or formats, granting additional relations between schemas, and adding new schemas (if they do not require relational changes in existing schemas). Except for typo corrections, these changes are typically tagged as sub-releases for the respective major version (e.g., v1.1). If a version branch does not have an official release tag, yet, also non-backwards compatible changes can be merged on this branch. This can include renaming of existing properties, increasing constraints on expected value numbers or formats, removing relations between schemas and adding new schemas, if they cause relational changes in existing schemas. In case all version branches have official release tags, a new non-backwards compatible change would lead to the creation of a new version branch (with a respectively increased major version number).
++**(2)** The GitHub repository should have at least one **version branch** (e.g., "v1").
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--As mentioned already above, the setup of the central openMINDS GitHub repository is maintained by the openMINDS integration pipeline (cf. below). Note that the pipeline is configured in such a way, that each commit on one of the openMINDS submodules will trigger a new build of the central openMINDS repository ensuring that its content is always up-to-date.
++**(3)** The version branch should have the following **main directory folders**: **##schemas##** (required), **##tests##** (recommended),  **##examples##** (recommended), and **##img##** (optional).
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--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:
++**(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.
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--**(1)** The openMINDS metadata model has to be located on a **public GitHub repository** and published under an **MIT license**.
++**(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
++(% style="text-align: center;" %)
++**##<<XXX>>-<<YYY>>.jsonld##**
++
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--**(2)** The GitHub repository of such a metadata model should have at least one **version branch** (naming convention: vX, where X is a major version number).
++for files that should pass the tests, and
++(% style="text-align: center;" %)
++**##<<XXX>>-<<YYY>>-nok.jsonld##**
++
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--**(3)** The version branch should have the following **folders** & **files**:
++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##**).
--* **##schemas/##** (required) - contains the schemas of the respective metadata model implemented in the reduced openMINDS syntax (cf. below). The sub-directory of the "schemas" folder can be further structured or flat.
--* **##tests/##** (recommended) - contains test-instances (JSON-LDs) for checking the constraints defined in the schemas of the respective metadata model. The sub-directory of the "tests" folder should follow the same structure as the "schemas" folder with an additional sub-directory for each schema. The file names of the test-instances should be written in lowerCamelCase and state first the name of the respectively tested schema and second, separated with an underscore, what schema constrain is tested (e.g., **##contactInformation_validEmail.jsonld##**). If a test-instance is expected to fail the schema validation the file name should receive the postfix **##"_nok"##** (e.g., **##contactInformation_invalidEmail_nok.jsonld##**).
--* **##examples/##** (recommended) - contains examples for valid instance collections for the respective 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.
--* **##img/##** (optional) - contains typically the logo of the openMINDS submodule.
--* **##instances/##** (optional) - contains the controlled metadata instances (JSON-LDs) for selected schemas of the respective metadata model. The sub-directory of the "instances" folder should follow the same structure as the "schemas" folder with an additional sub-directory for each schema. The file names of the controlled instances should be written in lowerCamelCase and state the simple, human-readable identifier of the instance (e.g., **##homoSapiens.jsonld##** for the controlledTerms schema **##Species##**).
--* **##version.txt##** (required) - states the identifier of the version branch (e.g., **##v1##**) of the respective metadata model.
--* **##README.md##** (required) - contains a short content description of the respective metadata model.
--* **##LICENSE.txt##** (required) - states the license for the respective metadata model (has to be MIT).
++(% style="text-align: justify;" %)
++**(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.
++(% style="text-align: justify;" %)
++**(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 ===
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--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##**>>https://raw.githubusercontent.com/HumanBrainProject/openMINDS/v2/vocab/types.json||rel="noopener noreferrer" target="_blank"]] and [[**##properties.json##**>>https://raw.githubusercontent.com/HumanBrainProject/openMINDS/v2/vocab/properties.json||rel="noopener noreferrer" target="_blank"]]). 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.
++Through the integration pipeline of the openMINDS generator, the openMINDS vocabulary is automatically gathered and stored in the main openMINDS GitHub in order to centrally maintain general definitions and references for **types** and **properties** used in schemas across all openMINDS repositories. How this works is explained in the following.
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--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:
++Schema types and properties are stored in dedicated JSON files (**##types.json##** and **##properties.json##**) under the folder **##vocab##** located in the main openMINDS GitHub directory. Each schema type and property occurring in the openMINDS metadata models is automatically represented in those files as nested dictionaries. Here a cutout of the **##types.json##**:
  {{code language="json"}}
  {
--  "OPENMINDS_SCHEMA_TYPE": {
--    "description": "GENERAL_DESCRIPTION",
--    "name": "DISPLAY_LABEL",
++  ...,
++  "https://openminds.ebrains.eu/core/Person": {
++    "description": "Structured information on a person (alive or dead).",
++    "name": "Person",
      "translatableTo": [
--      "REFERENCE_TO_RELATED_SCHEMA_OF_OTHER_INITIATIVE"
++      "https://schema.org/Person"
      ]
--  }
++  },
++  ...
  }
  {{/code}}
--(% style="text-align: justify;" %)
--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.
++... and a cutout of the **##properties.json##**:
--(% style="text-align: justify;" %)
--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:
--
  {{code language="json"}}
  {
--  "PROPERTY_NAME": {
--    "description": "GENERAL_DESCRIPTION",
--    "name": "DISPLAY_LABEL",
--    "nameForReverseLink": "DISPLAY_LABEL_OF_REVERSED_LINK",
++  ...,
++  "givenName": {
++    "description": "Name given to a person, including all potential middle names, but excluding the family name.",
++    "name": "Given name",
++    "nameForReverseLink": "Is given name of",
      "sameAs": [
--      "REFERENCE_TO_MATCHING_SCHEMA-PROPERTY_OF_OTHER_INITIATIVE"
++      "https://schema.org/givenName"
      ],
      "schemas": [
--      "RELATIVE_PATH_TO_OPENMINDS-SCHEMA_USING_THIS_PROPERTY"
++      "core/v3/actors/person.schema.tpl.json"
      ]
--  }
++    },
++  ...
  }
  {{/code}}
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--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 keywords of those nested dictionaries are pre-defined to consistently capture for all schema types and properties their namespace, their occurrence (cf. **##"schemas"##** in **##properties.json##**), their general description (cf. **##"description"##** in **##types.json##** and **##properties.json##**), and possible references to related or matching schema types (cf. **##"translatableTo"##** in **##types.json##**) and properties  (cf. **##""sameAs""##** in **##properties.json##**) of other metadata initiatives (e.g., schema.org).
--=== The openMINDS syntax ===
--
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--All openMINDS metadata models are defined using a light-weighted schema syntax. Although this schema 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.
++This setup also allows us to define some values/entries to be automatically filled in by the openMINDS integration pipeline with each commit to one of the openMINDS repositories (**##"name"##**, **##"schemas"##**) and others to be manually editable later on (**##"description"##**, **##"translatableTo"##**, **##"sameAs"##**, **##"nameForReverseLink"##**).
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--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.
++For security, outdated entries in those openMINDS vocabulary files (e.g., because the namespace of the schema type or property changed or the schema type or property was deleted) are not automatically deleted, but kept and marked as being deprecated. After evaluation, deprecated schema types or properties can be deleted manually from openMINDS vocabulary.
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--==== Basic openMINDS schema structure ====
++With that, the openMINDS vocab reflects always an up-to-date status of the schema types and properties in use across all openMINDS metadata models, while providing the opportunity to centrally review and maintain their consistency and references.
--(% style="text-align: justify;" %)
--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:
++=== The openMINDS schema template syntax ===
--{{code language="json"}}
--{
--  "_type": "https://openminds.ebrains.eu/LABEL_OF_METADATA_MODEL/SCHEMA_NAME",
--  "properties": {
--    "PROPERTY_NAME": {
--      "type": "DATA_TYPE",
--      "_instruction": "METADATA_ENTRY_INSTRUCTION"
--  },
--  "required": [
--    "PROPERTY_NAME"
--  ]
--}
--{{/code}}
--
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--**##"_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.
++All openMINDS metadata models use a light-weighted schema template syntax for defining the expected metadata. The correspondingly formatted schema files use the extension: **##.schema.tpl.json##**.
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--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.
++Although, as the file extension suggests, this openMINDS schema template syntax is inspired by JSON-Schema, it facilitates or even excludes technical aspects making the openMINDS schemas more human-readable, especially for untrained eyes. Behind the scenes, within the openMINDS integration pipeline (cf. below), this schema template syntax is then interpreted and flexibly translated to various formal metadata formats (e.g., JSON-Schema).
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--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.
++Despite the simplification in comparison to JSON-Schema, the openMINDS schema templates are also, at the core, specially formatted JSON files using a particular syntax, meaning special key-value pairs that define the validation rules of a schema. Please find in the following a full documentation of the openMINDS schema template syntax and how it's key-value pairs need to be defined and interpreted.
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--==== Schemas extending a context-schema ====
++For the more inexperienced programmers, let's start by explaining first some general terms that will be later used in the openMINDS schema template syntax specification. More experienced programmers can of course skip these explanations and jump directly further down to Specifications.
--(% style="text-align: justify;" %)
--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.
++**What are strings, integers, floats or booleans?** Generally speaking strings, integers, floats or booleans are derived **data types**. A **string** is defined as a sequence of characters between quotes (e.g., ##"Is this a string? YES!"## or ##'thisIsAlsoAString'##). For a string, openMINDS accepts Unicode characters. An **integer** is a whole number, positive or negative, without decimals, of unlimited length (e.g., ##5##, ##-5## or ##1238921234##). A **float** represents a real number, written with a decimal point dividing the integer and fractional part, both of unlimited length (e.g., ##5.15##, ##-5.15## or ##1238921234.1345##). A **boolean** represents a logical proposition by means of the binary digits ##0## (##false##) and ##1## (##true##), especially in computing and electronics. How a boolean is written depends highly on the format or computational language.
--(% style="text-align: justify;" %)
--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:
++**What is a list or array?** A **list** is a data structure that is a mutable ordered sequence of values (also called items). The values of a list are typically defined between square brackets (e.g., ##[value1, value2, value3]##). Note that the values within a list do not have to have the same data type. In contrast, an **array** is a data structure that is a mutable unordered sequence of values of the same data type. What data types are accepted for values in a list or in an array is highly depending on the format or computational language.
--(% style="text-align: center;" %)
--**##"_extends": "RELATIVE_PATH_TO_OPENMINDS-CONTEXT-SCHEMA"##**
++**What is a key-value pair or an associative array?** A **key-value pair** (sometimes also called name-value pair, attribute-value pair, property-value pair, or field-value pair) is a basic data representation and standard language feature in computing languages, systems and applications. In most cases this concept is used to build an **associative array** (also called **dictionary**), meaning an unordered list of unique keys with associated values typically defined within curly brackets (e.g., ##{key1: value1, key3: value3, key2:value2}##). What data types are accepted for keys and values highly depends on the format or computational language. Note that a value could also be a data structure, such as a list, an array or an associative array.
--(% style="text-align: justify;" %)
--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>>https://raw.githubusercontent.com/HumanBrainProject/openMINDS_core/v3/schemas/products/researchProduct.schema.tpl.json||rel="noopener noreferrer" target="_blank"]] which is extended by the following schema set: [[Dataset>>https://raw.githubusercontent.com/HumanBrainProject/openMINDS_core/v3/schemas/products/dataset.schema.tpl.json||rel="noopener noreferrer" target="_blank"]], [[MetaDataModel>>https://raw.githubusercontent.com/HumanBrainProject/openMINDS_core/v3/schemas/products/metaDataModel.schema.tpl.json]], [[Model>>https://raw.githubusercontent.com/HumanBrainProject/openMINDS_core/v3/schemas/products/model.schema.tpl.json||rel="noopener noreferrer" target="_blank"]], and [[Software>>https://raw.githubusercontent.com/HumanBrainProject/openMINDS_core/v3/schemas/products/software.schema.tpl.json||rel="noopener noreferrer" target="_blank"]].
++**What is JSON?** JSON is short for **J**ava**S**cript **O**bject **N**otation, a lightweight data-interchange format which is built on associative arrays with key-value pairs and lists. Each JSON file begins as associative array. The keys are separated from the values via a colon and key-value pairs are separated by a comma. While a key always has to be a string in double quotes, a value can be a string in double quotes, an integer, a float, a boolean (written as true or false), null, a list or an associative array. Nesting of these structures is unlimited. For more information please go to the official webpage: [[https:~~/~~/www.json.org/>>https://www.json.org/]].
--(% style="text-align: justify;" %)
--==== Data type depending constraints ====
++==== Specifications ====
--(% style="text-align: justify;" %)
--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"##**.
++(coming soon)
--(% style="text-align: justify;" %)
--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