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10	10	Please find below a documentation of the layout and requirements needed to keep the openMINDS modularity, the syntax of the openMINDS schema template, as well as the openMINDS integration pipeline.
11	11	)))
12	12
13		-=== The openMINDS umbrella ===
	13	+=== Overview of the openMINDS layout ===
14	14
15	15	(% style="text-align: justify;" %)
16	16	In summary, openMINDS is the overall umbrella for a set of distributed GitHub repositories, each defining a particular metadata model for neuroscience research products.
17	17
18		-(% style="text-align: justify;" %)
19		-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).
	18	+=== The openMINDS schema template syntax ===
20	20
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22		-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:
	21	+All openMINDS metadata models use a light-weighted schema template syntax for defining the metadata. The correspondingly formatted schema files use the extension: **##.schema.tpl.json##**.
23	23
24		-(% style="text-align:justify" %)
25		-* The openMINDS metadata model has to be located on a **public GitHub repository** and published under an **MIT license**.
26		-* The GitHub repository should have at least one **version branch** (e.g. "v1").
27		-* The version branch should have the following **main directory folders**: **##schemas##** (required), **##tests##** (recommended),  **##examples##** (recommended), and **##img##** (optional).
28		-* 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.
29		-* 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##**).
30		-* 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 to group related instances.
31		-* 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.
32		-
33		-=== The openMINDS vocabulary ===
34		-
35	35	(% style="text-align: justify;" %)
36		-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.
	24	+Although, as the file extension suggests, this openMINDS schema template syntax is inspired by JSON-Schema, it facilitates or even excludes technical aspects that are generally expected for the openMINDS schemas making it more human-readable, especially for untrained eyes.
37	37
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39		-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.
	27	+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). Please find in the following a full documentation of the openMINDS schema template syntax and how it needs to be interpreted.
40	40
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42		-The keywords of those nested dictionaries are pre-defined to consistently capture for all schema types and properties their namespace, their occurrence, their general description, and possible references to related or matching schema types and properties of other metadata initiatives (e.g. schema.org). 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 (e.g., the namespace and occurrence) and others to be manually editable later on (e.g., the general description and references).
	30	+===== Target & context templates =====
43	43
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45		-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.
	33	+All openMINDS schemas have to have a **##"_type"##** to be recognized as target templates. In other words, the **##"_type"##** is used to define the openMINDS namespace of a corresponding schema using the following naming convention:
46	46
47		-(% style="text-align: justify;" %)
48		-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.
	35	+(% style="text-align: center;" %)
	36	+**##"_type": "https:~/~/openminds.ebrains.eu/<<schema-model>>/<<schema-name>>"##**,
49	49
50		-=== The openMINDS schema template syntax ===
51		-
52	52	(% style="text-align: justify;" %)
53		-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##**.
	39	+where **##<<schema-model>>##** has to be replaced with the label of the openMINDS metadata model the corresponding schema belongs to and **##<<schema-name>>##** exchanged with the label of that schema.
54	54
55	55	(% style="text-align: justify;" %)
56		-Although, as the file extension suggests, this openMINDS schema template syntax is inspired by JSON-Schema, it facilitates or even excludes technical aspects that are generally expected for the openMINDS schemas making them 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).
	42	+If an openMINDS schema template file //DOES NOT// define a **##"_type"##**, it is interpreted as a context template which requires an extension to become a target template.
57	57
58	58	(% style="text-align: justify;" %)
59		-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.
	45	+Context templates are and should be used when multiple openMINDS schemas (target templates) have the same subset of properties. This common subset of properties can then be defined within a single context schema instead of each target template which facilitates the long-term maintenance of these properties.
60	60
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62		-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.
	48	+===== String properties =====
63	63
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65		-===== Target & concept templates =====
	51	+(//**coming soon**//)
66	66
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68		-Same as in JSON-Schema, all openMINDS schema templates define the expected name (written in **##lowerCamelCase##**) and value of the metadata, typically called property, under the key **##properties##** as nested dictionaries. Furthermore, the names of obligatory metadata can be listed under the key **##required##**. Here a generalized example:
	54	+===== Numerical properties =====
69	69
70		-{{code language="json"}}
71		-{
72		- "properties": {
73		- "propertyNameA": {},
74		- "propertyNameB": {},
75		- "propertyNameC": {}
76		- },
77		- "required": [
78		- "propertyNameA",
79		- "propertyNameC"
80		- ]
81		-}
82		-{{/code}}
83		-
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85		-In addition, an openMINDS schema //has to have// a key **##"_type"##** to be recognized as **target template**. In other words, the **##"_type"##** is used to define the openMINDS namespace of a corresponding schema using a particular naming convention. Here again a generalized example:
	57	+(//**coming soon**//)
86	86
87		-{{code language="json"}}
88		-{
89		- "_type": "https:~/~/openminds.ebrains.eu/<<schema-model>>/<<schema-name>>",
90		- "properties": {}
91		-}
92		-{{/code}}
93		-
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95		-Note that **##<<schema-model>>##** has to be replaced with the label of the openMINDS metadata model to which the corresponding schema belongs to, and **##<<schema-name>>##** has to be replaced with the corresponding name of the schema (written in **##CamelCase##**).
	60	+===== Object properties =====
96	96
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98		-If an openMINDS schema template //does not// define a key **##"_type"##** (as in the first example above), it is interpreted as a **concept template** which //has to be// extended to a target template.
	63	+(//**coming soon**//)
99	99
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101		-Concept templates are and should be used when multiple target templates have the same subset of properties, because they facilitate the long-term maintenance of those shared properties: Instead of defining the same properties repeatedly within multiple target templates, the common subset can be defined within a single concept template and passed on to all extending target templates.
	66	+===== Property arrays =====
102	102
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104		-To define that a target template is the extension of a concept template, the target template can state under **##"_extends"##** the relative path to the concept template. For example, the openMINDS core target template **##Dataset##** extends the core concept template **##researchProduct##** as indicated here:
	69	+(//**coming soon**//)
105	105
106		-{{code language="json"}}
107		-{
108		- "_type": "https:~/~/openminds.ebrains.eu/core/Dataset",
109		- "_extends": "products/researchProduct.schema.tpl.json"
110		-}
111		-{{/code}}
112	112
113		-(% style="text-align: justify;" %)
114		-Note that this convention requires the concept and corresponding target templates to be located in the same openMINDS metadata model repository. Note also that for properties, the following rules apply for target and concept template:
115		-
116		-1. A concept template has to define some properties which will be inherited by all extending target templates.
117		-1. If a concept template additionally states that some of these properties are required, all extending target templates will require the same properties.
118		-1. A target template can require properties of the concept template, that are not explicitly required within the concept template. In such a case, the other target templates extending the same concept template will not require those properties.
119		-1. A target template can (but does not have to) define and require additional properties that were not defined and required in the concept template. These additionally defined and required properties will not be shared with the other target templates extending the same concept template.
120		-
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122		-How to define the expected value of a property will be explained for the different property types in the following sections.
123		-
124		-(% style="text-align: justify;" %)
125		-===== Defining expected values =====
126		-
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128		-The expected value of a property can be defined in large parts in the same way as in JSON-Schema, with some openMINDS syntax specific simplifications and modifications.
129		-
130		-(% style="text-align: justify;" %)
131		-On the first level, the **##"type"##** of the expected property value needs to be defined. In principle, the openMINDS template syntax supports the same value types as JSON-Schema Draft 7.0, meaning:
132		-+ **##"string"##**
133		-+ **##"number"##**
134		-+ **##"integer"##**
135		-+ **##"array"##**
136		-+ **##"boolean"##**
137		-+ **##"null"##**
138		-+ **##"object"##**
139		-
140		-Also very similar to JSON-Schema, additional type-specific keys can be used to set further requirements for the expected value. H
141		-
142		-
143	143	=== The openMINDS integration pipeline ===
144	144
145	145	(//**coming soon**//)