409 lines
11 KiB
Markdown
409 lines
11 KiB
Markdown
---
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warn: This is just a prototype.
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---
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# YASD, Yet Another Schema Definition
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YASD is a YAML format for human writable XSDs (XML Schema Definition), humans
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declare what is indispensable, leaving the machines to do the rest of the
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unreadable `<syntaxis who_can_read_this="?" />`.
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## CLI Workflow
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The following chart is the YASD CLI workflow:
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``` mermaid
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flowchart LR
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direction LR
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yasd --- convert
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yasd --- check
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yasd --- sample
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yasd --- document
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yasd --- man
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convert --- |from| YASD1([YASD])
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YASD1 --> |to| XSD([XSD])
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check --- |validates| YASD2([YASD])
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sample --- |from| YASD3([YASD])
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YASD3 --> |to| XML([XML])
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document --- |from| YASD4([YASD])
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YASD4 --> |to| RST([reStructuredText])
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man --- |prints| README
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```
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## Example
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To better understad what YASD does, see the inputs and outputs:
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- Input: human workable schema in [YASD].
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- Output: computer processable schema in [XSD].
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- Output: human readable documentation in [reStructuredText][RST].
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## Table of Contents
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[TOC]
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## Structure
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### General structure
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schema:
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SCHM
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elements:
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- ELMT
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...
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attributeElements:
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- ATTR
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...
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groups:
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- GRPS
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### Schema (SCHM) structure
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elementFormDefault: qualified|unqualified
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targetNamespace: http://a.link
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xmlns: http://a.link
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schemaLocation: http://a-link-to.xsd
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version: 0.1
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### Element (ELMT) structure
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name: element_name
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description: Element description
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type: simple|empty|no_text|no_elements|mixed
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datatype: string|integer|decimal|date|time|language|duration|token|boolean|byte|int|double|float|long|short|normalizedString|dateTime|gDay|gMonth|gMonthDay|gYear|gYearMonth|negativeInteger|nonNegativeInteger|nonPositiveInteger|positiveInteger|unsignedLong|unsignedInt|unsignedShort|unsignedByte|anyURI|base64Binary|hexBinary|Name|QName|NCName|ID|IDREF|IDREFS|ENTITY|ENTITIES|NMTOKEN|NMTOKENS|NOTATION
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attributes:
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- name: attribute_name
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- group: group_name
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...
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children_order: all|choice|sequence
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children:
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- name: element_name
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maxOccurs: INTEGER
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minOccurs: INTEGER
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- group: group_name
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...
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### Attribute (ATTR) structure
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name: attribute_name
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description: Attribute description
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datatype: string|integer|decimal|date|time|language|duration|token|boolean|byte|int|double|float|long|short|normalizedString|dateTime|gDay|gMonth|gMonthDay|gYear|gYearMonth|negativeInteger|nonNegativeInteger|nonPositiveInteger|positiveInteger|unsignedLong|unsignedInt|unsignedShort|unsignedByte|anyURI|base64Binary|hexBinary|Name|QName|NCName|ID|IDREF|IDREFS|ENTITY|ENTITIES|NMTOKEN|NMTOKENS|NOTATION
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default: a_value
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fixed: a_value
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use: required
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restriction:
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- CONSTRAIN
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...
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### Group (GRPS) structure
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name: group_name
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attribute_group: true|false
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children_order: all|choice|sequence
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children:
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- name: element_name
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maxOccurs: INTEGER|unbounded
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minOccurs: INTEGER
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## Reference
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### `elementFormDefault`
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Indicates that any elements used by the XML instance document which were
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declared in this schema must be namespace qualified.
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Optional; if not present by default is `unqualified`.
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### `taget_namespace`
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Indicates that the elements defined by this schema come from the specified URL
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namespace.
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Optional.
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### `xmlns`
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Indicates that the default namespace is the specified URL.
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Mandatory.
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### `schemaLocation`
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Indicates the location of the XML schema to use for that namespace.
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Optional.
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### `version`
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Indicates XML schema version.
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Mandatory.
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### `name`
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Indicates element or attribute name.
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Mandatory.
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For elements, its name is commonly known as tag name.
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Naming rules:
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- Element names are case-sensitive
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- Element names must start with a letter or underscore
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- Element names cannot start with the letters xml (or XML, or Xml, etc)
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- Element names can contain letters, digits, hyphens, underscores, and
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periods
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- Element names cannot contain spaces
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### `description`
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Indicates element or attribute description in human readable form.
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Optional.
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### `type`
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Indicates element type.
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Mandatory.
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Allowed types:
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- `simple`. Only text node allowed.
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- `empty`. Only attributes allowed.
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- `no_text`. No children text nodes allowed.
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- `no_elements`. No children elements allowed.
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- `mixed`. Children elements, text node and attributes allowed.
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Chart:
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| type | children elements | children text node | attributes |
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|------------|:-----------------:|:------------------:|:----------:|
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|simple | ✗ | ✓ | ✗ |
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|empty | ✗ | ✗ | ✓ |
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|no_text | ✓ | ✗ | ✓ |
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|no_elements | ✗ | ✓ | ✓ |
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|mixed | ✓ | ✓ | ✓ |
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> **Note**: attributes are never mandatory; they could be zero or more.
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### `datatype`
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Indicates element or attribute data types.
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Only mandatory for 'simple' and 'no_elements' elements, and attributes.
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Allowed String Data Types:
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- `ENTITIES`.
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- `ENTITY`.
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- `ID`. A string that represents the ID attribute in XML (only used with
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schema attributes).
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- `IDREF`. A string that represents the IDREF attribute in XML (only used
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with schema attributes).
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- `IDREFS`.
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- `language`. A string that contains a valid language id.
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- `Name`. A string that contains a valid XML name.
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- `NCName`.
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- `NMTOKEN`. A string that represents the NMTOKEN attribute in XML (only used
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with schema attributes).
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- `NMTOKENS`.
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- `normalizedString`. A string that does not contain line feeds, carriage
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returns, or tabs.
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- `QName`.
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- `string`. A string.
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- `token`. A string that does not contain line feeds, carriage returns, tabs,
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leading or trailing spaces, or multiple spaces.
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Allowed Date and Time Data Types:
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- `date`. Defines a date value.
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- `dateTime`. Defines a date and time value.
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- `duration`. Defines a time interval.
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- `gDay`. Defines a part of a date - the day (DD).
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- `gMonth`. Defines a part of a date - the month (MM).
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- `gMonthDay`. Defines a part of a date - the month and day (MM-DD).
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- `gYear`. Defines a part of a date - the year (YYYY).
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- `gYearMonth`. Defines a part of a date - the year and month (YYYY-MM).
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- `time`. Defines a time value.
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Allowed Numeric Data Types:
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- `byte`. A signed 8-bit integer.
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- `decimal`. A decimal value.
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- `int`. A signed 32-bit integer.
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- `integer`. An integer value.
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- `long`. A signed 64-bit integer.
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- `negativeInteger`. An integer containing only negative values (..,-2,-1).
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- `nonNegativeInteger`. An integer containing only non-negative values
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(0,1,2,..).
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- `nonPositiveInteger`. An integer containing only non-positive values
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(..,-2,-1,0).
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- `positiveInteger`. An integer containing only positive values (1,2,..).
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- `short`. A signed 16-bit integer.
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- `unsignedLong`. An unsigned 64-bit integer.
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- `unsignedInt`. An unsigned 32-bit integer.
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- `unsignedShort`. An unsigned 16-bit integer.
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- `unsignedByte`. An unsigned 8-bit integer.
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Allowed Miscellaneous Data Types:
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- `anyURI`.
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- `base64Binary`.
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- `boolean`.
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- `double`.
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- `float`.
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- `hexBinary`.
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- `NOTATION`.
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- `QName`.
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### `default`
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Indicates default value when element or attribute is empty.
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Optional.
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Only allowed for simple elements or attributes.
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### `fixed`
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Indicates fixed value to element or attribute.
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Optional; ignored if 'default' is present.
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Only allowed for simple elements or attributes.
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### `use`
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Indicates that the attribute is required.
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Optional.
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Only `required` is valid as value.
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### `restriction`
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Indicates accepted constrained values for attribute.
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Optional; if present, must contain at least one constrain.
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Allowed constrains:
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- `enumeration`. Specifies a list of acceptable values.
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- `fractionDigits`. Specifies the maximum number of decimal places allowed;
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must be equal to or greater than zero.
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- `length`. Specifies the exact number of characters or list items allowed;
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must be equal to or greater than zero.
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- `maxExclusive`. Specifies the upper bounds for numeric values (the value
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must be less than this value).
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- `maxInclusive`. Specifies the upper bounds for numeric values (the value
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must be less than or equal to this value).
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- `maxLength`. Specifies the maximum number of characters or list items
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allowed; must be equal to or greater than zero.
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- `minExclusive`. Specifies the lower bounds for numeric values (the value
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must be greater than this value).
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- `minInclusive`. Specifies the lower bounds for numeric values (the value
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must be greater than or equal to this value).
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- `minLength`. Specifies the minimum number of characters or list items
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allowed; must be equal to or greater than zero.
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- `pattern`. Defines the exact sequence of characters that are acceptable.
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- `totalDigits`. Specifies the exact number of digits allowed; must be
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greater than zero.
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- `whiteSpace`. Specifies how white space (line feeds, tabs, spaces, and
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carriage returns) is handled; accepted values are
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`preserve|replace|collapse`.
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### `attributes`
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Indicates a list of attributes for an element.
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### `children_order`
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Indicates order indicators for children elements.
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Mandatory in `no_text` or `mixed` elements, and group.
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Allowed values:
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- `all`. Children elements can occur in any order.
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- `choice`. Only one children element can accur.
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- `sequence`. Children elements must occur in specified order.
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### `children`
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Indicates a list of children elements.
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Mandatory in `no_text` or `mixed` elements, and group.
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### `maxOccurs`
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Indicates max number of times a children element can accur.
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Optional; if not present by default is `1`.
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Valid values are non negative integer or `unbounded` for unlimited number of
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times.
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### `minOccurs`
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Indicates min number of times a children element can accur.
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Optional; if not present by default is `1`.
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Valid value is non negative integer.
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### `group`
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Indicates group name.
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Optional.
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### `groups`
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Indicates element or attribute groups for schema.
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Optional.
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### `attribute_group`
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Indicates if group is an attribute group.
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Optional; if not present by default is `false`.
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Allowed values:
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- `true`.
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- `false`.
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### `elements`
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Indicates elements for schema.
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Mandatory.
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### `attributeElements`
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Indicates attributes elements for schema.
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Optional.
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### `schema`
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Indicates schema general information.
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Mandatory.
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## References
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* “XML Schema Reference”, [W3ref]
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* “XML Schema Tutorial”, [W3Schools].
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* “XSD Tutorial”, [Tutorials Point].
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[YASD]: https://gitlab.com/amlengua/apal/esquema/-/blob/main/apal.yaml
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[XSD]: https://gitlab.com/amlengua/apal/esquema/-/blob/main/apal.xsd
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[RST]: https://gitlab.com/amlengua/apal/esquema/-/blob/main/apal.rst
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[W3ref]: https://www.w3schools.com/xml/schema_elements_ref.asp
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[W3Schools]: https://www.w3schools.com/xml/schema_intro.asp
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[Tutorials Point]: https://www.tutorialspoint.com/xsd/
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