)? ($P_LEVEL)* (<sec>)*` **Definition**: Elements with constraint `$P_LEVEL` have any one of the following tags: ``` <code> <disp-quote> <list> <p> <preformat> <table-wrap> ``` ### `<back>` element tree **Criterion** `<back>` has exactly one child element `<ref-list>`. **Criterion**: The `<ref-list>` element contain a sequence of child elements with tags matching the regular expression: `(<title>)? (<ref>)*` **Criterion**: `<ref>` elements have one attribute and it is `id=`. **Criterion**: `<ref>` elements have exactly one child element of `<element-citation>`. **Criterion**: `<element-citation>` elements only have child elements with any one the following tags: ``` <article-title> <comment> <date-in-citation> <edition> <fpage> <isbn> <issn> <issue> <lpage> <person-group> <pub-id> <publisher-loc> <publisher-name> <source> <uri> <volume> ``` **Criterion**: For `<element-citation>` elements, there are one or zero child elements for each possible tag, with the exception of `<pub-id>`, which can appear more than once. **Criterion**: For `<element-citation>` elements, all child elements with tag `<pub-id>` have different values for attribute `pub-id-type=`. **Criterion**: `<person-group>` elements have an attribute `person-group-type=` with either value `"author"` or `"editor"`. **Criterion**: `<person-group>` elements have zero or more child elements with either tag `<name>` or `<string-name>`. **Criterion**: The following elements have string content only: ``` <comment> <fpage> <isbn> <issn> <issue> <lpage> <publisher-loc> <publisher-name> <string-name> <uri> <volume> ``` **Criterion**: `<date-in-citation>` attribute `content-type=` equals value `"access-date"`. **Criterion**: `<date-in-citation>` have all child elements with tag `<year>`, `<month>`, or `<day>` and at most once for each tag. **Criterion**: `<date-in-citation>` elements contain child element `<year>`. **Criterion**: `<date-in-citation>` has child element `<month>` only if `<year>` is also present. **Criterion**: `<date-in-citation>` has child element `<day>` only if `<month>` is also present. **Criterion**: `<edition>` elements have just an integer as content and do not have any non-digit characters. **Criterion**: `<pub-id>` `pub-id-type=` attributes have values `"doi"` or `"pmid"`. **Criterion**: `<pub-id>` elements with attribute value `pub-id-type="doi"` have string content that starts with "10." and not "http". ### HTML-like content **Criterion**: Elements with constraint `$HYPOTEXT` have tag `{TYPO_TAG}`. **Criterion**: Elements with constraint `$HYPOTEXT` have all child elements also with constraint `$HYPOTEXT`. #### Hypertext elements **Criterion**: Elements with constraint `$HYPERTEXT` have any one of the following tags ``` <ext-link> <xref> {TYPO_TAG} ``` **Criterion**: Elements with constraint `$HYPERTEXT` and `{TYPO_TAG}` have all child elements with constraint `$HYPERTEXT`. **Criterion**: Elements with tag `<ext-link>` have all child elements with constraint `$HYPOTEXT`. **Criterion**: Every `<ext-link>` has an `href=` attribute from the XML namespace `http://www.w3.org/1999/xlink`. **Criterion**: Every `<ext-link>` attribute `ext-link-type=` takes the value `"uri"` (if present). **Criterion**: Elements with tag `<xref>` have all child elements with constraint `$HYPOTEXT`. **Criterion**: Every element with tag `<xref>` and constraint `$HYPERTEXT` has an attribute `rid=`. **Criterion**: Every element with tag `<xref>` and constraint `$HYPERTEXT` has no attribute other than `rid=`. #### Paragraph elements **Criterion**: Elements with constraint `$P_CHILD` have one of the following tags ``` <code> <def-list> <disp-quote> <ext-link> <list> <preformat> <xref> {TYPO_TAG} ``` **Criterion**: `<p>` elements have all child elements with constraint `$P_CHILD`. **Criterion**: Elements with constraint `$P_CHILD` and `{TYPO_TAG}` but not tag `<sup>` have constraint `$HYPERTEXT`. **Criterion**: Elements with constraint `$P_CHILD` and tag `<sup>` have constraint `$HYPERTEXT` or `$CITATION` (but not both). #### Citation elements **Criterion**: Elements with constraint `$CITATION` and tag `<sup>` have text content of: * optional whitespace before the first child element * optional whitespace after the last child element, and * a comma and optional whitespace between child elements. **Criterion**: Elements with constraint `$CITATION` have all child elements with constraint `$CITATION` and tag `<xref>`. **Criterion**: Elements with constraint `$CITATION` and tag `<xref>` have an attributes of `ref-type=` with value `bibr`. **Criterion**: Elements with constraint `$CITATION` and tag `<xref>` have exactly two attributes of `rid=` and `ref-type=`. **Criterion**: Elements with constraint `$CITATION` and tag `<xref>` have a value for `rid=` that matches the value of attribute `id=` in an element with tag `<ref>`. **Criterion**: Elements with constraint `$CITATION` and tag `<xref>` have content of only a single integer, surrounded by optional whitespace, and no child elements. The integer corresponds to the position in `<ref-list>` of the `<ref>` element with an `id=` attribute value that equals the `rid=` attribute of the `<xref>` element. #### List elements **Criterion**: `<list>` element attributes `list-type=` have either value `"bullet"` or `"order"`. **Criterion**: `<list>` elements only have child elements with tag `<list-item>`. **Criterion**: `<list-item>` elements only have child elements with either tag `<p>` or `<list>`. **Criterion**: `<def-list>` elements only have child elements with tag `<def-item>`. **Criterion**: `<def-list>` elements only have child elements with either tag `<term>` or `<def>`. **Criterion**: `<term>` elements only have child elements with `{TYPO_TAG}` or `{LINK_TAG}`. **Criterion**: `<term>` elements have all child elements with constraint `$HYPERTEXT`. **Criterion**: `<def>` elements only have child elements with tag `<p>`. #### Table elements **Criterion**: `<table-wrap>` elements contains a single `<table>` element. **Criterion**: `<table>` child elements are `<thead>` or `<tbody>` elements. **Criterion**: `<thead>` and `<tbody>` child elements are `<tr>` elements. **Criterion**: `<tr>` child elements are `<th>` or `<td>` elements. **Criterion**: `<th>` and `<td>` elements have all child elements with constraint `$P_CHILD`. **Criterion**: `<th>` and `<td>` attributes `align=` have values `"left"`, `"center"`, or `"right"`. #### Other elements **Criterion**: `<disp-quote>` elements only contain child elements with tag `<p>`. **Criterion**: `<code>` and `<preformat>` elements have all child elements with constraint `$HYPERTEXT`. Interoperability Issues ----------------------- * HTML `<table>` has `<thead>` before `<tbody>` * HTML `<table>` probably (?) has exactly one `<tbody>` and at most one `<thead>` * `<xref>` attribute `rid=` values that might not match an `id=` attribute of an element converted to HTML with the same `id=` (e.g., `<sec>`, `<ref>`). </article></body></html>

--- title: "Baseprint Document Format (BpDF)" abstract: | **DOCUMENT TYPE**: Living Technical Specification The Baseprint Document Format is the digital encoding of a Baseprint document snapshot. These snapshots are immutable and are referenced using a [SoftWare Hash IDentifier (SWHID)](https://swhid.org). This format is designed for self-archived scientific and technical documents for long-term redistribution. The XML component of the format is a subset of the [JATS XML Article Authoring Tag Set](https://jats.nlm.nih.gov/articleauthoring/) and approximates XML found in [PubMed Central](https://pmc.ncbi.nlm.nih.gov/). After archiving, document snapshots are rendered into HTML pages and PDF files by independent websites using Baseprint-compatible software. --- Feedback -------- In addition to email, feedback can also be communicated through the GitHub repository of the source files for this edition at [github.com/castedo/bpdf-spec/](https://github.com/castedo/bpdf-spec/). The online forum at is available for discussions related to Baseprint topics and specifications. Interoperability ---------------- Websites such as and use free open-source software, like the Python package [Epijats](https://gitlab.com/perm.pub/epijats), to render Baseprint document snapshots into HTML pages and PDF files. This specification is for interoperability with reference software implementations. As of 2024, the only reference implementation is the Python package [Epijats](https://gitlab.com/perm.pub/epijats). For this edition of this specification, version 2.0 of Epijats is the reference software. Epijats is used by the authoring software [Baseprinter](https://gitlab.com/perm.pub/baseprinter), the Single-Page Application (SPA) [BaseprintLens](https://gitlab.com/perm.pub/baseprintlens), and the website generation software [BaseprintPress](https://gitlab.com/perm.pub/baseprintpress). Snapshots vs. Successions ------------------------- This specification of the Baseprint Document Format (BpDF) is for Baseprint document *snapshots* rather than Baseprint document *successions*. Snapshots are archived and redistributed as part of a *Baseprint document successions* whose digital encoding format is specified by the separate specification, the [Document Succession Git Layout (DSGL)](https://perm.pub/VGajCjaNP1Ugz58Khn1JWOEdMZ8). While snapshots are immutable, successions, in contrast, can be amended. The SWHID for a snapshot is distinct from the [Document Succession Identifier (DSI)](https://perm.pub/1wFGhvmv8XZfPx0O5Hya2e9AyXo) used to identify a succession. ### Document Dates Like [JATS XML Article Authoring Tag Set](https://jats.nlm.nih.gov/articleauthoring/) [@jats_authoring], BpDF does not store a date for a document. Instead, dates for a Baseprint document are recorded in the Git commit records of the [Document Succession Git Layout (DSGL)](https://perm.pub/VGajCjaNP1Ugz58Khn1JWOEdMZ8) [@dsgl]. These dates are set when an author amends a succession in DSGL with a snapshot as a new edition. JATS XML in a Directory ----------------------- Technically, BpDF is not a file format but rather a format for a directory-like data structure. This structure is addressable as a [SWHID](https://swhid.org) version 1 directory (equivalent to a [Git](https://en.wikipedia.org/wiki/Git) tree). When generating BpDF data, it is temporarily stored in a file system directory. However, for long-term public storage, BpDF data is preserved in a SWHID addressable directory in the [Software Heritage Archive](https://softwareheritage.org) (or an equivalent tree in a Git repository). At the top level of a BpDF directory, a file named `article.xml` is encoded in a subset of the [JATS Article Authoring Tag Set](https://jats.nlm.nih.gov/articleauthoring/) [@jats_authoring] and is inspired and influenced by JATS4R [@jats4r_2015; @jats4r_2019]. Most of BpDF is a specification of this JATS XML file format, which will be referred to as *Baseprint JATS XML*. BpDF differs from the [Manuscript Exchange Common Approach (MECA)](https://meca.niso.org/) in that a BpDF snapshot is automatically rendered into HTML pages and PDF files, and is not designed for a non-automated publishing process. Restyling to JATS4R ------------------- Since the Baseprint JATS XML format is a small subset of JATS and is not intended for real journal articles, a Baseprint JATS XML file can be restyled by adding fictitious data to conform to the XML schema of a JATS4R validator or the [PMC Style Checker](https://pmc.ncbi.nlm.nih.gov/tools/stylechecker/). The [source code repository for Epijats](https://gitlab.com/perm.pub/epijats) includes an XSLT file for such restyling. Some of the information that must be added is fictitious, such as journal title. This restyling is for testing and facilitating possible interoperability with other JATS systems. Notable Features/Limitations ---------------------------- XML elements for images and mathematics are absent from this edition of Baseprint JATS. These important features of JATS are planned for a future edition. Citations and references in Baseprint JATS XML are styled by the application software that generates HTML pages and/or PDF files. Authors do not control the citation styling. References are in `` elements and not ``. Furthermore, there is no `publication-type` attribute. Depending on the bibliographic fields present inside the ``, the application software must choose appropriate styling. If the `` "looks" like a journal reference, then the software should style it like a journal reference. This means it is challenging for rendering software to exactly match popular citation styles. Software can approximate these styles or rely on services like [Crossref](https://www.crossref.org/) to get addition reference metadata absent from the document snapshot data. Another notable restriction is `` XML elements being in top-level `^{` elements,
which are interpreted to have the semantic meaning
of a group of citations
to be styled together (e.g., `[7,11]`),
not necessarily superscripted text.

Formal Specification
--------------------

### Terminology

#### Element

In this specification, the term "element" means a specific XML element within an XML
document parse tree. The notation of `` may refer to an XML tag or elements with
that tag, depending on context. When an element "has a tag" it never refers a child element.

#### Criterion

The formal part of this specification is defined in terms of *criteria* and does not
prescribe what criteria XML files must or should satisfy.
However, to accurately claim that an XML file "satisfies all the criteria" of this
specification, the XML file MUST satisfy all the criteria of this specification.

Each formal criterion is a true or false statement for a given XML file.
Each criterion is documented to facilitate communication about which criteria
might not be satisfied in particular contexts.
Depending on the context, it might or might not make sense to satisfy specific criteria.
In general, the more criteria that are satisfied by an XML file, the higher
the level of interoperability it will achieve with the reference software of this specification.

#### Constraints

Due to the complexities of where XML elements can appear within an XML document tree,
some criteria are specified in terms of *constraints*.
XML elements in a document may have zero, one, or more constraints.
As an example, consider the following JATS paragraph:
```

^{e^x}
¹

```
The above example satisfies the criteria of this specification because
constraints can be assigned in the following manner:

* the first `^{` has constraint `$HYPERTEXT`,
* the second `^{` (nested inside the first) has constraint `$HYPOTEXT` (in addition
to `$HYPERTEXT`), and
* the last `^{` has constraint `$CITATION`.

### Definitions/Symbols

**Definition**:
Criteria of this specification imply XML elements in an XML document tree must have
zero, one, or more of the following *constraints*:
```
$CITATION
$HYPERTEXT
$HYPOTEXT
$P_CHILD
$P_LEVEL
```

**Definition**:
Symbol `{TYPO_TAG}` means any one of the following tags:
```

_{^{```

### Snapshot Directory Encoding

**Criterion**:
The directory is encoded such that its computed hash interoperates with
[Git software](https://en.wikipedia.org/wiki/Git) as a Git tree hash.

**Criterion**:
The directory is encoded such that its computed hash interoperates with
the hash following the `swh:1:dir:` prefix of a
[SWHID (SoftWare Hash IDentifier)](https://www.swhid.org/).

**Criterion**:
The directory is encoded such that its computed hash interoperates with
[Git software](https://en.wikipedia.org/wiki/Git) as a Git tree hash.

**Criterion**:
There is only one file in the directory and its filename is `article.xml`.
This file is in the Baseprint JATS XML format described in this specification.

**Criterion**:
The tree (directory) entry for `article.xml` has normal file mode in Git and does not
have the executable bit set.

### XML Basics

**Criterion**:
"Well-formed" per the [XML 1.0](https://www.w3.org/TR/REC-xml/) W3C recommendation.

**Criterion**:
No dependency on any external XML DTD (not even a dependency to an official JATS DTD).

**Criterion**:
The following elements contain only optional whitespace between start tag, any child
elements, and end tag:

* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``

### Minimal attributes

**Criterion**:
The following elements have no attributes:

* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* ``
* `_{`
* `^{`
* ``
* `}}
`
* ``
* ``
* ``
* ``
* ``
* ``

**Criterion**:
The elements with the following tags only have the following possible attributes:

| Tag | Possible Attributes |
|----------------------|----------------------------|
| `` | `lang=` |
| `` | `contrib-type=` \
`id=` |
| `` | `content-type=` |
| `` | `href=` \
`ext-link-type=` |
| `` | `content-type=` |
| `` | `list-type=` |
| `` | `person-group-type=` |
| `` | `pub-id-type=` |
| `` | `id=` |
| `
` | `align=` |
| ` ` | `align=` |

### `` element

**Criterion**:
`` is the root element of the XML document.

**Criterion**:
The `` attribute `lang=` (if present) has value `"en"`.

**Criterion**:
`` has a sequence of child elements matching regular expression:
```
() () ()?
```

### `` element tree

**Criterion**:
`` has exactly one child element ``.

**Criterion**:
`` has a sequence of child elements matching regular expression:
```
() () ()? ()
```

**Criterion**:
`` has exactly one child element ``.

**Criterion**:
`` has constraint `$HYPERTEXT`.

**Criterion**:
`` has only child elements with tag ``.

**Criterion**:
`` elements have an attribute of `contrib-type=` and it has value the
`"author"`.

**Criterion**:
`` elements have only child elements with a tag of any one of:

* `` (exactly one)
* `` (zero or one)
* `` (zero or one)

**Criterion**:
`` has child elements `` and/or `` (zero or one of each).

**Criterion**:
`` and `` have string content with no child elements.

**Criterion**:
`` has exactly one attribute with value `contrib-id-type="orcid"`.

**Criterion**:
`` has just string content of a valid an ORCID including the
`https://orcid.org/` prefix.

**Criterion**:
`` has only child elements `` and `` (zero or
one each).

**Criterion**:
`` has constraint $HYPERTEXT.

**Criterion**:
`` has only child elements `` and ``.

**Criterion**:
`` has constraint $HYPERTEXT.

**Criterion**:
`` tags are in the XML namespace:

`"http://www.niso.org/schemas/ali/1.0/"`.

**Criterion**
`` element content is just a string (URL).

**Criterion**:
Attributes values of `content-type=` of element `` are any one of the
following:
```
"cc0license"
"ccbylicense"
"ccbysalicense"
"ccbynclicense"
"ccbyncsalicense"
"ccbyndlicense"
"ccbyncndlicense"
```

**Criterion**:
If the non-whitespace string contents of `` has one of the following prefixes:
```
"https://creativecommons.org/publicdomain/zero/"
'https://creativecommons.org/licenses/by/"
'https://creativecommons.org/licenses/by-sa/"
'https://creativecommons.org/licenses/by-nc/"
'https://creativecommons.org/licenses/by-nc-sa/"
'https://creativecommons.org/licenses/by-nd/"
'https://creativecommons.org/licenses/by-nc-nd/"
```
then the `content-type=` value, if present, must equal the corresponding respective
value:
```
"cc0license"
"ccbylicense"
"ccbysalicense"
"ccbynclicense"
"ccbyncsalicense"
"ccbyndlicense"
"ccbyncndlicense"
```

### `` element tree

**Criterion**:
Elements `` and `` contain a sequence of child elements with tags
matching the regular expression:

`()* ()*`

**Criterion**:
`` elements contain a sequence of child elements with tags and constraints matching
the regular expression:

`()? ($P_LEVEL)* (<sec>)*`

**Definition**:
Elements with constraint `$P_LEVEL` have any one of the following tags:
```
<code>
<disp-quote>
<list>
<p>
<preformat>
<table-wrap>
```

### `<back>` element tree

**Criterion**
`<back>` has exactly one child element `<ref-list>`.

**Criterion**:
The `<ref-list>` element contain a sequence of child elements with tags matching the
regular expression:

`(<title>)? (<ref>)*`

**Criterion**:
`<ref>` elements have one attribute and it is `id=`.

**Criterion**:
`<ref>` elements have exactly one child element of `<element-citation>`.

**Criterion**:
`<element-citation>` elements only have child elements with any one the following tags:
```
<article-title>
<comment>
<date-in-citation>
<edition>
<fpage>
<isbn>
<issn>
<issue>
<lpage>
<person-group>
<pub-id>
<publisher-loc>
<publisher-name>
<source>
<uri>
<volume>
```

**Criterion**:
For `<element-citation>` elements, there are one or zero child elements for each
possible tag, with the exception of `<pub-id>`, which can appear more than once.

**Criterion**:
For `<element-citation>` elements, all child elements with tag `<pub-id>` have different
values for attribute `pub-id-type=`.

**Criterion**:
`<person-group>` elements have an attribute `person-group-type=` with either value
`"author"` or `"editor"`.

**Criterion**:
`<person-group>` elements have zero or more child elements with either tag `<name>` or
`<string-name>`.

**Criterion**:
The following elements have string content only:
```
<comment>
<fpage>
<isbn>
<issn>
<issue>
<lpage>
<publisher-loc>
<publisher-name>
<string-name>
<uri>
<volume>
```

**Criterion**:
`<date-in-citation>` attribute `content-type=` equals value `"access-date"`.

**Criterion**:
`<date-in-citation>` have all child elements with tag `<year>`, `<month>`, or `<day>`
and at most once for each tag.

**Criterion**:
`<date-in-citation>` elements contain child element `<year>`.

**Criterion**:
`<date-in-citation>` has child element `<month>` only if `<year>` is also present.

**Criterion**:
`<date-in-citation>` has child element `<day>` only if `<month>` is also present.

**Criterion**:
`<edition>` elements have just an integer as content and do not have any non-digit
characters.

**Criterion**:
`<pub-id>` `pub-id-type=` attributes have values `"doi"` or `"pmid"`.

**Criterion**:
`<pub-id>` elements with attribute value `pub-id-type="doi"` have string content
that starts with "10." and not "http".

### HTML-like content

**Criterion**:
Elements with constraint `$HYPOTEXT` have tag `{TYPO_TAG}`.

**Criterion**:
Elements with constraint `$HYPOTEXT` have all child elements also with constraint
`$HYPOTEXT`.

#### Hypertext elements

**Criterion**:
Elements with constraint `$HYPERTEXT` have any one of the following tags
```
<ext-link>
<xref>
{TYPO_TAG}
```

**Criterion**:
Elements with constraint `$HYPERTEXT` and `{TYPO_TAG}` have all child elements with
constraint `$HYPERTEXT`.

**Criterion**:
Elements with tag `<ext-link>` have all child elements with constraint `$HYPOTEXT`.

**Criterion**:
Every `<ext-link>` has an `href=` attribute from the XML namespace
`http://www.w3.org/1999/xlink`.

**Criterion**:
Every `<ext-link>` attribute `ext-link-type=` takes the value `"uri"` (if present).

**Criterion**:
Elements with tag `<xref>` have all child elements with constraint `$HYPOTEXT`.

**Criterion**:
Every element with tag `<xref>` and constraint `$HYPERTEXT` has an attribute `rid=`.

**Criterion**:
Every element with tag `<xref>` and constraint `$HYPERTEXT` has no attribute other than
`rid=`.

#### Paragraph elements

**Criterion**:
Elements with constraint `$P_CHILD` have one of the following tags
```
<code>
<def-list>
<disp-quote>
<ext-link>
<list>
<preformat>
<xref>
{TYPO_TAG}
```

**Criterion**:
`<p>` elements have all child elements with constraint `$P_CHILD`.

**Criterion**:
Elements with constraint `$P_CHILD` and `{TYPO_TAG}` but not tag `<sup>` have constraint
`$HYPERTEXT`.

**Criterion**:
Elements with constraint `$P_CHILD` and tag `<sup>` have constraint `$HYPERTEXT` or `$CITATION` (but not both).

#### Citation elements

**Criterion**:
Elements with constraint `$CITATION` and tag `<sup>` have text content of:

* optional whitespace before the first child element
* optional whitespace after the last child element, and
* a comma and optional whitespace between child elements.

**Criterion**:
Elements with constraint `$CITATION` have all child elements with constraint `$CITATION` and tag `<xref>`.

**Criterion**:
Elements with constraint `$CITATION` and tag `<xref>` have an attributes of `ref-type=`
with value `bibr`.

**Criterion**:
Elements with constraint `$CITATION` and tag `<xref>` have exactly two attributes of
`rid=` and `ref-type=`.

**Criterion**:
Elements with constraint `$CITATION` and tag `<xref>` have a value for `rid=` that
matches the value of attribute `id=` in an element with tag `<ref>`.

**Criterion**:
Elements with constraint `$CITATION` and tag `<xref>` have content of only
a single integer, surrounded by optional whitespace, and no child elements.
The integer corresponds to the position in `<ref-list>` of the `<ref>` element
with an `id=` attribute value that equals the `rid=` attribute of the `<xref>` element.

#### List elements

**Criterion**:
`<list>` element attributes `list-type=` have either value `"bullet"` or `"order"`.

**Criterion**:
`<list>` elements only have child elements with tag `<list-item>`.

**Criterion**:
`<list-item>` elements only have child elements with either tag `<p>` or `<list>`.

**Criterion**:
`<def-list>` elements only have child elements with tag `<def-item>`.

**Criterion**:
`<def-list>` elements only have child elements with either tag `<term>` or `<def>`.

**Criterion**:
`<term>` elements only have child elements with `{TYPO_TAG}` or `{LINK_TAG}`.

**Criterion**:
`<term>` elements have all child elements with constraint `$HYPERTEXT`.

**Criterion**:
`<def>` elements only have child elements with tag `<p>`.

#### Table elements

**Criterion**:
`<table-wrap>` elements contains a single `<table>` element.

**Criterion**:
`<table>` child elements are `<thead>` or `<tbody>` elements.

**Criterion**:
`<thead>` and `<tbody>` child elements are `<tr>` elements.

**Criterion**:
`<tr>` child elements are `<th>` or `<td>` elements.

**Criterion**:
`<th>` and `<td>` elements have all child elements with constraint `$P_CHILD`.

**Criterion**:
`<th>` and `<td>` attributes `align=` have values `"left"`, `"center"`, or `"right"`.

#### Other elements

**Criterion**:
`<disp-quote>` elements only contain child elements with tag `<p>`.

**Criterion**:
`<code>` and `<preformat>` elements have all child elements with constraint `$HYPERTEXT`.

Interoperability Issues
-----------------------

* HTML `<table>` has `<thead>` before `<tbody>`
* HTML `<table>` probably (?) has exactly one `<tbody>` and at most one `<thead>`
* `<xref>` attribute `rid=` values that might not match an `id=` attribute
of an element converted to HTML with the same `id=` (e.g., `<sec>`, `<ref>`).

</article></body></html>}}}}}}