In order to ensure interoperability between Indieweb WordPress plugins, as much as possible, the same data structures should be used.

Metadata

WordPress allows for for metadata to be attached to various objects.

By default, WordPress includes a metadata table for post types(posts, pages, etc), comments, and users.

WordPress contains a Metadata API that it uses to handle metadata. Metadata can also be created for other object types, but is not part of a default installation.

Microformats data

Proposal by Ryan Barrett: store a post's top-level microformats2 string properties in post metadata with the property names as the keys, prefixed by mf2_. wordpress-micropub does this now.

For example, this RSVP snippet:

<data class="p-rsvp" value="yes">I'm in!</data>

would be stored in post meta with the key mf2_rsvp and value yes.

For mf2 properties with multiple values, just store multiple values for the post meta key. WordPress supports this with e.g. add_post_meta.

Use code like this to get multiple post meta values in a single database query:

$query = new WP_Query(array('meta_query' => array(array(
  'key' => 'meta_key',
  'value' => array('mf2_name', 'mf2_content', ...),
  'compare' => 'IN'))));

use uf2 instead of mf2

Tantek Çelik minor revision of Ryan Barrett's proposal - same but use "uf2" instead of "mf2" because the "u" looks closer to a µ for "micro":

Store a post's top-level microformats2 string properties in post metadata with the property names as the keys, prefixed by uf2_. For example, this RSVP snippet:

<data class="p-rsvp" value="yes">I'm in!</data>

would be stored in post meta with the key uf2_rsvp and value yes.

For uf2 properties with multiple values, just store multiple values for the post meta key. WordPress supports this with e.g. add_post_meta.

Use code like this to get multiple post meta values in a single database query:

$query = new WP_Query(array('meta_query' => array(array(
  'key' => 'meta_key',
  'value' => array('uf2_name', 'uf2_content', ...),
  'compare' => 'IN'))));

why mf2 is better than uf2

Per Ryan Barrett's follow-up in IRC:

• mf2 is seen in existing code much more often than uf2
  • e.g. php-mf2, mf2py, mf2util, etc
• mf2 is more obvious (and maybe less clever)

Mirror the structure of jf2

David Shanske has proposed that the structure of storage in WordPress meta mirror the simplified jf2 structure to allow for more consistency.

Location

WordPress currently provides a Geodata data structure.

• geo_latitude REQUIRED

   (float) decimal degrees -90 to 90 (negative values are in the southern hemisphere). 

• geo_longitude REQUIRED

  (float) decimal degrees -180 to 180 (negative values are in the western hemisphere). 

• geo_altitude OPTIONAL

  (int) Not part of the WordPress standard

• geo_public OPTIONAL

  (int) is the geodata public (1) or private (0)? If value is missing, assume public. 

• geo_address OPTIONAL

    (string) freeform textual description of coordinates. 
   "221B Baker St, Westminster, London NW1 6XE, UK", 
   "Pasadena, CA", "Soho, NYC", "Idaho", etc. 
   Accuracy level and language is arbitrary. 

As an enhancement for geo_address, which is freeform text, David Shanske is implementing mf2_adr in his Simple Location plugin, which is an h-adr stored to allow for structured data. geo_address will remain as the "Display Name" If blank, a name will be generated from the h-adr components.

• street-address - house/apartment number, floor, street name
• extended-address - additional street details/boro/neighborhood/etc
• locality - city/town/village
• region - state/county/province
• postal-code
• country-name
• country-code

As of WordPress 4.4, metadatas is allowed to attach to a taxonomy term. Therefore, David Shanske is planning to update the above to declare a venue as a taxonomy term, and address fields as taxonomy term meta attached to them.

User

WordPress supports user metadata. As part of the revamping of the Indieweb plugin, metadata reflecting rel-me and reflecting h-card properties were added to the user profile.

However, the rel-me silo URLs were not prefaced with mf2_ as using just the sitename...e.g. twitter instead of mf2_twitter allows for cross compatibility with other plugins that store this data.

Comment

Webmention Plugin adds an additional comment type of 'webmention' to comments.

Semantic Linkbacks stores extra information in the comment metadata.

• semantic_linkbacks_canonical - the canonical source url
• semantic_linkbacks_avatar - the author avatar URL
• semantic_linkbacks_type - the comment type. The plugin currently supports the following types:
  • mention(default)
  • reply
  • repost
  • like
  • favorite
  • tag
  • rsvp:yes, rsvp:no, rsvp:maybe, rsvp:invited, rsvp:tracking.

Taxonomies

A taxonomy called 'kind' is currently used for the Post Kinds Plugin. This is meant to indicate the post kind

Current post kinds are all lowercase. List appears below:

• article
• note
• reply
• repost
• like
• favorite
• bookmark
• photo
• tag
• rsvp
• listen
• watch
• play
• checkin
• wish

Many can be disabled by sites not using them

Considering the following additions:

• weather
• exercise

Post Kinds Plugin

In response to Ryan Barrett's proposal to organize using mf2_ as a key prefix, David Shanske changed to using 'mf2_cite' as a key instead of 'response'. All fields are optional(See Below)

• mf2_cite
  • ['url'] - The URL the post is responding to.
  • ['name'] - The title of same
  • ['author'] - The URL of an h-card (if external)
  • ['published'] - URL publish date in ISO8601 with timezone offset
  • ['updated'] - URL updated date in ISO8601 with timezone offset
  • ['publication'] - The name of the site, or for citing articles in publications with more than one author.
  • ['content'] - the content or partial content of the work itself.
  • ['card']['name'] = Author Name / Artist Name
  • ['card']['photo'] = Author photo
• mf2_in-reply-to, mf2_like-of, mf2_repost-of are now supported as URL properties. Any details are still stored in mf2_cite.
• mf2_dt-start and mf2_dt-end to indicate duration
• mf2_duration is deprecated in the interface, but will still be used in lieu of dt-end minus dt-start if set.

Future Data Plans

• All properties to support either multi-dimensional or not, in order to allow for multi-replies and other multiple property situations

Deprecated

The Post Kinds Plugin, prior to Version 1.2.0,used the following array of metadata using the key 'response' to store details on what a post is responding to. All fields are optional.

• response['url'] - The URL the post is responding to.
• response['title'] - The title of same
• response['author'] - The author name
• response['icon'] - The author icon/image/avatar
• response['published'] - URL publish date in ISO8601 with timezone offset
• response['content'] - Content or a Citation...to allow for an excerpt for context.

Syndication

David Shanske's Syndication Links plugin uses a single data field with the key 'syndication_urls' with URLs separated by newlines for syndication URLs to be marked up for syndication. Entry is a textbox with one URL per line. This means there is no requirement that WordPress know about a service to add a link to it.

It also supports reading from mf2_syndication if it exists per the standardization proposal.

The plugin formerly stored an array of URLs of various syndication services under the metadata key 'synlinks'. This is now deprecated.

Themes

Both David Shanske's mf2_s fork and  Matthias Pfefferle's SemPress theme register theme support for 'microformats2'. This allows both themes to tell plugins and other functions that they support the microformats2 standard and to act appropriately.

This usually means workarounds such as adding in microformats by the plugin can and should be disabled if this is set.