A reply context is the display of what a reply post is in reply to, including linking to that original post with in-reply-to markup, showing some amount of that original post like author name, icon, summary / ellipsed content, and datetime published.
Reply contexts became more important when replies started to have their own top level permalinks, which appears to have been popularized by Twitter treating @-replies like any other tweet. Twitter started by displaying the immediate reply-context of what an @-reply was in reply to, but eventually started recursively displaying reply-contexts on up to the tweet at the start of a thread.
Why show reply contexts?
How should reply contexts be displayed?
For general guidance on primarily textual reply-context presentation best practices, see
reply to a photo
How to reply to a photo, see this real world photo reply-context example:
How should reply contexts be marked up?
<div class="h-entry"> <div class="p-in-reply-to h-cite"> <p class="p-author h-card">Emily Smith</p> <p class="p-content">Blah blah blah blah</p> <a class="u-url" href="permalink"><time class="dt-published">YYYY-MM-DD</time></a> <p>Accessed on: <time class="dt-accessed">YYYY-MM-DD</time></p> </div> <p class="p-author h-card">James Bloggs</p> <p class="e-content">Ha ha ha too right emily</p> </div>
Why use h-cite instead of h-entry for reply contexts?
Why not use h-entry in addition?
There is a broad spectrum of reply-context presentation that can be roughly ordered in terms of fidelity and difficulty, from simplest/easiest to richest (silo-parity) and most challenging.
Since a reply has to be in-reply-to to something (a URL), the simplest reply context is to simply show the URL (hyperlinked of course) of the original with perhaps a text label like:
In reply to: hyperlinked-URL-of-original
IndieWeb Examples of URL-only :
The next easiest thing to add is the icon (or avatar) of the author of the original post.
For example, replies to tweets can retrieve the icon purely by inspecting the URL for the first path segment for the Twitter username, and then embedding a dynamic image redirect URL, e.g. https://twitter.com/benwerd/profile_image: See Twitter: Profile Image URLs for details.
Replies to indieweb posts can retrieve the icon from a nicknames-cache.
IndieWeb Examples of icon plus URL:
Next, you can sometimes determine the author's name from a nicknames-cache.
Determining the author's name and their icon (more broadly/reliably than above), requires implementing the authorship algorithm on the original post, which requires more work than just parsing it for its h-entry as above.
IndieWeb Examples of icon URL dt-published and author name:
The original's published date is the next interesting (and slightly harder) thing to retrieve and display in a reply-context. With this step, an implementation must retrieve the original post and determine its "dt-published" (e.g. from parsing its h-entry).
The date and time of the original should be displayed and hyperlinked to the original's URL.
IndieWeb Examples of icon URL and dt-published:
Lastly, the content of an original post is the hardest thing to display well in a singular reply-context, due to numerous additional variables. Some challenges:
IndieWeb Examples of icon URL dt-published author name and original content:
Main article: recursive reply-contexts
(previously called: reply thread and history thread)
Popular silos (e.g. Twitter) recursively display reply-contexts of originals/replies from the tweet that you're replying to, and if it was a reply itself, what it replies to etc. on up through the original tweet at the start of the thread.
IndieWeb Examples of icon URL dt-published author name original content for reply-contexts up through the original post that started the thread:
Main article: reply-context-examples
In order of deployment:
of silo posts
Reply contexts where the original is on a silo may sometimes need or deserve special treatment.
If you reply to a silo post where the silo does not mark up their HTML pages with h-entry, (e.g. post a comment on your own site, and the POSSE it to an Instagram post), you will need to do further processing in order to display the reply context as high fidelity as other indieweb posts.
You may find the following tools useful:
Though one advantage of storing and showing a reply-context is freezing the original context of what you're replying to, it may make sense to accept some updates.
Downstream vs Upstream
Webmentions to responses inefficiency
Even though possible, it may be inefficient to send individual webmentsions from an original post to all the responses of that post.
With each nth response (reply, like, etc.), the source then has to send n-1 webmentions to all the previous responses.
It results in a geometrically growing responsibility of sending webmentions.
There may be other notification mechanisms that should be explored such as PuSH, e.g. if a response wants updates on that post in particular, perhaps it could do PuSH discover on the post, and then explicitly subscribe to receive PuSH updates on that post. (suggestion from Aaron Parecki)
Events RSVPs Invitations
So that they can update their respective reply-contexts accordingly.
See event: Response context CRUD for more details on how event posts should send webmentions to enable RSVP/reply-context CRUD.
Fork On Text
Fork On Text is an open source project in development to provide reply-contexts as a service, self-described as "Service to upgrade simple reply contexts with full reply contexts by fetching and storing remote content."
Main article: reply-context-examples#Silo_Examples