- From: Ian Hickson <ian@hixie.ch>
- Date: Thu, 23 Apr 2009 20:46:09 +0000 (UTC)
[bcc'ed previous participants in this discussion]
Earlier this year I asked for use cases that HTML5 did not yet cover, with
an emphasis on use cases relating to semantic microdata. I list below the
use cases and requirements that I derived from the response to that
request, and from related discussions.
I would appreciate it if people could review this list for errors or
important omissions, before I go through the list to work out whether
these use cases already have solutions, or whether we should have
solutions for these use cases in HTML, or whether we should address these
use cases with other technologies, or whatnot.
I encourage people to focus on the use cases themselves, rather than on
potential solutions; various solutions to all these use cases have already
been argued in great detail and I have already read all those e-mails,
blog comments, wiki faqs, etc, carefully.
My primary concern right now is in making sure that these are indeed the
use cases people care about, so that whatever we add to the spec can be
carefully evaluated to make sure it is in fact solving the problems that
we want solving.
==============================================================================
Exposing known data types in a reusable way
USE CASE: Exposing calendar events so that users can add those events to
their calendaring systems.
SCENARIOS:
* A user visits the Avenue Q site and wants to make a note of when
tickets go on sale for the tour's stop in his home town. The site says
"October 3rd", so the user clicks this and selects "add to calendar",
which causes an entry to be added to his calendar.
* A student is making a timeline of important events in Apple's history.
As he reads Wikipedia entries on the topic, he clicks on dates and
selects "add to timeline", which causes an entry to be added to his
timeline.
* TV guide listings - browsers should be able to expose to the user's
tools (e.g. calendar, DVR, TV tuner) the times that a TV show is on.
* Paul sometimes gives talks on various topics, and announces them on
his blog. He would like to mark up these announcements with proper
scheduling information, so that his readers' software can
automatically obtain the scheduling information and add it to their
calendar. Importantly, some of the rendered data might be more
informal than the machine-readable data required to produce a calendar
event. Also of importance: Paul may want to annotate his event with a
combination of existing vocabularies and a new vocabulary of his own
design. (why?)
* David can use the data in a web page to generate a custom browser UI
for adding an event to our calendaring software without using brittle
screen-scraping.
REQUIREMENTS:
* Should be discoverable.
* Should be compatible with existing calendar systems.
* Should be unlikely to get out of sync with prose on the page.
* Shouldn't require the consumer to write XSLT or server-side code to
read the calendar information.
* Machine-readable event data shouldn't be on a separate page than
human-readable dates.
* The information should be convertible into a dedicated form (RDF,
JSON, XML, iCalendar) in a consistent manner, so that tools that use
this information separate from the pages on which it is found have a
standard way of conveying the information.
* Should be possible for different parts of an event to be given in
different parts of the page. For example, a page with calendar events
in columns (with each row giving the time, date, place, etc) should
still have unambiguous calendar events parseable from it.
---------------------------------------------------------------------------
USE CASE: Exposing contact details so that users can add people to their
address books or social networking sites.
SCENARIOS:
* Instead of giving a colleague a business card, someone gives their
colleague a URL, and that colleague's user agent extracts basic
profile information such as the person's name along with references to
other people that person knows and adds the information into an
address book.
* A scholar and teacher wants other scholars (and potentially students)
to be able to easily extract information about who he is to add it to
their contact databases.
* Fred copies the names of one of his Facebook friends and pastes it
into his OS address book; the contact information is imported
automatically.
* Fred copies the names of one of his Facebook friends and pastes it
into his Webmail's address book feature; the contact information is
imported automatically.
* David can use the data in a web page to generate a custom browser UI
for including a person in our address book without using brittle
screen-scraping.
REQUIREMENTS:
* A user joining a new social network should be able to identify himself
to the new social network in way that enables the new social network
to bootstrap his account from existing published data (e.g. from
another social nework) rather than having to re-enter it, without the
new site having to coordinate (or know about) the pre-existing site,
without the user having to give either sites credentials to the other,
and without the new site finding out about relationships that the user
has intentionally kept secret.
(http://w2spconf.com/2008/papers/s3p2.pdf)
* Data should not need to be duplicated between machine-readable and
human-readable forms (i.e. the human-readable form should be
machine-readable).
* Shouldn't require the consumer to write XSLT or server-side code to
read the contact information.
* Machine-readable contact information shouldn't be on a separate page
than human-readable contact information.
* The information should be convertible into a dedicated form (RDF,
JSON, XML, vCard) in a consistent manner, so that tools that use this
information separate from the pages on which it is found have a
standard way of conveying the information.
* Should be possible for different parts of an event to be given in
different parts of the page. For example, a page with contact details
for people in columns (with each row giving the name, telephone
number, etc) should still have unambiguous grouped contact details
parseable from it.
---------------------------------------------------------------------------
USE CASE: Allow users to maintain bibliographies or otherwise keep track
of sources of quotes or references.
SCENARIOS:
* Frank copies a sentence from Wikipedia and pastes it in some word
processor: it would be great if the word processor offered to
automatically create a bibliographic entry.
* Patrick keeps a list of his scientific publications on his web site.
He would like to provide structure within this publications page so
that Frank can automatically extract this information and use it to
cite Patrick's papers without having to transcribe the bibliographic
information.
* A scholar and teacher wants other scholars (and potentially students)
to be able to easily extract information about what he has published
to add it to their bibliographic applications.
* A scholar and teacher wants to publish scholarly documents or content
that includes extensive citations that readers can then automatically
extract so that they can find them in their local university library.
These citations may be for a wide range of different sources: an
interview posted on YouTube, a legal opinion posted on the Supreme
Court web site, a press release from the White House.
* A blog, say htmlfive.net, copies content wholesale from another, say
blog.whatwg.org (as permitted and encouraged by the license). The
author of the original content would like the reader of the reproduced
content to know the provenance of the content. The reader would like
to find the original blog post so he can leave comments for the
original author.
* Chaals could improve the Opera intranet if he had a mechanism for
identifying the original source of various parts of a page. (why?)
REQUIREMENTS:
* Machine-readable bibliographic information shouldn't be on a separate
page than human-readable bibliographic information.
* The information should be convertible into a dedicated form (RDF,
JSON, XML, BibTex) in a consistent manner, so that tools that use this
information separate from the pages on which it is found have a
standard way of conveying the information.
---------------------------------------------------------------------------
USE CASE: Help people searching for content to find content covered by
licenses that suit their needs.
SCENARIOS:
* If a user is looking for recipes of pies to reproduce on his blog, he
might want to exclude from his results any recipes that are not
available under a license allowing non-commercial reproduction.
* Lucy wants to publish her papers online. She includes an abstract of
each one in a page, but because they are under different copyright
rules, she needs to clarify what the rules are. A harvester such as
the Open Access project can actually collect and index some of them
with no problem, but may not be allowed to index others. Meanwhile, a
human finds it more useful to see the abstracts on a page than have to
guess from a bunch of titles whether to look at each abstract.
* There are mapping organisations and data producers and people who take
photos, and each may place different policies. Being able to keep that
policy information helps people with further mashups avoiding
violating a policy. For example, if GreatMaps.com has a public domain
policy on their maps, CoolFotos.org has a policy that you can use data
other than images for non-commercial purposes, and Johan Ichikawa has
a photo there of my brother's cafe, which he has licensed as "must pay
money", then it would be reasonable for me to copy the map and put it
in a brochure for the cafe, but not to copy the data and photo from
CoolFotos. On the other hand, if I am producing a non-commercial guide
to cafes in Melbourne, I can add the map and the location of the cafe
photo, but not the photo itself.
* At University of Mary Washington, many faculty encourage students to
blog about their studies to encourage more discussion using an
instance of WordPress MultiUser. A student with have a blog might be
writing posts relevant to more than one class. Professors would like
to then aggregate relevant posts into one blog.
* Tara runs a video sharing web site for people who want licensing
information to be included with their videos. When Paul wants to blog
about a video, he can paste a fragment of HTML provided by Tara
directly into his blog. The video is then available inline in his
blog, along with any licensing information about the video.
* Fred's browser can tell him what license a particular video on a site
he is reading has been released under, and advise him on what the
associated permissions and restrictions are (can he redistribute this
work for commercial purposes, can he distribute a modified version of
this work, how should he assign credit to the original author, what
jurisdiction the license assumes, whether the license allows the work
to be embedded into a work that uses content under various other
licenses, etc).
REQUIREMENTS:
* Content on a page might be covered by a different license than other
content on the same page.
* When licensing a subpart of the page, existing implementations must
not just assume that the license applies to the whole page rather than
just part of it.
* License proliferation should be discouraged.
* License information should be able to survive from one site to another
as the data is transfered.
* Expressing copyright licensing terms should be easy for content
creators, publishers, and redistributors to provide.
* It should be more convenient for the users (and tools) to find and
evaluate copyright statements and licenses than it is today.
* Shouldn't require the consumer to write XSLT or server-side code to
process the license information.
* Machine-readable licensing information shouldn't be on a separate page
than human-readable licensing information.
* There should not be ambiguous legal implications.
==============================================================================
Annotations
USE CASE: Annotate structured data that HTML has no semantics for, and
which nobody has annotated before, and may never again, for private use or
use in a small self-contained community.
SCENARIOS:
* A group of users want to mark up their iguana collections so that they
can write a script that collates all their collections and presents
them in a uniform fashion.
* A scholar and teacher wants other scholars (and potentially students)
to be able to easily extract information about what he teaches to add
it to their custom applications.
* The list of specifications produced by W3C, for example, and various
lists of translations, are produced by scraping source pages and
outputting the result. This is brittle. It would be easier if the data
was unambiguously obtainable from the source pages. This is a custom
set of properties, specific to this community.
* Chaals wants to make a list of the people who have translated W3C
specifications or other documents, and then use this to search for
people who are familiar with a given technology at least at some
level, and happen to speak one or more languages of interest.
* Chaals wants to have a reputation manager that can determine which of
the many emails sent to the WHATWG list might be "more than usually
valuable", and would like to seed this reputation manager from
information gathered from the same source as the scraper that
generates the W3C's TR/ page.
* A user wants to write a script that finds the price of a book from an
Amazon page.
* Todd sells an HTML-based content management system, where all
documents are processed and edited as HTML, sent from one editor to
another, and eventually published and indexed. He would like to build
up the editorial metadata used by the system within the HTML documents
themselves, so that it is easier to manage and less likely to be lost.
* Tim wants to make a knowledge base seeded from statements made in
Spanish and English, e.g. from people writing down their thoughts
about George W. Bush and George H.W. Bush, and has either convinced
the people making the statements that they should use a common
language-neutral machine-readable vocabulary to describe their
thoughts, or has convinced some other people to come in after them and
process the thoughts manually to get them into a computer-readable
form.
REQUIREMENTS:
* Vocabularies can be developed in a manner that won't clash with future
more widely-used vocabularies, so that those future vocabularies can
later be used in a page making use of private vocabularies without
making the earlier annotations ambiguous.
* Using the data should not involve learning a plethora of new APIs,
formats, or vocabularies (today it is possible, e.g., to get the price
of an Amazon product, but it requires learning a new API; similarly
it's possible to get information from sites consistently using 'class'
values in a documented way, but doing so requires learning a new
vocabulary).
* Shouldn't require the consumer to write XSLT or server-side code to
process the annotated data.
* Machine-readable annotations shouldn't be on a separate page than
human-readable annotations.
* The information should be convertible into a dedicated form (RDF,
JSON, XML) in a consistent manner, so that tools that use this
information separate from the pages on which it is found have a
standard way of conveying the information.
* Should be possible for different parts of an item's data to be given
in different parts of the page, for example two items described in the
same paragraph. ("The two lamps and A and B. The first is $20, the
second $30. The first is 5W, the second 7W.")
* It should be possible to define globally-unique names, but the syntax
should be optimised for a set of predefined vocabularies.
* Adding this data to a page should be easy.
* The syntax for adding this data should encourage the data to remain
accurate when the page is changed.
* The syntax should be resilient to intentional copy-and-paste
authoring: people copying data into the page from a page that already
has data should not have to know about any declarations far from the
data.
* The syntax should be resilient to unintentional copy-and-paste
authoring: people copying markup from the page who do not know about
these features should not inadvertently mark up their page with
inapplicable data.
---------------------------------------------------------------------------
USE CASE: Allow authors to annotate their documents to highlight the key
parts, e.g. as when a student highlights parts of a printed page, but in a
hypertext-aware fashion.
SCENARIOS:
* Fred writes a page about Napoleon. He can highlight the word Napoleon
in a way that indicates to the reader that that is a person. Fred can
also annotate the page to indicate that Napoleon and France are
related concepts.
==============================================================================
Search
USE CASE: Site owners want a way to provide enhanced search results to the
engines, so that an entry in the search results page is more than just a
bare link and snippet of text, and provides additional resources for users
straight on the search page without them having to click into the page and
discover those resources themselves.
SCENARIOS:
* For example, in response to a query for a restaurant, a search engine
might want to have the result from yelp.com provide additional
information, e.g. info on price, rating, and phone number, along with
links to reviews or photos of the restaurant.
REQUIREMENTS:
* Information for the search engine should be on the same page as
information that would be shown to the user if the user visited the
page.
---------------------------------------------------------------------------
USE CASE: Search engines and other site categorisation and aggregation
engines should be able to determine the contents of pages with more
accuracy than today.
SCENARIOS
* Students and teachers should be able to discover each other -- both
within an institution and across institutions -- via their blogging.
* A blogger wishes to categorise his posts such that he can see them in
the context of other posts on the same topic, including posts by
unrelated authors (i.e. not via a pre-agreed tag or identifier, not
via a single dedicated and preconfigured aggregator).
* A user whose grandfather is called "Napoleon" wishes to ask Google the
question "Who is Napoleon", and get as his answer a page describing
his grandfather.
* A user wants to ask about "Napoleon" but, instead of getting an
answer, wants the search engine to ask him which Napoleon he wants to
know about.
REQUIREMENTS:
* Should not disadvantage pages that are more useful to the user but
that have not made any effort to help the search engine.
* Should not be more susceptible to spamming than today's markup.
---------------------------------------------------------------------------
USE CASE: Web browsers should be able to help users find information
related to the items discussed by the page that they are looking at.
SCENARIOS:
* Finding more information about a movie when looking at a page about
the movie, when the page contains detailed data about the movie.
* For example, where the movie is playing locally.
* For example, what your friends thought of it.
* Exposing music samples on a page so that a user can listen to all the
samples.
* Students and teachers should be able to discover each other -- both
within an institution and across institutions -- via their blogging.
* David can use the data in a web page to generate a custom browser UI
for calling a phone number using our cellphone without using brittle
screen-scraping.
REQUIREMENTS:
* Should be discoverable, because otherwise users will not use it, and
thus users won't be helped.
* Should be consistently available, because if it only works on some
pages, users will not use it (see, for instance, the rel=next story).
* Should be bootstrapable (rel=next failed because UAs didn't expose it
because authors didn't use it because UAs didn't expose it).
---------------------------------------------------------------------------
USE CASE: Finding distributed comments on audio and video media.
SCENARIOS:
* Sam has posted a video tutorial on how to grow tomatoes on his video
blog. Jane uses the tutorial and would like to leave feedback to
others that view the video regarding certain parts of the video she
found most helpful. Since Sam has comments disabled on his blog, his
users cannot comment on the particular sections of the video other
than linking to it from their blog and entering the information there.
Jane uses a video player that aggregates all the comments about the
video found on the Web, and displays them as subtitles while she
watches the video.
REQUIREMENTS:
* It shouldn't be possible for Jane to be exposed to spam comments.
* The comment-aggregating video player shouldn't need to crawl the
entire Web for each user independently.
---------------------------------------------------------------------------
USE CASE: Allow users to price-check digital media (music, TV shows, etc)
and purchase such content without having to go through a special website
or application to acquire it, and without particular retailers being
selected by the content's producer or publisher.
SCENARIOS:
* Joe wants to sell his music, but he doesn't want to sell it through a
specific retailer, he wants to allow the user to pick a retailer. So
he forgoes the chance of an affiliate fee, negotiates to have his
music available in all retail stores that his users might prefer, and
then puts a generic link on his page that identifies the product but
doesn't identifier a retailer. Kyle, a fan, visits his page, clicks
the link, and Amazon charges his credit card and puts the music into
his Amazon album downloader. Leo instead clicks on the link and is
automatically charged by Apple, and finds later that the music is in
his iTunes library.
* Manu wants to go to Joe's website but check the price of the offered
music against the various retailers that sell it, without going to
those retailers' sites, so that he can pick the cheapest retailer.
* David can use the data in a web page to generate a custom browser UI
for buying a song from our favorite online music store without using
brittle screen-scraping.
REQUIREMENTS:
* Should not be easily prone to clickjacking (sites shouldn't be able to
charge the user without the user's consent).
* Should not make transactions harder when the user hasn't yet picked a
favourite retailer.
==============================================================================
Cross-site communication
USE CASE: Copy-and-paste should work between Web apps and native apps and
between Web apps and other Web apps.
SCENARIOS:
* Fred copies an e-mail from Apple Mail into GMail, and the e-mail
survives intact, including headers, attachments, and multipart/related
parts.
* Fred copies an e-mail from GMail into Hotmail, and the e-mail survives
intact, including headers, attachments, and multipart/related parts.
---------------------------------------------------------------------------
USE CASE: Allow users to share data between sites (e.g. between an online
store and a price comparison site).
SCENARIOS
* Lucy is looking for a new apartment and some items with which to
furnish it. She browses various web pages, including apartment
listings, furniture stores, kitchen appliances, etc. Every time she
finds an item she likes, she points to it and transfers its details to
her apartment-hunting page, where her picks can be organized, sorted,
and categorized.
* Lucy uses a website called TheBigMove.com to organize all aspects of
her move, including items that she is tracking for the move. She goes
to her "To Do" list and adds some of the items she collected during
her visits to various Web sites, so that TheBigMove.com can handle the
purchasing and delivery for her.
REQUIREMENTS:
* Should be discoverable, because otherwise users will not use it, and
thus users won't be helped.
* Should be consistently available, because if it only works on some
pages, users will not use it (see, for instance, the rel=next story).
* Should be bootstrapable (rel=next failed because UAs didn't expose it
because authors didn't use it because UAs didn't expose it).
* The information should be convertible into a dedicated form (RDF,
JSON, XML) in a consistent manner, so that tools that use this
information separate from the pages on which it is found have a
standard way of conveying the information.
==============================================================================
Blogging
USE CASE: Remove the need for feeds to restate the content of HTML pages
(i.e. replace Atom with HTML).
SCENARIOS:
* Paul maintains a blog and wishes to write his blog in such a way that
tools can pick up his blog post tags, authors, titles, and his
blogroll directly from his blog, so that he does not need to maintain
a parallel version of his data in a "structured format." In other
words, his HTML blog should be usable as its own structured feed.
---------------------------------------------------------------------------
USE CASE: Allow users to compare subjects of blog entries when the
subjects are hard to tersely identify relative to other subjects in the
same general area.
SCENARIOS:
* Paul blogs about proteins and genes. His colleagues also blog about
proteins and genes. Proteins and genes are identified by long
hard-to-compare strings, but Paul and his colleagues can determine if
they are talking about the same things by having their user agent
compare some sort of flags embedded in the blogs.
* Rob wants to publish a large vocabulary in RDFS and/or OWL. Rob also
wants to provide a clear, human readable description of the same
vocabulary, that mixes the terms with descriptive text in HTML.
==============================================================================
Data extraction from uncooperative sources
USE CASE: Getting data out of poorly written Web pages, so that the user
can find more information about the page's contents.
SCENARIOS:
* Alfred merges data from various sources in a static manner, generating
a new set of data. Bob later uses this static data in conjunction with
other data sets to generate yet another set of static data. Julie then
visits Bob's page later, and wants to know where and when the various
sources of data Bob used come from, so that she can evaluate its
quality. (In this instance, Alfred and Bob are assumed to be
uncooperative, since creating a static mashup would be an example of a
poorly-written page.)
* TV guide listings - If the TV guide provider does not render a link to
IMDB, the browser should recognise TV shows and give implicit links.
(In this instance, it is assumed that the TV guide provider is
uncooperative, since it isn't providing the links the user wants.)
* Students and teachers should be able to discover each other -- both
within an institution and across institutions -- via their blogging.
(In this instance, it is assumed that the teachers and students aren't
cooperative, since they would otherwise be able to find each other by
listing their blogs in a common directory.)
* Tim wants to make a knowledge base seeded from statements made in
Spanish and English, e.g. from people writing down their thoughts
about George W. Bush and George H.W. Bush. (In this instance, it is
assumed that the people writing the statements aren't cooperative,
since if they were they could just add the data straight into the
knowledge base.)
REQUIREMENTS:
* Does not need cooperation of the author (if the page author was
cooperative, the page would be well-written).
* Shouldn't require the consumer to write XSLT or server-side code to
derive this information from the page.
---------------------------------------------------------------------------
USE CASE: Remove the need for RDF users to restate information in online
encyclopedias (i.e. replace DBpedia).
SCENARIOS:
* A user wants to have information in RDF form. The user visits
Wikipedia, and his user agent can obtain the information without
relying on DBpedia's interpretation of the page.
REQUIREMENTS:
* All the data exposed by DBpedia should be derivable from Wikipedia
without using DBpedia.
==============================================================================
--
Ian Hickson U+1047E )\._.,--....,'``. fL
http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,.
Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
Received on Thursday, 23 April 2009 13:46:09 UTC