dtend-issue-fr - Revision history

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2020-07-18T16:21:49Z

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	~~<entry-title>~~dtend-problématique~~</entry-title>~~		{{DISPLAYTITLE:dtend-problématique}}

	Une problématique [[hcalendar-fr\|hCalendar]].		Une problématique [[hcalendar-fr\|hCalendar]].

ChristopheDucamp at 09:44, 10 January 2010

2010-01-10T09:44:41Z

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	== problèmes ==		== problèmes ==
	C'est problématique pour plusieurs raisons :		C'est problématique pour plusieurs raisons :
	* '''Incohérence.''' ~~It is odd that the value specified for~~ machine ~~consumption is different than the value specified for human consumption~~ - ~~regardless of~~ format/~~syntax~~ - ~~and appears inconsistent to anyone who sees the tooltip~~, ~~or views and copy~~/~~pastes the~~ source. ~~It looks like a~~ bug ~~or mistake~~, ~~and in fact has been errantly~~ "~~corrected~~" ~~as such~~ (e.~~g. even in the~~ hCalendar ~~spec itself~~).		* '''Incohérence.''' Il est étrange que la valeur spécifiée pour la consommation machine soit différente de la valeur spécifiée pour une consommation humaine - sans parler de format/syntaxe - et cela semble incohérent pour quiconque voit l'infobulle, ou voit et copie/colle la source. Cela ressemble à un bug ou une erreur, et en fait cela a été "corrigé" en tant que tel (par ex. même dans la spec hCalendar elle-même)
	* '''Non ~~inuitif~~ pour la rédaction.''' ~~When authors are writing up the end~~ date ~~for an event~~, ~~they write up what a human expects to see~~ - ~~the last day of the event~~. ~~It is an unintuitive leap to think to specify~~ +1 ~~day for~~ machine ~~consumption~~, ~~and an additional~~ cognitive ~~load (in order to get it right)~~.		* '''Non intuitif pour la rédaction.''' Quand les auteurs écrivent la fin de date d'un événement, ils écrivent ce que les humains s'attendent à voir - le dernier jour de l'événement. C'est un saut non intuitif de penser à spécifier +1 jour pour la consommation machine, et une charge cognitive supplémentaire.
	* '''Abus sémantique de abbr.''' An abbr'~~s title attribute provides an expansion for the inner text~~. ~~In no way is a~~ +1 ~~date an expansion of a date~~, ~~it appears more like a completely different value~~.		* '''Abus sémantique de abbr.''' Un attribut title de abbr fournit une expansion du texte à l'intérieur. En aucun cas ce n'est une date +1, il ressemble plus à une valeur complètement différente.
	* '''Violation Requise de DRY.''' ~~While the~~ <code>dtstart</code> ~~in the above example is specified only once~~, ~~readable to both humans and~~ machines, ~~the~~ dtend ~~must be specified twice~~, ~~once for humans~~, ~~and once for~~ machines, ~~thus requiring a particularly bad~~ DRY (Don't Repeat Yourself) ~~violation~~, ~~that of requiring data be specified twice~~, ~~but slightly different in one~~ instance ~~than another~~, ~~thus increasing the~~ chances of duplication ~~based errors even more~~ (~~since verifiability is more difficult~~).		* '''Violation Requise de DRY.'''Alors que le <code>dtstart</code> dans le code au-dessus n'est spécifié qu'une seule fois, lisible à la fois pour les humaines et les machines, le dtend doit être spécifié deux fois, une fois pour les humains, et une autres fois pour les machines, exigeant par conséquent une violation très mauvaise du principe DRY (Don't Repeat Yourself), que d'exiger à spécifier deux fois la donnée, mais légèrement différente d'une instance à l'autre, accroissant par conséquent les chances de duplication basées sur les erreurs. (parce que la vérification devient plus difficile)
	** '''Empêche l'utilisation d'un marquage simple''' ~~As a result of the forced~~ DRY ~~violation~~, ~~it is not~~ possible ~~to use~~ simple ~~markup like~~ <code><nowiki><span class="dtend">2010-03-16</span></nowiki></code> ~~because while a human reads that as an event that ends on the 16th~~, an hCalendar 1.0 ~~processor will read that as an event that ended the day before~~, ~~on the 15th~~.		** '''Empêche l'utilisation d'un marquage simple''' Résultat de la violation du DRY, il n'est pas possible d'utiliser un marquage simple comme <code><nowiki><span class="dtend">2010-03-16</span></nowiki></code> parce que pendant qu'un humain lit qu'un événement se termine le 16, un processeur hCalendar 1.0 lira q'un événement s'est terminé le jour d'avant, le 15.

	== solutions possibles ==		== solutions possibles ==

ChristopheDucamp: /* dtend dates incluses */ typo

2010-01-10T09:33:10Z

dtend dates incluses: typo

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	** Avantage : Reflétera l'usage dominant de dtend dans les exemples dans la jungle, (plus de recherche et citations demandées). En d'autres mots, les auteurs on DEJA utilisé dtend en supposant que ça fonctionne de cette façon (dates de fin incluses), et seront en fait surpris de trouver que ce ne l'est pas. Faire ce changement à la sémantique DtEND peut en fait refléter plus la réalité de publication hCalendar que de conserver la sémantique précise du DTEND iCalendar. <strong id="existing-inclusive">Exemples d'usage de dtend incluses dans la jungle :</strong>		** Avantage : Reflétera l'usage dominant de dtend dans les exemples dans la jungle, (plus de recherche et citations demandées). En d'autres mots, les auteurs on DEJA utilisé dtend en supposant que ça fonctionne de cette façon (dates de fin incluses), et seront en fait surpris de trouver que ce ne l'est pas. Faire ce changement à la sémantique DtEND peut en fait refléter plus la réalité de publication hCalendar que de conserver la sémantique précise du DTEND iCalendar. <strong id="existing-inclusive">Exemples d'usage de dtend incluses dans la jungle :</strong>
	*** http://barcamp.org/ - BarCamp wiki, dates pour les BarCamps		*** http://barcamp.org/ - BarCamp wiki, dates pour les BarCamps
	*** [[~~événements~~\|microformats.org/wiki/events/]] - plusieurs événements sur plusieurs jours, comme celui récemment de Glenn Jones (qui se décrit lui-même comme un développeur "très" connaisseur et prolifique de microformats) [[events/2010-03-12-sxsw\|la page événement SXSW 2010]] utilise des DTEND incluses, (notamment un élément span qui ne fait PAS de contenu dupliqué).		*** [[events\|microformats.org/wiki/events/]] - plusieurs événements sur plusieurs jours, comme celui récemment de Glenn Jones (qui se décrit lui-même comme un développeur "très" connaisseur et prolifique de microformats) [[events/2010-03-12-sxsw\|la page événement SXSW 2010]] utilise des DTEND incluses, (notamment un élément span qui ne fait PAS de contenu dupliqué).
	*** la version draft du livre d'Emily Lewis <cite>Microformats Made Simple</cite>, utilise dtend pour les dates de fin incluses.		*** la version draft du livre d'Emily Lewis <cite>Microformats Made Simple</cite>, utilise dtend pour les dates de fin incluses.
	*** La [http://simplebits.com/ page personnelle de Dan Cederholm SimpleBits] connaisseur et expert a un calendrier événements qui utilise des dates incluses dtend.		*** La [http://simplebits.com/ page personnelle de Dan Cederholm SimpleBits] connaisseur et expert a un calendrier événements qui utilise des dates incluses dtend.

ChristopheDucamp: [fr:sync'd with original]

2010-01-10T09:29:29Z

[fr:sync'd with original]

Show changes

ChristopheDucamp at 07:41, 22 November 2009

2009-11-22T07:41:33Z

← Older revision		Revision as of 07:41, 22 November 2009
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	</source>		</source>

	C'est du au fait que hCalendar a été spécifié initialement avec la même sémantique que iCalendar, ce qui place cette exigence sur la propriété DTEND de l'objet VEVENT.		C'est dû au fait que hCalendar a été spécifié initialement avec la même sémantique que iCalendar, ce qui place cette exigence sur la propriété DTEND de l'objet VEVENT.

	== problèmes ==		== problèmes ==
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	<div class="discussion">		<div class="discussion">
	* '''~~new~~ hCalendar 1.0.1 ~~property for end~~ dates'''. As noted in the first resolution of the issue, we could introduce a new property, '''dtlast''' (described more in [[hcalendar-brainstorming#dtlast\|hCalendar brainstorming: dtlast]]) which authors would use to specify the ''last'' day of an event, instead of dtend.		* '''nouvelle propriété hCalendar 1.0.1 pour les dates de fin'''. As noted in the first resolution of the issue, we could introduce a new property, '''dtlast''' (described more in [[hcalendar-brainstorming#dtlast\|hCalendar brainstorming: dtlast]]) which authors would use to specify the ''last'' day of an event, instead of dtend.
	** Advantage: Maintains iCalendar conceptual compatibility for DTEND values.		** Advantage: Maintains iCalendar conceptual compatibility for DTEND values.
	** Advantage: Compatibility with existing hCalendar 1.0 content that just happened to get the end date +1 distinction right.		** Advantage: Compatibility with existing hCalendar 1.0 content that just happened to get the end date +1 distinction right.
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	== origines ==		== origines ==
	~~This issue was raised to me (~~Tantek~~) in person pretty much since the first time I gave such an example back in~~ 2004, ~~was something I had to explicitly cover and point out in nearly every microformats~~ [[presentation]] ~~I gave~~, ~~was eventually pointed out on the~~ microformats discuss ~~mailing list (citation needed)~~, ~~and eventually explicitly documented as an issue on the~~ wiki [[hcalendar-issues]] ~~page by~~ Andy Mabbett on 2007-01-20.		Cette problématique a été soulevée par Tantek presque depuis le tout début où il donné un exemple en 2004, c'est quelque chose qu'il a dû explicitement couvrir et pointer dans chaque [[presentation-fr\|présentation]] qu'il a donné, cela a été soulevé sur la liste de discussion microformats-discuss, et documenté explicitement comme problématique sur la page wiki [[hcalendar-issues]] par Andy Mabbett le 2007-01-20.

	== voir aussi ==		== voir aussi ==
	* [[~~hCalendar~~-fr\|hCalendar]]		* [[hcalendar-fr\|hCalendar]]
	* [[hcalendar-issues]]		* [[hcalendar-issues]]
	* [[icalendar-fr\|iCalendar]]		* [[icalendar-fr\|iCalendar]]

ChristopheDucamp: [fr: sync'd with original - to be translated]

2009-11-22T07:30:04Z

[fr: sync'd with original - to be translated]

New page

<entry-title>dtend-problématique</entry-title>

Une problématique [[hcalendar-fr|hCalendar]].

== résumé ==

La propriété dtend [[hcalendar-fr|hCalendar]] de hCalendar 0.1. requiert que les dates de fin soient marquées comme arrivant un jour complet après ce que les personnes considèrent généralement comme la fin de la date d'un événement.

Par ex. si une conférence démarre le 12 mars 2010 et se termine le 16 mars 2010, alors la dtend doit être marquée avec la valeur de "2010-03-17" - ce qui s'apparente à un jour complet après la fin de la conférence. hCalendar suggère d'obscurcir cette disparité entre la date de fin visible par l'humain et la date machine spécifiée en utilisant la balise <code><nowiki><abbr></nowiki></code> :

<source lang=html4strict>
<div class="vevent">
<span class="summary">une conférence</span>
démarre le <span class="dtstart">2010-03-12</span>, et
se termine le <abbr class="dtend" title="2010-03-17">2010-03-16</abbr>.
</div>
</source>

C'est du au fait que hCalendar a été spécifié initialement avec la même sémantique que iCalendar, ce qui place cette exigence sur la propriété DTEND de l'objet VEVENT.

== problèmes ==
C'est problématique pour plusieurs raisons :
* '''Incohérence.''' It is odd that the value specified for machine consumption is different than the value specified for human consumption - regardless of format/syntax - and appears inconsistent to anyone who sees the tooltip, or views and copy/pastes the source. It looks like a bug or mistake, and in fact has been errantly "corrected" as such (e.g. even in the hCalendar spec itself).
* '''Non inuitif pour la rédaction.''' When authors are writing up the end date for an event, they write up what a human expects to see - the last day of the event. It is an unintuitive leap to think to specify +1 day for machine consumption, and an additional cognitive load (in order to get it right).
* '''Abus sémantique de abbr.''' An abbr's title attribute provides an expansion for the inner text. In no way is a +1 date an expansion of a date, it appears more like a completely different value.
* '''Violation Requise de DRY.''' While the <code>dtstart</code> in the above example is specified only once, readable to both humans and machines, the dtend must be specified twice, once for humans, and once for machines, thus requiring a particularly bad DRY (Don't Repeat Yourself) violation, that of requiring data be specified twice, but slightly different in one instance than another, thus increasing the chances of duplication based errors even more (since verifiability is more difficult).
** '''Empêche l'utilisation d'un marquage simple''' As a result of the forced DRY violation, it is not possible to use simple markup like <code><nowiki><span class="dtend">2010-03-16</span></nowiki></code> because while a human reads that as an event that ends on the 16th, an hCalendar 1.0 processor will read that as an event that ended the day before, on the 15th.

== solutions possibles ==
As noted in the [[hcalendar-issues#issues_2007|issue description]] on the hCalendar issues page, there are at least a couple of possible solutions.

<div class="discussion">
* '''new hCalendar 1.0.1 property for end dates'''. As noted in the first resolution of the issue, we could introduce a new property, '''dtlast''' (described more in [[hcalendar-brainstorming#dtlast|hCalendar brainstorming: dtlast]]) which authors would use to specify the ''last'' day of an event, instead of dtend.
** Advantage: Maintains iCalendar conceptual compatibility for DTEND values.
** Advantage: Compatibility with existing hCalendar 1.0 content that just happened to get the end date +1 distinction right.
** ... any other advantages?
** Disadvantage: Increased vocabulary. '''dtlast''' is a new term, even if it is not new functionality. Essentially this puts additional burden on authors.
** Disadvantage: Increased complexity/confusion. When to use dtend vs. dtlast? hCalendar authors would now have to remember, use dtend for end *times* and dtlast for end *dates*. More explanation of the additional burden on authors.
** ... any other disadvantages?
** Opinions:
*** -1 despite originally proposing this solution, I now think an additional term, and rule for when to use the new term vs. the old term will actually make this problem worse and more confusing to web authors. [[User:Tantek|Tantek]]
*** ... please add your +1/0/-1 opinion here and sign with three tildas (<nowiki>~~~</nowiki>)
* '''redefine hCalendar 1.0.1 dtend to be inclusive for whole dates'''. This is a bit more radical.
** Advantage: Zero impact on vocabulary.
** Advantage: No increase to hCalendar authoring complexity.
** Advantage: Will reflect dominant use of dtend in examples in the wild (more research and citations needed to back this up!). In other words, authors have ALREADY been using dtend assuming it works this way (inclusive end dates), and will actually be surprised to find out that it doesn't. Making this change to DTEND semantics may actually reflect hCalendar publishing reality more than keeping the precise iCalendar DTEND semantic. Examples of inclusive dtend usage in the wild:
*** http://barcamp.org/ - BarCamp wiki, dates for BarCamps
*** [[event|microformats.org/wiki/events/]] - several multi-day event listings, as recently as Glenn Jones (who himself is a ''very'' knowledgable and prolific microformats developer) [[events/2010-03-12-sxsw|event page for SXSW 2010]] use inclusive DTENDs (notably, using a span element that does NOT duplicate content).
*** draft of Emily Lewis' book <cite>Microformats Made Simple</cite>, uses dtend for inclusive end dates.
*** microformats.org co-founder and expert [http://simplebits.com/ Dan Cederholm's home page] has an events calendar that uses inclusive dtend dates.
*** ... more instances of existing use of DTEND for *inclusive* end dates.
** Advantage: Some number of implementations treat DTEND dates as *inclusive* (technically these are violating the current hCalendar spec, but they may be doing so deliberately to reflect actual hCalendar publishing practices). Implementations
*** Google's Rich Snippet validator. The [http://www.google.com/webmasters/tools/richsnippets?url=http%3A%2F%2Fmicroformats.org%2Fwiki%2Fevents Rich Snippet validator on microformats.org/wiki/events] shows the SXSW event as ending on 2010-03-16, consistent with the published intent.
*** ... more implementations that treat hCalendar dtend dates as inclusive
** ... any other advantages?
** Disadvantage: Redefines DTEND to be *slightly* different from how it is defined in iCalendar. This may lead to errors on the part of developers.
*** Mitigation: it may be possible to mitigate this disadvantage by providing ''both'' very precise hCalendar to iCalendar processor conformance requirements, and sufficient test cases for hCalendar to iCalendar processors for them to get this correct in their code.
** Disadvantage: breaking some amount of existing hCalendar content on the web (research needed to determine the extent of the problem)
*** Workarounds: Based on aforementioned research, workarounds may be possible, e.g. heuristics for when abbr is used similar to the example at the top of the page, to detect "off by one" cases and accommodate accordingly). Make it an explicit error for the human visible date to be different than the machine parsed date, and state specific error handling rules for hCalendar processors that "repair" this problem.
** ... any other disadvantages?
** Opinions:
*** +1 Based on the fact that this problem just hasn't gone away, and that people (smart knowledgable people!) continue to treat "dtend" end dates *inclusively*, I now think it makes more sense (and is more practical) to change the spec to be consistent with the dominant expectation of web authors, rather than continue attempting to change the expectations of web authors to be consistent with the spec. I think this is the simplest, most effective, and least risky option. [[User:Tantek|Tantek]]
*** +1 This appears logical and intuitive. We are effectively saying that end dates such as <code>DTEND</code> should parse to <code>YYYY-MM-DDT24:00:00</code>, and not <code>YYYY-MM-DDT00:00:00</code>. Seems simple, and entirely logical from a publishing stand —[[User:BenWard|BenWard]] 08:18, 27 August 2009 (UTC)
*** +1 The spec should reflect the intuitive publishing behaviour (inclusive end dates). Humans first. —[[User:Adactio|Jeremy Keith]]
*** +1 Though I'm worried about tools catching up to this change. [[User:EdwardOConnor|Ted]]
*** +1 The natural human way to think about dates is inclusively; if the dtend date and dtstart date are equal, that clearly doesn't imply zero duration. The microformats principle of making things easier for authors rather than parser writers wins here [[User:Kevin Marks|Kevin Marks]]
*** +1 It is much easier to migrate the limited number of tools and authors who already grok hCalendar 1.0 than to migrate publisher intuition. [[User:MatthewLevine|MatthewLevine]]
*** +1 I agree with MatthewLevine. Those who follow hCalendar development are likely to make the change to inclusive dates, and those who don't are likely using inclusive dates already. [[User:Chris Cressman|Chris Cressman]]
*** ... please add your +1/0/-1 opinion here and sign with three tildas (<nowiki>~~~</nowiki>)
* ... other possible solutions?
</div>

== origines ==
This issue was raised to me (Tantek) in person pretty much since the first time I gave such an example back in 2004, was something I had to explicitly cover and point out in nearly every microformats [[presentation]] I gave, was eventually pointed out on the microformats discuss mailing list (citation needed), and eventually explicitly documented as an issue on the wiki [[hcalendar-issues]] page by Andy Mabbett on 2007-01-20.

== voir aussi ==
* [[hCalendar-fr|hCalendar]]
* [[hcalendar-issues]]
* [[icalendar-fr|iCalendar]]