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<h1>Measure microformat</h1>
{{DISPLAYTITLE:Measure microformat research}}


Currently this microformat is in exploratory stage. Contributions should focus on real examples from the Web, existing formats/encoding of measures.
<div style="float:right;margin-left:1em">__TOC__</div>
 
This page is for researching and developing a [[measure]] microformat. Per the [[process]]:
* [[measure-examples]]
* [[measure-formats]]
* [[measure-brainstorming]]


== The problem ==
== The problem ==
Line 11: Line 16:
The Measurement microformat will enable unambiguous description of physical quantities and thus provide a solid ground for data sharing and automation in many areas.
The Measurement microformat will enable unambiguous description of physical quantities and thus provide a solid ground for data sharing and automation in many areas.


== Draft Schema==
== Next Steps ==
 
* clean-up [[measure-examples]] to refer to <em>current</em> real world examples
Rationale: The names "value" and "type" are taken from [[hCard]]; "item" is used from hReview.
* update [[measure-formats]] with formats from other recent efforts such as schema.org
 
* massive clean-up of [[measure-brainstorming]]
=== Standard Measure Schema ===
 
* '''<code>hmeasure</code>'''
** '''<code>value</code>''' {1} (numeric)
** '''<code>unit</code>''' {1} (unit)
** <code>item</code>?  (text | [[hcard|hCard]] | [[hcalendar|hCalendar]])
** <code>type</code> ? (text, e.g. "height", "width", "weight")
** <code>tolerance</code> ? (percentage | hmeasure)
 
=== Angular Measure Schema ===
 
* '''<code>hmeasure</code>'''
** '''<code>value</code>''' {1} (degree)
** <code>item</code>?  (text | [[hcard|hCard]] | [[hcalendar|hCalendar]])
** <code>type</code> ? (text, e.g. "angle of elevation")
** <code>tolerance</code> ? (percentage | hmeasure)
 
=== Money Schema ===
 
* '''<code>hmoney</code>'''
** '''<code>value</code>''' {1} (numeric)
** '''<code>unit</code>''' {1} ([http://en.wikipedia.org/wiki/ISO_4217 ISO 4217 code])
** <code>tolerance</code> ? (percentage | hmoney)
 
== Value ==
 
Arbitrary white space {{may}} be included in the value to improve readability. Parsers {{must}} strip out all white space before further processing.
 
In the standard and money schemas, the value {{must}} be a number, formatted according to the following EBNF pattern:
 
<pre>non-zero-digit = "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
digit          = "0" | non-zero-digit ;
natural        = non-zero-digit , {digit} ;
integer        = "0" | [ "-" ] , natural ;
dot-decimal    = integer , "." , {digit} ;
comma-decimal  = integer , "," , {digit} ;
e-sign        = "e" | "E" ;
mantissa      = dot-decimal | comma-decimal | integer ;
sci-number    = mantissa , e-sign , integer ;
number        = dot-decimal | comma-decimal | integer | sci-number ;</pre>
 
This roughly corresponds to a subset of [http://en.wikipedia.org/wiki/C_syntax#Floating_point_types C syntax] for floating points and integers, excluding octal and hexadecimal representations. However, note that both commas and stops may be used as decimal points.
 
The Unicode minus sign (U+2212) and ASCII-compatible hyphen-minus (U+002D) {{must}} both be treated as acceptable indicators of a negative number. In addition, the symbols &frac14; (U+00BC), &frac12; (U+00BD) and &frac34; (U+00BE) {{should}} be supported as aliases for 0.25, 0.5 and 0.75 respectively.
 
In the angular measure schema, a measure is expressed as a combination of up to three numeric components: called degrees, minutes and seconds. Any combination of these components may be used, except when degrees and seconds are given minutes {{must}} be present. The components {{must}} appear in the correct order (degrees, minutes, seconds). Each component must match the production rule for "mantissa" above, with the following additional constraints:
 
* Only the first component can bear a minus sign. Subsequent components "inherit" the negativity (or lack thereof) from their predecessors.
* All components except the last must match the production rule for "integer".
 
The numeric components {{must}} be indicated by appending a suffix to each component. Valid suffixes are:
 
* degree: "deg", U+00B0 degree symbol (&deg;)
* minute: "min", straight single quote ('), U+2032 prime (&prime;)
* second: "sec", straight double quote ("), U+2033 double prime (&Prime;)
 
=== Value Examples ===
 
* 1729 (the smallest number that can be expressed as the sum of two cubes in two different ways)
* 1.61803399 (the golden ratio)
* 2,99792458e8 (the speed of light in a vacuum, measured in metres per second)
* -40 (value at which Celcius and Farenheit scales are equal)
* 1,000,000,000 (''Invalid:'' commas may be used as decimal points, but not for grouping thousands.)
* 57.2958 deg (1 radian, in degrees)
* -57&deg; 17&prime; 45.1&Prime; (-1 radian, in degrees, minutes and seconds)
* 4&deg; 30&Prime; (''Invalid'': no minutes)
* 4&deg; -30&prime; (''Invalid'': only first component may be negative)
 
== Unit ==
 
In the standard schema, the "unit" class is defined as an arbitrary string. Any unit may be used, but authors {{should}} attempt to use official SI units of measurement where appropriate. Parsers {{must}} recognise the following case-sensitive list of units, derived from the SI list of base units and official recognised derived units, with the addition of bits and bytes, which are commonly used on web pages, and litres, degrees Celsius and radians. (Note that gram appears in this table instead of kilogram. This is deliberate.)
 
{| border="1"
|-
! Unit
! Symbols
! Aliases
|-
| metre
| m
| meter
|-
| gram
| g
| gramme
|-
| second
| s, sec
|-
| ampere
| A
| amp
|-
| candela
| cd
|-
| mole
| mol
|-
| kelvin
| K, &#x212a; (U+212A)
|-
| newton
| N
|-
| pascal
| Pa
|-
| joule
| J
|-
| watt
| W
|-
| coulomb
| C
|-
| volt
| V
|-
| ohm
| &Omega; (U+03A9), Ω (U+2126)
|-
| siemens
| S
|-
| farad
| F
|-
| weber
| Wb
|-
| henry
| H
|-
| tesler
| T
|-
| hertz
| Hz
|-
| byte
| B
|-
| bit
| b
|-
| litre
| L, l, &#x2113; (U+2113)
| liter
|-
| Celsius
| &#x2103; (U+2103), &#xB0;C (U+00B0 followed by captial C)
|-
| radian
| rad
|}
 
The following SI prefixes {{must}} be supported.
 
{| border="1"
! 10<sup>n</sup>
! Prefix
! Symbol
|-
| 10<sup>24</sup>
| yotta-
|  Y
|-
| 10<sup>21</sup>
| zetta-
|  Z
|-
| 10<sup>18</sup>
| exa-
|  E
|-
| 10<sup>15</sup>
| peta-
|  P
|-
| 10<sup>12</sup>
| tera-
|  T
|-
| 10<sup>9</sup>
| giga-
|  G
|-
| 10<sup>6</sup>
| mega-
|  M
|-
| 10<sup>3</sup>
| kilo-
|  k<!-- (K)-->
|-
| 10<sup>2</sup>
| hecto-
|  h<!-- (H)-->
|-  
| 10<sup>1</sup>
| deca-
|  da<!-- (D)-->
|-
| 10<sup>0</sup>
| (none)
| (none)
|-
| 10<sup>−1</sup>
| deci-
|  d
|-
| 10<sup>−2</sup>
| centi-
|  c
|-
| 10<sup>−3</sup>
| milli-
|  m
|-
| 10<sup>−6</sup>
| micro-
|  µ (U+00B5), μ (U+03BC), u
|-
| 10<sup>−9</sup>
| nano-
|  n
|-
| 10<sup>−12</sup>
| pico-
|  p
|-
| 10<sup>−15</sup>
| femto-
|  f
|-
| 10<sup>−18</sup>
| atto-
|  a
|-
| 10<sup>−21</sup>
| zepto-
|  z
|-
| 10<sup>−24</sup>
| yocto-
|  y
|}
 
The full names and for SI prefixes {{must}} only be combined with the full names for the units (or their aliases). Likewise the symbols for SI prefixes {{must}} only be combined with the symbols for the units.
 
* kilometre
* milligramme
* μL
* mΩ
* microV (''Invalid'')
* kgram (''Invalid'')
 
{{OpenIssue}} Perhaps, because of i18n issues, and the difficulty of supporting plurals, only the symbols should be ''required'' to be supported? (Using the ABBR design pattern it would still be possible to ''display'' the full name of the unit.)
 
=== Combining units ===
 
Units may be multiplied by separating with whitespace, or divided using a slash (/) or U+2215 division slash (&#x2215;). Units may be raised to an integer power using a caret character. The unicode superscript numerals 2 to 9 (U+00B2, U+00B3, U+2074-79) {{must}} be supported as aliases for raising to the appropriate integer powers. Multiplication is more associative than division.
 
Examples:
 
* &lt;span class="unit">kg m / s&lt;/span>
* &lt;span class="unit">m/s^2&lt;/span>
* &lt;span class="unit">meter&#xB3;&lt;/span>
* &lt;abbr class="unit" title="&mu;m">micron&lt;/abbr>
 
=== Angular units ===
 
Units {{must not}} be given for measurements expressed in the degree schema: the degree itself is the unit. If the standard schema is used, units may be given in radians (rad).
 
=== Other / Non-SI Units ===
 
Authors {{may}} specify units other than those defined above, but {{should not}} assume that parsers will be able to interpret them. Authors using other units {{may}} provide a [[existing-rel-values|rel=glossary]] link to a page or fragment that defines the units.
 
==== Explicitly Defining a Unit ====
 
hmeasure may be used with the &lt;dfn> element to explicitly define a unit in terms of pre-defined units. The "title" attribute (if any) is taken to be an alias of the unit name.
 
<pre><p class="hmeasure" id="dfn-inch">
  An <dfn class="item" title="in">inch</dfn> is defined as
  <span class="value">0.0254</span> <span class="unit">m</span>.
</p></pre>
 
Other instances of hmeasure may then refer to this definition, implicitly:
 
<pre><p class="hmeasure">
  The <span class="item">action figure</span> has a <span class="type">height</span> of
  <span class="value">5</span> <span class="unit">in</span>.
</p></pre>
 
or explicitly:
 
<pre><p class="hmeasure">
  The <span class="item">action figure</span> has a <span class="type">height</span> of
  <span class="value">5</span>
  <a class="unit" rel="glossary" href="#dfn-inch">in</a>.
</p></pre>
 
{{OpenIssue}} Farenheit is reasonably common in some parts of the world. As &deg;C and &deg;F do not share their zero points, it is impossible to use this pattern to define &deg;F. &deg;F thus remains an opaque string with no meaning assigned to it my this spec. Should we add it to the list of pre-defined units?
 
=== Currency Units ===
 
If the money schema is being used, the unit is not an arbitrary string. It {{must}} be a three-letter ISO 4217 code. The following aliases for the four largest reserve currencies (as of 2008) are allowed:
 
{| border="1"
|-
! Unit
! Aliases
|-
| EUR
| €
|-
| GBP
| £
|-
| JPY
| ¥
|-
| USD
| $
|}
 
Other currencies {{may}} be displayed using these symbols only through the [[abbr-design-pattern|ABBR design pattern]]:
 
<pre><span class="hmoney">
  <abbr class="unit" title="AUD">$</a><span class="value">5.00</span>
</span></pre>
 
== Item ==
 
An hCard, hCalendar event or textual description of the item being measured may be supplied.
 
<pre><p class="hmeasure">
  <span class="item vcard">The <span class="fn">Great Wall</span>of
  <span class="adr"><span class="country-name">China</span></span></span>
  is about <span class="value">6 700</span> <abbr title="km">kilometres</abbr>
  <abbr title="length" class="type">long</abbr>.
</p></pre>
 
The item is optional.
 
== Type ==
 
The type specifies the dimension being measured. A measurement in, say, metres may be ambiguous because it could refer to a depth, a height, a length or a width. The optional type parameter allows you to specify a human-readable dimension.
 
== Tolerance ==
 
An optional tolerance may be specified as a percentage or as a nested hmeasure/hmoney.
 
Examples:
 
<pre><span class="hmeasure">
  <span class="type">Height</span>:
  <span class="value">5</span> <span class="unit">m</span>
  ± <span class="tolerance">2%</span>
</span></pre>
 
<pre><span class="hmoney">
  <span class="unit">$</span><span class="value">5.00</span>
  ± <span class="tolerance hmoney"><span class="unit">$</span><span class="value">1.00</span></span>
</span></pre>
 
When no tolerance is provided, a default tolerance of 0% {{must not}} be assumed — the tolerance is simply unknown.
 
== Minimisation Techniques ==
 
=== hmeasure ===
 
If no "value" is given, then the first number conforming to the EBNF above is taken to be the value. If no unit is given, then the entire string within the "hmeasure" (less the value, item, type and tolerance) is taken to be the unit.
 
For example:
<pre><span class="hmeasure">3 pints <span class="item">beer</span></span></pre>
* '''Value:''' 3
* '''Unit:''' "pints"
* '''Item:''' "beer"
 
<pre><span class="hmeasure">4 m</span></pre>
* '''Value:''' 4
* '''Unit:''' metre
 
{{OpenIssue}} What about cases where there is no white space? SI says white space should always separate the quantity and unit, but in practice, many people do not include white space in measures.
 
{{OpenIssue}} When no unit is explicitly given, how do we know which of the following two behaviours to take?
* Assume unit minimisation and follow the procedures here; or
* Assume angular schema and treat number as a degree/minute/second.
 
=== hmoney ===
 
If no "value" is given, then the first number conforming to the EBNF above is taken to be the value. If no "unit" is given, the first three-letter word (or single character alias) is taken to be the unit. White space between the implied unit and value is considered optional. The following are to be equivalent:
 
<pre>
<span class="hmoney"><span class="unit">EUR</span> <span class="value">1,00</span></span>
<span class="hmoney">EUR <span class="value">1,00</span></span>
<span class="hmoney">EUR1,00</span>
<span class="hmoney">1,00 EUR</span>
<span class="hmoney">1.00 <abbr class="unit" title="EUR">euro</abbr></span>
<span class="hmoney">€1,00</span>
<abbr class="hmoney" title="EUR 1,00">a euro</abbr>
</pre>
 
=== Minimising Tolerence ===
 
If the tolerance is not a percentage (i.e. it is a nested hmeasure/hmoney) and it does not contain a unit (either explicit, or by minimisation rules), then the unit is taken to be the unit of the parent hmeasure/hmoney.
 
If no explicit tolerance is given, the hmeasure string should be examined for an occurrence of the substring "±". If this is present, the substring after it, and continuing to the end of the hmeasure string is taken to be a tolerance. If the tolerance contains a "%" character, the tolerance is taken to be a percentage. Otherwise is it taken to be an implicit nested hmeasure/hmoney.
 
=== Worked example ===
 
The following example shows a series of expansions taken by a parser encountering a minimised hmoney:
 
<pre><span class="hmoney">$1.54 ± 0.01</span></pre>
 
The "±" sign introduces a tolerance, which does not include a "%" symbol, so is treated as a nested hmoney.
 
<pre><span class="hmoney">$1.54 ±<span class="hmoney tolerance">0.01</span></span></pre>
 
No explicit units or values are given in either hmoney, so units and values are extracted as per hmoney minimisation:
 
<pre><span class="hmoney"><span class="unit">$</span><span class="value">1.54</span>
±<span class="hmoney tolerance"><span class="value">0.01</span></span></span></pre>
 
The nested hmoney contains no unit, so it inherits its unit from the parent hmoney:
 
<pre><span class="hmoney"><span class="unit">$</span><span class="value">1.54</span>
±<span class="hmoney tolerance"><span class="unit">$</span> <span class="value">0.01</span></span></span></pre>
 
Parsed values:
 
* '''Unit:''' USD
* '''Value:''' 1.54
* '''Tolerance:'''
** '''Unit:''' USD
** '''Value:''' 0.01
 
== Examples ==
 
An example weather forecast using hmeasure, [[adr]], [[geo]] and [[hCalendar]] with the [[include-pattern|include pattern]]:
 
<pre><div>
    Weather for
    <span id="loc-lewes">
        <span class="adr location">
            <span class="locality">Lewes</span>,
            <span class="region">East Sussex</span>
        </span>
        (<span class="geo">50.8730;0.005</span>)
    </span>,
    <span class="vevent item" id="day-20080325">
        <a class="include" href="#loc-lewes"></a>
        <span class="summary">Tuesday</span>
        <abbr class="dtstart" title="2008-03-25">25 March</abbr>
        <abbr class="dtend" title="2008-03-26"></abbr>
    </span>:
    <span class="hmeasure">
        <a class="include" href="#day-20080325"></a>
        <abbr title="Maximum temperature" class="type">High</abbr>
        8 &#x2103;
    </span>,
    <span class="hmeasure">
        <a class="include" href="#day-20080325"></a>
        <abbr title="Minimum temperature" class="type">Low</abbr>
        0 &#x2103;
    </span>
</div></pre>
 
(The above example does not necessarily represent best practice. Authors should make themselves aware of the accessibility issues currently being discussed around the include and abbr design patterns.)
 
== Parsing Hints ==
 
This section is ''informative''. Parsers should note that (with the exception of certain non-ascii characters, which can be converted manually first) all the pre-defined non-currency units can be understood by the [http://www.gnu.org/software/units/ GNU units] program. A parser could act as a wrapper to a GNU units installation, or make use of a GNU units-based web service to convert between units.


== Related microformats ==
== Related microformats ==
* [[hcalendar]] can provide a complete quantitative description of a natural event (for example an earthquake) occurring at a specified time (dtstart/dtend) and location (embedded [[geo]]), by just embedding measured physical quantities in the 'descrition' span.
* [[hcalendar]] can provide a complete quantitative description of a natural event (for example an earthquake) occurring at a specified time (dtstart/dtend) and location (embedded [[geo]]), by just embedding measured physical quantities in the 'descrition' span.
* [[job-listing]] can use time measure for specify per what period of time the salary is for.
* [[job-listing]] can use time measure for specify per what period of time the salary is for.
* [[hlisting]] product dimensions; weight/mass; time period (as above).  
* [[hlisting]] product dimensions; weight/mass; time period (as above); price.
* [[directions-examples]] can use length measure for mileage and time to go from one point to the next.
* [[directions-examples]] can use length measure for mileage and time to go from one point to the next.
* [[recipe-examples]] can use weight, volume and time measure for ingredients and preparation time.
* [[recipe-examples]] can use weight, volume and time measure for ingredients and preparation time.
* [[currency]] can be viewed as a measurement unit, or as a component of a measurement unit, as in $ per hour.
* [[currency]] can be viewed as a measurement unit, or as a component of a measurement unit, as in $ per hour.
== Contributors ==
* Guillaume Lebleu
* [[User:AndyMabbett|Andy Mabbett]]
* Luca Postpischl
* [[User:ManuSporny|Manu Sporny]]
* [[User:TobyInk|TobyInk]]


==References==
==References==

Latest revision as of 16:28, 18 July 2020


This page is for researching and developing a measure microformat. Per the process:

The problem

Measures (e.g. weights, sizes, temperatures) occur frequently on the Web, they are constituted of a value a unit-measure and, in scientific and technical contexts, an experimental uncertainty. These 3 elements should be marked-up consistently across websites so that they can be easily identified and acted upon (export, compute, convert) in collaborative distributed applications.

Unit-measures differ from locale to locale (e.g. Fahrenheit vs. Celsius, pound versus Kilogram), making comparison and matching of offerings difficult.

The Measurement microformat will enable unambiguous description of physical quantities and thus provide a solid ground for data sharing and automation in many areas.

Next Steps

Related microformats

  • hcalendar can provide a complete quantitative description of a natural event (for example an earthquake) occurring at a specified time (dtstart/dtend) and location (embedded geo), by just embedding measured physical quantities in the 'descrition' span.
  • job-listing can use time measure for specify per what period of time the salary is for.
  • hlisting product dimensions; weight/mass; time period (as above); price.
  • directions-examples can use length measure for mileage and time to go from one point to the next.
  • recipe-examples can use weight, volume and time measure for ingredients and preparation time.
  • currency can be viewed as a measurement unit, or as a component of a measurement unit, as in $ per hour.

References

See also

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