Template:Show data

This template contains various independently retrievable data items about [[{{{article|{{{1}}}}}}]] in the form of parameter values of a variable template of choice, in a standardized fashion. It is a member of a family of templates, those with names starting with "Data" in Category:Data templates. The system used is similar to that of Wikipedia:WikiProject Flag Template.

Parameters

Parameter name	Value	Meaning
1	{{{1}}}	last part of template name, used to identify it within the family of templates
article		article name; needs to be specified only if it differs from {{{1}}}; in applications, use [[{{{article|{{{1}}}}}}]] to link to the article (as has been done at the top of this page)
short name		shorter display name to be used in some contexts; an application or application parameter can specify whether this is used; only intended for dispensing with disambiguation in a context where it is not needed
type		type of entity, e.g. continent, country, province, municipality
code		code
code description		code description
continent		continent, if type is lower than "continent"
country		country, if type is lower than "country"
province		province, if type is lower than "province"
popbase		population on a given date (stored without commas)
popbaseyear		year for which the population base figure applies
popbasemonth		month for which the population base figure applies
popbaseday		day for which the population base figure applies
popinc		population increase per day; used to extrapolate the population figure
land area		land area in km2 (stored without commas)
total area		total area in km2 (stored without commas)
flag image		name of the flag image (or other illustration, if there is no flag) shown above

Throughout the family of templates, fixed names are used for the parameters. (The parameter names are kept short to reduce counts for the post expand include size and the template argument size in cases where these are applicable.) However, not necessarily all parameters have been given a value: some parameters may not be applicable, while for some other parameters the value may just have not been specified yet. The table shows all parameters, and for each the value, if specified.

Retrieval of data items

{{data {{{1}}}|pst2|land area}}, using parameter selection template Template:Pst2, gives the parameter land area, etc.

For retrieval of more data items it is more efficient to prepare a template for that, to be used as follows:

{{data {{{1}}}|template name|..|..|..|..}}

so that this data template needs to be called only once. The default template is Template:Show data, producing this page.

The four parameters are optional, they are passed on to the prepared template as parameters 2-5.

Special templates:

• Template:Linkd - link to article
• Template:Poptoday - used above
• Template:Popdens - for use on the page List of sovereign states and dependent territories by population density
• Template:Poptoday 1 - for use on the page List of countries by population
• Template:Popareadens - for use on the page List of countries by population

A parameter being undefined or empty typically means the same, see below. {{data ..|pst2|..}} gives the empty string and the text "{{{..}}}", respectively. Therefore an application checking the parameter has to check both. Checking whether a result is equal to e.g. the text "{{{popinc}}}" cannot be done directly with #ifeq in a template which itself has also a parameter with that name, because if that is defined, there would be a comparison with the value instead of the text itself. Instead, it can be checked whether the first character of the result is "{", e.g.: {{#ifeq:{{padleft:|1|{{data {{{continent}}}|pst2|popinc}}}}|{|..|..}}.

Creating new data templates

Template:Data/preload can be used to create new data templates. On the page of the data template of a province, if there is no data template yet for the country, a link appears to create that, preloading this template. Otherwise the wikitext can be copied to the new data template. For parameters which are not applicable, such as country for a country, the parameter definition "country=" can be deleted. For parameters to be filled in later the parameter definition like "popinc=" (specifying the empty string as value) can be left in the wikitext to be filled in later. Do not forget parameter 1.

Efficiency

In this template system each template contains various properties of a single entity, as opposed to the other common system, where a template contains one property (e.g. population or area) of many entities. Although that other system can be convenient if updates of a property for all these entities become available together, in the case of large-scale use of data on one page that other system can be problematic due to its inefficiency. This is because of the following:

• There are often more entities than properties, and page counts (or in the case of #switch, average page counts) are proportional to the number of data items in the data template (if they are stored in a linear way, not in a tree, and not stored as unnamed parameters).
• In the case of large-scale use of data on one page there are usually one or more tables, where an entity forms a row and a property a column, because there are often more entities than properties, and because this way the sorting feature allows sorting entities based on a property. In this template system this allows producing a row with only one call of the data template, making the count not grow faster than proportional to the average number of data items stored per data template, times the number of entities in the table.

The include part of the data template of an entity does not contain a long list of its sub-entities or their properties, because that would make this method inefficient too.

Until here the documentation is automatically generated by Template:Show data.

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