How Internationalization/Localization works in OpenACS

This document describes how to develop internationalized OpenACS packages, including writing new packages with internationalization and converting old packages. Text that users might see is "localizable text"; replacing monolingual text and single-locale date/time/money functions with generic functions is "internationalization"; translating first generation text into a specific language is "localization." At a minimum, all packages should be internationalized. If you do not also localize your package for different locales, volunteers may use a public "localization server" to submit suggested text. Otherwise, your package will not be usable for all locales.

The main difference between monolingual and internationalized packages is that all user-visible text in the code of an internationalized package are coded as "message keys." The message keys correspond to a message catalog, which contains versions of the text for each available language. Script files (.adp and .tcl and .vuh), database files (.sql), and APM parameters are affected.

Other differences include: all dates read or written to the database must use internationalized functions. All displayed dates must use internationalized functions. All displayed numbers must use internationalized functions.

Localizable text must be handled in ADP files, in Tcl files, and in APM Parameters. OpenACS provides two approaches, message keys and localized ADP files. For ADP pages which are mostly code, replacing the message text with message key placeholders is simpler. This approach also allows new translation in the database, without affecting the filesystem. For ADP pages which are static and mostly text, it may be easier to create a new ADP page for each language. In this case, the pages are distinguished by a file naming convention.

User Content

OpenACS does not have a general system for supporting multiple, localized versions of user-input content. This document currently refers only to internationalizing the text in the package user interface.

Separate Templates for each Locale

If the request processor finds a filenamed filename.locale.adp, where locale matches the user's locale, it will process that file instead of filename.adp. For example, for a user with locale tl_PH, the file index.tl_PH.adp, if found, will be used instead of index.adp. The locale-specific file should thus contain text in the language appropriate for that locale. The code in the page, however, should still be in English. Message keys are processed normally.

Message Catalogs

Message Keys in Template Files (ADP Files)

Internationalizing templates is about replacing human readable text in a certain language with internal message keys, which can then be dynamically replaced with real human language in the desired locale. Message keys themselves should be in ASCII English, as should all code. Three different syntaxes are possible for message keys.

"Short" syntax is the recommended syntax and should be used for new development. When internationalizing an existing package, you can use the "temporary" syntax, which the APM can use to auto-generate missing keys and automatically translate to the short syntax. The "verbose" syntax is useful while developing, because it allows default text so that the page is usable before you have done localization.

  • The short: #package_key.message_key#

    The advantage of the short syntax is that it's short. It's as simple as inserting the value of a variable. Example: #forum.title#

  • The verbose: <trn key="package_key.message_key" locale="locale">default text</trn>

    The verbose syntax allows you to specify a default text in a certain language. This syntax is not recommended anymore, but it can be convenient for development, because it still works even if you haven't created the message in the message catalog yet, because what it'll do is create the message key with the default text from the tag as the localized message. Example: <trn key="forum.title" locale="en_US">Title</trn>

  • The temporary: <#message_keyoriginal text#>

    This syntax has been designed to make it easy to internationalize existing pages. This is not a syntax that stays in the page. As you'll see later, it'll be replaced with the short syntax by a special feature of the APM. You may leave out the message_key by writing an underscore (_) character instead, in which case a message key will be auto-generated by the APM. Example: <_ Title>

We recommend the short notation for new package development.

Message Keys in Tcl Files

In adp files message lookups are typically done with the syntax #package_key.message_key#. In Tcl files all message lookups *must* be on either of the following formats:

  • Typical static key lookup: [_ package_key.message_key] - The message key and package key used here must be string literals, they can't result from variable evaluation.

  • Static key lookup with nondefault locale: [lang::message::lookup $locale package_key.message_key] - The message key and package key used here must be string literals, they can't result from variable evaluation.

  • Dynamic key lookup: [lang::util::localize $var_with_embedded_message_keys] - In this case the message keys in the variable var_with_embedded_message_keys must appear as string literals #package_key.message_key# somewhere in the code. Here is an example of a dynamic lookup: set message_key_array { dynamic_key_1 #package_key.message_key1# dynamic_key_2 #package_key.message_key2# } set my_text [lang::util::localize $message_key_array([get_dynamic_key])]

Translatable texts in page Tcl scripts are often found in page titles, context bars, and form labels and options. Many times the texts are enclosed in double quotes. The following is an example of grep commands that can be used on Linux to highlight translatable text in Tcl files:

# Find text in double quotes
find -iname '*.tcl'|xargs egrep -i '"[a-z]'

# Find untranslated text in form labels, options and values
find -iname '*.tcl'|xargs egrep -i '\-(options|label|value)'|egrep -v '<#'|egrep -v '\-(value|label|options)[[:space:]]+\$[a-zA-Z_]+[[:space:]]*\\?[[:space:]]*$'

# Find text in page titles and context bars
find -iname '*.tcl'|xargs egrep -i 'set (title|page_title|context_bar) '|egrep -v '<#'

# Find text in error messages
find -iname '*.tcl'|xargs egrep -i '(ad_complain|ad_return_error)'|egrep -v '<#'

You may mark up translatable text in Tcl library files and Tcl pages with temporary tags on the <#key text#> syntax. If you have a sentence or paragraph of text with variables and or procedure calls in it you should in most cases try to turn the whole text into one message in the catalog (remember that translators is made easier the longer the phrases to translate are). In those cases, follow these steps:

  • For each message call in the text, decide on a variable name and replace the procedure call with a variable lookup on the syntax %var_name%. Remember to initialize a Tcl variable with the same name on some line above the text.

  • If the text is in a Tcl file you must replace variable lookups (occurrences of $var_name or ${var_name}) with %var_name%

  • You are now ready to follow the normal procedure and mark up the text using a tempoarary message tag (<#_ text_with_percentage_vars#>) and run the action replace tags with keys in the APM.

The variable values in the message are usually fetched with upvar, here is an example from dotlrn: ad_return_complaint 1 "Error: A [parameter::get -parameter classes_pretty_name] must have <em>no</em>[parameter::get -parameter class_instances_pretty_plural] to be deleted" was replaced by: set subject [parameter::get -localize -parameter classes_pretty_name] set class_instances [parameter::get -localize -parameter class_instances_pretty_plural] ad_return_complaint 1 [_ dotlrn.class_may_not_be_deleted]

This kind of interpolation also works in adp files where adp variable values will be inserted into the message.

Alternatively, you may pass in an array list of the variable values to be interpolated into the message so that our example becomes:

set msg_subst_list [list subject [parameter::get -localize -parameter classes_pretty_name] class_instances [parameter::get -localize -parameter class_instances_pretty_plural]]

ad_return_complaint 1 [_ dotlrn.class_may_not_be_deleted $msg_subst_list]

When we were done going through the Tcl files we ran the following commands to check for mistakes:

# Message tags should usually not be in curly braces since then the message lookup may not be
# executed then (you can usually replace curly braces with the list command). Find message tags 
# in curly braces (should return nothing, or possibly a few lines for inspection)
find -iname '*.tcl'|xargs egrep -i '\{.*<#'

# Check if you've forgotten space between default key and text in message tags (should return nothing)
find -iname '*.tcl'|xargs egrep -i '<#_[^ ]'

# Review the list of Tcl files with no message lookups
for tcl_file in $(find -iname '*.tcl'); do egrep -L '(<#|\[_)' $tcl_file; done

When you feel ready you may vist your package in the package manager and run the action "Replace tags with keys and insert into catalog" on the Tcl files that you've edited to replace the temporary tags with calls to the message lookup procedure.

Dates, Times, and Numbers in Tcl files

Most date, time, and number variables are calculated in Tcl files. Dates and times must be converted when stored in the database, when retrieved from the database, and when displayed. All dates are stored in the database in the server's timezone, which is an APM Parameter set at /acs-lang/admin/set-system-timezone and readable at lang::system::timezone.. When retrieved from the database and displayed, dates and times must be localized to the user's locale.

APM Parameters

Some parameters contain text that need to be localized. In this case, instead of storing the real text in the parameter, you should use message keys using the short notation above, i.e. #package_key.message_key#.

In order to avoid clashes with other uses of the hash character, you need to tell the APM that the parameter value needs to be localized when retrieving it. You do that by saying: parameter::get -localize.

Here are a couple of examples. Say we have the following two parameters, taken directly from the dotlrn package.

Parameter NameParameter Value
class_instance_pages_csv #dotlrn.class_page_home_title#,Simple 2-Column;#dotlrn.class_page_calendar_title#,Simple 1-Column;#dotlrn.class_page_file_storage_title#,Simple 1-Column

Then, depending on how we retrieve the value, here's what we get:

Command used to retrieve ValueRetrieved Value
parameter::get -localize -parameter class_instances_pages_csvKurs Startseite,Simple 2-Column;Kalender,Simple 1-Column;Dateien,Simple 1-Column
parameter::get -localize -parameter departments_pretty_nameAbteilung
parameter::get -parameter departments_pretty_name#departments_pretty_name#

The value in the rightmost column in the table above is the value returned by an invocation of parameter::get. Note that for localization to happen you must use the -localize flag.

The locale used for the message lookup will be the locale of the current request, i.e. lang::conn::locale or ad_conn locale.

Developers are responsible for creating the keys in the message catalog, which is available at /acs-lang/admin/