Localization (i18n)

With ‘Localization’, we refer to adapting your app to the languages of specific target markets. This is particularly needed when serving UIs.

This guide focuses on static texts like labels. See CDS also Localized Data on how to manage and serve actual payload data in different translation.

Content

• Externalizing Texts Bundles
• Where to Place Text Bundles?
• CSV-Based Text Bundles
• Merging Algorithm
• Merging Reuse Bundles
• Determining User Locales
• Normalized locales

Externalizing Texts Bundles

All you have to do to internationalize your models is to externalize all your literal texts to text bundles and refer to the respective keys from your models as shown below.

srv/my-service.1.cds

service Bookshop {
  entity Books @(
    UI.HeaderInfo: {
      Title.Label: '{i18n>Book}',
      TypeName: '{i18n>Book}',
      TypeNamePlural: '{i18n>Books}',
    },
  ){/*...*/}
}

_i18n/i18n.properties

Book = Book
Books = Books
foo = Foo

Note: The keys of your properties entries can be freely chosen.

Then you can translate the texts in localized bundles each with a language/locale code appended to its name, for example,

_i18n/
  i18n.properties           # dev master -> 'default fallback'
  i18n_en.properties        # English    -> 'default language'
  i18n_de.properties        # German
  i18n_zh_TW.properties     # Traditional Chinese
  ...

Where to Place Text Bundles?

By default, text bundles can be placed in and are fetched from folders named _i18n, i18n, or assets/i18n. These folder are placed next to the model files or in a parent folder as follows:

srv/
   my-service.cds          # the model file
   _i18n/i18n.properties   # next to the model file
_i18n/i18n.properties      # in a parent folder

You can configure the folder names where cds searches for property bundles by setting cds.i18n.folders in your project’s package.json. The default is:

"cds":{"i18n":{
  "folders": [ "_i18n", "i18n", "/docs/03-Cookbook/51-Localization/assets/i18n" ]
}}

CSV-Based Text Bundles

For smaller projects you may choose CSV files instead of .properties files, which you can easily edit in Excel, Numbers or alike.

The format is like that:

With that CSV source:

key;en;de;zh_CN;...
Book;Book;Buch;...
Books;Books;Bücher;...
...

Merging Algorithm

Each localized model is constructed by applying:

1. The default fallback bundle (that is, i18n.properties), then …
2. The default language bundle (usually i18n_en.properties), then …
3. The requested bundle (for example, i18n_de.properties), in that order.

So, the complete stack of overlaid models for the given example would look like that (higher ones override lower ones):

Note: The default language is usually en but can be overridden by configuring cds.i18n.default_language in your project’s package.json.

Merging Reuse Bundles

In case your application is importing models from a reuse package, that package comes with own language bundles for localization. These are applied upon import, so can be overridden in your models as well as in your language bundles and translations thereof.

For example, assumed your data model imports from a foundation package, then the overall stack of overlays would look like that:

Determining User Locales

Upon incoming requests at runtime, the user’s preferred language is determined as follows:

1. Read the preferred language from first of:
   1. The value of URL parameter sap-language, if present
   2. A chosen language from the user’s applications settings, if available
   3. A chosen language in the user’s global settings, if available
   4. The first entry from the request’s Accept-Language header
   5. The default language configured on app level (for example, en)
2. Narrow to normalized locales as described below.

Normalized locales

To reduce the number of required translations, determined locales are normalized as follows:

• most locales are narrowed to their main language codes only
• for example, en_US, en_CA, en_AU → en
• except of these white-listed ones:

This white list is configurable, so if there’s a real need to change it, that is possible.