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+Alongside js files the src dir includes "exports files" (e.g. src/ol/map.exports). An export file declares symbols and properties that are to be exported when creating builds of the library. For example the src/ol/map.exports file includes this:
+
+```
+@exportClass ol.Map ol.MapOptions
+@exportProperty ol.Map.prototype.getControls
+```
+
+
+This declares that the `ol.Map` symbol, and that the `ol.Map.prototype.getControls` property, should be exported, i.e. made available to lib users.
+
+Exports files are processed by the `bin/generate-exports` script, using its `--exports` switch. This script receives a list of exports files as its input, and outputs `@exportSymbol` and `@exportProperty` statements. The `Makefile` places the output of the `generate-exports --exports` command in the `build/src/external/src/exports.js` file. This js file is then used as an input file for the `ol.js` build (see `build/ol.json`).
+
+Note: the `src/google.exports` file just makes the `goog.require` function be exported as a null function. This is just to be able to execute the examples both in dev mode (mode=RAW) – where `goog.require` statements are required – and with the `ol.js` build.
+
+The `src/objectlitterals.exports` file is specific. This file declares the config objects and properties for single-arg constructors. These declarations are done with the `@exportObjectLitteral` and `@exportObjectLitteralProperty` directives. This file is also processed with the `bin/generate-exports` script, but using the `--externs` and `--typedef` switches. The `generate-exports --externs` generates Closure externs from the `@exportObjectLitteral` and `@exportObjectLitteralProperty` directives. The Makefile places these externs in the `build/src/external/externs/types.js` file, which is used as a regular externs file by the Closure compiler (see `build/ol.json`). The `generate-exports --typedef` command generate typedef's for the object litterals declared with @exportObjectLitteral and `@exportObjectLitteralProperty`. The `Makefile` places the typedef's in the `build/src/external/src/types.js`, which, like `exports.js`, is used as an input file for the ol.js build (see `build/ol.json`). Externs define types for config objects created by lib users, while typedef's define types created internally by the lib.
+
+OL3 devs need to create new exports files when adding new API elements to the lib. They also need to declare single-arg constructors' config objects and properties in `src/objectlitterals.exports`.
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