Version: 5.4 beta (switch to 5.3)
AssetDatabase
Description of the Format

Text-Based Scene Files

As well as the default binary format, Unity also provides a text-based format for scene data. This can be useful when working with version control software, since text files generated separately can be merged more easily than binary files. Also, the text data can be generated and parsed by tools, making it possible to create and analyze scenes automatically. The pages in this section provide some reference material for working with the format.

See the Editor Settings page for how to enable this feature.

AssetDatabase
Description of the Format