private File expressionFileNameToFile(String name) {
        if (new File(name).isAbsolute())
            throw new IllegalArgumentException("Absolute path to ranking expression file is not allowed: " + name);

        Path path = Path.fromString(name);
        File expressionFile = applicationFile(appDir, SCHEMAS_DIR.append(path));
        if ( ! expressionFile.exists()) {
            expressionFile = applicationFile(appDir, SEARCH_DEFINITIONS_DIR.append(path));
        }
        return expressionFile;
    }
Reads a ranking expression from file to a string and returns it.

@param name the name of the file to return,
            relative to the search definition directory in the application package
@return the content of a ranking expression file
@throws IllegalArgumentException if the file was not found or could not be read
config-application-package/src/main/java/com/yahoo/config/model/application/provider/FilesApplicationPackage.java