No, XxxData[] is not a new function in Mathematica 11. I am just using that name for all curated data-related functions.

As you know, CountryData[] is one of such so called "curated data" functions in Mathematica. It basically presents a convenient way to access lots of information on all countries of the today's world.

In this question, an undocumented value for property passed to CountryData[] is discussed ("OfficialLanguages").

How to find out all undocumented values?

The same question for:

AstronomicalData[]
GraphData[]
WordData[]
...

(all XxxData[] from Mathematica's curated data)

I tried examining correspondent mx file, but no results. Is there a smart way?

I read several related questions here, that deal with undocumented options and other parameter values for certain Mathematica's functions, but none of presented methods for discovering undocumented values worked for CountryData[].

No, XxxData[] is not a new function in Mathematica 11. I am just using that name for all curated data-related functions.

As you know, CountryData[] is one of such so called "curated data" functions in Mathematica. It basically presents a convenient way to access lots of information on all countries of the today's world.

In this question, an undocumented value for property passed to CountryData[] is discussed ("OfficialLanguages").

How to find out all undocumented values?

The same question for:

AstronomicalData[]
GraphData[]
WordData[]
...

(all XxxData[] from Mathematica's curated data)

I tried examining correspondent mx file, but no results. Is there a smart way?

I read several related questions here, that deal with undocumented options and other parameter values for certain Mathematica's functions, but none of presented methods for discovering undocumented values worked for CountryData[].

No, XxxData[] is not a new function in Mathematica 11. I am just using that name for all curated data-related functions.

As you know, CountryData[] is one of these so called "curated data" functions in Mathematica. It basically presents a convenient way to access lots of information on all countries of the today's world.

In this question, an undocumented value for property passed to CountryData[] is discussed ("OfficialLanguages").

How to find out all undocumented values?

The same question for:

AstronomicalData[]
GraphData[]
WordData[]
...

(all XxxData[] from Mathematica's curated data)

I tried examining correspondent mx file, but no results. Is there a smart way?

I read several related questions here, that deal with undocumented options and other parameter values for certain Mathematica's functions, but none of presented methods for discovering undocumented values worked for CountryData[].

No, XxxData[] is not a new function in Mathematica 11. I am just using that name for all curated data-related functions.

As you know, CountryData[] is one of such so called "curated data" functions in Mathematica. It basically presents a convenient way to access lots of information on all countries of the today's world.

In this question, an undocumented value for property passed to CountryData[] is discussed ("OfficialLanguages").

How to find out all undocumented values?

The same question for:

AstronomicalData[]
GraphData[]
WordData[]
...

(all XxxData[] from Mathematica's curated data)

I tried examining correspondent mx file, but no results. Is there a smart way?

I read several related questions here, that deal with undocumented options and other parameter values for certain Mathematica's functions, but none of presented methods for discovering undocumented values worked for CountryData[].

As you know, CountryData[] is one of so called "curated data" functions in Mathematica. It basically presents a convenient way to access lots of information on all countries of the today's world.

In this question, an undocumented value for property passed to CountryData[] is discussed ("OfficialLanguages").

How to find out all undocumented values?

The same question for:

AstronomicalData[]
GraphData[]
WordData[]
...

(all XxxData[] from Mathematica's curated data)

I tried examining correspondent mx file, but no results. Is there a smart way?

I read several related questions here, that deal with undocumented options and other parameter values for certain Mathematica's functions, but none of presented methods for discovering undocumented values worked for CountryData[].

No, XxxData[] is not a new function in Mathematica 11. I am just using that name for all curated data-related functions.

As you know, CountryData[] is one of these so called "curated data" functions in Mathematica. It basically presents a convenient way to access lots of information on all countries of the today's world.

In this question, an undocumented value for property passed to CountryData[] is discussed ("OfficialLanguages").

How to find out all undocumented values?

The same question for:

AstronomicalData[]
GraphData[]
WordData[]
...

(all XxxData[] from Mathematica's curated data)

I tried examining correspondent mx file, but no results. Is there a smart way?

I read several related questions here, that deal with undocumented options and other parameter values for certain Mathematica's functions, but none of presented methods for discovering undocumented values worked for CountryData[].