Can get all triples with value null in specific field?
All people with date_of_birth equal null?
[
"type": "/people/person",
"date_of_birth":null,
"name":null
]
You need to use "optional":"forbidden" directive:
[{
"type": "/people/person",
"date_of_birth": {
"value": null,
"optional": "forbidden"
},
"name": null,
"id": null
}]
(I added "id":null so that the Query Editor gives clickable links)
Note that query has a default "limit":100, if you want more results then add an explicit limit clause. If that times out, then you'll need to use a MQL cursor.
If you need to deal with lots of results, the undocumented envelope parameter "page" provides more flexibility than "cursor", allowing you to move forward, back, or access a page at random, as opposed to just going forward like you can with the cursor.
The "optional": "forbidden" clause is the key to lots of useful queries. The "!everything" == "nothing" equivalency is just one of the most common ones.
Tom
Related
I am looking to extract list of tourist attractions and their city,state and country information from Freebase. The property that has location is
"/location/location/containedby". There are different types for this object, "location/location" or "/base/biblioness/bibs_location". If the object has "/base/biblioness/bibs_location" i can get the value of "city", "state" etc. however if the object only has the type "/location/location" i need to go and get its "containedby" field and redo the above logic.
My question is can i perform a conditional query in Freebase like if type == "/location/location/" get xyz. if type== "/base/biblioness/bibs_location" get abc
MQL:
[{
"type": "/travel/tourist_attraction",
"id": null,
"name": null,
"name~=": "^San Diego",
"/location/location/containedby": {
"type": "/base/biblioness/bibs_location",
"name": null,
"id": null
},
"/location/location/geolocation": [{
"id": null,
"latitude": null,
"longitude": null
}]
}]
MQL doesn't support conditional logic, but you can query all the information that you're potentially interested in, making the subqueries optional so they don't filter the results, and then look at what you get back. It'll require conditional code in your result processor, but you won't have to make multiple queries. For example, you could query multiple levels of /location/location/contained by as well as /base/biblioness/bibs_location/state and whatever else you want.
Before you go spending too much time on this though, you might want to check how well populated /base/biblioness/bibs_location is. It looks to me like it's got less than 2K entities.
I'm wondering if it is possible to get all info about a specific date from Freebase.
I can easily retrieve info about a date giving a specific topic, for example, to grab all persons of interest who were born on a specific date:
[{
"type":"/people/person",
"limit":1000,
"sort":"name",
"name":null,
"guid":null,
"timestamp":null,
"/people/person/date_of_birth":"1955-02-24"
}]
Is it possible to grab all types? I'm after things like people born on that date (which I have), major events (start of a war, assassination of a person of interest, etc), and so on.
Essentially I want to match all fields that are dates and return the full information about that entry, regardless of type.
Reflection is what you need here:
[{
"/type/reflect/any_value": [{
"type": "/type/datetime",
"value": "1955-02-24",
"link": {
"source": {
"id": null
},
"master_property": null
}
}]
}]
A couple of notes on that: the MQL manual I've linked to is somewhat bitrotted in its details but is still the best documentation that exists on MQL. Secondly, there's what I'm pretty sure is in MQL bug if you use "*": null or more specifically "target_value": null in the link clause above which makes it ignore the outer value you specified... so don't do that :-)
What would be the MQL query if I want to search for a property that has a particular string either in its name or the actual link path. For name, I was able to put a ~= matching on the name property, but not in the link path. I tried to use the ~= in the id, but it says we cannot do matching in the id.
[{
"/type/object/id": "wikipedia",
"name~=": "wikipedia",
"/type/object/type": "/type/property",
"/type/object/name": null
"limit": 200
}]
Is there a way to also search for strings in the id ?
A couple of things:
the ~= operator works on a whole word basis, so if you want to find the string "wikipedia" in all contexts, you'll want to use "*wikipedia*"
IDs aren't stored with fully formed paths, instead they're a sequence of keys in their respective namespaces (think filenames in directories)
You'll need two separate queries to match both the properties and their containing domains since you can't do unions like that in MQL.
For properties who's names contain wikipedia:
[{
"type": "/type/property",
"name~=" : "*wikipedia*",
"name": null,
"id":null,
"limit": 200
}]
and for properties which belong to types who's IDs contain wikipedia:
[{
"type": "/type/property",
"name": null,
"id":null,
"schema" : {"key":{"namespace":{"name~=":"*wikipedia*"}},"id":null},
"limit": 200
}]
That second query may need a little refinement, but it should give you the basic idea.
I have a little problem, maybe can you help me. I'm trying to get the "currency features" from freebase. So I tried to do : "/base/schemastaging/person_extra/net_worth": null but, I can't get the value written on freebase (for example, with Madonna, it's 650,000,000). Do you know, why it's not working ?
First of all, as the property path suggests, /base/schemastaging/person_extra/net_worth is just being staged right now so the final property ID will be something else (follow the mailing list to discuss new schema). You should NOT be using this property for anything other than experimentation.
The reason why you don't see the data that you want withe the following query is because this property is a CVT.
{
"id": "/en/madonna",
"type": "/base/schemastaging/person_extra",
"net_worth": null
}
CVT values are complex objects that need to be expanded to access the values that you want. In this case, net_worth is a CVT so that we can record a person's net worth at different points in time.
If you expand your query to include the relevant properties from /measurement_unit/dated_money_value you'll see the data that you're after.
{
"id": "/en/madonna",
"type": "/base/schemastaging/person_extra",
"net_worth": {
"amount": null,
"currency": null,
"valid_date": null
}
}
One other issue, that isn't obvious from this example, is that since there can be multiple dated money values, you'll need to make your query more precise so as to get only the latest value. You can do that like this;
{
"id": "/en/madonna",
"type": "/base/schemastaging/person_extra",
"net_worth": {
"amount": null,
"currency": null,
"valid_date": null,
"sort": "-valid_date",
"limit": 1,
"optional": true
}
}
Update: Made net worth an optional property value.
Trying to get some movies and their genres but leave out any records that contain the genre "Thriller" in the array of genres.
How do I not only ignore the genre key itself for "Thriller", but squelch that entire movie result? With my current query, Thriller is removed from the array of genres, but the parent object (film) is still displayed.
Here's my current workup in the query editor:
http://tinyurl.com/d2g54lj
[{
'type':'/film/film',
'limit':5,
'name':null,
'/film/film/genre': [],
'/film/film/genre!=': "Thriller",
}]
The answer provided is correct, but changes some other stuff in the query too. Here's the direct equivalent to the original query:
[{
"type": "/film/film",
"limit": 5,
"name": null,
"genre": [],
"x:genre": {"name":"Thriller",
"optional":"forbidden"},
}]
The important part is the "optional":"forbidden". The default property used is "name", but we need to specify it explicitly when we use a subclause (to allow us to specify the "optional" keyword). Using ids instead of names, as #kook did, is actually more reliable, so that's an improvement, but I wanted people to be able to see the minimum necessary to fix the broken query.
We can abbreviate the property name to "genre" from "/film/film/genre" since "type":"/film/film" is included (we also never need to use /type/object for properties like /type/object/name).
Answering my own question.
So the trick is to not use the != (but not) operator, but to actually flip it on its head and use the "|=" (one of) operator with 'forbid', like so:
[{
'type':'/film/film',
'limit':5,
'name':null,
'/film/film/genre': [{
"id": null,
"optional": true
}],
"forbid:/film/film/genre": {
"id|=": [
"/en/thriller",
"/en/slapstick"
],
"optional": "forbidden"
}
}]
Thanks to the following post:
Freebase query - exclusion of certain values