[Developers] More information on '/type/reflect'

Fri May 23 02:37:21 UTC 2008

Hi David,
I was trying the generic query you had carved out and ran into another
issue. Hopefully you can shed some light on this.

My subject, Peter Jackson, a New Zealand national and a screenwriter, is
married to Fran Walsh and works for Weta Digital. However if I try the
generic query with these names rather than 'new zealand' or 'screenwriter' I
don't get down to the subject. Fran Walsh and Weta Digital do not appear to
be linked *directly *to Peter Jackson, it looks like there is a relation
'spouse' or 'employer' which has a value.

Would greatly appreciate if you can help me understand what kind of link
exits between Peter Jackson and Fran Walsh or Weta Digital and if there is a
way I can include the latter in the generic query.

Thanks a lot.
Sumit

On Wed, May 7, 2008 at 6:12 PM, David Flanagan <david at davidflanagan.com>
wrote:

> Sumit wrote:
>
>> Hi,
>> Where can I find more reference on the '/type/reflect' properties i.e.
>> /type/reflect/any_master, /type/reflect/any_reverse and
>> /type/reflect/any_value. I see it being used in discussions and mailing
>> lists but was not able to find any info on these topics in the MQL tutorial
>> or the architecture/data model notes.
>>
>
> As far as I know, no such documentation exists yet.  I'm working on
> updating the MQL tutorial to add it, however.
>
>  Here is a case/problem that I am trying to solve
>>  - Given a person's name and related information like country of birth,
>> profession, etc. find its freebase id.
>>  - The query should not rely on specific types like /location/country as
>> the place associated with a persons name could be a state or city or county
>> too. Same with profession, employers, etc.
>>
>> After poking around into lists and discussions I tried the following query
>> which works, at least I think it is working. However I need to read up more
>> on the '/type/reflect' to be confident.
>>
>> {
>>  "query" : [
>>    {
>>      "/type/reflect/any_master" : [
>>        {
>>          "name" : "new zealand"
>>        }
>>      ],
>>      "id" : [],
>>      "name" : "peter jackson",
>>      "type" : "/people/person"
>>    }
>>  ]
>> }
>>
>
> Here are my comments on this query:
>
> 1) Queries of the id property always return a single value, even when an
> object has more than one possible id.  So you can safely use "id":null
>
> 2) When you use a /type/reflect property, you find any property with the
>  value you've specified. If you're interested in the name of the property
> that has been matched, add "link":null to the clause.
>
> 3) For the kind of generic search you're attempting here, it may not be
> sufficient to just use /type/reflect/any_master.  That will only find
> outgoing links to other objects. It won't find incoming links, and it won't
> find properties that refer to a value rather than to an object.  (So if "new
> zealand" was a value of /type/text rather than a /location/country object,
> it wouldn't be found.  And suppose that /location/country had a
> "famous_person_born_here" property and that this was a master property, with
> its reverse being /people/person/countries_claiming_this_person.  Your query
> using any_master wouldn't find a link like that between Peter Jackson and
> New Zealand because it is not a master property of /people/person.
>
> So here's how you might alter your query
>
>
> [{
>  "/type/reflect/any_master" : [{
>     "link":null,
>     "name":"new zealand"
>  }],
>  "/type/reflect/any_reverse" : [{
>     "link":null,
>     "name":"new zealand",
>     "optional":true
>  }],
>  "/type/reflect/any_value" : [{
>     "link":null,
>     "value":"new zealand"
>  }],
>  "id" : null,
>  "name" : "peter jackson",
>  "type" : "/people/person"
> }]
>
> Actually, however, the any_value portion of this query doesn't work: it
> won't let me specify a value for the "value" property, only query it with
> null.  I don't know if this is a bug or a legitimate restriction, so you
> either have to query all values of /type/text and see if any of them are
> country names or drop that clause from your query.
>
> If you really do care about searching reverse properties as well as
> outgoing properties, then the problem with the query above is that you've
> got to put optional:true in both clauses, and you'll get lots of results
> that don't match either clause.  A better way (also not yet documented)
> perhaps to do this is to query the links between objects:
>
> [{
>  "type":"/type/link",
>  "source": {
>    "type":"/people/person",
>    "name":"peter jackson",
>    "id":null
>  },
>  "target": {"name":"new zealand"},
>  "master_property":null,
>  "reverse":null
> }]
>
> This says: "Return the id of a person named peter jackson who has an
> outgoing or incoming link to or from something named "new zealand". Also
> return the master property name for the link and tell me whether the link
> was reversed in this case."
>
> Here's a version that looks for links to New Zealand or Screenwriter:
>
> [{
>  "type":"/type/link",
>  "source": {
>    "type":"/people/person",
>    "name":"peter jackson",
>    "id":null
>  },
>  "target":{
>      "name":null,
>      "name|=":["new zealand","screenwriter"]
>  },
>  "master_property":null,
>  "reverse":null
> }]
>
> Like the /type/reflect/any_master query you started with, this /type/link
> query does not find links that are to /type/text values rather than to
> objects.  To find those, you'd work with the target_value property of the
> link instead of target.
>
> While we're on the topic of undocumented syntax, here's a query that says
> "Return the id and nationality of people named Peter Jackson but exclude any
> who are nationals of any country other than New Zealand." This gets you the
> person you're looking for, plus about four others who don't have the
> nationality property filled in:
>
> [{
>  "nationality":null,
>  "but:nationality":{
>   "optional":"forbidden",
>   "name!=":"New Zealand"
>  },
>  "id" : null,
>  "name" : "peter jackson",
>  "type" : "/people/person"
> }]
>
> I've written some documentation for optional:forbidden and != but it is not
> published yet.  Stay tuned.
>
> Hope this helps!
>
>        David Flanagan
>
>
>> Thanks.
>> Sumit
>>
>>
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>>
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>
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