[Developers] Can a link's opposite direction name be retrieved with less queries?

[Jim Weaver]

Thanks Alec.  I'll post a link to the app on this list once I get it
into a working state.  I plan to improve it on it by showing images,
etc.  I'd like to also like to add the ability to navigate the
higher-level freebase ontology to arrive at a topic.  The information
visualization piece of that should be fun.

 

On a personal/professional note, the idea of applying structure to data
on the internet has been a passion of mine for many years, mainly for
the purpose of research and education.  I've made several attempts at
this, including using the Library of Congress Subject Headings as the
ontology to reach information, with a desire to see it be able get to
the granularity of primitive values (e.g. what is the population of New
York).  I am very excited that MetaWeb has done this by creating
freebase, and congratulate you!

 

Thanks,

Jim Weaver

http://jmentor.com/about.php

http://lat-inc.com <http://lat-inc.com/> 

 

 

________________________________

From: Alec Flett [mailto:alecf at metaweb.com] 
Sent: Friday, September 21, 2007 1:26 PM
To: Jim Weaver
Cc: developers at freebase.com
Subject: Re: [Developers] Can a link's opposite direction name be
retrieved with less queries?

 

To answer the question in the subject: absolutely - in one query
actually.

First of all, you might be interested in the 'explore' view - its a
debugging tool similar to what you've created here:

http://www.freebase.com/view/explore/topic/en/the_police

Look at the XmlHttpRequests that go by using Firebug - you'll learn
quite a bit.

(And a caveat - the code and the user interface are crude and unusual
because this is really just for debugging..)

On to the query:



This query has the right idea - the problem is that it is saying "Give
me all topics that have at least one master link, one reverse link, AND
one value link" - i.e. the topic has to have all three... so you're
going to miss topics that have only one of these.

So for a given topic, you're going to need to put an "optional": true
inside each of these /type/reflect/any_* clauses.



 

   "/type/reflect/any_reverse":[{

      "id":null,

      "link":null,

      "name":null,

      "type":[]

    }],

    "/type/reflect/any_value":[{

      "link":null,

      "type":null,

      "value":null

    }],

    "id":"/topic/en/the_police",

    "name":null

  }]

}

 

 

...



That works fine (e.g. "Musical Genres" in the screenshot), except when
the link is an "any_reverse".  In this case, the link (and the name that
comes back) is from the wrong perspective (like the "Recorded By" name
in the screenshot).  I know that I can do an additional query to get the
link from the opposite perspective:

You don't have to do an additional query but there is a bit of a trick
here. Some properties that come back on any_reverse don't have a
property name/id from the other direction (called a 'reciprocal
property'). Depending on what you want your tool to do, you might only
want the reverse values for properties that have a reverse back the
other way. That's actually what the history view for a topic shows you. 

Here's the query clause to show all reverse links:

  "/type/reflect/any_reverse":[{ 

      "id":null,

      "link": {"master_property": {
                 "id": null,

                 "name": null,
                 "reverse_property": {"id": null,
                                      "name": null,
                                      "optional": true }},

      "name":null,

      "type":[]

    }],


Note that inside the master_property, I'm asking for the reverse - so
you're essentially asking "On this reverse property, whats the reverse
of that, coming the other way?" 

Notice that I added "optional" here - without optional, you'll only get
values that have a reverse property coming in the other way. with
optional, the "reverse_property" clause in the result may be null - in
that case there isn't a property pointing back the other way.

Also note that I added "name" so I'd get the english name of the
property.



 

My question is, can the number of queries to accomplish these results be
reduced?  By the way, when a link name (e.g. "Musical Genres" is
returned, I'm caching that name so that I don't have to query for it
again.

 

You can always expand these things even further and add things like
expected_type, and/or by expanding the "type" field. The expected_type
shows you the type that the property expects, while the 'type' clause
actually asks for the list of types

  "/type/reflect/any_reverse":[{ 

      "id":null,

      "link": {"master_property": {
                 "id": null,

                 "name": null,

                 "expected_type": {"id": null, "name": null},
                 "reverse_property": {"id": null,
                                      "name": null,
                                      "optional": true }},

      "name":null,

      "type":[{"id": null, "name": null]

    }],


Hope that helps.

Alec

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