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Overview of querying

Within the top level query JSON object there is a query field "qt" that is an array of query term objects. Query term objects are described below and allow the following query types:

• Exact text
• Free text
• Entities
• Geospatial
• Temporal
• Events

These terms can then be combined in an arbitrary boolean expression (with the operators AND, OR, NOT and parantheses) using the (case insensitive) "logic" field of the top level object, where the different terms are denoted by their index in the array (counting from 1). For example:

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Finally, note that the combination of "qt" and "logic" can be replaced by the "raw" object described at the bottom of this page, which gives the user access to the raw ElasticSearch query API. If both "qt"/"logic" and "raw" are present, the "qt"/"logic" fields are ignored.

Exact text

The exact text query term object has the following format:

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For example (using dot notation), qt[0].etext="barack obama" will match on documents containing "barack obama" but not documents containing only (eg) "president obama", "barack 'barry' obama" etc.

Free text

The free text query term object has the following format:

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Note when using dot notation and typing queries directly into the URL bar that characters like '+' must be double-URL-encoded, eg to %25%32%4B (ie via %2B from +).

Entities

The entity query term object has the following 2 possible formats:

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Geospatial

The geospatial query term has the following possible formats:

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• qt[0].geo.centerll="40.12,-71.34"&qt[0].geo.dist="100km": within 100km of the specified lat/long.
• { "qt": [ { "geo": { "centerll": "40.12,-71.34", "dist": "100" } } ] }: uses the default unit (km), ie is the same query as above.
• qt[0].geo.minll="(4.1,-171.34)"&qt[0].geo.maxll="40.12,-71.34": bounding box showing lat/long format with and without parantheses.

Temporal 

The temporal query term has the following format:

...

• The "entity1" field is processed as follows:
  • "ftext" and "etext" terms are applied across both the "entity1" and "entity1_index" fields within the entity object (TBD link)
  • entity/entityValue/entityType terms are only applied to the "entity1_index" field
• The "entity2" field is processed analogously 
• The "verb" string is applied as an exact text query to the "verb_category" field and a free text query to the "verb" field within the entity object (TBD link)
• For events with a time range ("time_start" and "time_end" fields), any part of the event time range can match the "time" term.
• The difference between "Events", "Facts" or "Summaries" is described here (TBD link).
• If multiple terms are specified then these are ANDed together. There is currently no way of performing more complex boolean equations on individual events (obviously multiple event query terms can be specified and match across all events within a document).
• Event queries with multiple terms can be a bit slower than other queries (due to its implementation in ElasticSearch).

  Code Block
  language javascript title Example event queries
  // Any fact in which Barack Obama is the subject: { "event": { "entity1": { "entity": "barack obama/person" }, "type":"Fact" } } // Travel events involving Sarah Palin: { "event": { "entity1": { "entityValue":"sarah palin", "entityType":"person" }, "verb": "travel", } } // Events in the future: { "event": { "time": { "min": "now" }, "type":"Event" } }

Combining query terms

Multiple query terms can be combined in 2 ways:

• Using the "logic" field as described above under "Overview of querying". This is the standard way of combining separate queries.
• In addition, within a single query term multiple elements of different types can be merged into a single object - this has the effect of ANDing them together. For example:
  • { "qt": [ { "entity": "barack obama/person", "time": { "min": "1284666757164", "max": "now" } } ] }: documents containing the entity Barack Obama, from 16 Sep 2010 until now.
  • qt[0].etext="apple"&qt[0].ftext="pair": this is equivalent to qt[0].etext="apple"&qt[1].ftext="pair"&logic="1 and 2"

Raw ElasticSearch queries

At present ElasticSearch is used as the front end of the search engine. 

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