[[java-rest-high-x-pack-graph-explore]]
=== X-Pack Graph explore API

[[java-rest-high-x-pack-graph-explore-execution]]
==== Initial request

Graph queries are executed using the `explore()` method:

["source","java",subs="attributes,callouts,macros"]
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include-tagged::{doc-tests}/GraphDocumentationIT.java[x-pack-graph-explore-request]
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<1> In this example we seed the exploration with a query to find messages mentioning the mysterious `projectx`
<2> What we want to discover in these messages are the ids of `participants` in the communications and the md5 hashes
of any attached files. In each case, we want to find people or files that have had at least one document connecting them
to projectx.
<3> The next "hop" in the graph exploration is to find the people who have shared several messages with the people or files
discovered in the previous hop (the projectx conspirators). The `minDocCount` control is used here to ensure the people
discovered have had at least 5 communications with projectx entities. Note we could also supply a "guiding query" here e.g. a 
date range to consider only recent communications but we pass null to consider all connections.
<4> Finally we call the graph explore API with the GraphExploreRequest object.  


==== Response

Graph responses consist of Vertex and Connection objects (aka "nodes" and "edges" respectively):

["source","java",subs="attributes,callouts,macros"]
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include-tagged::{doc-tests}/GraphDocumentationIT.java[x-pack-graph-explore-response]
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<1> Each Vertex is a unique term (a combination of fieldname and term value). The "hopDepth" property tells us at which point in the 
requested exploration this term was first discovered. 
<2> Each Connection is a pair of Vertex objects and includes a docCount property telling us how many times these two
Vertex terms have been sighted together


[[java-rest-high-x-pack-graph-expand-execution]]
==== Expanding a client-side Graph

Typically once an application has rendered an initial GraphExploreResponse as a collection of vertices and connecting lines (graph visualization toolkits such as D3, sigma.js or Keylines help here) the next step a user may want to do is "expand". This involves finding new vertices that might be connected to the existing ones currently shown.

To do this we use the same `explore` method but our request contains details about which vertices to expand from and which vertices to avoid re-discovering. 

["source","java",subs="attributes,callouts,macros"]
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include-tagged::{doc-tests}/GraphDocumentationIT.java[x-pack-graph-explore-expand]
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<1> Unlike the initial request we do not need to pass a starting query
<2> In the first hop which represents our "from" vertices we explicitly list the terms that we already have on-screen and want to expand by using the `addInclude` filter.
We can supply a boost for those terms that are considered more important to follow than others but here we select a common value of 1 for all.
<3> When defining the second hop which represents the "to" vertices we hope to discover we explicitly list the terms that we already know about using the `addExclude` filter

