Hi Boris, Ah! You are using the REST API. That changes a lot, since Neo4j Spatial is only recently exposed in REST and we do not expose most of the capabilities I have discussed in this thread, or indeed in my other answer today.
I did recently add some REST methods that might work for you, specifically the addEditableLayer, which makes a WKB layer, and the addGeometryWKTToLayer, for adding any kind of Geometry (including LineString) to the layer. However, these were only added recently, and I have no experience using them myself, so consider this very much prototype code. From your other question today, can I assume you are having trouble making sense of the data coming back? So we need a better way to return the results in WKT instead of WKB? One option would be to enhance the addEditableLayer method to allow the creation of WKT layers instead of WKB layers, so the internal representation is more internet friendly. I've just added untested support for setting the format to WKT for the internal representation of the editable layer in the REST interface. This is untested (outside of my usual unit tests, that is), and is only in the trunk of neo4j-spatial, but you are welcome to try it out and see what happens. Regards, Craig On Fri, Jul 1, 2011 at 5:29 PM, Boris Kizelshteyn <bo...@popcha.com> wrote: > Hi Craig, > > Thanks so much for this reply. It is very insightful. Is it possible for me > to implement the LineString geometries and lookups using REST? > > Many thanks! > > On Wed, Jun 8, 2011 at 4:58 PM, Craig Taverner <cr...@amanzi.com> wrote: > > > OK. I understand much better what you want now. > > > > Your person nodes are not geographic objects, they are persons that can > be > > at many positions and indeed move around. However, the 'path' that they > > take > > is a geographic object and can be placed on the map and analysed > > geographically. > > > > So the question I have is how do you store the path the person takes? Is > > this a bunch of position nodes connected back to that person? Or perhaps > a > > chain of position-(next)->position-(next)->position, etc? However you > have > > stored this in the graph, you can express this as a geographic object by > > implementing the GeometryEncoder interface. See, for example, the 6 lines > > of > > code it takes to traverse a chain of NEXT locations and produce a > > LineString > > geometry in the SimpleGraphEncoder at > > > > > https://github.com/neo4j/neo4j-spatial/blob/master/src/main/java/org/neo4j/gis/spatial/encoders/SimpleGraphEncoder.java#L82 > > > > < > > > https://github.com/neo4j/neo4j-spatial/blob/master/src/main/java/org/neo4j/gis/spatial/encoders/SimpleGraphEncoder.java#L82 > > >If > > you do this, you can create a layer that uses your own geometry encoder > (or > > the SimpleGraphEncoder I referenced above, if you use the same graph > > structure) and your own domain model will be expressed as LineString > > geometries and you can perform spatial operations on them. > > > > Alternatively, if your data is more static in nature, and you are > analysing > > only what the person did in the past, and the graph will therefor not > > change, perhaps you do not care to store the locations in the graph, and > > you > > can just import them as a LineString directly into a standard layer. > > > > Whatever route you take, the final action you want to perform is to find > > points near the LineString (path the person took). I do not think the > > bounding box is the right approach for that either. You need to try, for > > example, the method findClosestEdges in the utilities class at > > > > > https://github.com/neo4j/neo4j-spatial/blob/master/src/main/java/org/neo4j/gis/spatial/SpatialTopologyUtils.java#L115 > > > > < > > > https://github.com/neo4j/neo4j-spatial/blob/master/src/main/java/org/neo4j/gis/spatial/SpatialTopologyUtils.java#L115 > > >This > > method can find the part of the persons path that it closest to the point > > of > > interest. There also also many other geographic operations you might be > > interested in trying, once you have a better feel for the types of > queries > > you want to ask. > > > > Regards, Craig > > > > On Wed, Jun 8, 2011 at 2:17 AM, Boris Kizelshteyn <bo...@popcha.com> > > wrote: > > > > > Thanks for the detailed response! Here is what I'm trying to do and I'm > > > still not sure how to accomplish it: > > > > > > 1. I have a node which is a person > > > > > > 2. I have geo data as that person moves around the world > > > > > > 3. I use the geodata to create a bounding box of where that person has > > been > > > today > > > > > > 4. I want to say, was this person A near location X today? > > > > > > 5. I do this by seeing if location X is in A's bounding box. > > > > > > From looking at what you suggest doing, it's not clear how I assign the > > > node > > > person A to a layer? Is it that the bounding box is now in the layer > and > > > not > > > in the node? The issue then becomes, how od I associate the two as the > > > RTree > > > relationship seems to establish itself on the bounding box between the > > node > > > and the layer. > > > > > > Many thanks for your patience as I learn this challenging material. > > > > > > On Tue, Jun 7, 2011 at 4:13 PM, Craig Taverner <cr...@amanzi.com> > wrote: > > > > > > > I think you need to differentiate the bounding boxes of the data in > the > > > > layer (stored in the database), and the bounding box of the search > > query. > > > > The search query is not stored in the database, and will not be seen > as > > a > > > > node or nodes in the database. So if you want to search for data > within > > > > some > > > > bounding box or polygon, then express that in the search query, and > you > > > do > > > > not need to care about how your nodes are stored in the database. > > > > > > > > So when you say you want to make a larger bounding box, I assume you > > are > > > > talking about the query itself. The REST API has the method > > > > findGeometriesInLayer, which takes minx, maxx, miny, maxy parameters > > and > > > > you > > > > can set those to whatever you want for your query. > > > > > > > > The REST API also exposes the CQL query language supported by > GeoTools. > > > > This > > > > allows you to perform SQL-like queries on geometries and feature > > > > attributes. > > > > For example, you can search for all objects within a specific polygon > > > (not > > > > just a rectangular bounding box), as well as conforming to certain > > > > attributes. See > > > > > > > > > > http://docs.geoserver.org/latest/en/user/tutorials/cql/cql_tutorial.htmlfor > > > > some examples of CQL. > > > > > > > > However, our current CQL support is not fully integrated with the > RTree > > > > index. This means that the CQL itself will not benefit from the > index, > > > but > > > > be a raw search. You can, however, still get the benefit of the index > > by > > > > passing in the bounding box separately. So, for example, you want to > > > search > > > > for data in a polygon. Make the polygon object, get it's bounding box > > and > > > > also the CQL query string. Then make a 'dynamic layer' using the CQL > > > (which > > > > is a bit like making a prepared statement). Then perform the same > > > > 'findGeometriesInLayer' method mentioned above, using the bounding > box > > > and > > > > the dynamic layer (containing the CQL). This has the effect of using > > the > > > > RTree index for a first approximate search, followed by pure CQL for > > the > > > > final mile. > > > > > > > > See examples of this in action in the Unit tests in the source code. > > > > > > > > > > > > > > https://github.com/neo4j/neo4j-spatial/blob/master/src/test/java/org/neo4j/gis/spatial/ServerPluginTest.java#L109 > > > > has > > > > examples of CQL queries on the REST API. > > > > > > > > On Tue, Jun 7, 2011 at 5:48 PM, Boris Kizelshteyn <bo...@popcha.com> > > > > wrote: > > > > > > > > > Thanks! So it seems you are saying that the bounding box represents > a > > > > > single > > > > > point and is the same as the lat/lat lon? What if I make the > bounding > > > box > > > > > bigger? What I am trying to do is geo queries against a bounding > box > > > made > > > > > of > > > > > a set of points, rather than individual points. So the query is, > find > > > the > > > > > nodes where the given point falls inside their bounding boxes. Can > I > > do > > > > > this > > > > > with REST? > > > > > > > > > > Thanks! > > > > > > > > > > On Tue, Jun 7, 2011 at 11:34 AM, Craig Taverner <cr...@amanzi.com> > > > > wrote: > > > > > > > > > > > Hi, > > > > > > > > > > > > The bounding boxes are used by the RTree index, which is a > typical > > > way > > > > to > > > > > > index spatial data. For Point data, the lat/long and the bounding > > box > > > > are > > > > > > the same thing, but for other shapes (streets/LineString and > > > Polygons), > > > > > the > > > > > > bounding box is quite different to the actual geometry (which is > > not > > > > just > > > > > a > > > > > > single lat/long, but a set of connected points forming a complex > > > > shape). > > > > > > > > > > > > The RTree does not differentiate between points and other > > geometries, > > > > > > because it cares only about the bounding box, and therefor we > > provide > > > > > that > > > > > > even for something as simple as a Point. > > > > > > > > > > > > Does that answer the question? > > > > > > > > > > > > Regards, Craig > > > > > > > > > > > > On Tue, Jun 7, 2011 at 4:57 PM, Boris Kizelshteyn < > > bo...@popcha.com> > > > > > > wrote: > > > > > > > > > > > > > Greetings! > > > > > > > > > > > > > > Perhaps someone using neo4j-spatial can answer this seemingly > > > simple > > > > > > > question. Nodes classified into layers have both lat/lon > > properties > > > > and > > > > > > > bounding boxes, the bounding box seems to be required to > > establish > > > > the > > > > > > > relationship between node and layer, however the node is not > > found > > > if > > > > > the > > > > > > > lat/lon does not match the query. Can someone explain the > > > > relationship > > > > > > > between these two properties on a node? > > > > > > > > > > > > > > Many thanks! > > > > > > > _______________________________________________ > > > > > > > Neo4j mailing list > > > > > > > User@lists.neo4j.org > > > > > > > https://lists.neo4j.org/mailman/listinfo/user > > > > > > > > > > > > > _______________________________________________ > > > > > > Neo4j mailing list > > > > > > User@lists.neo4j.org > > > > > > https://lists.neo4j.org/mailman/listinfo/user > > > > > > > > > > > _______________________________________________ > > > > > Neo4j mailing list > > > > > User@lists.neo4j.org > > > > > https://lists.neo4j.org/mailman/listinfo/user > > > > > > > > > _______________________________________________ > > > > Neo4j mailing list > > > > User@lists.neo4j.org > > > > > > > > > > > _______________________________________________ > > > Neo4j mailing list > > > User@lists.neo4j.org > > > https://lists.neo4j.org/mailman/listinfo/user > > > > > _______________________________________________ > > Neo4j mailing list > > User@lists.neo4j.org > > https://lists.neo4j.org/mailman/listinfo/user > > > _______________________________________________ > Neo4j mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user > _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
