ARLAS Exploration API
The ARLAS API makes the ARLAS catalog available for exploration and browsing. The catalog contains collections of geo-referenced elements. Every element has a geometry, a centroid, a timestamp and a set of fields specific to the collection.
URL Schema
The table below lists the URL endpoints and their optional "parts". A part is composed of optional parameters. The parameters are separated with the character &.
| PATH Template | Description |
|---|---|
| /arlas/explore/_list | List the collections configured in ARLAS |
/arlas/explore/{collection}/_describe?form |
Describes the structure and the content of the given collection |
/arlas/explore/{collection}/_count?filter & form |
Counts the number of elements found in the collection, given the filters |
/arlas/explore/{collection}/_compute?compute & filter & form |
Computes the metric of a field in the collection, given the filters |
/arlas/explore/{collection}/_search?filter & form & projection & page & returned_geometries |
Search and return the elements found in the collection, given the filters |
/arlas/explore/{collection}/_geosearch?filter & form & projection & page & returned_geometries |
Search and return the elements found in the collection as features, given the filters |
/arlas/explore/{collection}/_geosearch/{z}/{x}/{y}?filter & form & projection & page & returned_geometries |
Search and return the elements found in the collection and localized in the given tile(x,y,z) as features, given the filters |
/arlas/explore/{collections}/_aggregate?aggregation &filter & form |
Aggregate the elements in the collection(s), given the filters and the aggregation parameters |
/arlas/explore/{collections}/_geoaggregate?aggregation &filter & form |
Aggregate the elements in the collection(s) as features, given the filters and the aggregation parameters |
/arlas/explore/{collections}/_geoaggregate/{geohash}?aggregation &filter & form |
Aggregate the elements in the collection(s) and localized in the given {geohash} as features, given the filters and the aggregation parameters |
/arlas/explore/{collections}/_geoaggregate/{z}/{x}/{y}?aggregation &filter & form |
Aggregate the elements in the collection(s) and localized in the given zxy tile as features, given the filters and the aggregation parameters |
/arlas/explore/{collections}/_suggest?filter & form & size & suggest |
Suggest the the n (n=size) most relevant terms given the filters |
When multiple collections are permitted ({collections}), the comma is used for separating the collection names.
| Examples |
|---|
https://api.gisaia.com/demo/arlas/explore/_describe |
https://api.gisaia.com/demo/arlas/explore/city,state,country/_describe |
https://api.gisaia.com/demo/arlas/explore/city,state,country/_count?q=bord*&f=country:France&pretty=true |
https://api.gisaia.com/demo/arlas/explore/election/_search?f=country:France&f=$timestamp:range:[0<1490613808000]&pretty=true&size=1000&include=id,name |
https://api.gisaia.com/demo/arlas/explore/election/_aggregate?f=country:France&f=$timestamp:range:[0<1490613808000]&pretty=true&size=1000&include=id,name&agg=geohash&agg_interval=4 |
All URLs are accessible both with GET and POST requests. For POST requests, URL parts are passed as a JSON representation.
URL Parts
Part: aggregation
The [aggregation] url part allows the following parameters to be specified:
| Parameter | Default value | Description | Multiple |
|---|---|---|---|
| agg | None |
Gathers a set of sub-parameters indicating the type of aggregation, the field used as the aggregation key and possibly the interval for numeric values | true for _aggregate only |
The agg parameter should be given in the following format :
- {type}:{field}:interval-{interval}:format-{format}:collect_field-{collect_field}:collect_fct-{function}:order-{order}:on-{on}:size-{size}
Where the {type}:{field} part is mandatory
The other parts must be specified or not depending on the aggregation type. All the cases are sum up in the following table.
| Parameter | Aggregation type | Description |
|---|---|---|
| interval | datehistogram, histogram, geohash, geotile |
mandatory |
| format | datehistogram |
optional (default value : yyyy-MM-dd-HH:mm:ss) |
| (collect_field,collect_fct) | All types | optional and multiple |
| (order,on) | term, histogram, datehistogram |
optional |
| size | term, geohash, geotile |
optional |
| include | term |
optional |
| aggregated_geometries | All types | optional |
| raw_geometries | All types | optional |
| fetch_hits | All types | optional |
Example:
agg=datehistogram:date:interval-20day:format-dd.MM.yyyy&agg=term:sexe:collect_field-age:collect_fct-avg:order-asc:on-result:size-5
The sub-parameters possible values are:
| Parameter | Values | Description |
|---|---|---|
| {type} | datehistogram, histogram, geohash, geotile, term |
Type of aggregation |
| {field} | {field} | Aggregates on {field} |
| interval | {interval} | Size of the intervals.(1) |
| format | Date format for key aggregation | Date format for key aggregation. |
| collect_field | {collect_field} |
The field used to aggregate collections. |
| collect_fct | avg,cardinality,max,min,sum,geobbox,geocentroid (2) |
The aggregation function to apply to collections on the specified collect_field. |
| order | asc,desc |
Sorts the aggregation buckets on the field name, on the count of the buckets or on the the result of a metric sub-aggregation, ascending or descending. |
| on | field,count,result (3) (3') |
{on} is set to specify whether the order is on the field name, on the count of the aggregation or the result of a metric subaggregation. |
| size | {size} | Defines how many buckets should be returned. |
| include | Comma separated strings (4) | Specifies the values for which buckets will be created. |
| aggregated_geometries | Comma separated strings : bbox, centroid, tile_center, tile |
Allows to specify a list of aggregated forms of geometries that represent the bucket (5)(6) |
| raw_geometries | {geo_field1}(+{field1}, ...);{geo_field2}(-{field2}, ...) |
Allows to specify a list of raw geometries provided by hits that represent the bucket and that are elected by a sort (7)(8) |
| fetch_hits | {optionalNumberOfHist}(+{field1}, {field2}, -{field3}, ...) |
Specifies the number of hits to retrieve inside each aggregation bucket and which fields to include in the hits. The hits can be sorted according 0-* fields by preceding the field name by + for ascending sort, - for descending sort or nothing if no sort is desired on a field.(9) |
(1) Each aggregation type ({type}) has its own type of interval. The table below lists the semantic of the interval sub-parameter.
(2) (collect_field,collect_fct) should both be specified.
It's possible to apply multiple metric aggregations by defining multiple (collect_field,collect_fct) couples.
They should be unique in that case.
The metrics geobbox and geocentroid are returned as features collections.
(3) When on is result, then (collect_field,collect_fct) should be specified. Except when collect_fct = geobbox or geocentroid, then on=result is prohibited .
(3') If on is equal to result and two or more (collect_field,collect_fct) couples are specified, then the order is applied on the first collect_fct different from geobbox and geobbox".
Example:
agg=term:sexe:collect_field-location:collect_fct-geobbox:collect_field-age:collect_fct-avg:collect_field-height:collect_fct-max:order-asc:on-result
The order is applied on the first collect_fct avg (that is different from geobbox).
(4) If one value is specified then regular expressions can be used (only in this case) and buckets matching them will be created. If more than one value are specified then only buckets matching the exact values will be created.
(5) Available aggregated geometries :
bbox: returns the data extent (bbox) inside the bucket.centroid: returns the centroid of data inside the bucket.tile: returns the tile extent (zxy or geohash) of each bucket. This form is supported for geohash and geotile aggregation type only.tile_center: returns the 'center' of the tile extent that represents the bucket. This form is supported for geohash and geotile aggregation type only.
(6) The response:
- For
_aggregateservice: the aggregated geometries are returned ingeometrieslist in the json response. Each object inside this list has : thereferenceto the aggregated form, the geojsongeometryand an attributeis_rawset to false. - For
_geoaggregateservice: each bucket of the aggregation will be represented with as many features (in a feature collection) as there are specified aggregated geometries. The properties of each feature has :- geometry_ref attribute that informs which aggregated form is returned.
- geometry_type attribute set to aggregated.
(7) Any field of the collection whose type is geo-point or geo-shape can be set in raw_geometries.
- Sort fields are optional. If no sort is specified, an ascending sort on
collection.params.timestamp_pathis applied. - A sort field can be preceded by '-' for descending sort. Otherwise the sort is ascending
(8) The response :
- For
_aggregateservice: the aggregated geometries are returned ingeometrieslist in the json response. Each object inside this list has : thereferenceto the geometry path, the used sort, the geojsongeometryand an attributeis_rawset to true. - For
_geoaggregateservice: each bucket of the aggregation will be represented with as many features (in a feature collection) as there are specified raw geometries. The properties of each feature has :- geometry_ref attribute that informs which geometry path is returned.
- geometry_type attribute set to raw.
- geometry_sort attribute that informs how the geometry path is fetched (with what sort).
-
Example:
raw_geometries-geo_field1,geo_field2 || raw_geometries-geo_field(-field1,field2) || raw_geometries-geo_field1(field1);geo_field2(field2,field3)(9)
-
Example:
fetch_hits-3(-timestamp, geometry). The 3 last positions are retrieved for each bucket
Note that if the number of hits to fetch is not specified, 1 is considered as default.
-
Example:
fetch_hits:(-timestamp, geometry). The last position is retrieved for each bucket
| Service | Aggregation type | Interval | Description |
|---|---|---|---|
| _aggregate | datehistogram | {size}(year,quarter,month,week,day,hour,minute,second) |
Size of a time interval with the given unit (no space between number and unit). Size must be equal to 1 for year, quarter, month and week |
| _geoaggregate | geohash | {length} |
The geohash length: lower the length, greater is the surface of aggregation. See table below. |
| _geoaggregate | geotile | {zoom} |
The tile zoom: lower the zoom, greater is the surface of aggregation. |
| _aggregate | histogram | {size} |
The interval size of the numeric aggregation |
| _aggregate | term | None | None |
The table below shows the metric dimensions for cells covered by various string lengths of geohash. Cell dimensions vary with latitude and so the table is for the worst-case scenario at the equator.
| GeoHash length | Area width x height |
|---|---|
| 1 | 5,009.4km x 4,992.6km |
| 2 | 1,252.3km x 624.1km |
| 3 | 156.5km x 156km |
| 4 | 39.1km x 19.5km |
| 5 | 4.9km x 4.9km |
| 6 | 1.2km x 609.4m |
| 7 | 152.9m x 152.4m |
| 8 | 38.2m x 19m |
| 9 | 4.8m x 4.8m |
| 10 | 1.2m x 59.5cm |
| 11 | 14.9cm x 14.9cm |
| 12 | 3.7cm x 1.9cm |
agg parameter is multiple. Every agg parameter specified is a subaggregation of the previous one : the order matters.
For _geoaggregate service, the first (main) aggregation must be geohash,or geotile.
Part: filter
Available filter parameters
The filter url part allows the following parameters to be specified:
| Parameter | Default value | Values | Description | Multiple |
|---|---|---|---|---|
| f | None | {fieldName}{operator}{value} |
A triplet for filtering the result. Multiple filter can be provided. The order does not matter. A triplet is composed of a field name, a comparison operator and a value. The AND operator is applied between filters. For the :eq: and :range: filters, values can be comma separated (field:eq:v1,v2) which stands for an OR. For the :ne: filter, values can be comma separated (field:ne:v1,v2) which stands for an AND |
true |
| q | None | {text} or {fieldname}:{text} |
A full text search. Optionally, it's possible to search the text on a specific field | false |
| dateformat | None | Joda time pattern | A date format pattern that respects the Joda-time syntax | false |
| righthand | false | Boolean | A parameter that indicates how to consider the given WKT orientation. (Check Important 2) | false |
Important 1
The given BBOX must respect the following rules :
- west and east must be between -180 and 180 inclusive
- west must be different from east (west=east is invalid)
- You can specify west>east which means the bbox crosses the dateline
- south and north must be between -90 and 90 inclusive and south<north
Important 2
For parameters that accept WKT, in case of a Polygon or MultiPolygon, ARLAS-server will treat the orientation of the WKT according to the value of righthand parameter.
If righthand = true, the passed WKT should be counter clock-wise; otherwise, ARLAS-server will attempt to parse it as the "Complementary" Polygon on the other facet of the planet.
Inversely, if righthand = false, the passed WKT should be clock-wise; otherwise, ARLAS-server will attempt to parse it as the "Complementary" Polygon on the other facet of the planet.
Important 3
Coordinates of the given WKT must be contained in the Envelope -360, 360, -180, 180
Filter parameters algebra
For each parameter, you can provide multiple filters. There are 2 different ways to do this : - in distinct filter parameters = AND operator between filters - in the same filter parameter as a semi-colon separated list = OR operator between filters
| Multiple type | Example | Operator | Result |
|---|---|---|---|
| Distinct filter parameters | f=age:gte:18&f=age:lte:60 |
AND | elements whose/which age between 18 and 60 |
| Same filter parameter | f=age:gte:18;age:lte:60 |
OR | elements with any age |
Of course, you can combine both way to handle complex multiple filters for each filter parameter type.
f parameter syntax
| Operator | Description | Value type |
|---|---|---|
:eq: |
{fieldName} equals {comma separated values}. OR operation is applied for the specified values |
numeric or strings |
:ne: |
{fieldName} must not equal {comma separated values }. AND operation is applied for the specified values |
numeric or strings |
:like: |
{fieldName} is like {value}. |
numeric or strings |
:gte: |
{fieldName} is greater than or equal to {value} |
numeric |
:gt: |
{fieldName} is greater than {value} |
numeric |
:lte: |
{fieldName} is less than or equal to {value} |
numeric |
:lt: |
{fieldName} is less than {value} |
numeric |
:range: |
{fieldName} is between {comma separated [min<max] values}. OR operation is applied for the specified ranges |
numeric or strings. If the field's type is date, min & max should be timestamps in millisecond or Date expression Note that dates in date expressions can either be now or timestamp in millisecond. Other date formats are not supported. |
:within: |
{GeofieldName} is within the {given WKT string or the given BBOX : west, south, east, north}. |
a WKT string or the BBOX string : "west, south, east, north" |
:notwithin: |
{GeofieldName} is not within the {given WKT string or the given BBOX : west, south, east, north}. |
a WKT string or the BBOX string : "west, south, east, north" |
:intersects: |
{GeofieldName} intersects the {given WKT string or the given BBOX : west, south, east, north}. |
a WKT string or the BBOX string : "west, south, east, north" |
:notintersects: |
{GeofieldName} does not intersect the {given WKT string or the given BBOX : west, south, east, north}. |
a WKT string or the BBOX string : "west, south, east, north" |
The :range: operator has a specific syntax to indicates if range bounds are taken into account or not.
| Range operator syntax | Meaning |
|---|---|
x:range:]min<max[ |
min<x<max |
x:range:[min<max] |
min<=x<=max |
x:range:]min<max] |
min<x<=max |
x:range:[min<max[ |
min<=x<max |
x:range:]min1<max1[,]min2<max2[ |
min1<x<max1 OR min2<x<max2 |
On top of that, :range: operator supports generic aliases to represent collection configured fields :
* $timestamp refers to collection's timestamp field.
Example:
f=city:eq:Toulouse&f=city:eq:Bordeaux&f=$timestamp:range:[0<1490613808000]
Special syntax for date queries using lt, gt, lte, gte and range operations
In the case of lt, gt, lte, gte, range operations that are applied on date fields, the date values have four possible forms :
- a timestamp in millisecond OR a date in a custom format(*).
- a timestamp in millisecond OR a date in a custom format(*) followed by
||and followed by a date operation (+1h, /M, -2y, ...) nownowfollowed by a date operation (+1h, /M, -2y, ...)
Note
(*) If a custom format is given in the query, then the dateformat parameter must be set.
Note
The dateformat parameter must not contain ||.
Note
The dateformat parameter can be set only if a date field is queried in f param; when using gt, lt, gte, lte and range operations.
Note
Some examples of dates operations :
-
+1h : adds one hour
-
-1M : substracts one month
-
/d : rounds up or down to the nearest day
The date is rounded up when using lte and gt and rounded down when using lt and gte
A date operation can be the concatenation of an add/substract operation and a round operation : i.e now-1M/d
The date expression:
timestamp:gte:now-1M/Msubstracts 1 month from now then the resulted date is rounded down to the beginning of the month. Assumingnowis 2018-06-15.timestamp:gte:now-1M/Mis equivalent totimestamp:gte:2016-05-01
Partition filtering
filter part can also be passed in request header partition-filter as a serialized json for partitioning concerns.
Example:
curl --header "partition-filter: {"f":[[{"field":"city","op":"eq","value":"Bordeaux"}]]}" https://api.gisaia.com/demo/arlas/explore/cities/_count
When dealing with multi collections, filter can also be specified in a JSON map
Example:
curl --header "partition-filter: {"mycollection1": {"f":[[{"field":"city","op":"eq","value":"Bordeaux"}]]}}" https://api.gisaia.com/demo/arlas/explore/cities/_count
You can pass several filter in partition-filter, separated by comma :
Example:
curl --header "partition-filter: {"f":[[{"field":"city","op":"eq","value":"Bordeaux"}]]},{"f":[[{"field":"city","op":"eq","value":"Paris"}]]}" https://api.gisaia.com/demo/arlas/explore/cities/_count
In this case a OR combination is done.
Column filtering
A comma-separated list of columns can be passed in request header column-filter. Wildcards are supported.
A column filter stands for the fields that are available to a request body:
- if a request body field doesn't belong to the column filter, a 403 is returned with the message
The field '%s' isn't availableorThe fields '%s' aren't available; - only fields that belong to the column filter can be returned.
A column filter can be related to a collection, e.g. mycollection:myfield or it can be related to every collection, e.g. myfield. Trying to access a collection with no available field returns a 403.
Collection names can be omitted or end with a '*'.
Examples of column-filter:
mycollection:params.city,mycollection:params.countrymakes availableparams.cityandparams.countryfor collectionmycollectionmycollection*:params.citymakes availableparams.cityfor all collections whose names start withmycollectionparams,params*,params.*,*paramsmake availableparams.city,params.country,params.weight, and so on. for every collectionparams,:params,*:paramsmake availableparamsand subfields for every collection*makes all fields available*.*makes only subfields available, e.g.params.cityandparams.countrybut notid- `` (empty value) makes all fields and collections forbidden.
If no column filter, then no filtering is done. An empty column filter will forbid all collections and columns.
The following endpoints use this header:
| Endpoint | Filtering result |
|---|---|
| /arlas/explore/_list | Only fields and collections matching this filter will be returned (if no field of a collection is available, this one is not returned at all). |
/arlas/explore/{collection}/_describe |
Only fields matching this filter will be returned. Return a 403 if target collection is not available. |
/arlas/explore/{collection}/_count |
Return a 403 if one of the filter fields is not in the column filter. Return a 403 if target collection is not available. |
/arlas/explore/{collection}/_compute |
Return a 403 if the field, or one of the filter fields, is not in the column filter. Return a 403 if target collection is not available. |
/arlas/explore/{collection}/_search |
Return a 403 if one of the filter, projection and page fields is not in the column filter. Otherwise only fields matching the filter will be returned. Return a 403 if target collection is not available. |
/arlas/explore/{collection}/_geosearch |
Return a 403 if one of the filter, projection or page fields is not in the column filter. Otherwise only fields matching the filter will be returned. Return a 403 if target collection is not available. |
/arlas/explore/{collection}/_geosearch/{z}/{x}/{y} |
Return a 403 if one of the filter, projection or page fields is not in the column filter. Otherwise only fields matching the filter will be returned. Return a 403 if target collection is not available. |
/arlas/explore/{collections}/_aggregate |
Return a 403 if one of the aggregation or filter fields is not in the column filter. Return a 403 if target collection is not available. |
/arlas/explore/{collections}/_tile/{z}/{x}/{y}.png |
Return a 403 if one of the filter, projection or page fields is not in the column filter. Return a 403 if target collection is not available. |
/arlas/explore/{collections}/_geoaggregate |
Return a 403 if one of the aggregation or filter fields is not in the column filter. Return a 403 if target collection is not available. |
/arlas/explore/{collections}/_geoaggregate/{geohash} |
Return a 403 if one of the aggregation or filter fields is not in the column filter. Return a 403 if target collection is not available. |
/arlas/explore/{collections}/_geoaggregate/{z}/{x}/{y} |
Return a 403 if one of the aggregation or filter fields is not in the column filter. Return a 403 if target collection is not available. |
| /arlas/explore/ogc/opensearch/{collection} | Only fields matching this filter will be returned. Return a 403 if target collection is not available. |
On top of that, a query ("q" parameter) filter MUST target a specific field:
fullname:johnis validjohnisn't valid and will return a 403params*:johnisn't valid neither and will return a 403
If a projection with an includes parameter is used, then:
- included fields that are wildcards aren't checked; they do not return a 403 if they don't match the column filter;
- and only included fields that match the column filter are returned
Part: form
The form url part allows the following parameters to be specified:
| Parameter | Default value | Values | Description | Multiple |
|---|---|---|---|---|
| pretty | false |
true,false |
Pretty print | false |
| flat | false |
true,false |
Flats the data property map | false |
Example:
pretty=true&flat=false
Part: field
The compute url part is used in _compute service.
| Parameter | Default value | Values | Description | Multiple |
|---|---|---|---|---|
| field | false |
true,false |
The field on which the metric is calculated | false |
| metric | `` | max, min, avg, sum, cardinality, spanning, geobbox, geocentroid |
The metric to compute | false |
!!! note 'Note'
- max : the maximum value of the given field. Field should be numeric or date.
- min : the minimum value of the given field. Field should be numeric or date.
- avg : the average of the given field values. Field should be numeric or date.
- sum : the sum of the given field values. Field should be numeric or date.
- cardinality : the number of distinct values of the given field.
- spanning : the range value (max-min) of the given field. Field should be numeric or date.
- geobbox : the extend of data based on the given geo-point field.
- geocentroid : the centroid of data based on the given geo-point field.
!!! info '_range endpoint is removed'
Starting from v13.7.0, _range endpoint is removed. You can use the endpoint _compute instead.
- If you used _range to get the (max-min) value of the given field, then you can call : _compute?field=your_field&metric=spanning
- If you used _range to get separately the min and max values of the given field, then you can call _compute twice using _compute?field=your_field&metric=min and _compute?field=your_field&metric=max
Example:
field=timestamp
Part: projection
The projection url part allows the following parameters to be specified:
| Parameter | Default value | Values | Description | Multiple |
|---|---|---|---|---|
| include | * |
{fieldNamePattern} |
List the name patterns of the field to be included in the result. Seperate patterns with a comma. | true |
| exclude | * |
{fieldNamePattern} |
List the name patterns of the field to be excluded in the result. Seperate patterns with a comma. | true |
Example:
include=*&exclude=city,state
Part: returned_geometries
The returned_geometries url part can be specified in _search & _geosearch services:
| Parameter | Default value | Values | Description | Multiple |
|---|---|---|---|---|
| returned_geometries | {Comma separated geofieldNamePattern} |
Comma separated geometry field_paths to be included in the result. If not specified, only geometry_path is returned. If geometry_path is null, then centroid_path is returned | false |
Example:
include=*&exclude=city,state
Part: suggest
The suggest url part allows the following parameters to be specified:
| Parameter | Default value | Values | Description | Multiple |
|---|---|---|---|---|
| field | _all |
{fieldName} |
Name of the field to be used for retrieving the most relevant terms | false |
Example:
field=recommended
Part: page
The page url part allows the following parameters to be specified:
| Parameter | Default value | Values | Description | Multiple |
|---|---|---|---|---|
| size | 10 | > 0 | The maximum number of entries or sub-entries to be returned. | false |
| from | 0 | > 0 | An offset to start the search from. Defaults to 0. | false |
| sort | None | ((-?)({field} OR geodistance:{lat} {lon}))(,(-?){field})* |
Sorts the resulted hits on the given fields and/or by distance to a given point | false (separate fields with comma in the same parameter) |
| after | None | {value1},{value2},... |
List of values of fields present in sort param that are used to get the following hits of a previous search | false (separate values with comma in the same parameter) |
| before | None | {value1},{value2},... |
List of values of fields present in sort param that are used to get the precedent hits of a previous search | false (separate values with comma in the same parameter) |
sort parameter
Syntax
sort=((-?)({field} OR geodistance:{lat} {lon}))(,(-?){field})*.
Notes
{field}can be preceded by '-' for descending sort. By default, sort is ascending.- The order of fields matters.
Tip : geodistance sort
Along with the comma separated fields, you can add geodistance:{lat} {lon} (at most 1 time) to sort the hits centroids by distance to the given {lat} {lon} (ascending sort).
Example 1
sort=age,-timestamp. Resulted hits are sorted by age. For same age hits, they are decreasingly sorted in time.
Example 2
sort=age,geodistance:89 179. Resulted hits are sorted by age. For same age hits, they are sorted by the closest distance to the point (89°,179°).
after and before parameter
Important
after and before parameter work only combined with sort parameter.
Syntax
after={value1},{value2},...,{valueN} & sort={field1},{field2},...,{fieldN}
Notes
{value1}and{value2}are the values of{field1}and{field2}in the last hit returned in the previous search.- The last field
{fieldN}must be the id field specified in the collection collection.params.idPath (returned as md.id) and{valueN}its corresponding value. - from parameter must be set to 0 or kept unset
The difference between after and from
afteris used to scroll over the fetched hits.fromis more an offset from which fetching hits starts and is not exclusively used for scrolling (scrolling is possible by combiningfromandsizeparameters).
Example
sort=-date,id & after=01/02/2019,abcd1234. Gets the following hits of the previous search that stopped at date 01/02/2019 and id abcd1234.
OpenSearch
If enabled, ARLAS offers an Opensearch Description document (/arlas/ogc/opensearch/{collection}).