LDES structure Discoverer

A lightweight application that discovers the structure of an LDES or a view by retrieving all the tree node relations of that LDES or view.

A use case for this could be when you are only interested in a part of the event stream. To know what part you can follow, the structure can be discovered first.

Config

Property	Description	Required	Default	Example	Supported values
url	Url where from the discoverer needs to start	Yes	N/A	http://example.com/my-api	HTTP and HTTPS url
source-format	The ‘Content-Type’ that should be requested to the server.	No	application/n-quads	text/turtle	Any type supported by Apache Jena
output-format	The RDF format that will be used to display all the found relations	No	text/turtle	application/ld+json	Any type supported by Apache Jena

How to run

This tutorial will show how to use the discoverer in Docker. In this example, we will try to discover the structure of an event stream of Geomobility.

For simplicity, we recommend passing the config as arguments, like shown below:

docker run ldes/ldes-discoverer --url="http://ldes-server/observations/by-time?year=2023&month=05&day=11"

NOTE: when an url contains a & symbol, which will be picked up by the shell as an operator. In this example, if the url was not wrapped in quotation marks, the shell will try to execute three different command, where the last two will be month=05 and day=11, which will fail of course.

To resolve this, make sure the url is encapsulated in quotation marks.

Example output

In the logging of the application, both the total number of relations and the relations itself will be displayed. This will be present as the last logging statement of the app and would look something like this:

2024-02-08T14:26:25.279+01:00  INFO 48176 --- [           main] b.v.i.l.l.d.common.LdesDiscoverer        : Total of 97 relations found for url http://ldes-server/observations/by-time?year=2023&month=05&day=11

@prefix prov: <http://www.w3.org/ns/prov#> .
@prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix tree: <https://w3id.org/tree#> .

<http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=05&pageNumber=3>
        tree:relation  [ rdf:type   tree:Relation;
                         tree:node  <http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=05&pageNumber=4>
                       ] .

<http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=05&pageNumber=2>
        tree:relation  [ rdf:type   tree:Relation;
                         tree:node  <http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=05&pageNumber=3>
                       ] .

<http://ldes-server/observations/by-time?year=2023&month=05&day=11>
        tree:relation  [ rdf:type    tree:InBetweenRelation;
                         tree:node   <http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=00>;
                         tree:path   prov:generatedAtTime;
                         tree:value  "2023-05-11T00"
                       ];
        tree:relation  [ rdf:type    tree:InBetweenRelation;
                         tree:node   <http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=05>;
                         tree:path   prov:generatedAtTime;
                         tree:value  "2023-05-11T05"
                       ];
        [...]
        tree:relation  [ rdf:type    tree:InBetweenRelation;
                         tree:node   <http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=20>;
                         tree:path   prov:generatedAtTime;
                         tree:value  "2023-05-11T20"
                       ] .

[...]

<http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=05>
        tree:relation  [ rdf:type   tree:Relation;
                         tree:node  <http://ldes-server/observations/by-time?year=2023&month=05&day=11&hour=05&pageNumber=1>
                       ] .