Knowledge Graph Documentation
ℹī¸ This is the new documentation of the EBRAINS KG. Please note, that it is not yet fully complete - it's going to be extended continuously.
If you find any issues / have any comment, please contact kg@ebrains.eu to give us your feedback!

Components and dependencies

The KG Search is split into a user interface as well as two different ways of how to get the underlying metadata according to the use-case:

graph LR INDEXING_API[kg-indexing] --> ES[ElasticSearch] INDEXING_API -- reading metadata --> KG_CORE[KG Core API] style KG_CORE fill:lightgrey,stroke:#333,stroke-width:2px

The default is the index based search. Here, the kg-indexing service reads the metadata from the KG Core API, translates it and indices it in a ElasticSearch index. This can be done for different levels such as "released" and "in progress".

The kg-indexing service provides an API to trigger different levels of the indexing mechanism. For EBRAINS, these endpoints are triggered by a scheduled automation job.

graph LR REV_PROXY[search.kg.ebrains.eu] -->|Reverse proxy| UI(KG Search UI) UI --> KG_SEARCH_API[kg-search] KG_SEARCH_API --> ES[Elasticsearch]

As soon as the index is available, the user-interface can request the precomputed, denormalized metadata from the ElasticSearch instance and apply access restrictions based on user account roles (e.g. to restrict the "in progress" indices to curators only).

Scalabilty

Please note that the "index-based search" can easily be scaled horizontally either by replication of the indices or clustering of the ElasticSearch database.

To allow review mechanism and to simplify development, the KG Search also knows a "live mode". When querying instances on the KG Search in live mode, the underlying data structures are not consumed from the ElasticSearch instance but rather directly from the KG Core API which makes it "live" (no delay). It also profits from the permission management of the KG Core since the requesting user will only be able to access those resources which are available from the specific account.

Due to the fact that some representations in KG Search are rather complex and transitioning many levels of the graph, this mode can suffer from some performance penalties compared to the "index-based search".

graph LR REV_PROXY[search.kg.ebrains.eu] -->|Reverse proxy| UI(KG Search UI) UI --> KG_SEARCH_API[kg-search] UI --> KEYCLOAK[Keycloak] KG_SEARCH_API -- live view --> KG_CORE[KG Core API] style KEYCLOAK fill:lightgrey,stroke:#333,stroke-width:2px style KG_CORE fill:lightgrey,stroke:#333,stroke-width:2px
This open source software code was developed in part or in whole in the Human Brain Project, funded from the European Union's Horizon 2020 Framework Programme for Research and Innovation under Specific Grant Agreements No. 720270, No. 785907 and No. 945539 (Human Brain Project SGA1, SGA2 and SGA3).
Co-funded by the European Union