Welcoming the QGIS Metadata Store

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Support to standards based metadata (e.g.: ISO) has been greatly missed in QGIS. We would like for that to no longer be the case in QGIS 3.0, with this enhancement proposal.

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This blog post focuses on WP3: “QGIS Metadata Store”, which will introduce an external physical format for storing metadata internally in QGIS. The goal is to support portability, enabling users to share their layer metadata, even in offline scenarios. This WP will build directly on the outputs of WP1, which will define an “internal metadata schema” and WP2, “QGIS metadata API”, which will encode/decode from the internal schema to the supported schemas.

The final goal is for QGIS to support two types of metadata stores: remote and local. In this WP we will focus on local stores, only.

qgis_diagram1

In the diagram below we depict the inheritance model for metadata stores, where an abstract metadata store will have a polymorphic behavior, according to the particular data format. For instance in the case of a PostgreSQL DB, the method “save” will create a table on the database, whether in the case of a Shapefile, it would create an XML file.

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Some formats, such as text files, can be more limited than others. As an example, searches in text files can be quite slow. For that reason, we will create a “prime” format, the “QGIS metadata store”, which can accompany more restrictive formats.The prime format will be an SQLite database, because of its lightweight, and because it is well-known within the QGIS community.

As the goal is to support all these different formats in the future, we will design an infrastructure to accommodate that, but in this first iteration we will focus on the simple use case of creating an xml file, and an SQLite data store.

The metadata contents will be passed by the metadata API. In this WP we will implement format translation, but not schema translation.

Along with these developments we will implement a user interface to allow the user to configure serialisation/deserialisation behaviour, e.g.: in which format we should write metadata, and where.

The QGIS metadata store will be synced with any changes that we apply to the metadata. In the moment that we export metadata into XML, it will write those changes to the XML file.

Metadata search will also be polymorphic, according to the data format. In this iteration, as a proof of concept, we will implement some simple text search, which will enable users to query their metadata.

We envision this WP to deliver the following:

  • An infrastructure to accommodate the external storage of metadata in QGIS, fully implemented for the use case of XML files.
  • Support for searching the metadata store.
  • UI for saving/loading metadata.

I will submit a proposal for these developments to the QGIS Grant Applications Programme and will be looking forward to having the support of the community to welcome the QGIS metadata store ?

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