Evaluate data and transformation visualization

[fsteeg]

Visualization of data and workflows can ease the development of processing rules and workflows:

• Metafacture IDE alreay includes the GEF4 Zest feature which can automatically visualize simple DOT files written to the workspace (as an interactive SWT-based graph inside Eclipse, see the Metafacture IDE sample at https://github.com/culturegraph/metafacture-ide)
• Metafacture Morph can generate a DOT visualization of the transformation logic, which can be rendered to a file by Graphviz (but cannot be rendered by Zest, which does not support HTML-like labels in DOT, see https://bugs.eclipse.org/321775)

Based on this, there are different possible improvements to visualization components in the Metafacture IDE:

• Improve data visualization with Zest: currently, this feature is only useful for very small data sets. To make it useful for larger data sets we could improve interaction with the graph (e.g. everything could be collapsed by default, and we could drill into the data by double-clicking nodes etc., see http://wiki.eclipse.org/Zest#New_subgraph_rendering)
• Automatically generate an image file for transformations in the Eclipse workspace using the Metafacture Morph visualization and calling a local Graphviz installation or the Google charts API (see https://developers.google.com/chart/image/docs/gallery/graphviz)
• Interactive transformation visualization with Zest, based on the Metafacture Morph output (when the HTML-like labels are supported in Zest, see above). This could provide something like a visual outline view, where nodes in the Morph visualization could link into the morph.xml or Flux files

[fsteeg]

Over the last year, support for HTML-like labels in GEF has made some progress (see https://bugs.eclipse.org/321775). So we could check how far we get with the final approach mentioned in the original comment (visualizing the Metafacture Morph DOT output with Zest). The DOT visualizer however is outdated and no longer part of metafacture-core (see https://github.com/culturegraph/metafacture-core/commit/73efd633c0be47e58e35fae6254fd8c829fdd6a1).

A different approach would be a full graphical editor directly based on the Morph XML.

For both approaches, we'll have to add back a current dependency on GEF (see https://github.com/culturegraph/metafacture-ide/commit/29873eb501bd6c471544ad90a65d7bd49dca7adb).