how to visualize SPARQL queries and execution plans

[VladimirAlexiev]

(This merely promotes a good practice and asks for more ideas)

@JervenBolleman makes some amazing SPARQL visualizations.
See eg https://sib-swiss.github.io/sparql-examples/examples/dbgi/001.html .
This is a rather complex query, and the diagram really helps to understand it and debug it (eg you'd see immediately if some var is misspelled):

The diagram is SVG and is made with:

• https://github.com/sib-swiss/sparql-examples-utils/blob/master/src/main/java/swiss/sib/rdf/sparql/examples/SparqlInRdfToMermaid.java
• https://mermaid.js.org/

Questions:

• Do you find this useful?
• Would you change something?
  • (I posted something about node presentation show literals in some different way sib-swiss/sparql-examples-utils#11)
• Do you know of other SPARQL Viz?
  • Virtuoso had "Query By Example?"

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A related need is to visualize execution PLANS.

• But there the order of execution (trying patterns) matters: how can this be shown?
• Can the top-to-bottom ordering of patterns in a plan be shown as left-to-right ordering of some links?

[VladimirAlexiev]

@afs @kasei @lisp These diagrams are so very different from SPARQL Algebra trees... But they are great to see the connectivity of graph patterns in the query, so very useful while writing the query.
Can you give your wisdom on this topic?

[JervenBolleman]

To visualize execution plans we first need a standard to describe a query plan. This would be good to do to share development resources.

[kasei]

I think these are really useful to quickly visualize query patterns (as are algebra visualizations – they just visualize different things).

Regarding query plans, I've used mermaid to play around with visualizing query plans coming out of Neptune in the past, with some success. I think the challenge is that query plans from different systems can look very different (not just different operators, but also structurally different), so may be difficult to visualize in a common way while supporting plans from disparate systems.

[VladimirAlexiev]

@kasei

• Can you show an algebra visualization? for me that should be something like a tree, but with lateral links connecting variable occurrences
• Vendor differences aside: can you describe or show an example of a diagram like Jerven's, but showing the order of execution?

[kasei]

@VladimirAlexiev –

It sounds like you want more than the algebraic structure so that it also shows variable co-occurrence? I don't have anything like that, and think that might be more confusing than useful (?).

Here's part of a Neptune explain visualized using mermaid (this happens to be an OpenCypher query, but the explain format is basically the same for SPARQL). This is a very generic data flow diagram with operators as nodes, with no real specialization for specific operators:

[lisp]

• a trivial repository: demo
• a minimal view: sliced-join-all-sub
• a simple html presentation of results
• the parsed form as sse
• the expression as sparql algebra
• the execution plan
• the executed plan
• a d3-based rendering of a more complex executed plan

an authenticated user has these available from the html result page.
some agreement on a schema would be valuable.
beyond the sse and algebra views, which rely on jena conventions and the sparql recommendation, respectively, the other renderings are rather literal externalizations of internal processor state.
the d3-based rendering uses observable,hq's json-based graphics library.

[JervenBolleman]

The qlever analytics tree is very nice too.

But for the moment these are all custom to each engine, because there is no current standard for sharing an execution plan. Which makes generic tooling to difficult to develop.