Change dependency retrievals

[ajnelson-nist]

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[ajnelson-nist]

Well, there's an unfortunate discovery in this PR. rdf-toolkit 1.10.0 (the prior version) reaches a looping steady state when asked to re-normalize a normalized file. We have not seen this to date because the Make-based workflows would generate an un-normalized file, which rdf-toolkit would then normalize once. Normalizing twice is not guaranteed to generate the same results...but the 4th re-run will.

By some strange luck, one of the files in this repository (examples/illustrations/exif_data/exif_data_validation-unstable.ttl) loops through three states when repeatedly run through rdf-toolkit:

SHA2-256	State description
07b8cc3600bf6ad5be4db87c87bc119...	Checked out state
39afb357b6a8cccc0fd691bd7e7588a...	First run of pre-commit
85a9c0203a846a8e67ce3a99b451a48...	Second run of pre-commit
07b8cc3600bf6ad5be4db87c87bc119...	...and back.
39afb357b6a8cccc0fd691bd7e7588a...	...looping.

(I didn't calculate the hashes or loop-lengths for the three other files where this occurs.)

Unfortunately, the behavior also occurs with rdf-toolkit 1.11.0 (today's current version).

We'll need to think of how to deal with this.

Cc: @kchason

[ajnelson-nist]

I've tried a potential resolution to this issue: attempting to guarantee normalization only "runs once". First, de-normalize the input file by round-tripping it through something aside the turtle--turtle rdf-toolkit normalization. Then, normalize the de-normalized output with rdf-toolkit.

Unfortunately, through several de-normalizing strategies, this consistently didn't work as well as the Make process had.

1. Round-trip with rdflib to Turtle - same problem (albeit, shorter state cycles), where rdf-toolkit is sensitive to sort order, and rdflib is as well until Issue 1890 is resolved.
2. Round-trip with rdflib to RDF-XML - same problem, with the added defect of the xsd: prefix getting lost.
3. Round-trip with rdflib to JSON-LD - same problem, with extra issues with namespace management that will be resolved with the next rdflib release (Issue 1679).
4. Round-trip with rdf-toolkit to RDF-XML - won't work due to issue with XML Entities.
5. Round-trip with rdf-toolkit to JSON-LD - namespace prefixes are lost and namespace-prefix associations are broken, at least with rdf-toolkit 1.10.0.
6. (No other output options are available for rdf-toolkit, and Turtle-Turtle was the initial case.)

I'm currently unsure if there is a resolution available aside from working with the rdf-toolkit developers to fix the sorting bug.

[ajnelson-nist]

This PR should be revisited on resolution of RDF Toolkit Issue 49.