shaclAPI

The shaclAPI is a project meant to integrate the SHACL validation into the SPARQL query execution. Given a knowledge graph a SPARQL query gives a set of solution mappings. The SHACL validation of a SHACL shape schema over the knowledge graph gives validation results per pair of shape in the network and target entitiy assigned to the shape. The shaclAPI annotates the entities in the solution mappings with the validation result assigned by the SHACL validation. Further SHACL engine - agnostic heuristics are implemented, to reduce the overhead of the validation.

Setup

Webservice

Docker

In order to run the shaclAPI, build the Docker image from the source code:

docker build . -t sdmtib/shaclAPI:latest

Once the Docker image is built, you can start the shaclAPI:

docker run --name api -d -p 9999:5000 sdmtib/shaclAPI:latest

The shaclAPI will be reachable at http://localhost:9999. For the following examples execute:

API=localhost:9999

Docker Compose

A docker-compose file is provided, therefore the shaclAPI can be run using:

docker-compose up --build -d

The shaclAPI will be accessible at http://localhost:9999. For the following examples execute:

API=localhost:9999

Python

To run the shaclAPI directly using python 3.8.11 with the flask development server, the python dependencies need to be installed:

python -m pip install -r requirements.txt

Depending on the operating system start.bat or start.sh can now be used to start the shaclAPI. The shaclAPI will be accessible at http://localhost:5000. For the following examples execute:

API=localhost:5000

Library

To use the shaclAPI as a library it is recommended to use python 3.8.11, however other versions might work as well. Install the python dependencies using:

python -m pip install -r requirements.txt

Usage

Webservice

You can use the shaclAPI by making HTTP requests. The following describes the different API calls:

GET: /

Returns Hello World and should be used to check whether the API is running or not.

Example call:

curl -X GET $API/

POST: /multiprocessing

This is the main API call, used to send a query to the SPARQL endpoint and simultaneously execute the SHACL validation to validate the query results. There are various options, which can be provided as parameters of the HTTP POST request. Additionally, a configuration file formatted as JSON can be provided with the config option. HTTP POST parameters will override the options configured in the configuration file.

Example configuration:

{
    "external_endpoint": "http://dbpedia.org/sparql",
    "query": "PREFIX dbo:<http://dbpedia.org/ontology/>\nPREFIX dbr:<http://dbpedia.org/resource/>\nPREFIX dbp:<http://dbpedia.org/property/>\nSELECT DISTINCT ?x WHERE {\n    ?x a dbo:Film. \n ?x dbp:studio dbr:Walt_Disney_Pictures\n}",
    "schemaDir": "./examples/dbpedia/shapes/",
    "targetShape": "MovieShape",
    "backend": "travshacl",
    "output_format": "simple"
}

Example call:

curl -X POST -d "config=./examples/dbpedia/config.json" $API/multiprocessing

Example output:

[
	[
		{"?x": "dbr:Tex_(film)"},  # The query result given in the form of the original SPARQL bindings
		[ # Triples to explain the SPARQL bindings
			["dbr:Tex_(film)", "dbp:studio", "dbr:Walt_Disney_Pictures"], 
			["dbr:Tex_(film)", "a", "dbo:Film"], 
			["dbr:Tex_(film)", "dbo:imdbId", "<0084783>"], 
			["dbr:Tex_(film)", "dbo:starring", "dbr:Matt_Dillon"]
		], 
		[ # The validation result assigned to the SPARQL bindings. Each entity occuring in the SPARQL bindings can violate (ts:violatesShape) or satisfy (ts:satisfiesShape) a given instance:
			["dbr:Tex_(film)", "ts:violatesShape", "MovieShape"]
		]
	], 
	[
		{"?x": "dbr:Night_Crossing"}, 
		[
			["dbr:Night_Crossing", "dbp:studio", "dbr:Walt_Disney_Pictures"], 
			["dbr:Night_Crossing", "a", "dbo:Film"], 
			["dbr:Night_Crossing", "dbo:imdbId", "<0082810>"], 
			["dbr:Night_Crossing", "dbo:starring", "dbr:Doug_McKeon"]
		], 
		[
			["dbr:Night_Crossing", "ts:violatesShape", "MovieShape"]
		]
	], ...
]

There are further examples provided in the examples directory.

POST: /validation

This API call can be used to execute the SHACL validation over the given SPARQL endpoint, while reducing the workload using the given heuristics and give the number of valid/invalid instances per Shape. There are various options, which can be provided as parameters of the HTTP POST request. Additionally, a configuration file formatted as JSON can be provided with the config option. HTTP POST parameters will override the options configured in the configuration file.

Using the same configuration as with /multiprocessing:

Example call:

curl -X POST -d "config=./examples/dbpedia/config.json" $API/validation

Example output:

{"MovieShape":{"invalid":50,"valid":0}}

POST: /reduce

This API call can be used to retrieve the shape names of the reduced shape schema given a starting shape. The options for this call can be provided as parameters of the HTTP POST request or as a JSON file using the config option. HTTP POST parameters will override the options configured in the configuration file.

Example call:

curl -X POST -d "schemaDir=./examples/lubm/shapes/" -d "targetShape=Department" $API/reduce

Example output:

{"shapes":["Department","University"]}

Library

See the available sphinx documentation: https://sdm-tib.github.io/shaclAPI/html/index.html

Configuration

The shaclAPI is highly configurable and supports the following options.

Required	Option	Default	Description
x	query	-	The query to be executed over the SPARQL endpoint.
	target_shape / targetShape	None	The target shape selected for the given query and the given shape schema.
x	external_endpoint	-	The URL of the SPARQL endpoint, which contains the data to be validated and retrieved.
x	schema_directory	-	The directory containing the shape files (.ttl or .json)
	config	None	The path to a json formatted configuration file. Has to be absolute or relative w.r.t. run.py.
	output_directory	./output/	The directory which will be used by the SHACL engine and the shaclAPI to save the validation output and statistics to files (depending on the other configurations)
	shape_format / shapeFormat	SHACL	The format of the shape files. Can be JSON or SHACL
	work_in_parallel / workInParallel	False	Whether the SHACL engine should work in parallel
	use_selective_queries / useSelectiveQueries	True	Whether the SHACL engine should use more selective queries.
	maxSplit	256	The maximal number of entities in FILTER or VALUES clause of a SPARQL query, used by the SHACL engine.
	order_by_in_queries	True	Whether the SHACL engine should use queries with a ORDER BY clause.
	backend	travshacl	The SHACL engine, which will be used by the shaclAPI.
	traversal_strategy / traversalStrategy	DFS	The traversal strategy used by the backend to reduce the shape graph and by the backend to find the execution order. Can be DFS or BFS.
	heuristic	TARGET IN BIG	Only if Trav-SHACL is used as backend. The heuristic used to determine the validation order of the shapes.
	replace_target_query	True	Whether or not the shaclAPI should replace the target query of the target shape.
	start_with_target_shape	True	Whether the SHACL engine is forced to start the validation process with the target shape.
	start_shape_for_validation	None	The shape which is used as starting point for the validation in the backend. It will override the start point determined by the SHACL engine (in case of Trav-SHACL) and only applies if start_with_target_shape is false)
	merge_old_target_query	True	Whether the shaclAPI should merge the query with the given target query in the target shape file. If this option is inactive the target query of the target shape is basically replaced with the star shaped query.
	remove_constraints	False	Whether the shaclAPI should remove constraints of the target shape not mentioned in the query.
	output_format	simple	Which output format the api should use. This can be "test" or "simple".
	memory_size	100000000	Number of tuples, which can be stored in main memory during the join process.
	prune_shape_network	True	Whether or not prune the shape schema to the shapes reachable from the target shapes.
	test_identifier	random uuid1	The test identifier will be used in output files identifing the run.
	run_in_serial	False	This option can be turned on to force the steps of the shaclAPI to be executed in serial.
	reasoning	True	This option will turn reasoning in terms of extended output on and off.
	use_pipes	False	Whether to use pipes during the multiprocessing. Otherwise the shaclAPI will use queues.
	collect_all_validation_results	False	Whether to collect all validation results for each mapping. Otherwise at least one validation result is collected for each given target_shape. Collecting all results will make the approach blocking.
	write_stats	True	Whether to write statistics to the output directory.
	outputs	False	Whether to save the validation output of the backend to a file.
	query_extension_per_target_shape	None	For each given target shape a query extension can be given. The given query is extended, when merged or replaced with the target definition of the target shape. The query is extended by replacing the last '}' in the query with the extension followed by a '}'.