[w3ctag/design-reviews] WG Revision: SHACL 1.2 Core (Issue #1166)

nicholascar created an issue (w3ctag/design-reviews#1166)

### Specification

https://w3c.github.io/data-shapes/shacl12-core/

### Explainer

https://w3c.github.io/data-shapes/shacl12-overview/#whatsnew

### Links

- The WG's request for this TAG review: https://www.w3.org/2025/11/03-data-shapes-minutes.html
- TAG review of the previous version of this specification, if any: I can't find links to the review back in 2017
- A description of what has changed since our previous review: As per the features below.

Feature 1:  
**Derived Properties**  
In the original SHACL specifications, shapes and constraints could only operate on asserted triples in a graph, and inferencing was left as an optional pre-processing step using languages like RDF Schema and OWL. SHACL 1.2 introduces its own inferencing and reasoning capabilities, which make SHACL more self-contained and cover different use cases than RDFS/OWL. 

Feature 2:  
**Better Syntax for Unions of Datatypes and Classes** 
In the original SHACL specifications, when you wanted to express that the datatype of a property was either xsd:string, rdf:langString, or rdf:HTML, you needed to use a verbose, repetitive construct. In SHACL 1.2, this can be written as a single list. 

Feature 3:  
**Constraints on RDF 1.2 Reification**  
The major new feature in RDF 1.2 is reification, enabling RDF statements to be easily made about other RDF statements. SHACL 1.2 introduces new constraint properties (sh:reifierShape and sh:reificationRequired) which allow a shape targeting a triple to be chained to another shape targeting reification elements.

Feature 4:  
**Use of Reification in Constraint Definitions**  
In the original SHACL specifications, the severity and messages of a constraint had to be declared for the surrounding shape, sometimes requiring artificial intermediate shapes to be introduced to change only the severity or a message. SHACL 1.2 syntax is more flexible, allowing severity and messages to be directly attached to individual constraint triples. 

Feature 5:  
**The sh:ShapeClass Metaclass**  
A new class, sh:ShapeClass, comparable to owl:Class, is used to define classes that can declare constraints that apply to all instances of the class. It is equivalent to OWL syntax for declaring a class that may hold [OWL axioms](https://www.w3.org/TR/owl2-primer/#Annotating_Axioms_and_Entities). This allows SHACL to be a more self-contained ontology modeling language.

Feature 6:  
**Cleaner Separation between Core and SPARQL**  
We now have a cleaner separation of Core and SPARQL concerns into separate specifications. This helps indicate SHACL Core is not dependent on SPARQL, clarify other dependencies, and make some implementations easier. 

### The specification

- [ ] Follows the [Web Platform Design Principles](https://www.w3.org/TR/design-principles/).
- [x] Includes Security and Privacy Considerations sections based on answers to the [Security/Privacy Questionnaire](https://www.w3.org/TR/security-privacy-questionnaire/).

### Where and by whom is the work is being done?

- GitHub repo:
- Primary contacts:
  - $name (@-mention), $organization/s, $role in developing specification
  - <!-- repeat as necessary, we recommend including group chairs and editors in this list -->
- Organization/project driving the specification:
- This work is being funded by:
- Primary standards group developing this feature:
- Incubation and standards groups that have discussed the design:
  - {{ABC CG}} <!-- Include a link to minutes or issues in this group if possible. -->
  - {{DEF WG}}


### Feedback so far

- Active horizontal reviews: https:// <!-- Link to an issue like https://github.com/webmachinelearning/webnn/issues/239, https://github.com/WebAssembly/spec/issues/1804, or https://github.com/w3c/did/issues/885, which itself links to the other horizontal reviews. If you haven't started the rest of the horizontal reviews, please consider doing so. -->
- Multi-stakeholder feedback:
  - Chromium comments:
  - Mozilla comments: https://github.com/mozilla/standards-positions/issues/NNN <!-- And/or other places they've given feedback -->
  - WebKit comments: https://github.com/WebKit/standards-positions/issues/NNN <!-- And/or other places they've given feedback -->
  - {{...include feedback/review from developers, implementers, civil society, and others}}
- Major unresolved issues with or opposition to this specification:
- Status/issue trackers for implementations: <!-- Include links to [Chrome Status](https://chromestatus.com/), [Mozilla's](https://bugzilla.mozilla.org/), [WebKit's Bugzilla](https://bugs.webkit.org/), and trackers for other implementations if those are known to you. -->


### You should also know that...

_No response_

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