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arxiv: 2606.01760 · v2 · pith:QISUYTP7new · submitted 2026-06-01 · ✦ hep-ex · stat.ME

HS3: A Descriptive, Interoperable Serialization Standard for Statistical Models in High-Energy Physics

Carsten Burgard , Oliver Schulz , Giordon Stark , Jonas Rembser , Simon Cello , Cornelius Grunwald This is my paper

Pith reviewed 2026-06-28 12:03 UTC · model grok-4.3

classification ✦ hep-ex stat.ME
keywords statistical modelsserialization standardhigh-energy physicslikelihoodscomputational graphsmodel interoperabilityFAIR principlesHEPData
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The pith

HS3 represents statistical models in high-energy physics as extensible computational graphs of named distributions, functions, datasets, domains, and analysis prescriptions.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper introduces HS3 as an implementation-agnostic serialization format for statistical models in high-energy physics. It encodes likelihoods as computational graphs so that model descriptions can be exchanged, validated, and preserved independently of any one software stack. Existing formats remain tied to specific tools such as ROOT workspaces or pyhf JSON, limiting portability and long-term reuse. HS3 is designed to support binned and unbinned likelihoods, hierarchical models, and backward-compatible extensions while leaving inference execution to downstream frameworks. The stated goal is to establish a foundation for FAIR, machine-readable statistical models at the LHC and beyond.

Core claim

HS3 is an implementation-agnostic, human-readable, and extensible serialization format for statistical models. Likelihoods are represented as computational graphs composed of named distributions, functions, datasets, domains, and analysis prescriptions. It supports binned and unbinned likelihoods as well as hierarchical composite models, is convertible from and to ROOT/RooFit, and is a superset of pyhf. Inference procedures and implementation-specific execution details remain the responsibility of downstream frameworks.

What carries the argument

The HS3 serialization format, which encodes likelihoods as computational graphs composed of named distributions, functions, datasets, domains, and analysis prescriptions to separate model description from execution.

If this is right

  • Models become exchangeable between frameworks such as ROOT/RooFit and pyhf without format-specific rewriting.
  • Public likelihoods on HEPData can be stored and reused in a standardized, machine-readable form.
  • Cross-framework validation of statistical models becomes possible through a common representation.
  • Long-term preservation of analyses is supported because the model description is decoupled from any single software version.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The graph structure may allow automated tools to combine or compare models from different experiments once multiple frameworks adopt the format.
  • The explicit separation of model description from inference could be tested for use in domains outside high-energy physics that rely on likelihood-based inference.

Load-bearing premise

The design principles and structure of HS3 will be sufficient to capture all relevant statistical constructs in HEP models while remaining backward-compatible through extensions.

What would settle it

A concrete LHC statistical model that cannot be fully serialized in HS3 without information loss or a non-backward-compatible change to the format.

Figures

Figures reproduced from arXiv: 2606.01760 by Carsten Burgard, Cornelius Grunwald, Giordon Stark, Jonas Rembser, Oliver Schulz, Simon Cello.

Figure 1
Figure 1. Figure 1: Comparison of profile likelihood curves, showing the [PITH_FULL_IMAGE:figures/full_fig_p009_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Dependency graph of a product of two Gaussian [PITH_FULL_IMAGE:figures/full_fig_p016_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Call graph extracted from pyhs3 for a product of two Gaussian distributions [PITH_FULL_IMAGE:figures/full_fig_p017_3.png] view at source ↗
read the original abstract

Statistical models in high-energy physics formally encode the relationship between observed data, physics parameters of interest, and experimental and theoretical uncertainties. Likelihood-based inference is the central tool for precision measurements, effective field theory fits, and cross-analysis combinations. Consequently, there is an increasing need for machine-readable, descriptive, and portable model representations. Existing formats such as ROOT workspaces, pyhf JSON, and CMS DataCards provide valuable capabilities but remain tied to specific software stacks and offer no universal standard for exchange, validation, or long-term preservation. We introduce HS3, the High-Energy Physics Statistics Serialization Standard, an implementation-agnostic, human-readable, and extensible serialization format for statistical models. HS3 is designed such that new statistical constructs can be incorporated through backward-compatible extensions, while inference procedures and implementation-specific execution details remain the responsibility of downstream frameworks. HS3 represents likelihoods as computational graphs composed of named distributions, functions, datasets, domains, and analysis prescriptions. It supports binned and unbinned likelihoods as well as hierarchical composite models. HS3 is convertible from and to ROOT/RooFit and is a superset of pyhf. We describe the design principles, structure, and semantics of HS3 and summarize existing implementations in C++, Python, and Julia. We also present early applications to public likelihoods on HEPData, cross-framework validation, and reproducibility efforts. HS3 provides a foundation for FAIR (Findable, Accessible, Interoperable, Reusable), long-lived statistical models at the LHC and beyond. The standard is intended to serve the broader scientific community and to evolve over time for application across a wide range of domains.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 0 minor

Summary. The manuscript proposes HS3, an implementation-agnostic, human-readable, and extensible serialization format for statistical models in high-energy physics. Likelihoods are represented as computational graphs composed of named distributions, functions, datasets, domains, and analysis prescriptions. The format supports binned and unbinned likelihoods as well as hierarchical composite models, is convertible to and from ROOT/RooFit, and is positioned as a superset of pyhf. Design principles emphasize backward-compatible extensions, with inference details left to downstream frameworks. The paper summarizes implementations in C++, Python, and Julia, along with early applications to public likelihoods on HEPData, cross-framework validation, and reproducibility efforts, with the goal of enabling FAIR, long-lived models.

Significance. If the design proves sufficient and is adopted, HS3 would address a genuine need for portable, machine-readable statistical models that facilitate interoperability, validation, and long-term preservation across software stacks in HEP. The graph-based representation, extensibility mechanism, and explicit multi-language implementations with conversion paths to existing formats (ROOT, pyhf) are concrete strengths that support the interoperability claim. Early applications to HEPData likelihoods further indicate practical utility.

major comments (1)
  1. [Abstract] Abstract (applications paragraph): the description of 'cross-framework validation' is high-level and does not include quantitative metrics, specific test cases, or coverage statistics for the set of public likelihoods converted; without these details it remains unclear whether the graph representation fully supports all required HEP constructs (e.g., certain nuisance-parameter correlations or unbinned components) without gaps, which is load-bearing for the central claim of being a superset of pyhf and a general foundation.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their positive evaluation of the HS3 proposal and for recommending minor revision. We address the single major comment below.

read point-by-point responses

  1. Referee: [Abstract] Abstract (applications paragraph): the description of 'cross-framework validation' is high-level and does not include quantitative metrics, specific test cases, or coverage statistics for the set of public likelihoods converted; without these details it remains unclear whether the graph representation fully supports all required HEP constructs (e.g., certain nuisance-parameter correlations or unbinned components) without gaps, which is load-bearing for the central claim of being a superset of pyhf and a general foundation.

    Authors: We agree that the abstract's reference to cross-framework validation is high-level. The manuscript body (sections describing the C++/Python/Julia implementations, conversion paths, and early HEPData applications) contains the concrete test cases, coverage details for public likelihoods, and explicit checks for constructs including nuisance-parameter correlations and unbinned components. In the revised version we will expand the applications paragraph of the abstract to incorporate the key quantitative metrics and coverage statistics from those sections, thereby strengthening the substantiation of the superset claim. revision: yes

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper is a standards proposal that defines the HS3 serialization format for statistical models, including its graph-based representation of likelihoods, extensibility rules, and claimed conversions to existing tools. No derivations, predictions, fitted parameters, or mathematical results are claimed or presented; the text consists entirely of design descriptions, structure definitions, and implementation summaries. Consequently there are no load-bearing steps that could reduce to self-definition, fitted inputs, or self-citation chains.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

HS3 is a proposed descriptive standard with no fitted parameters or new physical entities. It rests on the domain assumption that statistical models are adequately captured by computational graphs of named components.

axioms (1)
  • domain assumption Statistical models in HEP can be represented as computational graphs of named distributions, functions, datasets, domains, and analysis prescriptions.
    This representation is invoked as the core structure of HS3 in the abstract description of the format.

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discussion (0)

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