REVIEW 2 major objections 6 minor 1 cited by
Overview of the TREC 2023 deep learning track
T0 review · 2 major / 6 minor · reviewed 2026-08-06 · deepseek-v4-flash
Pith's one-line read LLM-prompted rerankers outscored the four-year-best nnlm approach at TREC 2023, and human-filtered synthetic queries reproduced human-query system rankings with Kendall tau 0.8487.
desk verdict Solid track overview; the synthetic-query reliability claim in the abstract is overstated given it rests on only 31 human-filtered queries. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing mechanism is the reusable test collection: 82 judged queries spanning three query types, with four-point relevance judgments and expanded qrels that copy a judged passage's label to every near-duplicate passage in its cluster. The comparison engine is NDCG@10, with Kendall's tau measuring whether systems keep their order when human queries are swapped for synthetic ones; tau = 0.8487 is the number that carries the synthetic-query conclusion. The synthetic pipeline has four stages: a GPT-4 prompt scores sampled passages for self-containedness, T5 generates many candidate queries stratified to match human query length and lexical overlap, GPT-4 generates one zero-shot query per seed passage, and human assessors reject most candidates, 66 of 97, before judging. The prompt-run result rests on comparing prompt-classified runs against nnlm runs at the system level and on per-query comparisons.
What would settle it
Take all 97 T5- and GPT-4-generated queries that went to the assessors, including the 66 rejected ones, judge them under the same relevance-assessment protocol, and recompute Kendall's tau between system NDCG@10 on those synthetic queries and on the 51 human queries; if the tau drops materially below 0.8487, the reported agreement is an artifact of the human filter rather than a property of synthetic queries in general.
Extended reading notes
Core claim
The paper's central claim is that prompt-based LLM ranking overtook fine-tuned nnlm stacks as the best-performing approach on the TREC 2023 Deep Learning track, and that synthetic queries, once filtered by human assessors, rank systems almost as well as real user queries do. The track judged 82 passage queries on the MS MARCO v2 collections: 51 from held-out human queries, 13 produced by a fine-tuned T5 query generator, and 18 by a GPT-4 prompt; labels were then propagated from passages to source documents for the document task, and expanded qrels spread each judgment through its cluster of near-duplicate passages. The best prompt run reaches NDCG@10 of 0.6994 on passage ranking versus 0.5972 for the best nnlm run, and the prompt methods win on most individual queries. Across submitted systems, Kendall's tau between system orderings on human queries and on synthetic queries is 0.8487, and 0.9395 when the collection is evaluated on all real plus synthetic track queries. The authors conclude that synthetic queries can be reliably used in test collection construction, but only after human selection, and they find no clear evidence that GPT-4-generated queries inflate GPT-based systems or that T5-generated queries inflate T5-based systems.
Load-bearing premise
The load-bearing premise is that the 31 synthetic queries that survived human filtering are representative of synthetic queries in general; if the filter removes exactly the difficult, ambiguous, or biased queries, the observed agreement of tau = 0.8487 will not carry over to unfiltered synthetic queries.
Editorial extensions
If this is right
- Prompt-based LLM ranking now becomes the reference point for retrieval track benchmarks, replacing the fine-tuned nnlm stacks that had dominated the previous four years.
- Test collection builders can generate candidate queries with T5 or GPT-4 and still obtain system orderings close to those from human queries, provided a human quality filter is applied first.
- Passage-level judgments remain sufficient for document ranking: propagating passage labels to source documents yields usable document qrels without separate document judging.
- With two consecutive years of harder held-out query sets, year-over-year comparisons on this collection are more discriminative than the earlier MS MARCO test queries.
- Even the best prompt runs mostly self-reported using MS MARCO training data somewhere in the stack, so prompting does not remove the need for fine-tuned retrieval components.
Reading between the lines
- Editorial inference: the 0.8487 tau is measured on only 31 accepted synthetic queries, and 66 of 97 generated queries were discarded by human assessors, so the practical cost saving depends on automating or outsourcing that filter, which this paper does not attempt.
- Editorial inference: GPT-4 queries are nearly twice as long as human queries, and both synthetic types return fewer relevant documents per query, so a synthetic-query collection is a harder and somewhat different evaluation surface, not a free replacement for the historical human-query series.
- Editorial inference: the no-bias conclusion is drawn from very few systems in each family, for example one document-ranking prompt run, so the absence of clear bias is a weak bound; a larger paired sampling of generators and system families could detect smaller or conditional biases.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper is the overview of the TREC 2023 Deep Learning Track. It describes the passage and document ranking tasks, the MS MARCO v2 datasets, the submitted runs, and the main evaluation results. The authors report two headline findings: (1) runs that use large language model (LLM) prompting in some part of the pipeline outperformed runs using the previous best "nnlm" approach, and (2) evaluation using synthetically generated queries (from T5 and GPT-4) produced system orderings similar to those from human queries, with a Kendall tau of 0.8487. The paper also analyzes potential bias from using T5 or GPT-4 generated queries toward systems based on the same model family, finding no clear bias. The track is the final year of the Deep Learning Track, and the paper emphasizes the construction of a reusable test collection.
Significance. If the findings hold, they are of considerable significance to the IR community. The prompt-vs-nnlm result suggests that LLM prompting is now a state-of-the-art technique on this benchmark, while the synthetic-query analysis speaks directly to the cost and feasibility of building test collections without human queries. The paper is transparent about its query generation pipeline, including the prompts used, the filtering rates, and the final query counts, and it makes the official NIST judgments the basis of all reported metrics. These are genuine strengths. However, the synthetic-query claim is based on a small, human-filtered subset of the generated queries, and the prompt-vs-nnlm comparison relies on self-classified run categories without significance testing. Both limitations constrain the strength of the conclusions as stated in the abstract, although the paper itself uses cautious language in places (e.g., "initial results suggest" and "more analysis is needed").
major comments (2)
- [Section 4, Table 2, Figure 2] The headline agreement tau = 0.8487 is computed on only 31 synthetic queries (13 T5-generated and 18 GPT-4-generated) that survived a human filtering step. The paper states that assessors removed queries that "do not look reasonable" or that contain "too few or too many relevant documents" because they are "noisy or not very informative for evaluation purposes." This filtering is not random, and it plausibly removes exactly the difficult, ambiguous, or atypical synthetic queries where system agreement with human-query evaluation could be lowest. The reported Kendall tau therefore may substantially overstate the agreement that an unfiltered synthetic-query test collection would achieve. The conclusion in Section 5 that "test collections consisting of synthetically generated queries could be reliably used" is not supported for unfiltered synthetic generation. The authors should either report the agreement on the full set of generated queries (if judgments exist), provide a confidence interval or significance test for the tau value, or explicitly qualify the claim to apply only to synthetic queries that pass a human quality filter. The abstract's substitution claim currently goes beyond what the data show.
- [Section 4, Table 2, Figure 2] The headline claim about prompt runs outperforming nnlm runs is not supported by significance testing, and the self-classified run categories plus the concentration of top runs in two groups make the comparison less controlled than the abstract implies.
minor comments (6)
- [Section 4] There is a typo in "one or mpre phases" (should be "more"), and the sentence "The best 'prompt' run outperforms the best 'nnlm' on on the majority of queries" has a duplicated "on."
- [Figure 2 caption] The caption says "As in the previous two years, 'nnlm' runs continue to outperform over 'trad' runs for both tasks," but the figure includes the 'prompt' category; the caption should describe all three run types shown.
- [Figure 4 caption] The caption refers to "mean performance between 'prompt' and 'llm' runs," but the correct category name is "nnlm".
- [Section 5, Table 6] Table 6 reports the final number of queries per type (82 total) but not the numbers of queries initially generated and provided to assessors (200 human, 250 T5, 250 GPT-4, of which 147/48/49 were provided to assessors). Adding the initial counts and the selection rates would make the filtering step clearer.
- [Section 5] The sentence "For all query types, depth-10 pooling was used to select the documents to be judged by the NIST assessors" is potentially confusing because the track judged passages, not documents, and document labels were inferred from passage labels; please clarify that the depth-10 pooling applies to passage pooling, with document labels propagated afterward.
- [Conclusion] The Conclusion contains a typo: "we repeated the updats that were first introduced last year" should be "updates."
Circularity Check
No significant circularity: the headline claims are empirical comparisons against independent NIST judgments, not derivations from their own inputs.
full rationale
This paper is an evaluation overview, not a derivation. The two headline claims—that LLM-prompted runs outperformed the previous best 'nnlm' approach, and that synthetic queries yield system orderings close to real queries (tau = 0.8487)—are both empirical measurements against NIST relevance judgments. The prompt-vs-nnlm comparison is computed from submitted runs and externally judged relevance labels; no parameter is fitted to the outcome and then reported as a prediction. The synthetic-query analysis compares system NDCG@10 computed on real queries with the same systems' NDCG@10 computed on separately generated and separately judged synthetic queries; one set of scores is not an input to the other. The paper even tests the most plausible circularity threat—that query generators from a given model family bias evaluation in favor of systems from that family—and reports no clear evidence of such bias, which is an explicit check rather than an assumption. The human filtering of synthetic queries (13 of 48 T5 and 18 of 49 GPT-4 queries retained) is a real validity limitation on generalization, but it is not a circular step: the retained synthetic queries are still assessed independently, and the agreement statistic is not constructed to equal any input. Citations to the track's own previous overviews provide empirical context and dataset provenance, but no load-bearing mathematical claim in this paper reduces to those citations. No equation, fitted parameter, renamed result, or self-citation chain is used to manufacture the stated conclusions.
Assumptions & free parameters
free parameters (4)
- passage quality score threshold =
50
- GPT-4 sampling temperature for passage quality scoring =
0.8
- T5 query generation count per passage =
100
- T5 query sampling stratification =
matched to 2022 NIST qrels on query length and lexical overlap
assumptions (4)
- domain assumption NIST assessor judgments are ground-truth relevance labels for both human and synthetic queries
- domain assumption Depth-10 pooling over submitted runs yields a sufficiently complete set of relevant documents for fair evaluation
- domain assumption The stratification of T5 queries by query length and lexical overlap with the passage makes them comparable to human queries
- domain assumption The GPT-4 and T5 prompts used for query generation produce queries similar in intent to real user queries
Cite this review
Pith. "Pith review of Overview of the TREC 2023 deep learning track." pith.science (2026). https://pith.science/paper/JYPIFE6V
@misc{pith2026250708890,
author = {Pith},
title = {Pith review of: Overview of the TREC 2023 deep learning track},
year = {2026},
howpublished = {\url{https://pith.science/paper/JYPIFE6V}},
note = {Machine review of arXiv:2507.08890}
}
abstract
This is the fifth year of the TREC Deep Learning track. As in previous years, we leverage the MS MARCO datasets that made hundreds of thousands of human-annotated training labels available for both passage and document ranking tasks. We mostly repeated last year's design, to get another matching test set, based on the larger, cleaner, less-biased v2 passage and document set, with passage ranking as primary and document ranking as a secondary task (using labels inferred from passage). As we did last year, we sample from MS MARCO queries that were completely held out, unused in corpus construction, unlike the test queries in the first three years. This approach yields a more difficult test with more headroom for improvement. Alongside the usual MS MARCO (human) queries from MS MARCO, this year we generated synthetic queries using a fine-tuned T5 model and using a GPT-4 prompt. The new headline result this year is that runs using Large Language Model (LLM) prompting in some way outperformed runs that use the "nnlm" approach, which was the best approach in the previous four years. Since this is the last year of the track, future iterations of prompt-based ranking can happen in other tracks. Human relevance assessments were applied to all query types, not just human MS MARCO queries. Evaluation using synthetic queries gave similar results to human queries, with system ordering agreement of $\tau=0.8487$. However, human effort was needed to select a subset of the synthetic queries that were usable. We did not see clear evidence of bias, where runs using GPT-4 were favored when evaluated using synthetic GPT-4 queries, or where runs using T5 were favored when evaluated on synthetic T5 queries.
Figures
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Forward citations
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Reference graph
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Reviewed August 6, 2026 · model on record in the stance chip above.
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