Talk:Opaque set

Opaque set has been listed as one of the Mathematics good articles under the good article criteria. If you can improve it further, please do so. If it no longer meets these criteria, you can reassess it.
Review: November 18, 2021. (Reviewed version).

Mathematics Mid‑priority

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	This article was accepted on 23 November 2013 by reviewer TKK public (talk · contribs).

GA Review[edit]

This review is transcluded from Talk:Opaque set/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: Bryanrutherford0 (talk · contribs) 19:06, 15 November 2021 (UTC)[reply]

GA review (see here for what the criteria are, and here for what they are not)

It is reasonably well written.
a (prose, spelling, and grammar): b (MoS for lead, layout, word choice, fiction, and lists):
The article is written in clear, professional prose, and it appears to comply with the relevant sections of MoS. I have a couple of clarifications to request: in the section "Lower bound", I think "the expected number of intersections with the opaque set is at least $x$ " should maybe be "... is at least $p$ ", which would be, as the text says, "half that for $K$ " ( $2p$ ). Am I missing something there? Also, maybe some sort of transition at the beginning of the second paragraph of that section could clarify that what follows is a second, alternate argument that half of the perimeter is a minimal value for the length of the barrier set. Also, there are at least a few calculated figures throughout that are missing "math" tags that should probably have them for stylistic consistency.
Typo fixed and purpose of second paragraph clarified. (It is not an alternative argument for the lower bound. It is an argument that the lower bound cannot be improved.) —David Eppstein (talk) 20:05, 16 November 2021 (UTC)[reply]
That looks great; I've made the style consistent on all the calculations, I think. -Bryan Rutherford (talk) 23:17, 16 November 2021 (UTC)[reply]

Since I can't see past the first page of the Smart 1966 source, could you clarify its formulation of the problem (currently "painted walls in a glass house")? Is it something like "making a glass house opaque by raising some painted walls inside"? -Bryan Rutherford (talk) 16:42, 18 November 2021 (UTC)[reply]
"Think of the line segments as painted walls in a house otherwise made of glass. For an opaque set a flashlight beam cannot pass through the house." —David Eppstein (talk) 18:07, 18 November 2021 (UTC)[reply]
Got it; I've tried to bring that phrase into a structural parallel with the others in the sentence. -Bryan Rutherford (talk) 21:44, 18 November 2021 (UTC)[reply]
It is factually accurate and verifiable.
a (reference section): b (citations to reliable sources): c (OR): d (copyvio and plagiarism):
The article contains a reference section with numerous citations to reputable published sources. Some comments on the sources: Provan et al. seems to refer to the objects that are the topic of this article as "opaque covers"; should this alternate name be included in the lead section and first paragraph of "Definitions"? Then, in "Lower bound", I'm not finding the Crofton formula argument for half the perimeter being a minimal length for the barrier or the newly added explanation at the beginning of the second paragraph in Dumitrescu & Jiang; am I missing it? The claims are supported by the citations I can access, and there's no sign of inappropriate use of copyrighted material.
Alternative name added. In Dumitrescu & Jiang, the Crofton formula is the second-to-last sentence of page 3 (arxiv version): "For a planar convex body K, the measure of all lines that meet K is equal to per(K)." —David Eppstein (talk) 19:36, 17 November 2021 (UTC)[reply]
Got it, thanks! -Bryan Rutherford (talk) 16:42, 18 November 2021 (UTC)[reply]
It is broad in its coverage.
a (major aspects): b (focused):
The article appears to achieve broad coverage of the topic, with sections on the concept's definition, processes for establishing bounds for its length, algorithms for estimating optimal solutions, and the history of the topic and progress in studying it, together with a more niche section on curve-free opaque sets. It doesn't stray from the topic or omit any major aspects of it that occur to me.
It follows the neutral point of view policy.
Fair representation without bias:
The article takes a suitably neutral point of view on the topic, not exaggerating its significance or e.g. advocating for particular mathematicians or perspectives.
It is stable.
No edit wars, etc.:
The article is stable, with no major edits since before its nomination.
It is illustrated by images and other media, where possible and appropriate.
a (images are tagged and non-free content have fair use rationales): b (appropriate use with suitable captions):
The article is illustrated by suitable, relevant images with clear captions. All appear to have suitable licenses for use on WP.
Overall:
Pass/Fail:
One point to clarify in the prose, and otherwise the article seems clear and broad. I'll look through the sources next and update this. -Bryan Rutherford (talk) 21:00, 15 November 2021 (UTC)[reply]
One final prose clarification, and I also wonder: should this article go into any other categories, like maybe Category:Discrete geometry (which the first sentence says is the field this topic most belongs to)? After these issues, I think we should be finished. -Bryan Rutherford (talk) 16:42, 18 November 2021 (UTC)[reply]
I'm not sure how discrete it is, really, but I moved it to that category and also added Visibility. —David Eppstein (talk) 18:38, 18 November 2021 (UTC)[reply]
Alright, all of my concerns have been addressed. This article is hereby approved for GA. Good work! -Bryan Rutherford (talk) 21:44, 18 November 2021 (UTC)[reply]