Talk:Distributive lattice

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Finally distributivity entails several other pleasant properties. For example, an element of a distributive lattice is meet-prime if and only if it is meet-irreducible, though the latter is in general a weaker property. By duality, the same is true for join-prime and join-irreducible elements.

Can someone provide a reference for this?--Malcohol 09:01, 16 October 2006 (UTC)

I have added a proof in Distributive lattice/Proofs. Ceroklis 21:14, 28 September 2007 (UTC)

External links

A link to a short document providing equivalent statements of distributivity was recently dismissed as spam. I do not understand the reasoning behind this. Surely you cannot argue that the document has NO merit. The material is directly relevant to the article. If you think it has LITTLE merit, then the "Related Links" section is precisely where it belongs. If you think it has MUCH merit, then it should have been incorporated into the article rather than deleted. Austinmohr (talk) 04:04, 20 March 2010 (UTC)
Hello, I removed the link for three reasons. First, because Wikipedia is not a collection of links. Although one or two external links may be appropriate, it's better to add information to the article, with references to reliable sources. External links sections can, over time, become swamped with links. Links should only be included if they add something to the article that would be missing if the article ever became a Featured Article; ie. it provides a unique resource that couldn't be provided by Wikipedia. I couldn't see anything when I followed this link that couldn't be added to the article. Please see Wikipedia:External links#Links normally to be avoided for more information. I would recommend you add useful information to the article, and reference it to reliable sources.
Secondly, the link is to a PDF file. Although that would be fine as a reference, it's best not have links in the EL section that require a reader to have an external application or plugin to read. This is also covered by Wikipedia:External links#Links normally to be avoided.
Thirdly, I was concerned by the fact that you appear to be linking to your own website, which is considered a conflict of interest, and could be seen as External link spamming.
Thankyou for bringing this up here, where others can weigh in if they wish to. If you have further concerns, feel free to ask. If you want other opinions on this (and they aren't forthcoming here) then you can also ask at Wikipedia:External links/Noticeboard. Regards, --BelovedFreak 08:52, 20 March 2010 (UTC)
And I meant to say that I have no particular knowledge of distributive lattices, so if others that do deem this to be a valuable link, then that's fine, but it should be someone unconnected to the website.--BelovedFreak 09:08, 20 March 2010 (UTC)
I am the author of Modular lattice. I saw your link here and the one at that article and decided not to bother doing anything about it at once, but I agree with Belovedfreak. Your notes provide very little insight. Moreover: There are free lecture notes available on the net, by distinguished lattice theorists and universal algebraists, that contain the same information, plus proofs, plus a lot more. It's absurd to link to a mere short list of equivalent properties. It might be useful for someone as a handy reference, but that's not sufficient reason to include the link. Hans Adler 11:48, 20 March 2010 (UTC)


The left object in the picture captioned "Distributive lattice which contains N5..." is misleading in that it is not a Hasse diagram and so not a standard representation of a lattice; the line connecting b and c is extraneous (c is already clearly below b through the c-f-b connection). I would suggest removing that object and making separate objects displaying the pentagon with f removed, and the standard Hasse diagram with the connection between b and c erased.

The right-hand object is very confusing for some of the same reasons (the b-c and c-e connectors are extraneous), and the claim that M3 is a subset is incorrect. I believe the contributor is trying to demonstrate that by taking the full transitive closure of the Hasse diagram (almost) represented by the left image, you can find M3. A lattice is a set X with an order <, which can be represented by the Hasse diagrams; therefore a subset of the lattice is a subset of X with < restricted to the subset. Using the definition of subset, the claim that you can find M3 in a subset of this lattice is wrong. By taking the transitive closure of the diagram, you can find M3 as a *subdiagram* of the diagram (by forgetting some edges), but this is not the same as a subset of the lattice. JoelleJay (talk) 16:43, 10 May 2016 (UTC)

As far as I remember, I happend to find that picture at wikimedia commons, and tried to figure out its purpose from its appearance and its use in Polish wikipedia (without speaking any Polish); I didn't think too much it then. Also, you are right that the diagrams are not Hasse diagrams in a strict sense, as they both don't show transitive reductions of orderings.
That said, I still think they can be understood in a way such they make sense:
Each diagram represents two lattices, the first and second one being obtained as the transitive closure of the solid lines and of all lines, respectively. That is, in the left diagram the line c-b is redundant in the all-lines lattice (it doesn't hurt there, on the other hand) but is needed for the solid-only lattice. Similarly, the lines c-d, c-e, and b-a in the right diagram are redundant in the all-lines lattice, but needed in the solid-only lattice. (While I check the diagrams for writing this response, I see that admittedly some vertice names are hard to read, and the distinction solid/dashed is sometimes hard to recognize.)
All four (left/right diagram with solid-only/all lines) structures are in fact lattices, which can be checked by drawing them with irrelevant lines omitted. (Admittedly, the picture should be improved to ease that task - possibly the redundant lines could be in grey?) The solid-only lattices are obviously N5 and M3. The all-lines lattices are obviously ordered subsets of the solid-only lattices (viewed as ordered sets); in the right diagram, the vertice sets agree, but the ordering relations are one included the other.
So, I'd suggest to add a note that the pictures are Hasse diagrams not in the strict sense, but in a weak sense (allowing for redundant lines), and eventually to improve the picture (should better be svg, anyway). Would that be sufficient in your view, or did I miss something? - Jochen Burghardt (talk) 18:46, 10 May 2016 (UTC)
I suppose there is a question of what is meant by "contained as a subset." In the first case (on the left side), we have that the dark edges are giving an induced subposet, i.e., a subset of the vertices with induced order relation. In the second case (on the right side), we have that the dark edges are giving a non-induced subposet, i.e., we are taking both a subset of the vertices (well, all of them) and a subset of the relations. The first operation is natural; the second one is very not natural, and in particular no one would ever imagine that the second operation would preserve the lattice property. I think that for this reason the right half of the question is not very helpful. I do not have a problem with the non-Hasse diagram on the left side, this could be easily clarified in the caption. --JBL (talk) 19:45, 10 May 2016 (UTC)

Confused by intro

Will someone take the time to explain what is meant by the operations of "join" and "meet"? If articles about these operations exist a hyperlink will most likely suffice. (talk) 21:49, 14 December 2011 (UTC)

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