P. 188 of Theorem List - Metamath Proof Explorer

Theorem List for Metamath Proof Explorer - 18701-18800   *Has distinct variable group(s)

Type	Label	Description
Statement
Theorem	isdlat 18701*	Property of being a distributive lattice. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐵 = (Base‘𝐾)    &   ⊢ ∨ = (join‘𝐾)    &   ⊢ ∧ = (meet‘𝐾)    ⇒   ⊢ (𝐾 ∈ DLat ↔ (𝐾 ∈ Lat ∧ ∀𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 ∀𝑧 ∈ 𝐵 (𝑥 ∧ (𝑦 ∨ 𝑧)) = ((𝑥 ∧ 𝑦) ∨ (𝑥 ∧ 𝑧))))
Theorem	dlatmjdi 18702	In a distributive lattice, meets distribute over joins. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐵 = (Base‘𝐾)    &   ⊢ ∨ = (join‘𝐾)    &   ⊢ ∧ = (meet‘𝐾)    ⇒   ⊢ ((𝐾 ∈ DLat ∧ (𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ∧ 𝑍 ∈ 𝐵)) → (𝑋 ∧ (𝑌 ∨ 𝑍)) = ((𝑋 ∧ 𝑌) ∨ (𝑋 ∧ 𝑍)))
Theorem	dlatl 18703	A distributive lattice is a lattice. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ (𝐾 ∈ DLat → 𝐾 ∈ Lat)
Theorem	odudlatb 18704	The dual of a distributive lattice is a distributive lattice and conversely. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐷 = (ODual‘𝐾)    ⇒   ⊢ (𝐾 ∈ 𝑉 → (𝐾 ∈ DLat ↔ 𝐷 ∈ DLat))
Theorem	dlatjmdi 18705	In a distributive lattice, joins distribute over meets. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐵 = (Base‘𝐾)    &   ⊢ ∨ = (join‘𝐾)    &   ⊢ ∧ = (meet‘𝐾)    ⇒   ⊢ ((𝐾 ∈ DLat ∧ (𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ∧ 𝑍 ∈ 𝐵)) → (𝑋 ∨ (𝑌 ∧ 𝑍)) = ((𝑋 ∨ 𝑌) ∧ (𝑋 ∨ 𝑍)))
9.5.4  Subset order structures
Syntax	cipo 18706	Class function defining inclusion posets.
class toInc
Definition	df-ipo 18707*	For any family of sets, define the poset of that family ordered by inclusion. See ipobas 18710, ipolerval 18711, and ipole 18713 for its contract. EDITORIAL: I'm not thrilled with the name. Any suggestions? (Contributed by Stefan O'Rear, 30-Jan-2015.) (New usage is discouraged.)
⊢ toInc = (𝑓 ∈ V ↦ ⦋{⟨𝑥, 𝑦⟩ ∣ ({𝑥, 𝑦} ⊆ 𝑓 ∧ 𝑥 ⊆ 𝑦)} / 𝑜⦌({⟨(Base‘ndx), 𝑓⟩, ⟨(TopSet‘ndx), (ordTop‘𝑜)⟩} ∪ {⟨(le‘ndx), 𝑜⟩, ⟨(oc‘ndx), (𝑥 ∈ 𝑓 ↦ ∪ {𝑦 ∈ 𝑓 ∣ (𝑦 ∩ 𝑥) = ∅})⟩}))
Theorem	ipostr 18708	The structure of df-ipo 18707 is a structure defining indices up to 11. (Contributed by Mario Carneiro, 25-Oct-2015.)
⊢ ({⟨(Base‘ndx), 𝐵⟩, ⟨(TopSet‘ndx), 𝐽⟩} ∪ {⟨(le‘ndx), ≤ ⟩, ⟨(oc‘ndx), ⊥ ⟩}) Struct ⟨1, ;11⟩
Theorem	ipoval 18709*	Value of the inclusion poset. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐼 = (toInc‘𝐹)    &   ⊢ ≤ = {⟨𝑥, 𝑦⟩ ∣ ({𝑥, 𝑦} ⊆ 𝐹 ∧ 𝑥 ⊆ 𝑦)}    ⇒   ⊢ (𝐹 ∈ 𝑉 → 𝐼 = ({⟨(Base‘ndx), 𝐹⟩, ⟨(TopSet‘ndx), (ordTop‘ ≤ )⟩} ∪ {⟨(le‘ndx), ≤ ⟩, ⟨(oc‘ndx), (𝑥 ∈ 𝐹 ↦ ∪ {𝑦 ∈ 𝐹 ∣ (𝑦 ∩ 𝑥) = ∅})⟩}))
Theorem	ipobas 18710	Base set of the inclusion poset. (Contributed by Stefan O'Rear, 30-Jan-2015.) (Revised by Mario Carneiro, 25-Oct-2015.)
⊢ 𝐼 = (toInc‘𝐹)    ⇒   ⊢ (𝐹 ∈ 𝑉 → 𝐹 = (Base‘𝐼))
Theorem	ipolerval 18711*	Relation of the inclusion poset. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐼 = (toInc‘𝐹)    ⇒   ⊢ (𝐹 ∈ 𝑉 → {⟨𝑥, 𝑦⟩ ∣ ({𝑥, 𝑦} ⊆ 𝐹 ∧ 𝑥 ⊆ 𝑦)} = (le‘𝐼))
Theorem	ipotset 18712	Topology of the inclusion poset. (Contributed by Mario Carneiro, 24-Oct-2015.)
⊢ 𝐼 = (toInc‘𝐹)    &   ⊢ ≤ = (le‘𝐼)    ⇒   ⊢ (𝐹 ∈ 𝑉 → (ordTop‘ ≤ ) = (TopSet‘𝐼))
Theorem	ipole 18713	Weak order condition of the inclusion poset. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐼 = (toInc‘𝐹)    &   ⊢ ≤ = (le‘𝐼)    ⇒   ⊢ ((𝐹 ∈ 𝑉 ∧ 𝑋 ∈ 𝐹 ∧ 𝑌 ∈ 𝐹) → (𝑋 ≤ 𝑌 ↔ 𝑋 ⊆ 𝑌))
Theorem	ipolt 18714	Strict order condition of the inclusion poset. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐼 = (toInc‘𝐹)    &   ⊢ < = (lt‘𝐼)    ⇒   ⊢ ((𝐹 ∈ 𝑉 ∧ 𝑋 ∈ 𝐹 ∧ 𝑌 ∈ 𝐹) → (𝑋 < 𝑌 ↔ 𝑋 ⊊ 𝑌))
Theorem	ipopos 18715	The inclusion poset on a family of sets is actually a poset. (Contributed by Stefan O'Rear, 30-Jan-2015.)
⊢ 𝐼 = (toInc‘𝐹)    ⇒   ⊢ 𝐼 ∈ Poset
Theorem	isipodrs 18716*	Condition for a family of sets to be directed by inclusion. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ ((toInc‘𝐴) ∈ Dirset ↔ (𝐴 ∈ V ∧ 𝐴 ≠ ∅ ∧ ∀𝑥 ∈ 𝐴 ∀𝑦 ∈ 𝐴 ∃𝑧 ∈ 𝐴 (𝑥 ∪ 𝑦) ⊆ 𝑧))
Theorem	ipodrscl 18717	Direction by inclusion as used here implies sethood. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ ((toInc‘𝐴) ∈ Dirset → 𝐴 ∈ V)
Theorem	ipodrsfi 18718*	Finite upper bound property for directed collections of sets. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ (((toInc‘𝐴) ∈ Dirset ∧ 𝑋 ⊆ 𝐴 ∧ 𝑋 ∈ Fin) → ∃𝑧 ∈ 𝐴 ∪ 𝑋 ⊆ 𝑧)
Theorem	fpwipodrs 18719	The finite subsets of any set are directed by inclusion. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ (𝐴 ∈ 𝑉 → (toInc‘(𝒫 𝐴 ∩ Fin)) ∈ Dirset)
Theorem	ipodrsima 18720*	The monotone image of a directed set. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ (𝜑 → 𝐹 Fn 𝒫 𝐴)    &   ⊢ ((𝜑 ∧ (𝑢 ⊆ 𝑣 ∧ 𝑣 ⊆ 𝐴)) → (𝐹‘𝑢) ⊆ (𝐹‘𝑣))    &   ⊢ (𝜑 → (toInc‘𝐵) ∈ Dirset)    &   ⊢ (𝜑 → 𝐵 ⊆ 𝒫 𝐴)    &   ⊢ (𝜑 → (𝐹 “ 𝐵) ∈ 𝑉)    ⇒   ⊢ (𝜑 → (toInc‘(𝐹 “ 𝐵)) ∈ Dirset)
Theorem	isacs3lem 18721*	An algebraic closure system satisfies isacs3 18729. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ (𝐶 ∈ (ACS‘𝑋) → (𝐶 ∈ (Moore‘𝑋) ∧ ∀𝑠 ∈ 𝒫 𝐶((toInc‘𝑠) ∈ Dirset → ∪ 𝑠 ∈ 𝐶)))
Theorem	acsdrsel 18722	An algebraic closure system contains all directed unions of closed sets. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ ((𝐶 ∈ (ACS‘𝑋) ∧ 𝑌 ⊆ 𝐶 ∧ (toInc‘𝑌) ∈ Dirset) → ∪ 𝑌 ∈ 𝐶)
Theorem	isacs4lem 18723*	In a closure system in which directed unions of closed sets are closed, closure commutes with directed unions. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ 𝐹 = (mrCls‘𝐶)    ⇒   ⊢ ((𝐶 ∈ (Moore‘𝑋) ∧ ∀𝑠 ∈ 𝒫 𝐶((toInc‘𝑠) ∈ Dirset → ∪ 𝑠 ∈ 𝐶)) → (𝐶 ∈ (Moore‘𝑋) ∧ ∀𝑡 ∈ 𝒫 𝒫 𝑋((toInc‘𝑡) ∈ Dirset → (𝐹‘∪ 𝑡) = ∪ (𝐹 “ 𝑡))))
Theorem	isacs5lem 18724*	If closure commutes with directed unions, then the closure of a set is the closure of its finite subsets. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ 𝐹 = (mrCls‘𝐶)    ⇒   ⊢ ((𝐶 ∈ (Moore‘𝑋) ∧ ∀𝑡 ∈ 𝒫 𝒫 𝑋((toInc‘𝑡) ∈ Dirset → (𝐹‘∪ 𝑡) = ∪ (𝐹 “ 𝑡))) → (𝐶 ∈ (Moore‘𝑋) ∧ ∀𝑠 ∈ 𝒫 𝑋(𝐹‘𝑠) = ∪ (𝐹 “ (𝒫 𝑠 ∩ Fin))))
Theorem	acsdrscl 18725	In an algebraic closure system, closure commutes with directed unions. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ 𝐹 = (mrCls‘𝐶)    ⇒   ⊢ ((𝐶 ∈ (ACS‘𝑋) ∧ 𝑌 ⊆ 𝒫 𝑋 ∧ (toInc‘𝑌) ∈ Dirset) → (𝐹‘∪ 𝑌) = ∪ (𝐹 “ 𝑌))
Theorem	acsficl 18726	A closure in an algebraic closure system is the union of the closures of finite subsets. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ 𝐹 = (mrCls‘𝐶)    ⇒   ⊢ ((𝐶 ∈ (ACS‘𝑋) ∧ 𝑆 ⊆ 𝑋) → (𝐹‘𝑆) = ∪ (𝐹 “ (𝒫 𝑆 ∩ Fin)))
Theorem	isacs5 18727*	A closure system is algebraic iff the closure of a generating set is the union of the closures of its finite subsets. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ 𝐹 = (mrCls‘𝐶)    ⇒   ⊢ (𝐶 ∈ (ACS‘𝑋) ↔ (𝐶 ∈ (Moore‘𝑋) ∧ ∀𝑠 ∈ 𝒫 𝑋(𝐹‘𝑠) = ∪ (𝐹 “ (𝒫 𝑠 ∩ Fin))))
Theorem	isacs4 18728*	A closure system is algebraic iff closure commutes with directed unions. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ 𝐹 = (mrCls‘𝐶)    ⇒   ⊢ (𝐶 ∈ (ACS‘𝑋) ↔ (𝐶 ∈ (Moore‘𝑋) ∧ ∀𝑠 ∈ 𝒫 𝒫 𝑋((toInc‘𝑠) ∈ Dirset → (𝐹‘∪ 𝑠) = ∪ (𝐹 “ 𝑠))))
Theorem	isacs3 18729*	A closure system is algebraic iff directed unions of closed sets are closed. (Contributed by Stefan O'Rear, 2-Apr-2015.)
⊢ (𝐶 ∈ (ACS‘𝑋) ↔ (𝐶 ∈ (Moore‘𝑋) ∧ ∀𝑠 ∈ 𝒫 𝐶((toInc‘𝑠) ∈ Dirset → ∪ 𝑠 ∈ 𝐶)))
Theorem	acsficld 18730	In an algebraic closure system, the closure of a set is the union of the closures of its finite subsets. Deduction form of acsficl 18726. (Contributed by David Moews, 1-May-2017.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ (𝜑 → 𝑆 ⊆ 𝑋)    ⇒   ⊢ (𝜑 → (𝑁‘𝑆) = ∪ (𝑁 “ (𝒫 𝑆 ∩ Fin)))
Theorem	acsficl2d 18731*	In an algebraic closure system, an element is in the closure of a set if and only if it is in the closure of a finite subset. Alternate form of acsficl 18726. Deduction form. (Contributed by David Moews, 1-May-2017.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ (𝜑 → 𝑆 ⊆ 𝑋)    ⇒   ⊢ (𝜑 → (𝑌 ∈ (𝑁‘𝑆) ↔ ∃𝑥 ∈ (𝒫 𝑆 ∩ Fin)𝑌 ∈ (𝑁‘𝑥)))
Theorem	acsfiindd 18732	In an algebraic closure system, a set is independent if and only if all its finite subsets are independent. Part of Proposition 4.1.3 in [FaureFrolicher] p. 83. (Contributed by David Moews, 1-May-2017.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ 𝐼 = (mrInd‘𝐴)    &   ⊢ (𝜑 → 𝑆 ⊆ 𝑋)    ⇒   ⊢ (𝜑 → (𝑆 ∈ 𝐼 ↔ (𝒫 𝑆 ∩ Fin) ⊆ 𝐼))
Theorem	acsmapd 18733*	In an algebraic closure system, if 𝑇 is contained in the closure of 𝑆, there is a map 𝑓 from 𝑇 into the set of finite subsets of 𝑆 such that the closure of ∪ ran 𝑓 contains 𝑇. This is proven by applying acsficl2d 18731 to each element of 𝑇. See Section II.5 in [Cohn] p. 81 to 82. (Contributed by David Moews, 1-May-2017.) Remove dependency on ax-reg 9589 and ax-inf2 9645. (Revised by Timothy J. O'Malley, 15-Oct-2026.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ (𝜑 → 𝑆 ⊆ 𝑋)    &   ⊢ (𝜑 → 𝑇 ⊆ (𝑁‘𝑆))    ⇒   ⊢ (𝜑 → ∃𝑓(𝑓:𝑇⟶(𝒫 𝑆 ∩ Fin) ∧ 𝑇 ⊆ (𝑁‘∪ ran 𝑓)))
Theorem	acsmap2d 18734*	In an algebraic closure system, if 𝑆 and 𝑇 have the same closure and 𝑆 is independent, then there is a map 𝑓 from 𝑇 into the set of finite subsets of 𝑆 such that 𝑆 equals the union of ran 𝑓. This is proven by taking the map 𝑓 from acsmapd 18733 and observing that, since 𝑆 and 𝑇 have the same closure, the closure of ∪ ran 𝑓 must contain 𝑆. Since 𝑆 is independent, by mrissmrcd 17819, ∪ ran 𝑓 must equal 𝑆. See Section II.5 in [Cohn] p. 81 to 82. (Contributed by David Moews, 1-May-2017.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ 𝐼 = (mrInd‘𝐴)    &   ⊢ (𝜑 → 𝑆 ∈ 𝐼)    &   ⊢ (𝜑 → 𝑇 ⊆ 𝑋)    &   ⊢ (𝜑 → (𝑁‘𝑆) = (𝑁‘𝑇))    ⇒   ⊢ (𝜑 → ∃𝑓(𝑓:𝑇⟶(𝒫 𝑆 ∩ Fin) ∧ 𝑆 = ∪ ran 𝑓))
Theorem	acsinfd 18735	In an algebraic closure system, if 𝑆 and 𝑇 have the same closure and 𝑆 is infinite independent, then 𝑇 is infinite. This follows from applying unirnffid 9339 to the map given in acsmap2d 18734. See Section II.5 in [Cohn] p. 81 to 82. (Contributed by David Moews, 1-May-2017.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ 𝐼 = (mrInd‘𝐴)    &   ⊢ (𝜑 → 𝑆 ∈ 𝐼)    &   ⊢ (𝜑 → 𝑇 ⊆ 𝑋)    &   ⊢ (𝜑 → (𝑁‘𝑆) = (𝑁‘𝑇))    &   ⊢ (𝜑 → ¬ 𝑆 ∈ Fin)    ⇒   ⊢ (𝜑 → ¬ 𝑇 ∈ Fin)
Theorem	acsdomd 18736	In an algebraic closure system, if 𝑆 and 𝑇 have the same closure and 𝑆 is infinite independent, then 𝑇 dominates 𝑆. This follows from applying acsinfd 18735 and then applying unirnfdomd 10655 to the map given in acsmap2d 18734. See Section II.5 in [Cohn] p. 81 to 82. (Contributed by David Moews, 1-May-2017.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ 𝐼 = (mrInd‘𝐴)    &   ⊢ (𝜑 → 𝑆 ∈ 𝐼)    &   ⊢ (𝜑 → 𝑇 ⊆ 𝑋)    &   ⊢ (𝜑 → (𝑁‘𝑆) = (𝑁‘𝑇))    &   ⊢ (𝜑 → ¬ 𝑆 ∈ Fin)    ⇒   ⊢ (𝜑 → 𝑆 ≼ 𝑇)
Theorem	acsinfdimd 18737	In an algebraic closure system, if two independent sets have equal closure and one is infinite, then they are equinumerous. This is proven by using acsdomd 18736 twice with acsinfd 18735. See Section II.5 in [Cohn] p. 81 to 82. (Contributed by David Moews, 1-May-2017.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ 𝐼 = (mrInd‘𝐴)    &   ⊢ (𝜑 → 𝑆 ∈ 𝐼)    &   ⊢ (𝜑 → 𝑇 ∈ 𝐼)    &   ⊢ (𝜑 → (𝑁‘𝑆) = (𝑁‘𝑇))    &   ⊢ (𝜑 → ¬ 𝑆 ∈ Fin)    ⇒   ⊢ (𝜑 → 𝑆 ≈ 𝑇)
Theorem	acsexdimd 18738*	In an algebraic closure system whose closure operator has the exchange property, if two independent sets have equal closure, they are equinumerous. See mreexfidimd 17829 for the finite case and acsinfdimd 18737 for the infinite case. This is a special case of Theorem 4.2.2 in [FaureFrolicher] p. 87. (Contributed by David Moews, 1-May-2017.)
⊢ (𝜑 → 𝐴 ∈ (ACS‘𝑋))    &   ⊢ 𝑁 = (mrCls‘𝐴)    &   ⊢ 𝐼 = (mrInd‘𝐴)    &   ⊢ (𝜑 → ∀𝑠 ∈ 𝒫 𝑋∀𝑦 ∈ 𝑋 ∀𝑧 ∈ ((𝑁‘(𝑠 ∪ {𝑦})) ∖ (𝑁‘𝑠))𝑦 ∈ (𝑁‘(𝑠 ∪ {𝑧})))    &   ⊢ (𝜑 → 𝑆 ∈ 𝐼)    &   ⊢ (𝜑 → 𝑇 ∈ 𝐼)    &   ⊢ (𝜑 → (𝑁‘𝑆) = (𝑁‘𝑇))    ⇒   ⊢ (𝜑 → 𝑆 ≈ 𝑇)
Theorem	mrelatglb 18739	Greatest lower bounds in a Moore space are realized by intersections. (Contributed by Stefan O'Rear, 31-Jan-2015.) See mrelatglbALT 50203 for an alternate proof.
⊢ 𝐼 = (toInc‘𝐶)    &   ⊢ 𝐺 = (glb‘𝐼)    ⇒   ⊢ ((𝐶 ∈ (Moore‘𝑋) ∧ 𝑈 ⊆ 𝐶 ∧ 𝑈 ≠ ∅) → (𝐺‘𝑈) = ∩ 𝑈)
Theorem	mrelatglb0 18740	The empty intersection in a Moore space is realized by the base set. (Contributed by Stefan O'Rear, 31-Jan-2015.)
⊢ 𝐼 = (toInc‘𝐶)    &   ⊢ 𝐺 = (glb‘𝐼)    ⇒   ⊢ (𝐶 ∈ (Moore‘𝑋) → (𝐺‘∅) = 𝑋)
Theorem	mrelatlub 18741	Least upper bounds in a Moore space are realized by the closure of the union. (Contributed by Stefan O'Rear, 31-Jan-2015.) See mrelatlubALT 50202 for an alternate proof.
⊢ 𝐼 = (toInc‘𝐶)    &   ⊢ 𝐹 = (mrCls‘𝐶)    &   ⊢ 𝐿 = (lub‘𝐼)    ⇒   ⊢ ((𝐶 ∈ (Moore‘𝑋) ∧ 𝑈 ⊆ 𝐶) → (𝐿‘𝑈) = (𝐹‘∪ 𝑈))
Theorem	mreclatBAD 18742*	A Moore space is a complete lattice under inclusion. (Contributed by Stefan O'Rear, 31-Jan-2015.) TODO (df-riota 7377 update): Reprove using isclat 18679 instead of the isclatBAD. hypothesis. See commented-out mreclat above. See mreclat 50204 for a good version.
⊢ 𝐼 = (toInc‘𝐶)    &   ⊢ (𝐼 ∈ CLat ↔ (𝐼 ∈ Poset ∧ ∀𝑥(𝑥 ⊆ (Base‘𝐼) → (((lub‘𝐼)‘𝑥) ∈ (Base‘𝐼) ∧ ((glb‘𝐼)‘𝑥) ∈ (Base‘𝐼)))))    ⇒   ⊢ (𝐶 ∈ (Moore‘𝑋) → 𝐼 ∈ CLat)
9.6  Posets, directed sets, and lattices as relations
9.6.1  Posets and lattices as relations See commented-out notes for lattices as relations.
Syntax	cps 18743	Extend class notation with the class of all posets.
class PosetRel
Syntax	ctsr 18744	Extend class notation with the class of all totally ordered sets.
class TosetRel
Definition	df-ps 18745	Define the class of all posets (partially ordered sets) with weak ordering (e.g., "less than or equal to" instead of "less than"). A poset is a relation which is transitive, reflexive, and antisymmetric. (Contributed by NM, 11-May-2008.)
⊢ PosetRel = {𝑟 ∣ (Rel 𝑟 ∧ (𝑟 ∘ 𝑟) ⊆ 𝑟 ∧ (𝑟 ∩ ◡𝑟) = ( I ↾ ∪ ∪ 𝑟))}
Definition	df-tsr 18746	Define the class of all totally ordered sets. (Contributed by FL, 1-Nov-2009.)
⊢ TosetRel = {𝑟 ∈ PosetRel ∣ (dom 𝑟 × dom 𝑟) ⊆ (𝑟 ∪ ◡𝑟)}
Theorem	isps 18747	The predicate "is a poset" i.e. a transitive, reflexive, antisymmetric relation. (Contributed by NM, 11-May-2008.)
⊢ (𝑅 ∈ 𝐴 → (𝑅 ∈ PosetRel ↔ (Rel 𝑅 ∧ (𝑅 ∘ 𝑅) ⊆ 𝑅 ∧ (𝑅 ∩ ◡𝑅) = ( I ↾ ∪ ∪ 𝑅))))
Theorem	psrel 18748	A poset is a relation. (Contributed by NM, 12-May-2008.)
⊢ (𝐴 ∈ PosetRel → Rel 𝐴)
Theorem	psref2 18749	A poset is antisymmetric and reflexive. (Contributed by FL, 3-Aug-2009.)
⊢ (𝑅 ∈ PosetRel → (𝑅 ∩ ◡𝑅) = ( I ↾ ∪ ∪ 𝑅))
Theorem	pstr2 18750	A poset is transitive. (Contributed by FL, 3-Aug-2009.)
⊢ (𝑅 ∈ PosetRel → (𝑅 ∘ 𝑅) ⊆ 𝑅)
Theorem	pslem 18751	Lemma for psref 18753 and others. (Contributed by NM, 12-May-2008.) (Revised by Mario Carneiro, 30-Apr-2015.)
⊢ (𝑅 ∈ PosetRel → (((𝐴𝑅𝐵 ∧ 𝐵𝑅𝐶) → 𝐴𝑅𝐶) ∧ (𝐴 ∈ ∪ ∪ 𝑅 → 𝐴𝑅𝐴) ∧ ((𝐴𝑅𝐵 ∧ 𝐵𝑅𝐴) → 𝐴 = 𝐵)))
Theorem	psdmrn 18752	The domain and range of a poset equal its field. (Contributed by NM, 13-May-2008.)
⊢ (𝑅 ∈ PosetRel → (dom 𝑅 = ∪ ∪ 𝑅 ∧ ran 𝑅 = ∪ ∪ 𝑅))
Theorem	psref 18753	A poset is reflexive. (Contributed by NM, 13-May-2008.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ ((𝑅 ∈ PosetRel ∧ 𝐴 ∈ 𝑋) → 𝐴𝑅𝐴)
Theorem	psrn 18754	The range of a poset equals it domain. (Contributed by NM, 7-Jul-2008.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ (𝑅 ∈ PosetRel → 𝑋 = ran 𝑅)
Theorem	psasym 18755	A poset is antisymmetric. (Contributed by NM, 12-May-2008.)
⊢ ((𝑅 ∈ PosetRel ∧ 𝐴𝑅𝐵 ∧ 𝐵𝑅𝐴) → 𝐴 = 𝐵)
Theorem	pstr 18756	A poset is transitive. (Contributed by NM, 12-May-2008.) (Revised by Mario Carneiro, 30-Apr-2015.)
⊢ ((𝑅 ∈ PosetRel ∧ 𝐴𝑅𝐵 ∧ 𝐵𝑅𝐶) → 𝐴𝑅𝐶)
Theorem	cnvps 18757	The converse of a poset is a poset. In the general case (◡𝑅 ∈ PosetRel → 𝑅 ∈ PosetRel) is not true. See cnvpsb 18758 for a special case where the property holds. (Contributed by FL, 5-Jan-2009.) (Proof shortened by Mario Carneiro, 3-Sep-2015.)
⊢ (𝑅 ∈ PosetRel → ◡𝑅 ∈ PosetRel)
Theorem	cnvpsb 18758	The converse of a poset is a poset. (Contributed by FL, 5-Jan-2009.)
⊢ (Rel 𝑅 → (𝑅 ∈ PosetRel ↔ ◡𝑅 ∈ PosetRel))
Theorem	psss 18759	Any subset of a partially ordered set is partially ordered. (Contributed by FL, 24-Jan-2010.)
⊢ (𝑅 ∈ PosetRel → (𝑅 ∩ (𝐴 × 𝐴)) ∈ PosetRel)
Theorem	psssdm2 18760	Field of a subposet. (Contributed by Mario Carneiro, 9-Sep-2015.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ (𝑅 ∈ PosetRel → dom (𝑅 ∩ (𝐴 × 𝐴)) = (𝑋 ∩ 𝐴))
Theorem	psssdm 18761	Field of a subposet. (Contributed by FL, 19-Sep-2011.) (Revised by Mario Carneiro, 9-Sep-2015.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ ((𝑅 ∈ PosetRel ∧ 𝐴 ⊆ 𝑋) → dom (𝑅 ∩ (𝐴 × 𝐴)) = 𝐴)
Theorem	istsr 18762	The predicate is a toset. (Contributed by FL, 1-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ (𝑅 ∈ TosetRel ↔ (𝑅 ∈ PosetRel ∧ (𝑋 × 𝑋) ⊆ (𝑅 ∪ ◡𝑅)))
Theorem	istsr2 18763*	The predicate is a toset. (Contributed by FL, 1-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ (𝑅 ∈ TosetRel ↔ (𝑅 ∈ PosetRel ∧ ∀𝑥 ∈ 𝑋 ∀𝑦 ∈ 𝑋 (𝑥𝑅𝑦 ∨ 𝑦𝑅𝑥)))
Theorem	tsrlin 18764	A toset is a linear order. (Contributed by Mario Carneiro, 9-Sep-2015.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ ((𝑅 ∈ TosetRel ∧ 𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋) → (𝐴𝑅𝐵 ∨ 𝐵𝑅𝐴))
Theorem	tsrlemax 18765	Two ways of saying a number is less than or equal to the maximum of two others. (Contributed by Mario Carneiro, 9-Sep-2015.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ ((𝑅 ∈ TosetRel ∧ (𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋 ∧ 𝐶 ∈ 𝑋)) → (𝐴𝑅if(𝐵𝑅𝐶, 𝐶, 𝐵) ↔ (𝐴𝑅𝐵 ∨ 𝐴𝑅𝐶)))
Theorem	tsrps 18766	A toset is a poset. (Contributed by Mario Carneiro, 9-Sep-2015.)
⊢ (𝑅 ∈ TosetRel → 𝑅 ∈ PosetRel)
Theorem	cnvtsr 18767	The converse of a toset is a toset. (Contributed by Mario Carneiro, 3-Sep-2015.)
⊢ (𝑅 ∈ TosetRel → ◡𝑅 ∈ TosetRel )
Theorem	tsrss 18768	Any subset of a totally ordered set is totally ordered. (Contributed by FL, 24-Jan-2010.) (Proof shortened by Mario Carneiro, 21-Nov-2013.)
⊢ (𝑅 ∈ TosetRel → (𝑅 ∩ (𝐴 × 𝐴)) ∈ TosetRel )
Theorem	ledm 18769	The domain of ≤ is ℝ*. (Contributed by FL, 2-Aug-2009.) (Revised by Mario Carneiro, 4-May-2015.)
⊢ ℝ* = dom ≤
Theorem	lern 18770	The range of ≤ is ℝ*. (Contributed by FL, 2-Aug-2009.) (Revised by Mario Carneiro, 3-Sep-2015.)
⊢ ℝ* = ran ≤
Theorem	lefld 18771	The field of the 'less or equal to' relationship on the extended real. (Contributed by FL, 2-Aug-2009.) (Revised by Mario Carneiro, 4-May-2015.)
⊢ ℝ* = ∪ ∪ ≤
Theorem	letsr 18772	The "less than or equal to" relationship on the extended reals is a toset. (Contributed by FL, 2-Aug-2009.) (Revised by Mario Carneiro, 3-Sep-2015.)
⊢ ≤ ∈ TosetRel
9.6.2  Directed sets, nets
Syntax	cdir 18773	Extend class notation with the class of directed sets.
class DirRel
Syntax	ctail 18774	Extend class notation with the tail function for directed sets.
class tail
Definition	df-dir 18775	Define the class of directed sets (the order relation itself is sometimes called a direction, and a directed set is a set equipped with a direction). (Contributed by Jeff Hankins, 25-Nov-2009.)
⊢ DirRel = {𝑟 ∣ ((Rel 𝑟 ∧ ( I ↾ ∪ ∪ 𝑟) ⊆ 𝑟) ∧ ((𝑟 ∘ 𝑟) ⊆ 𝑟 ∧ (∪ ∪ 𝑟 × ∪ ∪ 𝑟) ⊆ (◡𝑟 ∘ 𝑟)))}
Definition	df-tail 18776*	Define the tail function for directed sets. (Contributed by Jeff Hankins, 25-Nov-2009.)
⊢ tail = (𝑟 ∈ DirRel ↦ (𝑥 ∈ ∪ ∪ 𝑟 ↦ (𝑟 “ {𝑥})))
Theorem	isdir 18777	A condition for a relation to be a direction. (Contributed by Jeff Hankins, 25-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ 𝐴 = ∪ ∪ 𝑅    ⇒   ⊢ (𝑅 ∈ 𝑉 → (𝑅 ∈ DirRel ↔ ((Rel 𝑅 ∧ ( I ↾ 𝐴) ⊆ 𝑅) ∧ ((𝑅 ∘ 𝑅) ⊆ 𝑅 ∧ (𝐴 × 𝐴) ⊆ (◡𝑅 ∘ 𝑅)))))
Theorem	reldir 18778	A direction is a relation. (Contributed by Jeff Hankins, 25-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ (𝑅 ∈ DirRel → Rel 𝑅)
Theorem	dirdm 18779	A direction's domain is equal to its field. (Contributed by Jeff Hankins, 25-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ (𝑅 ∈ DirRel → dom 𝑅 = ∪ ∪ 𝑅)
Theorem	dirref 18780	A direction is reflexive. (Contributed by Jeff Hankins, 25-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ ((𝑅 ∈ DirRel ∧ 𝐴 ∈ 𝑋) → 𝐴𝑅𝐴)
Theorem	dirtr 18781	A direction is transitive. (Contributed by Jeff Hankins, 25-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ (((𝑅 ∈ DirRel ∧ 𝐶 ∈ 𝑉) ∧ (𝐴𝑅𝐵 ∧ 𝐵𝑅𝐶)) → 𝐴𝑅𝐶)
Theorem	dirge 18782*	For any two elements of a directed set, there exists a third element greater than or equal to both. Note that this does not say that the two elements have a least upper bound. (Contributed by Jeff Hankins, 25-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ 𝑋 = dom 𝑅    ⇒   ⊢ ((𝑅 ∈ DirRel ∧ 𝐴 ∈ 𝑋 ∧ 𝐵 ∈ 𝑋) → ∃𝑥 ∈ 𝑋 (𝐴𝑅𝑥 ∧ 𝐵𝑅𝑥))
Theorem	tsrdir 18783	A totally ordered set is a directed set. (Contributed by Jeff Hankins, 25-Nov-2009.) (Revised by Mario Carneiro, 22-Nov-2013.)
⊢ (𝐴 ∈ TosetRel → 𝐴 ∈ DirRel)
9.7  Chains
Syntax	cchn 18784	Extend class notation with the class of (finite) chains.
class ( < Chain 𝐴)
Definition	df-chn 18785*	Define the class of (finite) chains. A chain is defined to be a sequence of objects, where each object is less than the next one in the sequence. The term "chain" is usually used in order theory. In the context of algebra, chains are often called "towers", for example for fields, or "series", for example for subgroup or subnormal series. (Contributed by Thierry Arnoux, 19-Jun-2025.)
⊢ ( < Chain 𝐴) = {𝑐 ∈ Word 𝐴 ∣ ∀𝑛 ∈ (dom 𝑐 ∖ {0})(𝑐‘(𝑛 − 1)) < (𝑐‘𝑛)}
Theorem	ischn 18786*	Property of being a chain. (Contributed by Thierry Arnoux, 19-Jun-2025.)
⊢ (𝐶 ∈ ( < Chain 𝐴) ↔ (𝐶 ∈ Word 𝐴 ∧ ∀𝑛 ∈ (dom 𝐶 ∖ {0})(𝐶‘(𝑛 − 1)) < (𝐶‘𝑛)))
Theorem	chnwrd 18787	A chain is an ordered sequence, i.e. a word. (Contributed by Thierry Arnoux, 19-Jun-2025.)
⊢ (𝜑 → 𝐶 ∈ ( < Chain 𝐴))    ⇒   ⊢ (𝜑 → 𝐶 ∈ Word 𝐴)
Theorem	chnltm1 18788	Basic property of a chain. (Contributed by Thierry Arnoux, 19-Jun-2025.)
⊢ (𝜑 → 𝐶 ∈ ( < Chain 𝐴))    &   ⊢ (𝜑 → 𝑁 ∈ (dom 𝐶 ∖ {0}))    ⇒   ⊢ (𝜑 → (𝐶‘(𝑁 − 1)) < (𝐶‘𝑁))
Theorem	pfxchn 18789	A prefix of a chain is still a chain. (Contributed by Thierry Arnoux, 19-Jun-2025.)
⊢ (𝜑 → 𝐶 ∈ ( < Chain 𝐴))    &   ⊢ (𝜑 → 𝐿 ∈ (0...(♯‘𝐶)))    ⇒   ⊢ (𝜑 → (𝐶 prefix 𝐿) ∈ ( < Chain 𝐴))
Theorem	nfchnd 18790	Bound-variable hypothesis builder for chain collection constructor. (Contributed by Ender Ting, 20-Jan-2026.)
⊢ (𝜑 → Ⅎ𝑥 < )    &   ⊢ (𝜑 → Ⅎ𝑥𝐴)    ⇒   ⊢ (𝜑 → Ⅎ𝑥( < Chain 𝐴))
Theorem	chneq1 18791	Equality theorem for chains. (Contributed by Ender Ting, 17-Jan-2026.)
⊢ ( < = 𝑅 → ( < Chain 𝐴) = (𝑅 Chain 𝐴))
Theorem	chneq2 18792	Equality theorem for chains. (Contributed by Ender Ting, 17-Jan-2026.)
⊢ (𝐴 = 𝐵 → ( < Chain 𝐴) = ( < Chain 𝐵))
Theorem	chneq12 18793	Equality theorem for chains. (Contributed by Ender Ting, 17-Jan-2026.)
⊢ (( < = 𝑅 ∧ 𝐴 = 𝐵) → ( < Chain 𝐴) = (𝑅 Chain 𝐵))
Theorem	chnrss 18794	Chains under a relation are also chains under any superset relation. (Contributed by Ender Ting, 20-Jan-2026.)
⊢ ( < ⊆ 𝑅 → ( < Chain 𝐴) ⊆ (𝑅 Chain 𝐴))
Theorem	chndss 18795	Chains with an alphabet are also chains with any superset alphabet. (Contributed by Ender Ting, 20-Jan-2026.)
⊢ (𝐴 ⊆ 𝐵 → ( < Chain 𝐴) ⊆ ( < Chain 𝐵))
Theorem	chnrdss 18796	Subset theorem for chains. (Contributed by Ender Ting, 20-Jan-2026.)
⊢ (( < ⊆ 𝑅 ∧ 𝐴 ⊆ 𝐵) → ( < Chain 𝐴) ⊆ (𝑅 Chain 𝐵))
Theorem	chnexg 18797	Chains with a set given for range form a set. (Contributed by Ender Ting, 21-Nov-2024.) (Revised by Ender Ting, 17-Jan-2026.)
⊢ (𝐴 ∈ 𝑉 → ( < Chain 𝐴) ∈ V)
Theorem	nulchn 18798	Empty set is an increasing chain for every range and every relation. (Contributed by Ender Ting, 19-Nov-2024.) (Revised by Ender Ting, 17-Jan-2026.)
⊢ ∅ ∈ ( < Chain 𝐴)
Theorem	s1chn 18799	A singleton word is always a chain. (Contributed by Thierry Arnoux, 19-Oct-2025.)
⊢ (𝜑 → 𝑋 ∈ 𝐴)    ⇒   ⊢ (𝜑 → ⟨“𝑋”⟩ ∈ ( < Chain 𝐴))
Theorem	chnind 18800*	Induction over a chain. See nnind 12356 for an explanation about the hypotheses. (Contributed by Thierry Arnoux, 19-Jun-2025.)
⊢ (𝑐 = ∅ → (𝜓 ↔ 𝜒))    &   ⊢ (𝑐 = 𝑑 → (𝜓 ↔ 𝜃))    &   ⊢ (𝑐 = (𝑑 ++ ⟨“𝑥”⟩) → (𝜓 ↔ 𝜏))    &   ⊢ (𝑐 = 𝐶 → (𝜓 ↔ 𝜂))    &   ⊢ (𝜑 → 𝐶 ∈ ( < Chain 𝐴))    &   ⊢ (𝜑 → 𝜒)    &   ⊢ (((((𝜑 ∧ 𝑑 ∈ ( < Chain 𝐴)) ∧ 𝑥 ∈ 𝐴) ∧ (𝑑 = ∅ ∨ (lastS‘𝑑) < 𝑥)) ∧ 𝜃) → 𝜏)    ⇒   ⊢ (𝜑 → 𝜂)