Adopt Proper Graph Theory Terminology For Tag Graph

[bbappserver]

I know because of all the legacy and documentation that has to change, modifying the tag graph terminology would be kind of a pain. But I also believe that a lot of time could be saved in explaining to new users or discussing in a technical sense if the terminology was brought in line with how people typically think of trees in a genealogical sense or its mathematical analog. I know the features is based on one particular booru that happened to use those terms... but to put it charitably, that booru was just plain incorrect.

The most intuitive way to describe how the tag graph works is to show a picture, but for that to work you have to talk about nodes in a genealogical sense and then every single time you have to double back and say "but remember it's actually the reverse of that for hydrus".

It is very confusing to discuss the tag graph. The first time any new user wants to use it I have to start by explaining that "parent" means "superset" and sibling means "lexical alias". This runs counter to the way anyone thinks of a lineage, and the opposite of how mathematicians and computer scientists like to think of tree structures.

Then when you try to explain tag resolution you have to mentally invert your model of how a tree works because children of the parent graph are parents in hydrus terminology, and sibling in the parent graph have nothing to do with being a parent(in hydrus terminology) that shares a child(in hydrus terminology) (That is a node that shares a parent in graph theory).

God forbid you need to talk about ancestors and descendants for tag maintenance or a bug report. Because then you really want to talk about how a->{b,c,d}->{e}->{f,g,h} means {b,c,d,e,f,g,h} are descendant of a, nooooo, not in hydrus in hydrus those are all ancestors.

children(a)={aa,ab}
descendants(a)={aa,ab,aaa,aab,aac}
siblings(aa)={ab}
ancestors(aaa)={aa,a}
siblings(aab)={aaa,aac}

aliases(clark kent)= {character:superman, kal-el,clark kent}
king(clark kent)=character:superman
descendants(clark kent)= descendants(aliases(clark kent) U {clark kent})= descendants ({character:superman, kal-el,clark kent}) = {kryptonian,series:superman,dc comics}
ancestors(dc comics)={aliases(series:superman),aliases(wonder woman), aliases(character:superman)}

Then you can talk about the graph traversal without having to specify everything twice.

def descendants(tagset):
'''Pseudocode explaining tag resolution that doesn't need everything explained twice'''
  if not tagset: return {}
  if len(tagset) == 1 and tagset[0] in descentant_cache: return descendant_cache[tagset]
  alias_set=aliases(tagset)
  child_set=children(alias_set)
  alias_child_set=aliases(child_set).union(child_set)
  desc= descendants(alias_child_set)
  for x in alias_child_set: descendant_cache.put(x,desc)
  return desc.union(child_set).union(alias_child_set)

[TheElo]

What is a tag graph and where/how you even find them in hydrus?

[vickyorlo]

I have no clue what you're trying to say. I think you either don't understand graph theory as well as you think you do, you don't understand what's commonly intuitive, both, or something else. "DC Comics" is not the child of "Superman" but the other way around, in the sense that without DC Comics existing Superman would not exist, and that a child can only have one parent which makes far more sense than a parent being able to have only one child, but a child having many parents. DC Comics is far easier to think of as an ancestor of Superman. Your second graph is directed in the wrong direction. Do note that directed rooted trees can be both in-tree and out-tree and there's nothing "wrong" with either approach.

also what elo said

[SwordfishBooks]

The idea that Superman wouldn't exist without DC Comics is ridiculous.

Firstly, Clark Kent/Superman debuted in 1938's Action Comics 1 published by "National Allied Publications". "DC Comics" is a 1977 rebranding of "National Comics" which is a 1946 merger of "National Allied Publications", "Detective Comics Inc", and "All-American Publications". In short, saying "DC Comics" created Superman is like saying Gogeta is Gohan's father.

Second, Clark Kent/Superman was created before Jerry Siegel and Joe Shuster started working at "National Allied Publications". Therefore, even if "DC Comics" was synonymous "National Allied Publications", the claim that Superman wouldn't exist without "DC Comics" is still false.

[bbappserver]

What is a tag graph and where/how you even find them in hydrus?

The tag graph is not a visually represented UI element, it is in an abstract sense how the tagging engine resolves what are currently called siblings and parents into the virtual tags from the real tags. Let superman be kryptonian and male, then you walk from superman to kryptionan and superman to male in the tag graph to collect the virtual tags which also apply to an image tagged with superman.

Please also ignore whether or not you agree with the example tagging representation of superman, and consider it only as a possible use of siblings and parents used to exemplify how the graph works. I haven't thought it through too deeply I just needed a decent example. Instead I'll let superman be male and kryptonian so we don't have to debate about superman appearing in other works.

To clarify what the images are showing.

• If an edge points from a to b in tree-graph terminology this is called a child because node b is an offshoot from node a.
• Confusingly in hydrus if b is pointed to from a, this is referred to as adding parent b to a. This is because hydrus thinks of all tags as nested sets. The simplest analog and what is shown in the documentation where it's kind of like folders of tags.
  • The male directory contains superman for example.
  • But now what if the kryptonian directory contains superman, that is kryptonian is also a parent of superman. Going back to the filesystem analogy you have a file with the same identity in two seperate folders. And as the end-user you might say this is a perfectly fine analogy you understand, but that's not actually how hydrus is storing the information, and it makes it confusing to talk about internally, or implement any extension that makes use of the graph.
• Internally, there are just three nodes {superman,male,kryptonian} because superman implies male and kryptonian, then there is an edge coming out of superman and pointing to male and and edge from superman to kryptonian. As you walk this graph to try and collect all the descendants, imagine say that kryptonian always had green eyes then you would say green eyes is a child of kryptonian and a descendant of superman, because you can walk from superman to kryptonian and then to green eyes.
• Siblings are even worse. Think of genealogy, siblings share a parent. In hydrus sibling just means alias though, there is actually no descendants at all, but it sounds like it should be a node sharing the same parent as another.