Taxonomy and the Echelon Reference Series

In the last couple of posts it’s pretty clear I was wearing my geek hat. Time to lower the flaps and tie the strings under my chin, because this is going to get busy.


Echelon Game Design Logo
Echelon Game Design Logo

Straight from

taxonomy [tak-sonuh-mee]

noun, plural taxonomies

  1. the science or technique of classification
  2. a classification into ordered categories:
    a proposed taxonomy of educational objectives
  3. Biology. the science dealing with the description, identification, naming, and classification of organisms.

Moving to a more abstract representation of the game data means I need some way of identifying what a particular object is. At one point this was done using styles, but now ‘object’ is the only style left related to game objects. I have others for document structure and for certain types of information belonging to objects (the ‘abstract’ styles described in my last post, ‘attribute’ style from the last post, a ‘brief’ style for things like one-line spell descriptions), but these are not game objects.

I have styles in place for type declaration (d20-1-Decl, d20-2-Decl, d20-3-Decl), but what do I put in them? Well, I’m working a hierarchical taxonomy.

Hierarchical Taxonomy

Almost all taxonomies are hierarchical. Biological taxonomy has seven levels (kingdom, phylum, class, order, family, genus, and species), with each becoming more specialized and specific. At any given level, a member of a group is a member of that group’s parent group. For instance, a dog is canis lupus (or canis lupus familiaris, for domesticated dogs)… which means that it is of the canidae family, carnivora order, mammalia class, chordata phylum, and animalia kingdom. It shares characteristics with all canidae, all carnivora, all mammalia, all chordata, and all animalia. These characteristics become a smaller and smaller set the higher you get the taxonomy, but ultimately there are identifiable characteristics shared between dogs and cats (same order, carnivora), and dogs and humans (same class, mammalia), and dogs and sea slugs (same kingdom, animalia).

Game object taxonomy can be similar. I don’t plan to be nearly so rigorous or have so many levels, but having a hierarchy makes many things easier for me down the road.

Hierarchical Parsing

I can take advantage of this when parsing content. Because an object has all types at its level and above in the hierarchy, I can resolve many references I can’t now. Consider the partial hierarchy below:

  • Ability Something a creature can do
    • Feat Learned ability gained using a feat slot
    • Class Feature Ability granted by a class or archetype
      • Class Subfeature An element of a class feature, often chooseable (rage powers) but sometimes not (bardic performance)
        • Class Subsubfeature An element of a class subfeature, sometimes choosable (revelation) but often not (bloodline power, granted power)
          • Bloodline Power Ability granted by a bloodline
          • Granted Power Ability granted by a domain
          • Revelation Ability granted by a mystery
        • Bardic Performance Ability granted by the bardic performance class feature, not choosable but determined by class or archetype
        • Domain Ability granted by the domains class feature (or domain class feature for classes and archetypes that just get one), usually choosable
        • Mystery Ability granted by the mystery class feature, choosable
        • Oracle’s Curse Ability granted by the curse class feature, choosable
        • Rage Power Ability granted by the rage powers class feature, choosable
        • Rogue Talent Ability granted by the rogue talents class feature, choosable
    • Sense Sensory ability; included here as a universal monster rule but I’m not sure that’s appropriate for the taxonomy.
    • Skill Learned ability with variable degrees of expertise (skill ranks)
    • Trait Ability inherent to a creature
      • Character Trait Trait of characters, choosable
        • Class Trait Trait available to characters of a specific class
        • Race Trait Trait available to characters of a specific race [note collision with ‘racial trait’, below; personal peeve]
        • Regional Trait Trait available to characters from a particular region
      • Racial Trait Trait inherent to a race, common to all members of that race
      • Monster Trait Trait inherent to a species of monster, common to all members of that species
  • Magic Non-abilities that do fantastic things
    • Spell Castable magic
    • Magic Item Magic in physical form
      • Magic Armor Physical protection, magically enhanced
      • Magic Quality Magic that can be added to an item
        • Armor Quality Magic that can be added to magic armor
        • Weapon Quality Magic that can be added to a magic weapon
      • Wondrous Item Miscellaneous magic item
  • Affliction Persistent (usually bad) thing that happens to a creature or object
    • Curse Supernatural stuff that happens to a creature or object
    • Disease Illness that happens to a creature or object [O.o for consitent definition… –kjd]
    • Poison Venom or toxin that happens to a creature or object [well, applied to an object, so it affects a creature –kjd]

“Darkvision” is both a racial trait (dwarves have it) and a monster trait (dragons have it). There is also a sense (universal rules) called ‘darkvision’.

In the second and third versions of the Echelon Reference Series, ‘darkvision trait’ could not be readily resolved. I could find ‘darkvision racial trait’ or ‘darkvision monster trait’, but ‘darkvision trait’ did not exist. I also couldn’t find ‘darkvision’ because there were multiple objects with that name.

Under this taxonomy, I am in a much better position.

  • I can now resolve ‘darkvision trait’ because racial traits and monster traits also are traits (specializations of ‘trait’). If I search for ‘darkvision trait’ I find an implied ‘darkvision trait’. That there are two variations (racial and monster) doesn’t matter to me because I specified the ‘trait’ level. If I wanted the racial trait specifically, I would have said.
  • Similarly, ‘darkvision ability’ will resolve at the ‘ability’ level: I just care that you have the darkvision ability, and not whether it is a sense or a trait.
  • ‘Darkvision’ alone won’t resolve. There are traits (abilities) and a darkvision spell (magic). Without something to further identify the target, I can’t tell which is the correct link. ‘Heal’ is another challenging one (skill and spell).
    • I do get some benefit out of implied rules. If I see heal (that is, ‘heal’ in italics), by convention that is the magic heal, the spell, rather than the skill.

This can still lead to ambiguity, and I need to decide what to do. The ghost touch quality resolves to two different concrete items (armor quality and weapon quality) with different characteristics, and I do care about the distinction. Similarly, bane (weapon quality and spell) and spell resistance (armor quality and spell) conflict. I suspect marking certain elements of the hierarchy ‘abstract’ or ‘not implied’ could handle it. That is, while both are under ‘Magic’ for classification reasons, spells and magic items are to be considered sufficiently separate from each other and cannot be equated. For ‘bane‘ to resolve, it must be specifically the spell or the weapon quality (or technically it could be the quality, or the magic item).

Obviously the exact hierarchy will be in flux for a while. I’m still not satisfied with the class feature/subfeature bit.

On further consideration, I think I like the “blocker” possibility. While in many ways the taxonomy holds for many purposes, for some there might be a restriction on climbing the hierarchy for reference purposes. That there is both a “bane spell” and a “bane weapon quality” doesn’t mean there is a meaningful “bane magic”… but they are both still magic for other purposes. Must consider further, this seems very strange in a hierarchy, like it can be a thing without being a thing.

Hierarchical Rendering Rules

The Echelon Reference Series is quite consistent in how it renders game objects. Most often, each game object has a heading (rounded rectangle containing the name) that may have additional elements.

  • A stat block (spells, feats with prerequisites, archetype class features that replace or alter features of the associated class);
    • Because the stat blocks are so long, monsters and characters have a ‘relaxed stat block’: the stat lines are still grouped together, but are not contained inside the heading because it looks really, really bad when it doesn’t fit in the column. Though I think I haven’t had any single stat block fail to fit on a page; I could go full page width and two column within that. Hmm…)
  • a level marker (feats and other character options that have a minimum level derived from level, skill rank, or base attack bonus prerequisites);
  • a type marker (abilities can be (Ex), (Sp), or (Su); abilities might have other types such as (Combat) or (Item Creation) feats; some abilities have special rules, such as rogue talents that modify the sneak attack ability and only one can be applied at once).

Often the only visible difference between objects is color (class features are dark brown, class subfeatures are a medium brown, feats are pale brown). The rendering in documents is otherwise identical. When rendering an object I can take the type and work up the taxonomy hierarchy until I find rules for how to render the object: ‘rogue talent’ and ‘rage power’ are both ‘class subfeatures’ and have no special formatting, so I can fall back on the inherited rendering rules for ‘class subfeature’ when I want to render one of these objects. I might want to render bloodlines differently, so I override the rendering rules for bloodlines and they will look different… and when I add ‘draconic bloodline’ to the taxonomy, it gets rendered the same was as normal bloodlines.

The head of this taxonomy, ‘ability’ (which is ‘something a creature can inherently do’ — includes skills and feats, does not include spells) would thus provide a default rendering mechanism that will let me see the content. It might be very generic, it might be very ugly (I like to make undefined things red so they jump out when I’m reviewing documents — which is why some ‘links’ are red in my PDFs, it means I had identified some text as a link but no target was found, while green means a target was found but is not in this document), but it is presented in the document.

Closing Comments

Building a hierarchy gives me a lot of functionality by letting me ‘inherit’ parsing and rendering behavior, without really adding or changing code. For instance, I can add ‘draconic bloodline’ (child of ‘bloodline’ class subfeature, in the taxonomy) and objects marked as draconic bloodlines will be correctly identified as this kind of bloodline, but still parse and render as normal bloodlines.

I can also use the more more specific taxonomy to change behavior correctly. When I added ‘bloodline’ to the taxonomy it was rendered the same as any other class subfeature, and while that works, I’d like to do something a bit different. I can add code to change how bloodlines are rendered, without affecting other types… except draconic bloodlines, because they inherit this code.

Between the increased abstraction and the use of hierarchical taxonomy, I can get rid of a great deal of complex and redundant code, while making the processing more powerful and specific.

One comment

  1. This isn’t helpful for your document-styling goals, but the structure could also be interpreted from a category-theory perspective, with “build choices” as morphisms and partially- or completely-specified characters as objects. I can’t think of any particularly interesting results of that though.

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