A few posts back, I wrote the following as a rule for detecting enforcement events:

An event is an enforcement if it is an Enforcer Action taking place within 2 minutes after a Violent Action against one of the teammates of the Enforcer.

Since then, a few parts of this rule have been bugging me:

  • what’s an enforcer action?
  • why two minutes?
  • what’s a violent action?

So I’m going to take a step back and look at this again.  I’m defining enforcement event to be a manifestation of an enfoo quantity (like gravitational attraction would be for a mass quantity).  If these manifestations are what makes somebody an enforcer, then it may be that a pattern amongst these events can be extracted that determines an ordering of players sufficiently close to the original crude orderings of enforcers. So,

  1. hockey players can be crudely ordered according to their capabilities as an enforcer.
  2. I dub this capability enfoo
  3. I hypothesize that enfoo manifests in certain ways that can be analyzed to yield an ordering of players according to their degree of enfoo
    • That is, I hypothesize that enfoo can be measured via enfoo manifestations, which I call enforcements
  4. A scale for measuring enfoo via enforcements is defined, and is called the barce scale.
  5. Barce measurements are made on NHL play-by-play data, and the resulting player orderings are compared to crude orderings.
    • If the barce orderings track the crude orderings closely, then the barce scale captures the intuitions of the creators of the crude orderings (i.e. experts).
    • If the barce and crude orderings are very different, then all is not lost.  If the semantics of the barce scale are interesting, then the scale provides a new perspective on the concept of enforcement.

This all tracks the 1968 work of Brian Ellis quite well (this would be a fundamental derived measurement in his theory).  However, not everything rests on solid ground here.  Ellis didn’t really discuss social quantities (like enfoo), instead concentrating on physical quantities like mass, pressure, and electrical resistance.  Thus, the idea of looking at events (manifestations of enfoo) brings with it some difficulties.

One difficulty is that the units of the barce scale are quite unlike grams and meters.  When defining the meter, experts talk about how far light travels in a vacuum in a very short period of time.  The gram is based on an actual object known as the IPK (International Prototype Kilogram).

The barce scale introduces two kinds of difficulties, which I alluded to at the top of this post: subjectivity and causal influence.

The events of a hockey game, such as penalties and goals, are only identified by certain officials on the ice and in the booth.  It doesn’t matter whether you or I think a hit was a cross-check, even if the officials for that game agree with us the next day – if an official doesn’t identify the hit as a cross-check (thus penalizing the hitter) during the game, then it’s not a cross-check.  The events of a hockey game, then, cannot be be determined without knowing the officials’ in-game decisions.  Fortunately, these decisions are themselves objectively verifiable due to their documentation.

A more worrisome difficulty is the detection of causal influence.  Enforcements are defined as events that are in some sense caused by a provocation by a member of the other team.  For example, we might consider the following causal influences:

  1. An enforcement would not have occurred had it not been for the provocation.
  2. A provocation increased the probability of an enforcement occurring.
  3. A provocation inclined a player to perform an enforcement.

An added difficulty builds on the problem with subjectivity mentioned above: a provocation may not be noticed by an official, but nevertheless be noticed by a player who subsequently goes after the provoker.

I think one way to resolve this is to take a page out of moral theory.  Let’s say that an enforcer is a player who goes after players on the other team who do something provocative.  Let’s further say that there are good definitions for what it means to go after somebody and to be provocative in the context of a hockey game.  Then we expect that a good enforcer should go after opponents who are being provocative.  In other words, the more a player retaliates, the better he is at enforcing.

The form in use here looks like this:


"quantity Q manifest as event E"
(Q manifests-as E)

"things with Q should perform events of type E"
(x has Q) => should(x do E)

"all things being equal, x has more Q having performed e"
Q(x|e) > Q(x|~e) c.p.

It’s pseudo-logic, for sure, but hopefully the intent is somewhat clear.  Looking at that pseudo-logic, there’s nothing that prevents a quantity from manifesting in more than one way.  And that’s a good thing, because good enforcers do more than retaliate – they also deter provocations.  If a player has reputation for retaliating harshly, then opponents may be less likely to provoke.  This result is even better for the enforcer’s team, since an enforcer’s retaliations sometimes land him in the penalty box.  Thus, we can say that a good enforcer plays in games where the opposing side doesn’t often provoke.  In other words, the less an opposing team provokes, the better an enforcer is doing.

I updated the analysis file with a new query to reflect this new bi-valued barce scale:

prefix nhl: <http://www.nhl.com/>
prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
select ?name (sum(?enfActs) as ?enf)  (sum(?totChances) as ?opp)
where { ?x a nhl:Enforcement . ?x nhl:actor ?player .
  ?x nhl:value ?enfActs . ?x nhl:game ?game .
  ?y a nhl:ViolentPenaltyTally . ?y nhl:game ?game .
  ?y nhl:team ?otherTeam . ?y nhl:value ?totChances .
  ?z a nhl:GameRoster . ?z nhl:game ?game . ?z nhl:player ?player .
  ?z nhl:team ?team . ?player rdfs:label ?name .
  filter( ?team != ?otherTeam) }
group by ?name

The retaliation value is ?enf and the deterrent value is ?opp.  I haven’t gotten around to changing the variable names to something more suitable, so don’t read too much into them yet.

I also haven’t changed the definitions of nhl:Enforcement, nhl:ViolentPenalty, or nhl:EnforcerAction yet, so those are still on the docket for review.  I also opted to skip the Sparql Construct I used for the other two barce formulations and just spit the measurement out into a result set (which is interpreted as an Incanter dataset in seabass).  For purposes of ranking, the two values for this barce measurement can be multiplied (the inverse of the deterrent value has to be used, since enfoo is inversely proportional to the number of provocations).

Maybe I’ll get to some charts and analysis tomorrow, if the theory bug doesn’t bite me again.

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