Experiments of Form
<P>
(Numerous ifMUDders made significant contributions to the research and scholarship underlying this article, especially Andrew Plotkin, Dan Shiovitz, Emily Short, and Carl Muckenhoupt.)
<P>
There's a risk in trying to define Interactive Fiction by enumerating some set of properties that are true of the things we consider IF: the possibility of including properties that just happen to be true of all known works of IF but are not really necessary for a work to be IF. In fact, over the years, a number of games have broken the "rules", violating our expectations of how a work of Interactive Fiction should behave, while leaving us agreeing that those works were still IF. (Other works have done similarly but left us disagreeing.) It seems valuable to take stock of these rules-that-are-not-rules, the expectations that we as readers/players bring to our interactions, if for no other reason than to add to the discussion of just what IF is -- or isn't.
<P>
Andrew Plotkin first drew the community's attention to the issue with a Usenet post in 1997 titled "Assumptions in most IF" featuring a list of such assumptions. Dan Shiovitz's reply expanded the list and pointed out it was tempting to intentionally break these rules; in truth, Plotkin was already planning out "Spider & Web" (1998), a game which did just that. But even before this public commentary, Infocom had pulled a few tricks, notably the multiple protagonists in "Suspended" (Michael Berylyn, 1983) and the breaking of the fourth wall and non-linear narrative in "The Hitchhiker's Guide to the Galaxy" (Stephen Meretzky & Douglas Adams, 1984).
<P>
Still, it's been more than five years since Plotkin's post; plenty of time for most of those rules, and many more, to get broken. The below combines Plotkin's and Shiovitz' list with a few possibilities of my own.
<P>
-  The work is "solvable" in some sense. (Shiovitz 1997)<br>
-  The work is communicated as a dialogue between player and narrator/protagonist/avatar.<br>
-  The text of the work is written in a language read/spoken by the target audience.<br>
<P>
-  The player's commands affect the protagonist. (Plotkin 1997)<br>
-  There is a protagonist. (Plotkin)<br>
-  There is only one protagonist.<br>
-  The protagonist is a sentient being. (Plotkin)<br>
-  The protagonist is not aware of the player.<br>
-  The protagonist is not aware of being fictional. (Shiovitz)<br>
<P>
-  The events described in the transcript are actually occurring. (Plotkin)<br>
-  The events described in the transcript are happening to the protagonist. (Plotkin)<br>
-  The descriptions in the transcript are perceptions by the protagonist.<br>
-  The descriptions in the transcript are correct perceptions by the protagonist. (Plotkin)<br>
-  The descriptions in the transcript are written by someone who is honest. (Plotkin)<br>
-  The events described in the transcript all occur, as a single consecutive sequence of events. (Plotkin)<br>
<P>
-  The player's commands do not affect anything except the protagonist's actions. (Plotkin)<br>
-  Everything that the protagonist does comes from the player's commands. (Plotkin)<br>
-  The protagonist correctly understands the player's commands. (Plotkin)<br>
-  The protagonist has no will that conflicts with the effects of the player's commands. (Plotkin)<br>
<P>
So which of these "rules" have been broken, and by which works? (I'm restricting my attention to works of textual IF, simply to limit the scope of this article.)
<P>
Nature and Form of the Work
<P>
The audience for IF has a number of expectations about the fundamental building blocks of IF and of what it means to sit down an interact with a work of IF: expectations of interactivity, of closure, and of language.
<P>
-  The work is a game.
<P>
I omitted this rule from the initial list above because the modern IF community takes it for granted that this is not inherent to IF. But it's worth keeping in mind that in the early days, all works of IF were games, and had anyone tried to define what IF was then, they might well have assumed that IF meant games.
<P>
-  The work is "solvable" in some sense.
<P>
Linear works of fiction have an ending; we tend to expect an ending from works of IF as well. But by ending here I don't mean simply that the work terminates and no longer accepts input, but that there is some sense of closure for the interactor, some sense that one has gotten the "complete" experience intended by the author. (Of course, even in static fiction, this may not be literally true -- there can be obscure references or coded comments that leave the reader's knowledge incomplete, or require multiple readings to understand.)
<P>
Traditionally in IF, there has been one "winning" ending and (possibly) several "losing" endings, the latter typically being notably early in the narrative, leaving plots and subplots dangling and incomplete -- not being "proper" endings. Reaching the winning ending constitutes solving the work. Two classes of works remove this sense of solvability; many of the works entered in Marnie Parker's IF Art Show offer an environment or object to explore and play with until the interactor tired of playing with it, but no ending or closure or "solution". These works are more like toys than games in some sense (for example, as described in Greg Costikyan's essay "I Have No Words and I Must Design"). Alternatively, there are works like "Galatea" (Emily Short, 2000) and "One Week" (Papillon, 2001) which reach an ending which is one of many possible endings, but there is no clear sense that any one ending is "right" or achieves more "closure". In such works, an interactor could attempt to "vie
w all the text" or "reach all the endings" and consider the work "solved" on accomplishing this goal, but it's not an explicit goal in the work itself, the way "*** You have won ***" traditionally makes clear.
<P>
There are even games which simply don't ever terminate, which have no built-in conclusion at all; but there is some debate whether these works are even IF.
<P>
-  The work is communicated as a dialogue between player and narrator/protagonist/avatar.
<P>
Textual IF is traditionally a dialogue between the player and the computer: the player gives a command to the computer, and the computer prints a response to this command -- the outcome of the command -- and the cycle repeats. This dialogue for any given play session can be recorded in a "transcript", which is effectively a piece of static fiction. (Many of the other "rules" in this article are defined relative to this transcript.)
<P>
I think that generally any work that didn't implement this alternation of command and response would be something we wouldn't consider IF (or at least not textual IF). Occasional works do follow the pattern of alternation, but don't really produce a transcript; discounting games with graphical elements, the most extreme example is "My Angel" (Jon Ingold, 2000) and its "novel mode", which captures the interactor's input in a separate window and restricts the transcript to text output by the game, allowing multiple commands to be combined within a single paragraph of the "transcript", which then more closely resembles a piece of static prose.
<P>
-  The text of the work is written in a language read/spoken by the target audience.
<P>
This assertion seems rather obvious; a game written in Spanish is for a Spanish-speaking audience; a game written in English is for an English-speaking audience. Perhaps a game written in Latin might be for a Latin-learning audience, but it's much the same thing.
<P>
However, in the last couple of years, several games have pushed the boundaries of this rule in a few directions. Dan Schmidt's "For a Change" (2000) introduced a fantasy world populated by unfamiliar objects known by unfamiliar names -- the 'toolman', 'songlantern' -- and things which may or may not be familiar, such as the 'fod'. At the same time, the game gave the sense of being written in an unfamiliar dialect of English, where words were used in odd ways that sound poetic to our ears. In some sense, this is like using a bit of made-up slang to capture the spirit of a foreign environment, but it's taken to extremes, especially for the objects that are entire fantastic; in another sense it's simply more poetry than prose.
<P>
"Lighan ses Lion" (Plotkin, 2000) was a faux transcript of a work of IF which offered an entirely foreign language that just happened to share some word shapes with English. Since "Lighan" is not really IF, however, the better example is probably Carl Muckenhoupt's "The Gostak" (2001), which uses a language lexically identical to English to describe a foreign universe which is only conceptualized through words: the words have no imaginary referents; the gostak distims the doshes, but the author had no deeper understanding of what a gostak is or what the act of distimming might be. This is similar to the fantastic elements of "For a Change", but because the game isn't grounded in a moderately familiar universe, it feels more like an entirely foreign language.
<P>
Protagonist (PC)
<P>
The notion of protagonist is basic to storytelling--whether he be Jesus or Macbeth or Hiro Protagonist--but IF takes the identification of the reader with the protagonist further than prose because the player is given control over the protagonist. I'll save discussion of the degree of this control for a separate section and here focus on the more essential notions of protagonist; many of the assumptions here are ones that apply to static fiction as well (and have, in fact, been violated numerous times there.)
<P>
-  The player's commands affect the protagonist.
<P>
If we define the character controlled by the player's commands as the player character (PC), then this assumption is: "The PC is the protagonist." It's easy to imagine a game where this isn't true: a Sherlock Holmes story where the player controls Watson and yet the story is really about Holmes.
<P>
In practice, this rule gets broken two different ways. The first way alters the player/PC relationship. The games "LASH" (Paul O'Brian, 2000) and "Fail-Safe" (Jon Ingold, 2000) each introduce a fictional boundary between the character-who-the-player-is-supposed-to-be and the character-who-obeys-the-commands. In "LASH", the player is imagined to be controlling a robot over a satellite link; in "Fail-Safe" the player communicates over the radio with a confused character on a damaged spacecraft. Curiously, the protagonist of "LASH" received an XYZZY nomination for Best PC, while the protagonist of "Fail-Safe" received a nomination for Best NPC. "Fail-Safe" makes a greater effort to separate the player from the protagonist from the start: words sometimes drop out on the radio, the protagonist is confused in ways the player isn't, and occasional information not available to the protagonist is given to the player; yet clearly from an implementation standpoint, the protagonist is just a 
PC. But in both works the player is still clearly ordering the protagonist around, so neither one deviates too far from the rule "the player's commands affect the protagonist".
<P>
The second way is to leave the player/PC relationship intact -- allowing the player full control over a PC in the world -- but to make another NPC the true protagonist, as in the Sherlock Holmes example. In practice, I can only come up with one game that really goes this far: "Galatea". Depending on which of the various storylines one pursues, the PC interviewer may be a crucial character in the story (the protagonist) or he may be a mere witness to the events that transpire, in which case Galatea is the protagonist. (The flexibility of IF -- that each interactor can perceive a different story -- potentially complicates the use of traditional terms from narratology, although very few works make such heavy use of non-linearity as "Galatea".)
<P>
For the rest of this article, I'll assume 'the player character' and 'the protagonist' mean the same thing.
<P>
-  There is a protagonist.
<P>
It is difficult to imagine a work of IF without a protagonist, since it is difficult to imagine a work of IF where the player has no opportunity to control someone or something, and we would tend to identify that someone or something as the protagonist. If someone wrote a piece in which we controlled the various doors, air conditioners, and lights of a house, we might tend to identify the house as a character -- a "living" haunted house.
<P>
In Adam Cadre's notes on the making of "Lock & Key" (2002, found by winning the game itself), he describes the protagonist-less game he imagined on the way to what he wrote: "So what if [...] the player instead manipulates the street environment, opening and closing windows, placing and removing fences, that sort of thing?" Since he ended up with a game with a normal player character, we can't be sure of how we'd have taken the original idea -- whether we'd have considered it IF. (Consider the computer game "The Sims" by Maxis for the closest analog I can think of; perhaps "Sim City" is a better example. However, the latter casts you in the role of a governor, and this whole genre of games is often referred to as "god games", suggesting a tendency to personify the role.)
<P>
-  The protagonist is a sentient being.
<P>
This rule has not, to my knowledge, been broken. It seems awkward to admit a protagonist who accepts commands -- who as a result takes varying actions, as if exhibiting free will -- without that being being sentient. (One possible approach would be imagine that the interactor is more of a "game master" who controls the ebb and flow of the universe without being personified; but that case would be the breaking of the previous rule instead of this one.)
<P>
The other problem -- besides the possibility of free will -- is the notion of potraying the world from the point of view of the controlled, non-sentient object. Thomas Nagel's essay "What Is It Like To Be a Bat?" argues that, fundamentally, attributing that there is "something it is like to be" an object is the same as attributing consciousness to it. It's difficult to communicate the experience of being something without communicating what that being experiences--and if the being has no perceptions and no inner life, it has no experience. This can be gotten around by shifting to an external point of view, but I can find no game has tried the combination of non-protagaonist-POV and non-sentient protagonist.
<P>
The two examples I can find are "Pumping!" (Stephen Granade, 1998) and part of "Acid Whiplash" (Cody Sandifier & Ryan Stevens, 1998). In the former, you play a beating heart, and each turn choose to beat or not; I find it impossible to read as anything other than that I play as a strangely sentient heart. Although I can understand that the literal telegrams from the brain are actually figurative, the continuous use of "You", my freedom to choose, and some other perceptual things that a heart has no right perceiving cause me to not believe that I am playing a normal heart with a poetic attempt at "what it is like to be a heart"; that might be the author's intent, though, and might be how others would interpret it. In "Acid Whiplash", there is a short scene in which you play a car dashboard, during which you can't do anything. (Except a number of default Inform verbs, but it's easy to imagine an implementation that did this correctly.) However, again, some of the writing ascribes pe
rceptions and attitudes that it might make sense that you, as a human-being-being-a-dashboard, might have but are not ones that a dashboard would have -- so it's difficult not to ascribe sentience again.
<P>
-  There is only one protagonist.
<P>
In the good old days of IF, there was exactly one PC, the protagonist, who we could closely identify with. Infocom branched off from this relatively quickly, most notably with "The Hitchhiker's Guide to the Galaxy", which gave the player a sequence of PCs, a different one for each section of the game, sometimes even revisting the same time and place. Numerous games have explored variations on this idea, such as "Common Ground" (Stephen Granade, 1999), "Being Andrew Plotkin" (J. Robinson Wheeler, 2000), and "No Time To Squeal" (Robb Sherwin & Mike Sousa, 2001).
<P>
"Suspended" posited a human protagonist trapped in a capsule, controlling five robots. Perhaps we might argue that the human is the PC, but the robots are the protagonists. Had the device of the human protagonist been omitted, we might view this as five PCs and five protagonists--or even a protagonist-less game, especially if we imagined the game to have fifty robots instead of five. My inclination, however, is that we would always have imagined that in the fictional universe of the gameworld there must have been some mentality--e.g. an AI supercomputer--giving these instructions to the robots so that they would cooperate appropriately; otherwise, they would be "cooperating" spontaneously without communicating with each other or some third party, which would seem odd fictionally. This is similar to the issues with the previous assumption.
<P>
-  The protagonist is not aware of the player.
<P>
Traditionally, IF tries to identify the player with the player character, to make one just an avatar or puppet of the other, but to make them the same. A very few games take exception to this, and allow the PC to directly address the audience, Ferris-Bueller-style. "Rameses" (Stephen Bond, 2000) takes a didactic tone at times:
<P>
   "Come on now lads, wake yourselves up, come on now,"
   he says in a thick country accent. He doesn't usually have
   a thick country accent. He's just making fun of Declan the
   Seminarian. You'll meet Declan later. 
<P>
A more extreme scenario is for the PC to be aware that the player is *controlling* the PC's actions. This is the central conceit of "Piece of Mind" (Giles Boutell, 1996):
<P>
   My GOD! I can move again - I just got up!!! All you have to do
   is tell me, and it happens.  That is sooo freaky. I guess I'm in
   your hands now - your wish is my command and all that jazz.
<P>
The only other example I'm aware of is Adam Cadre's "Shrapnel" (2000), which offers a brief moment of similar awareness in the middle of a cutscene: "Anyone else want to order me around?"
<P>
-  The protagonist is not aware of being fictional.
<P>
Even more extreme than the protagonist being aware that the player is there and controlling him or her is the awareness that the protagonist is part of a game--that the protagonist does not really exist, except fictionally. I am not aware of any games that have made this thoroughly postmodern move, although "A New Day" (Jonathan Fry, 1997) attempts something similar: the NPC Winston is the putative PC of an unfinished work of IF, and is well aware of the fact that he inhabits a work of IF. It's unclear what exactly is going on with the PC in "Piece of Mind" above; although he shows awareness that the work he's dropped into is fictional, it would appear to be a different work entitled "Piece of Mind" than the one the player is actually playing; the PC's "Piece of Mind" is entirely a sub-game of the real one, lacking (at a minimum) the introduction which establishes the PC as an entity outside of the internal "Piece of Mind" game.
<P>
Description of Events (Output)
<P>
As the work progresses, descriptions of objects and actions and events are delivered to the interactor. We tend to make assumptions about these descriptions. In a work of static fiction, we can have an "unreliable narrator", but it's possible to break the nature of the lack of reliability down in much more detail: a lying narrator, a deceived narrator, etc.
<P>
For the sake of this article, I'll describe each work that breaks the rules with the most specific rule that it breaks.
<P>
-  The events described in the transcript are actually occurring.
<P>
Our normal expectation is that the work is a fiction, but in the fictional world, the protagonist is actually experiencing the events. Due to the possibility of the use of the past or present tense, or of flashback, we at least expect that *at some point* the events actually occurred or are occurring or will occur. So I'm interpreting breaking this rule as incorporating events that are wholy fictional *in the world of the work*--the emphasis here is on "actually" not "occurring".
<P>
The most common variation on this is the dream sequence, especially a dream sequence that the PC doesn't realize is a dream, and so the player may not either. This has been done many times, notably in the opening sequence of Infocom's "Sorcerer" (Steve Meretzky, 1984).
<P>
Less frequently, the *whole* interactive sequence is revealed to be fictional within the universe. "Losing Your Grip" (Stephen Granade, 1998) stops short of this, spending most of its time in dream sequences but acknowleding them as such in the shorter real-world sequences between them. In "Triune" (Papillion, 2001) the protagonist escapes to an imaginary world of her own making; although the entire interactive sequence is fictional in the same way a dream is fictional, it is bookended by non-interactive real-world sequences.
<P>
Rather than dream-like experiences, though, it's also possible for the apparent events to themselves be narrative fiction in the fictional world. This is the final twist revelation in "Tale of the Kissing Bandit" (J. Robinson Wheeler, 2001). The prologue of "Heroes" (Sean Barrett, 2001) warns that, of the five stories about to be "told", only one is true.
<P>
There are a few rare cases where it is difficult to be sure what the mapping of the events are to reality. The second half of "No Time To Squeal" offers a "dark Alice in Wonderland" storyline that is somehow metaphorically related to the first storyline, but it is unclear what one should think the events themselves map to in the "real world" of that first half.
<P>
-  The events described in the transcript are happening to the protagonist.
<P>
The previous rule called into question whether the events were entirely fictional. I'm not positive what Plotkin intended to call into question with this assumption--that perhaps the events are happening to someone else? There are rare examples of this; some games cut away from the action to show a "cut scene" of events elsewhere; were they interactive, this would be an issue of the PC not being the protagonist, but since they're non-interactive, they are perhaps best considered as breaking this rule. The demo version of "And the Waves Choke the Wind" (Gunther Schmidl, 2000) offers non-protagonist cut-scenes still told in the second-person; more traditionally, "Augmented Fourth" (Brian Uri, 2000) cuts away to show the activities of the antagonist.
<P>
One variation that perhaps falls under this rule is when true events are being recounted by the protagonist after the fact. This is one place where "Spider & Web" twists our expectations: most of the first two-thirds of the game are spent with the protagonist not traversing an enemy base, but instead reconstructing his past actions while traversing the enemy base. Admittedly, "Spider & Web" takes this even further, discussed later.
<P>
-  The descriptions in the transcript are perceptions by the protagonist.
<P>
If we take the protagonist to be the PC, the character we are controlling, this rule seems entirely intuitive; it would be difficult to control the PC without seeing what the PC sees.
<P>
A few games have managed to find alternative approaches. In the introductory sequence to "Beetmonger's Journal" (Scott Starkey, 2001), the player controls the archeologist protagonist, but the story is told from the first-person POV of the sidekick, who always stays in the room with the protagonist, which is surprisingly effective. A different approach is taken in "Captain Chaos" (Shay Caron, 1999), told in third-person POV as if from a camera in the room with the titular protagonist; the game opens with Chaos asleep, and the player is free to examine the room and the objects in it, but cannot move nor manipulate objects. It is difficult to judge the success of "Captain Chaos" because the implementation is sufficiently incomplete that the effect isn't maintained consistently.
<P>
-  The descriptions in the transcript are correct perceptions by the protagonist.
<P>
Several games have explored the possibility that the protagonist is incorrectly perceiving the world. The most obvious of these is "Bliss" (Cameron Wilkin, 1999), in which the protagonist believes he is killing orcs as he escapes from a prison in a cliche fantasy universe, while in fact he is performing similar actions in a much more conventional world that he misperceives. More complex is "Shade" (Andrew Plotkin, 2000), in which both the world and the protagonist's actions are, presumably, misperceived. More subtle case is when the protagonist misperceives only a small component of reality, as with the PC in "My Angel" (Jon Ingold, 2000) and his relationship with the main NPC.
<P>
-  The descriptions in the transcript are written by someone who is honest.
<P>
Rather than the the protagonist being deceived or deceiving himself, it's always possible that the protagonist knows what's going on, but is deceiving the audience. The only memorable example of this is "Spider & Web", where the protagonist's audience isn't merely the player, but rather the interrogator for whom he is reconstructing the break-in. The game attempts to hint to the player that the deception is occurring, and the for the last third of the game the player is forced to figure out what really happened.
<P>
The protagonist isn't the only one who can lie; in one memorable sequence in "The Hitchhiker's Guide to the Galaxy", the narrator lies about the interesting features of a particular room. Here it's an explicit fourth-wall-breakage played for laughs; since it is more traditional to equate the viewpoint of the narrator with that of the protagonist, it would be difficult to do this in most works.
<P>
(Of course, the descriptions are also written by the *author* of the work of IF, so as written, one could claim that descriptions that have been phrased by the author so as to deceive the player, as in Adam Cadre's "9:05" (1999), break this rule; but then again, writing fiction at all is to write down things which aren't really true, so this isn't a very productive line of discussion.)
<P>
-  The events described in the transcript all occur, as a single consecutive sequence of events.
<P>
The tradition in the earliest works of IF were to drop you in the shoes of someone, turn you loose on a world, let you do stuff, and then bring things to a close. As IF authorship increased in sophistication, this changed. First, cut-scenes might bridge interactive sequences with non-interactive sequences, although still staying sequential in time. Then such sequences might simply skip sections of time that weren't important to the story. Non-interactive and interactive flashbacks disrupted the flow of time from strictly linear.
<P>
Time-travel games disrupt time flow more extremely, but normally strictly follow the perceived time of the time-travelling protagonist. For true narrative non-linearity, we again turn to "The Hitchhiker's Guide to the Galaxy"; at the same time that the player switched points of view--switched PCs--a new time would be chosen, sometimes earlier, sometimes later. Sometimes the time sequences overlapped, allowing playing the same sequence from the same point of view. Again, this was used for comic effect; the same technique was used for dramatic effect in "Photopia" (Adam Cadre, 1998).
<P>
A number of works go to a much greater extreme, focusing on a single period of time and revisiting it repeatedly. "Vicious Cycles" (Simon Mark, 2001) uses a time-travel machine to explain this; "Common Ground" revisits the exact same sequence of time and roughly the same events three times from three different points of view. Both of these have analogs in the world of static fiction (such as "Groundhog Day" and "Rashoman"), so perhaps the more dramatic examples are those that allow and require the interactor to revisit a sequence repeatedly without the revisiting being part of the *story*, as in the "one-turn" works "Aisle" (Sam Barlow, 1999) and "Rematch" (Andrew Pontious, 2000).
<P>
Commands (Input):
<P>
Typically, in IF, the interactor enters commands which are enacted in a simulated world by the PC. Ignoring possible distinctions between "protagonist" and "PC", there's still a wealth of possible ways to disrupt that sense of control, and these are unique to IF compared to non-interactive storytelling media.
<P>
-  The player's commands do not affect anything except the protagonist's actions. (Plotkin)
<P>
One possibly disturbing effect would be for commands to have an impact in the world without involving the PC. If there's no player character at all -- if this is just how commands always work -- it's not disturbing, but in the presence of communication between the player and the PC, we expect that communication to be privileged, to be outside the fiction: part of the user interface.
<P>
A few games have, in fact, allowed NPCs access, in the cases where the player is communicating with the NPC. While it makes sense that 'SAY "HELLO GENE" TO BOB' results in Bob hearing the word "Gene", it's a little surprising when 'BOB, HELLO' is heard by Bob as including 'Bob', as it seems to imply that *every* time the PC speaks to Bob, he repeats the name. Even more surprising is when Bob "hears" 'Bob' in 'ASK BOB ABOUT FRANCINE' . Games such as 'Erehwon' (Richard Litherland, 1999) and 'The HeBGB Horror' (Eric Mayer, 1999) have used variations on this device. In none of these cases do I think the author intended it to be disturbing; instead there is just confusion (or perhaps disagreement) in how the player's commands map to the fictional world and the protagonist's actions.
<P>
Clearly intentional is the effect in "The Hitchhiker's Guide to the Galaxy" (yes, again!): the *player* takes the fall for setting off an interstellar war due to a typoed command that has nothing to do with any action of the player character. More strangely, in "Ad Verbum" (Nick Montfort, 2000), the text of descriptions of rooms change in response to the interactor's choice of wording even though the state of the world doesn't change: if the input abbreviates compass directions as single letters, so will the output.
<P>
-  Everything that the protagonist does comes from the player's commands.
<P>
Many works break this rule in cut-scenes; in fact, by definition, not giving the player a chance to type something and having the protagonist act creates a cut-scene, in some sense. But such scenes tend to follow from the preceding actions, and so in some sense "come from the player's commands".
<P>
In general though there's something of an unwritten rule not to do this, since it disrupts the immersion, the sense that the player *is* the protagonist. A few works have addressed this in a rather surprising fashion: rather than allowing the protagonist to take action independent of the commands typed by the player, the works force the player to "type" the appropriate command. "Voices" (Aris Katsaris, 2001) forces the innocuous command WAKE after a character transition; "Pytho's Mask" (Emily Short, 2001) allows you to make a climactic choice, then makes it appear that you might have further options, but instead forces the very last command. Even more dramatically, "Shrapnel" goes postmodern, dropping the player to an apparent metagame prompt at which the metacommand RESTART is forced--but rather than restarting the work it resets the protagonist's experiences within the work while maintaining state from previous actions.
<P>
-  The protagonist has no will that conflicts with the effects of the player's commands. (Plotkin)
<P>
The idea of this rule is that the protagonist is the player's puppet. The player and the protagonist are unified to a single being; what the protagonist sees and knows, the interactor does too; and what the interactor attempts, so will the protagonist.
<P>
The reality is subtle. If I order the protagonist to go north, in most works, the protagonist will not walk north into a wall; instead, the protagonist will inform me that there's a wall in the way. Of course, this is an action the protagonist couldn't possibly complete anyway, so it's perhaps not really a conflict, but the same thing often occurs if there is instead a *cliff* to the north: the protagonist will refuse. I think the notion tends to be not so much that the protagonist has an independent will for self-preservation as that the interactor's view of the world is very removed, and less immediate, and this is more that the protagonist is guessing "that's not what the interactor really wants".
<P>
However, one of the trends in IF has been towards PCs with a more explicit personality which the interactor is forced to play along with. In such cases, the PC will often assert a will--namely a will to refuse to do things which are "out of character". In some cases, this is really just the author saving work--by having the PC refuse to take certain actions, the author is spared the burden of implementing the actions and possibly storyline branches induced by them.
<P>
Much more explicit is "Rameses", in which the PC is someone who is so passive, so unwilling to get involved, that the interactor is constantly teased with opportunities to try to do something, but the protagonist, while willing to entertain the possibility of doing such things, is not in fact willing to do them at all.
<P>
-  The protagonist correctly understands the player's commands. (Plotkin)
<P>
Not only do we expect the narrator of IF to give us useful, reasonably accurate information so that we have some opportunity to usefully interact with the work, but we also expect that the PC we're controlling to understand what we're ordering.
<P>
Thus it seems like it would be hardly surprising to find some work that went out of its way to break the fourth wall and intentionally misunderstand the player, but it's actually difficult to find any clear cut examples of this. The best I can find is the "SCORE" command in "Leather Goddesses of Phobos" (Steve Meretzky, 1986) and "I-0" (Adam Cadre, 1997), but in the context of those games the "misinterpretation" is not too surprising.
<P>
Experiments of Form
<P>
When we sit down to interact with a work of IF, we come with many preconceptions and expectations about what the experience will be like. Violating those expectations might make a work not feel like IF, but at the same time it can pull us in or push us away.
<P>
There are many possible ways to surprise the interactor: the author might appear as a character in the work or the plot might take an unexpected turn. These surprises are part of the *content* of the work, though, not the form. Surprising content would never make us doubt that a work was IF, so long as we consider IF a medium (determined by form) rather than a genre (determined by content).
<P>
In a non-interactive medium, questions like whether there is a protagonist and whether the narrator is unreliable are perhaps more properly questions of content. But once interactivity is involved, the question of which character the interactor controls -- if any -- and the nature of how information is provided to the interactor become part of the form of the work, since they heavily influence how the interaction works.
<P>
This article has identified a number of "rules" which are potentially part of the form of IF; most of them, though, have counter-examples, works that are still widely considered IF. For the few rules without counter-examples, it is unclear whether there could be an IF work that breaks them, or whether the rule is inherent to the nature of what we consider IF. Only time, attempts to define IF formally, and works that break these rules (and others) will tell.
<P>
Get crackin'.
<P>