You would want it if you want to inspect/debug/transmit/replay the whole the state of your application. Having nothing encapsulated and everything in a global state permits this.
Khalid aka DjebbZ @Dj3bbZ On Wed, May 20, 2015 at 3:51 PM, Jamie Orchard-Hays <jamie...@gmail.com> wrote: > For local state, I mean state that has to do only with the component > itself, nothing to do with the data itself. For example, if I have a > component that can switch between editing/reading states, I can't imagine > why I would want this information stored outside of the component itself. > > Jamie > > On May 19, 2015, at 11:58 AM, Daniel Kersten <dkers...@gmail.com> wrote: > > I don't think it implies local state, necessarily, although it may benefit > from it. I think alternatives can be modular too. > > For example, re-frame's approach of a central place to store data is like > a Blackboard system, which may even help modularity, not hinder it, because > modules don't need to know anything about each other - only that the data > they read and write is in the central place and may be (transparent to the > modules) be accessed/updated by multiple modules transparently (and > hopefully gets validated eg through a schema or constraint system to > prevent one module from writing data that breaks another module). > > On the other hand, local state implies encapsulation and encourages strict > interfaces to access it, which can also help modularity. In my personal > experience this has (more often than not) led to tightly coupled modules > instead, however. > > I personally prefer the re-frame single-place-for-data approach because in > my opinion its benefits outweigh its disadvantages, but perhaps I've just > been doing local state wrong :) (actually pretty likely!) > > > PS: It'll probably be some time before I get a chance to read Horrocks' > book. If anybody knows of any similar content available on the web for me > to read in the meantime, I'd love to hear of it! > > > On Tue, 19 May 2015 at 14:34 Jamie Orchard-Hays <jamie...@gmail.com> > wrote: > >> I agree. The word that came to mind while reading your comments, Daniel, >> was "modularity". Does modularity imply local state? Pondering... >> >> Jamie >> >> On May 18, 2015, at 1:26 PM, Khalid Jebbari <khalid.jebb...@gmail.com> >> wrote: >> >> I like how you break up the state machines, it has sense in web app. Page >> 1 has 2 widgets, page 2 has a form. Each widget/form can have a FSM >> associated with it, the higher level FSM knowing just the higher level >> state of all widget displayed. Mmmh... Interesting. >> >> Le 18 mai 2015 à 19:13, Daniel Kersten <dkers...@gmail.com> a écrit : >> >> From my understanding of it: >> >> Use higher level states and decouple them somewhat from the data. >> >> For example, games do have lots of dynamically changing data. In a modern >> shooter you might have dozens of characters with positions, orientation, >> velocity, health information, weapons, ammunition, etc all of which can be >> constantly changing. And that's just taking the characters into account. >> >> I wouldn't go and build a state machine that enumerates all of the >> possible transitions from a "twelve characters with done distribution of >> attributes in this location moving in that direction" state. I'd break it >> down so that each character has a high level state like "seeking powerup" >> or "running". >> >> Probably not a great example although it does illustrate that you might >> have a hierarchy of state machines. In the game example, the highest level >> might be something like "in play" or "paused" and the lowest might be an >> each characters "firing weapon". >> >> In client side web app, you could say that each configuration of data is >> a state (the re-frame readme mentions that you could think of the app-db >> like this), but I think that's too fine grained to be useful. >> >> Instead I'd define higher level states (possibly in a hierarchy). I'd ask >> myself, regardless of the data available, what are the logical states that >> a user could be in and for each one, what are the actions that they can >> perform (and what state does each action transition them to). >> This could be as simple as pages and links, but with a rich single page >> application it's more likely finer grained than that. Maybe what dialogs or >> widgets are accessible. >> >> Again, you could then layer these into a hierarchy of state machines. >> >> One advantage of this is you always know what a user can do at any given >> time because you can look at what state they're in. >> >> I think of FSM states as orthogonal to the data, not as the data itself. >> The states dictate what data is accessible and what can be done to it; the >> data doesn't dictate what state the application is in. >> >> I suppose terminology gets confusing, but this is the approach I'm toying >> with. I'll see how that goes :) >> >> But yeah, needs more thinking. >> >> On Mon, 18 May 2015 16:55 Marc Fawzi <marc.fa...@gmail.com> wrote: >> >>> Games are ideal candidate for straight-forward FSM implementation since >>> you normally download the data at game load time and from there on you have >>> a *relatively* small set of states that can be transitioned between based >>> in user input. You can even apply state minimization techniques to reduce >>> the total number of states. >>> >>> But in a web app you are continuously grabbing data from the server and >>> that data is generated based on not only user input but also the state of >>> the server side database and that server generated data would modify UI >>> side app state and you have to account for all possibilities so the total >>> number of states could grow wildly if your UI is data driven (where the >>> state of the UI depends on the data in non-trivial ways) but even if your >>> UI state dependence on server data was a trivial relationship you could >>> still end up with a huge state diagram for the simplest viable business app >>> if you include templating the view as part of the UI FSM on top of business >>> logic. You could segment your app into micro apps and that will help >>> regardless of whether you're building the app as FSM or not. >>> >>> And what if the state transitions are probability driven? How many >>> states will you end up having to chart? >>> >>> Not convinced YET... >>> >>> Sent from my iPhone >>> >>> > On May 18, 2015, at 6:57 AM, Sean Tempesta <sean.tempe...@gmail.com> >>> wrote: >>> > >>> > Hi Khalid. I found your topic interesting so I thought I'd chime in. >>> Regarding your comments on routing: >>> > >>> > So, under normal conditions, the initial URL sets the FSM in motion >>> (as an event). We could call this entry point a routing state. Afterward, >>> the state transitions are controlling the urls (not the other way around), >>> right? >>> > >>> > Outside of normal conditions (ie. people copying and pasting links >>> into random parts of the system), you also just send the url to the routing >>> state and then switch to a new state based on whatever rules and >>> definitions you've set. >>> > >>> > Or maybe I'm missing something. I haven't built an FSM in a while. :) >>> > >>> > Sean >>> > >>> >> On Monday, May 18, 2015 at 6:07:22 PM UTC+8, Khalid Jebbari wrote: >>> >> Trying to push forward the discussion about Web UI with state >>> machines. I came up with the following decomposition of the core components >>> of a web application : >>> >> >>> >> - application state >>> >> - application data >>> >> - business logic >>> >> - ui logic >>> >> - event processing >>> >> - presentation layer >>> >> - routing >>> >> >>> >> In this schema, I think the application state is the real core, >>> because every other components is directly related to it, at least if you >>> use a state machine. I came up with the following model. >>> >> >>> >> - application data : related to application state because both can >>> easily represented as data. If we want a web app that is completely >>> state-driven (I want this, for debugging, testing and time-travel >>> capabilities), simply merge the data and the state in the same data entity. >>> >> >>> >> - business logic/ui logic : in a state machine there's the notion of >>> "actions" executed with each transition (where necessary). So the logic >>> could just be executed by the state machine itself. >>> >> >>> >> - event processing : a state machine can be event-driven, and this a >>> perfect match with a web app since the web (and any UI for that matter) is >>> inherently event driven. So the event/input of the state machine could just >>> match the event triggered by the user, as well as custom events if >>> necessary. >>> >> >>> >> - presentation layer : simply display the current app-state as >>> HTML/CSS. In the React.js model, it would simply mean updating the app >>> state and letting React render everything. >>> >> >>> >> - routing : this is where stuff gets complicated in my mind. In a >>> proper application, lot of state is derived from the URLs. But not all >>> state, for instance whether a modal is displayed or not, or whether a form >>> is validated client side or not isn't tied to a URL. Which tend to let me >>> think that there's some kind of hierarchy in the state machine. The URLs >>> could be represented as events as well in the state machine, but could >>> happen at anytime, whereas other events and related transition depend on >>> the current state in a state machine. So it's like you have a top-level >>> state machine for URLs, and each URL has its own state machine for all >>> interactions in the page. Maybe page-state machine could be refined in >>> multiple levels state machines too, not sure about that. It seems like >>> Hierarchical State Machine may help here, but I haven't studied the subject >>> yet at all. >>> >> >>> >> What do you think ? >>> > >>> > -- >>> > Note that posts from new members are moderated - please be patient >>> with your first post. >>> > --- >>> > You received this message because you are subscribed to the Google >>> Groups "ClojureScript" group. >>> > To unsubscribe from this group and stop receiving emails from it, send >>> an email to clojurescript+unsubscr...@googlegroups.com. >>> > To post to this group, send email to clojurescript@googlegroups.com. >>> > Visit this group at http://groups.google.com/group/clojurescript. >>> >>> -- >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "ClojureScript" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to clojurescript+unsubscr...@googlegroups.com. >>> To post to this group, send email to clojurescript@googlegroups.com. >>> Visit this group at http://groups.google.com/group/clojurescript. >>> >> >> -- >> Note that posts from new members are moderated - please be patient with >> your first post. >> --- >> You received this message because you are subscribed to a topic in the >> Google Groups "ClojureScript" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/clojurescript/7STtgK5QiIc/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> clojurescript+unsubscr...@googlegroups.com. >> To post to this group, send email to clojurescript@googlegroups.com. >> Visit this group at http://groups.google.com/group/clojurescript. >> >> >> -- >> Note that posts from new members are moderated - please be patient with >> your first post. >> --- >> You received this message because you are subscribed to the Google Groups >> "ClojureScript" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to clojurescript+unsubscr...@googlegroups.com. >> To post to this group, send email to clojurescript@googlegroups.com. >> Visit this group at http://groups.google.com/group/clojurescript. >> >> >> >> -- >> Note that posts from new members are moderated - please be patient with >> your first post. >> --- >> You received this message because you are subscribed to the Google Groups >> "ClojureScript" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to clojurescript+unsubscr...@googlegroups.com. >> To post to this group, send email to clojurescript@googlegroups.com. >> Visit this group at http://groups.google.com/group/clojurescript. >> > > -- > Note that posts from new members are moderated - please be patient with > your first post. > --- > You received this message because you are subscribed to the Google Groups > "ClojureScript" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojurescript+unsubscr...@googlegroups.com. > To post to this group, send email to clojurescript@googlegroups.com. > Visit this group at http://groups.google.com/group/clojurescript. > > > -- > Note that posts from new members are moderated - please be patient with > your first post. > --- > You received this message because you are subscribed to a topic in the > Google Groups "ClojureScript" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/clojurescript/7STtgK5QiIc/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > clojurescript+unsubscr...@googlegroups.com. > To post to this group, send email to clojurescript@googlegroups.com. > Visit this group at http://groups.google.com/group/clojurescript. > -- Note that posts from new members are moderated - please be patient with your first post. --- You received this message because you are subscribed to the Google Groups "ClojureScript" group. 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