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附录1
破伤风怎么打The application of Ajax
Spend a few minutes using your application you lected(browr except),write it down to what ur interaction,and then immediately back.For the sake of brevity,I give an example of electronic form,however,points involved here is general enough for various cas,the text editor.
Well,we started.First in the spreadsheet to input some equalities,pay attention to,can interact in veral ways:edit data,browsing the data using the keyboard and mou,also can u the mou to drag to re organize the data.
I do the operations,the program gave me feedback.When moving the mou,the cursor changes shape;when the mou stops above,button bright;lected text can change color.When a window or dialog box is lected,and usually isnot the same,etc..The are the so-called"rich"interaction.Of cour,there are still some room for improvement,but this is a good start.
OK,a spreadsheet is a rich client program?Absolutely not.In a spreadsheet or similar desktop applications,business logic and data model is run in a clod environment.In this environment,they clea
rly understand each other,and can visit each other,and the environment outside of things,is unknown to them.What is the client?It is a parate process of mutual communication program,which is usually run on the rver.In general,the rver is always bigger than the client,ability,disposition is better,becau the rver is usually stored multitudeinformation.The client program enables the end urs can view and modify the information,when multiple clients connected to the same rver,can shareinformation between them.Shows a simple client/rver architecture.
In the n layer architecture in the modern,the rver often and further the back-end rver(such as a databa)communication,so called"middleware"layeralso plays a role of client and rver.End of our Ajax application in the chain,it is only as the client,therefore,for the convenience of discussion,we can put the whole n system as a labeled as"black box rver".
Spreadsheet applications I only need to manage its own saved a small amount of data in memory or in the local file system.If the design of well structure,couplingform data and it can be very loo,but I can't pass a network to split or sharethem through network.In this n,the application of electronic form is not a client.
The corresponding Web browr is a typical client,which communicate with the Web rver,the requ
est page.The browr has abundant functions,ud tomanage ur browsing behavior,the common function of the back button,the history list and tabbed browsing multiple documents etc..But when we put the site specific Web pages as an application,the general browsing function actuallyand application is,at best,such as spreadsheets and Windows began the relationship between button or the window list.
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We consider the application of modern Web.For the sake of simplicity,we earth people know"online bookstore.Open the Amazon site in the browr,becau before I visited,it will show me a friendly
greeting,somerecommended bibliography,and my purcha history information.
Click on any one of the recommended bibliography,will go to another page(at this time,the page to refresh,within a few conds I what also don't e).The new page is the information relevant to the book review:other books,cond-hand books,offer the same author,and other books I read.
In short,appears to be very rich,high degree of associated information in front of me.But for me,interactive way is to click on the hyperlink,and then fill in some forms.Suppo I at the keyboard accidentally fell asleep,wake up cond days,if not refresh the page,I don't know"Harry Porter"ries
of books have been published,nor will my list from one page to another page,if I want to e morethings too,becau I cannot change the local content area page size.
I em to be in the criticism of the Amazon interface,but it is not the ca,I justtook it as an example.In fact,in the traditional Web development of the shackles,they have done very well.But compared to the spreadsheet,and the interaction model is undoubtedly too limited.
Why Web is the application of modern still have so many limitations?The currentsituation has some reasonable technical reasons,we have to consider now.
The blueprint for the Internet is all the computer in the world are connected,forming a huge computing resources.If the local data and remote invocationequated,then both the analysis of protein components or crack signals from outer space,urs need not consider the physical location of the machines,the rest of the computation only pleasure.
But unfortunately,the local call and remote invocation is something totally different.Under the current level of technology,the network communication is still a costly things(that is to say,is usually very slow,but unreliable).In the abnce of a network called the situation,method and function of different data and theiroperations are located in the same local memory,to transfer data and return the results
obtained are very direct.
In a remote call,communication in the network at both ends of the two sides to nd and receive data requires a lot of computation at the bottom.Compared with the data back and forth on the line,the calculations require more time consuming.The transmission of a binary data,to go through many steps of coding and decoding,error checking,failure,packet retransmission split andreorganization,data into 0 and 1 binary signal,through the line(or wireless connection to the other party).
In the local,call the function call request is encoded as an object,then the object is rialized as a ries of bytes,the application layer protocol(usually HTTP)via the physical transmission medium(such as copper cable,optical fiber or radio)nd out.
On the remote machine,the application layer protocol decoding,the bytederialize the data obtained,to create a copy of the requested object.Then the data model is applied to the object and generates a respon object.In order to make the respon object is pasd to the callback function local,all rialization derialization operation,and the transport layer will be back again.Finally,the respon object is pasd to the function call local.
This interactive process is very complex,but fortunately,it can be done.Modern
programming environments such as Java and Microsoft framework are built with this ability.However,the execution of remote calls,all the operations will still be in the internal execution.If we were using there mote invocation,performance will be affected.
That is to say,a remote call is unlikely to have efficiency and local call.What is wor,the instability of network makes the efficiency loss is unpredictable,it is difficult to.In contrast,a local call to run on the local memory,will undoubtedly have an advantage more at this point.
And so on,said remote call half a day,between this and the availability of software?The answer is,a relationship.
A successful computer ur interface must be able to at least level simulation weexperience in the real world.One of the basic rules of interaction is,when wepush,prick or poke about something,it will immediately respon.Respon timeas long as a little bit out a little,will make people confud,distracted,to shift thefocus from the task at hand to the ur interface.
Remote calls across the network,need to perform additional operations in great quantities,they tend t
o put the system to slow down,the ur perceived delay.In desktop applications,only when the usability design is very bad,will appear this kind of makes urs feel full of bug,unresponsive to the ur interface,but in the application of network,what do not get a large number of such interface.
Becau the network delay is unpredictable,this kind of interface problems oftencome and go like a shadow,it is difficult to carry out the application respontest.In other words,the network delay is the result of a common cau of the practical application of the interaction.
Ur interface developers for network delay can only assume the worst.Say simply,is to try to make the ur interface and network activities unrelated to.Programmers have already created a truly effective and proven solutions,tosolve this problem.To ll a Guan,let us into the real world.
In the morning I will do,a very important is to wake my kids go to school.I can stand on the edge of the bed they toss up,cha them up and dresd,but thismethod is very time consuming,it takes me a lot of precious morning time
I want to wake up the children,have a look out the window,often neglected to feed the cat.After the children would ask me to breakfast.As the rver process,the children always get up slowly.If I follow the synchronous interaction pattern,will they all day.However,as long as they mumble"I woke up",I ca
n go to do other things,need to come back when they have a look.
In computer terms,I need to do is for every child to establish an asynchronous process in a parate thread.After the start,the children will wake up in their ownthreads,the parent thread unnecessary synchronization wait,they afterwards will inform me(which is often asked me to eat).In the process they wake up,I don't need interaction and they,when they had been up and dresd mylf,becau I have reason to believe that they will do so soon.
For any ur interface,which is a long established practice,namely to createasynchronous thread,let it in the background who need to calculate a long
timetask,so that the ur can continue to do other things.When starting this thread,it is necessary to block the ur operation,but after a short period of time can beaccepted,will relieve congestion.Becau of the existence of network delay,using asynchronous mode is a good practice to handle any time-consumingremote call.
In fact,the network latency problems and solutions related to long-standing.In the old client/rver mode,when the poor design of the client program met thehigh load of the rver,the ur interface will appear delay intolerable.Even in today's Internet era,when to switch the page,if the browr half t
he things not to,so this situation might be due to network delay caud by.The existing technical conditions,we have no way to remove the network delay,but at least onestrategy,that is the u of asynchronous processing remote calls,isn't it?
Wor,for Web developers to do so there is a problem:HTTP protocol is a"request respon"mode of the protocol.That is to say,the client requests a document,the rver or a return to this document,or tell the client can not findthe document or allows a client to another place to find,also can tell which the client can u the local cache,and so on.To make a long story short,"request respon"mode of the protocol is a one-way communication protocol.The clientinitiates a connection to the rver,b ut the rver can not initiates a connection to the client.Even when the next client,initiate the communication request,forgetful of the rver can't remember this client is who(HTTP is a connectionless).
Most Web developers to u modern programming language,for example,Java,PHP or,they are familiar with the ur ssion(ur ssion)concept,this is in fact the application rver for a remedy can't maintain a connection state of the HTTP protocol.HTTP for the initial design goal well,using some clever processing,it can adapt to the beginning of the design did not consider theoccasion.But the key features of the asynchronous callback scheme of our clientis,will receive two notice,is a time
in the thread creation,the other is a time in the end of the thread.The standard HTTP and the traditional Web application model can not provide the.榛树
The traditional Web application like Amazon,is built on the concept of the page.Show the ur a document,which includes various links and form,the ur canaccess further more documentation.This interaction model can support complex data ts on a large scale(like Amazon and other sites have demonstrated),which provides the ur experience is enough to meet the needs of business.
In ten years,this interaction model laid a deep imprint in our view of theapplication of Internet business.WYSIWYG interface(WYSIWYG)Web authoring tools,making the site more easily to be understood as a stack of pages.The framework of Web rver using the state diagram conversion on introduction,the traditional Web application that has been firmlybound in a page refresh operation,as if the refresh is behoove and inevitable,tried processing scheme for any asynchronous never.
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Of cour,no doubt,the traditional Web application must not nothing is right..After all,Amazon in this interaction model to create a successful commercial applications.But this applies to the way Amazon does not necessarily apply to all
people.Why do you say that?To understand this,we need to study the urmodel(usage pattern).
A general discussion of the bicycle and SUV(SUV)merits meaningless.Becau they have their own advantages and disadvantages--comfort,speed,fuel consumption or personal identity.Only discusd in particular u mode,this comparison is only meaningful.For example,is to in the rush hour through the center of the city,or to take the whole family,old and young to go on vacation,or just to find a shelter from the rain.In a similar situation like this,can we have a definite object in view to compare.For the ur interface,it is the same with.
Software usability expert Alan Cooper has written a lot of good articles aboutusage patterns,he defines two main us:transient(transient)and exclusive(sovereign).Transient applications may u occasionally every day,butalways as a condary activity,with a sudden.The contrast is sovereign applications,exclusive continued u of application to deal with the ur for veral hours a day.
Many applications have a natural monopoly or transient properties.For example,a word processing software writing is a sovereign application,possible applications also u veral transient,such as file management(file open andembed this function will often clo the window),dictionary or spell checking tools(many word processing program is also embedded in the functions),andcolleagues
contact email and chat tool.For software developers,text editor,debugger or IDE(integrated development environment)is the exclusive.
Sovereign applications often u more frequently.Y ou know,a good urinterface is not visible.The measure of a good scale ud frequently,is when theur interface has obvious pau,it affects the ur process.For example,from a directory to another directory file to 2 cond pau,I can accept with pleasure;but if the two conds is the place in my is full of passion for paintingsoftware to create an image,or I'm trying to debug a very difficult to deal with thegeneration of code certainly,this makes me feel very uncomfortable.
流逝拼音径的组词Amazon is a transient application,eBay,Google and most large public Web applications are transient applications.Since the date of birth,the experts had predicted that the traditional desktop applications under Web impact.Over the past ten years,the have not occurred,why?Bad on the Web page programfor transient applications is enough,but it is far from enough for a sovereign application.
The starting of modern Web browrs and it's original point(a document from a remote rver)has not matter,between them like a Swiss Army knife and neolithic hunting tools,it is a world of difference.A variety of interactive components,scripts and plug-ins,the years could not suppress th
e crazydevelopment,almost forced once again to create a new prehistoric times visitbrowr.In 1993,netscape founded before the Marc Andreesn(founder of netscape)are lobbying Tim Berners-Lee(founder of Web,the W3C leader)et al.,cited good into a picture label is HTML.
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A few years ago,a few pioneers began to treat JavaScript as a rious programming language.But on the whole,more people still u it and tho whomock
