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Client-Side Communication ActionScript 83

Compare this data structure to a shared object with the same attributes, but with a flat design that

occupies three slots instead of one:

so.data.year = someValue;

so.data.month = someValue;

so.data.dayOfMonth = someValue;

In this case, because each slot contains only one piece of information, less bandwidth is required

to update all connected clients when a single data attribute is changed.

You can use this information when designing your remote shared objects. For example, if an

object is designed to be updated frequently by multiple clients in real time, minimizing the

amount of data per slot can improve performance. This design can also help minimize data

collisions (multiple clients trying to change a single slot at the same time).

Conflict resolution

If more than one client (or a server application) can change the data in a single slot of your

shared object at the same time, you must implement a conflict resolution strategy. Here are

some examples:

Use different slots The simplest strategy is to use a different slot for each player or server that

might change data in the object. For example, in a shared object that keeps track of users in a chat

room, provide one slot per user and have users modify only their own slots.

Assign an owner A more sophisticated strategy is to define a single client as the owner of a

property in a shared object for a limited period of time. You might write server code to create a

“lock” object, where a client can request ownership of a slot. If the server reports that the

request was successful, the client knows that it will be the only client changing the data in the

shared object.

Notify the client When the server rejects a client-requested change to a property of the shared

object, the

SharedObject.onSync event handler notifies the client that the change was rejected.

Thus, an application can provide a user interface to let a user resolve the conflict. This technique

works best if data is changed infrequently, as in a shared address book. If a synchronization

conflict occurs, the user can decide whether to accept or reject the change.

Accept some changes and reject others Some applications can accept changes on a “first come,

first served” basis. This works best when users can resolve conflicts by reapplying a change if

someone else’s change preceded theirs.

Local disk space considerations

You can choose to make remote shared objects persistent on the client, the server, or both. (Local

shared objects are always persistent on the client, up to available memory and disk space.)

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MACROMEDIA FLASH COMMUNICATION SERVER MX-SERVER-SIDE COMMUNICATION ACTIONSCRIPT DICTIONARY Specifiche Pagina 274