Multi-User Applications -- Auction

A developer creates a NetAlive application and stores it in an archive. The application aids users in performing a specific activity. Several users load and execute the same application. Each user has a GUI for the activity. At various points, one user's screen changes in response to another user's actions.

The figure below shows this using iconography developed previously. Specifically, the NetAlive application runs on each user's computer. The cooperating computers communicate directly.

The security method depends on the application. NetAlive prevents an application from an untrusted source from writing to the local hard disk. An application from a trusted source can do anything.

Range of Uses

Task-directed communications

Several users jointly engage in an activity using the computer and Internet. Each user gets a screen showing and accepting information in a form specific to the activity. Some user actions communicate with other users, or perhaps another computer. Other actions effect only the local computer.

Example: Several users act as bidders in an on-line auction. Each user's screen shows the product and the bidding history for the product. A user may submit a bid, with the bid reflected on the screens of all other users. The computer enforces auction rules.

The same paradigm applies to multi-user games and problem-solving.

Example

The screen below shows two users (identified by the names of their computers -- COLOR and MONO) bidding on a rose. Each user types into "your bid" and presses "bid." If the computer accepts a bid, the "bidding" history changes on all user's screens and a "thank you" message appears. If the computer rejects the bid, a different message appears.

Technical

The figure below shows NetAlive implementing an auction application. Widget-tasks "Product," "Your bid," "Bid," and "Bidding" are enabled on all users' screens. The connection between Your bid and Bid is "dataparallel," as indicated by the double line. This means NetAlive sends the typed-in bid to the corresponding pushbutton on the same computer. Functional task "Auctioneer" is "scalar," meaning it exists on exactly one computer. Auctioneer checks bids for the minimum increment and adds them to the bidding history. The connection from Bid to Auctioneer is "reducing." This means NetAlive gathers bids on multiple computers to a single input. The connection from Auctioneer to Bidding is "broadcast." This means NetAlive broadcasts one bidding history to each computer. The box with heading Auctioneer is controlled by the task with that caption. NetAlive executes other tasks in the "mapping region" on a computer controlled by output from the controlling task. In this case, NetAlive displays the "Thank-you for your bid" message only on the computer submitting the bid.

NetAlive's features and benefits

Integrated design tool

Feature: NetAlive incudes a design tool.
Benefit: Application experts can use NetAlive to create applications of a complexity that previously required a programmer.

Client automation

Feature: NetAlive applications communicate client-client rather than through a server.
Benefit: Natural way to communicate, avoids awkward technical implementation.

Application is online

Feature: The NetAlive application is itself online.
Benefit: The Internet can distribute an application for pennies, and can help in advertising and customer suport.

No server required

Feature: The third-party developing the application does not require any physical asset or labor proportional to the volume of business.
Benefit: This creates a favorable business model for the developer.


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