Spellex Spelling Server Technical Support

This document describes the differences between the DE and XE versions of Spellex Spelling Server.

Before we discuss the differences, let's discuss the similarities. Outwardly, the DE and XE versions of Spellex Spelling Server are virtually identical. They use the same API, have the same features, and use the same dictionaries. An ASP application which uses Spellex Spelling Server/DE will need no changes whatsoever if the XE version is used instead. It is possible to start with the DE version and later upgrade to the XE version without changing the ASP application at all.

The difference between the DE and XE versions is one of throughput. Under heavy loads (i.e., a large number of clients checking spelling at the same time), the XE version will process more spelling requests than will the DE version in the same amount of time. Under light loads, each version will process roughly the same number of spelling requests. Under heavy loads, clients will have to wait longer for spelling requests to complete if the server is running the DE version of Spellex Spelling Server. Under light loads, clients will wait the same amount of time for a server running the DE version as they would for a server running the XE version.

What exactly is a spelling request? It's a request made by an instance of an ASP application (a session) acting on behalf of a web client to check the spelling of some text. When the client asks the ASP application to check spelling (e.g., when the user clicks a "Check Spelling" button on a form), the ASP application submits the text to Spellex Spelling Server for checking. The ASP application may do other things in response to the button click, but these other things are not affected by the differences between the DE and XE versions. The ASP application submitting text to Spellex Spelling Server is the spelling request, and the amount of time that request takes to process is what distinguishes the DE and XE versions.

The DE version of Spellex Spelling Server will process at most four spelling requests at the same time. The XE version will process an unlimited number of spelling requests. With the DE version, any requests issued beyond four are queued or blocked until one of the four completes, at which point one of the queued requests is processed. The additional requests are not rejected, they are simply delayed. On a quiet web site, one with only one active client, the time required to process a spelling request will be the same regardless of whether the DE or XE version of Spellex Spelling Server is installed on the server, because no queuing or blocking is required. The same can be said if two, three, or four clients click the "Check Spelling" button at exactly the same time. However, if five clients request a spelling check at the same time, and the DE version is used, one of the five requests must be queued. This request will remain queued until one of the first four requests is completed. Now, Spellex Spelling Server is very fast, so it's unlikely the fifth client could even tell it was queued (unless perhaps the first four clients were checking documents the size of War and Peace). However, if 100 clients request a spelling check at the same time, the 100th client may have to wait a noticeable amount of time -- perhaps a few seconds. With the XE version, the 100th client's spelling request would be processed as quickly as possible (given the multitasking capabilities of the server hardware, Windows, and IIS).

To summarize, the difference between the two comes down to the delay your site's clients will experience if large numbers of clients check spelling at the same time. With the XE version, the delay will be minimal (given the power of your server platform), and with the DE version, the delay will be greater.

How then, do you determine which version, DE or XE, is right for you? As a rough rule of thumb, if you anticipate that fewer than 50 clients will ever request a spelling check at the same time, the DE version is a good choice. If you believe more than 50 will request a spelling check at the same time, we recommend the XE version. If you're not sure of the number, but you think your site receives low to medium traffic, the DE version is recommended, and the XE version is recommended for sites receiving high traffic. If you're still not sure, you can start with the DE version and later upgrade to the XE version if the delays experienced by your clients becomes frustrating.

The DE version is also a good choice for development, maintenance, testing, QA, and staging servers, since it works identically to the XE version (except under heavy load).

Summary

DE Edition

• Suitable for low to moderate traffic sites

• Suitable for development, testing, QA, and staging servers

• Up to four simultaneous spelling requests

XE Edition

• Suitable for high traffic sites

• Unlimited number of simultaneous spelling requests