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Schema GmbH


Start-up company, Schema GmbH, has enjoyed impressive growth, gaining customers such as Mercedes-Benz, Hewlett-Packard, Bosch, and Siemens in short order due to its web authoring application, SchemaText, developed in Allegro CL for Windows.

"From the point of view of the customers, SchemaText allows them to manage very large web documents such as technical and legal documents, online help systems, product catalogues, and Internet and Intranet sites," says Marcus Kesseler, CTO and architect of SchemaText.

While SchemaText provides an environment for users to manage the entire web authoring process -- including authoring-in-the-large and authoring-in-the-small as well as prototyping, revisions and multi-platform production -- the application is particularly well-suited for the design of large-scale hypertext structures (authoring-in-the-large).

CLOS Ideal for Managing Large-Scale, Hypertext Structures

SchemaText makes use of the Common Lisp Object System (CLOS) of Allegro CL, which adds flexibility and productivity to the application. "Let's say you have an employee page where you assign layout properties of how it will look on the Web," explains Kesseler. "Later, when you want to make a change, all you have to do is manipulate the object or class. Because of CLOS' inheritance properties, the one change that you make to the one employee page will automatically be applied to all other employee pages. And because links are objects, you can do things like a table of contents automatically."

As an added example of the kind of powerful productivity possible with CLOS, the company used its object-oriented application to translate the Common Lisp ANSI-standard spec to standard, on-line html containing over 60,000 links for Franz's Allegro CL 5.0 release. "We couldn't have done this without a tool like SchemaText," says Kesseler. "We could have done it by hand, but it would have taken many months. With SchemaText, it took three weeks."

"We needed a tool with a high level of functionality and problem-solving capability," continues Kesseler. "CLOS was an ideal choice because of its runtime type dispatch. This feature was important because of the sheer flexibility of the different kinds of data that has to be collected and where the integrity of the object needs to be preserved. For example, the main complexity here is schema evolution. The problem when you describe a hypertext is that you never do it right the first time and you don't discover you've modeled it incorrectly until after you've already put in the data. When you revise it, you don't want to lose the information you've already put in. As a CLOS implementation, SchemaText allows you to revise your design on fundamental levels without compromising your data. It becomes a system specially designed to handle hypertext with the added ability to revise an entire structure, not just a single level, on demand."

Kesseler cites Lisp as the main factor in giving the company a "core competitive advantage," making it easy to accommodate special customer requirements. "We can come up with a solution in one to three weeks even for completely new problems we've never seen before. I would have to say that Lisp has given us a productivity advantage factored three to five over C/C++."

For more information about Schema GmbH, visit their web site at

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