Michael I. Schwartzbach
University of Aarhus
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Michael I. Schwartzbach is Associate Professor of Computer Science
at the University of Aarhus. He works with design and implementation
of programming languages, XML, and Web technology.
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Static Guarantees in Dynamic Web Services
Tuesday 10:45 - 12:00 (Java Room)
XML documents will often be generated dynamically by programs. A
common example is XHTML documents being generated by interactive Web
services in response to requests from clients. Typically, there are no
static guarantees that the generated documents are valid according to
the DTD for XHTML. In fact, a quick study of the outputs from many
large commercial Web services shows that most generated documents are
in fact invalid.
This is not a huge problem, since the browsers
interpreting this output are quite forgiving and do a fair job of
rendering invalid documents. Increasingly, however, Web services will
generate output in other XML languages for less tolerant clients, many
of whom will themselves be Web services.
Also, a Web service must trust that dynamically generated HTML forms
contain exactly those form fields that it next expects to receive. Thus it is certainly an interesting question to statically guarantee
validity of dynamically generated XML.
A positive answer could help to eliminate a whole class of errors in
a deployed Web service.
Current high-level abstractions
such as JSP, Servlets, and JDOM offer no help in solving this problem,
which is of course formally undecidable. The JWIG programming language, which is built on top of Java, uses
static analysis of class files to answer the validity question. The
precision of this analysis is boosted by new high-level concepts of
sessions and XML templates that are introduced by JWIG.
- The JWIG site
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