Exercises for Lecture 7

Regular Expressions

Consider the regular expression (a|b)+0(1|2|3|4)*(a|b) over the alphabet {a,b,0,1,2,3,4,5}

Which of the following strings are matched by the regular expression?
1. a04321b
2. a0135a
3. 022b
4. a042
Draw a finite state automaton for the regular expression.

DTD

Browse through the DTD for XHTML. Try to answer the following questions:
- what are the legal attributes for h3 tags?
- must input tags occur inside form tags?
- can a (anchor) tags be nested?
Write a DTD schema for your own XML version of the weblog.

Tips

To validate against a DTD Schema you can use an XML editor such as XMLSpy or Morphon, or use the sax.Writer example code from the Xalan Apache :
```
 java -classpath xercesImpl.jar:xercesSamples.jar sax.Writer -v yourfile.xml
		    
```
If you run sax.Writer without the parameters
```
java -classpath xercesImpl.jar:xercesSamples.jar sax.Writer
```
you can read about the options and defaults.
On Windows, replace ":" by ";".
NOTE: Some browsers may rename the ".jar" suffixes to ".zip" or ".html" during download. You must then rename the files such that they end with ".jar".