Annotation-Oriented Programming

Related link: http://java.sun.com/developer/technicalArticles/J2SE/constraints/annotations.htm…

Sun's developer list has this good article on JAVA annotations. It is one of the first articles that really makes explicit that annotations (as available in java 1.5 and C#) allow the same code to be processed in different ways for different applications: the declarative approach that has been so successful with SGML/HTML/XML.

Lets call using marked-up text and marked-up programs annotation-oriented programming: a new brand for symbolic processing. Perhaps we are heading towards a world where the two extreme philosophies of programming languages will be annotation-oriented programming on one hand, emphasizing the free annotation of any and all information to any granularity and to any depth of meta-ness, versus relational programming, emphasizing atomic facts and the relations between them. The practitioners of each, annotators and atomists, are a superset of XML's Docheads and Dataheads.

It would be interesting to do a Codd
and make up a list of the requirements for
an annotation-oriented programming system
and figure out its formal properties:
every item or WF sequence of items is capable of being annotated,
including annotations, might be one requirement.
Another might be that there every item can be
addressed.
What would be interesting then would be whether,
in fact, the two worlds are actually distinct,
or whether one is a layer or subset.

To be most successful, annotations will need to be accompanied by some fairly ubiquitous tools. Rather than growing the language or the API, extra functionality may be available from annotation-aware tools. For example, it would be great to have a standard XML view of a java file and of a java class that could be processed by XSLT.

In Java 1.5, I don't uch like the annotation syntax: the @ is cute, who on earth would decide to prefix annotations rather than in- or post-fix them?