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Streaming APIs like SAX and XMLPULL by their nature provide some of the content of a malformed document to the client application before the first well-formedness error is detected. The XML specification implicitly says this is OK, though in some use-cases roll-back or failure to commit may be desirable. Now consider the case of a tree-based API such as DOM, JDOM, or XOM which encounters a malformedness error. Traditionally, these APIs have reported no information from a malformed document to the client application. However, recently Laurent Bihanic submitted a patch to JDOM in which as much of the document as had been able to be successfully parsed was made available through the exception that was thrown to indicate the malformedness error. This was quite clever. It had never occurred to me, and I had never noticed any other API do anything similar. What I'd like to get broader discussion of is whether this is a good idea. There are certainly use cases for it. Bihanic wanted to read the envelope of an XML message even if the data was malformed. However, there are also problems. For instance, if the well-formedness error is a missing end-tag, then the element with the missing end-tag will still appear in the partial tree. And if the problem is a missing root element, then this may produce a Document object with no root element. On the other hand, rollback, failure to commit, or simply ignoring the malformed document is much easier than with a streaming API since you know in advance that the document is malformed. Is this approach something to be encouraged? Should other tree-based APIs like XOM and DOM copy this innovation? What advantages and disadvantages have I not thought of? -- +-----------------------+------------------------+-------------------+ | Elliotte Rusty Harold | elharo@m... | Writer/Programmer | +-----------------------+------------------------+-------------------+ | Processing XML with Java (Addison-Wesley, 2002) | | http://www.cafeconleche.org/books/xmljava | | http://www.amazon.com/exec/obidos/ISBN%3D0201771861/cafeaulaitA | +----------------------------------+---------------------------------+ | Read Cafe au Lait for Java News: http://www.cafeaulait.org/ | | Read Cafe con Leche for XML News: http://www.cafeconleche.org/ | +----------------------------------+---------------------------------+
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