[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] SAX: Processing Instructions (question 6 of 10)
[SAX is a proposal for a simple, event-based XML API, using callbacks. This is one in a series of ten design questions that we need to answer to implement the API.] Should SAX implement a callback for processing instructions? public void processingInstruction (String name, String data); (In XML, all processing instructions begin with a name, followed optionally by whitespace and then other characters). CON --- - this method would make SAX slightly larger; - processing instructions are difficult for non-specialists to understand -- the HTML world never managed to figure them out, and used specialised comments instead; - processing instructions are not part of a document's logical element structure, and providing a callback event might encourage people to abuse them. PRO --- - processing instructions are required for most proposed XML-related standards, including XSL and architectural forms; - novice users can extend the XmlAppBase class and simply ignore processing instructions altogether. MY RECOMMENDATION ----------------- Yes. Omitting PI's would cripple SAX beyond any but the most trivial uses. PI's provide the only way to make new types of declarations in XML, and nearly every XML-related standard requires at least one special enabling declaration (to locate a stylesheet, declare a namespace, etc.). OTHER CONSIDERATIONS -------------------- XML processing instructions consist of two parts: a name, and (optional) data. It makes sense to report the two of these separately, since the name can be an internalized string and may be the name of a declared notation. Should the data (if present) be a string, or should it be an array of characters on the model of charData? public void processingInstruction (String name, char data[], int length) On a different point, I am assuming that SAX-based parsers will not report the XML declaration or text declaration using this event, even though they resemble PIs. All the best, David -- David Megginson ak117@f... Microstar Software Ltd. dmeggins@m... http://home.sprynet.com/sprynet/dmeggins/ xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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