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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: XML syntax for XPath?
 Sean McGrath wrote: > > > At 06:05 PM 12/26/2000 -0500, Jonathan Borden wrote: > >Simon St.Laurent wrote: > > > > > > Yes, but it might be interesting to create an 'XPath parser' > which reads > >in > > > XPath and spits out SAX events, making these critters a bit easier to > > > process and transform internally. Then maybe an XPath writer > which takes > > > those events and reports them as XPath again. > > > > So what you want is an XPath grove parser. > > What would the grove approach offer that an XML notation approach > would not? What I mean by an XPath grove parser is very simply a parser that parses XPath and emits SAX events; converting the XPath syntax into a *logical* XML processing structure that can be manipulated by the SAX filter chain that we all know and love. Anyone who has written a parser that emits SAX events has worked with groves (whether you knew it or not :-) The XPath grove simply refers to the logical structure of the XPath character string as opposed to the actual character string. Such a grove, if represented by a series of SAX events, can be manipulated by XSLT. To distinguish the logical 'XML' represented by the series of SAX events (or perhaps a DOM) from actual XML in a character stream, we use the term 'grove'. So the XPath need not be actually transformed into an XML character stream rather parsed as a grove. An "XPath grove parser" in this case simply parses an XPath and emits SAX events. A notation is a way of naming a non XML or SGML structure but does not itself handle grove processing. One might link a structure defined by a notation to a grove parser in order to import such a structure into an XML processing chain. > > I like the idea of a blessed XML expression of notations that are not > natively XML (XPath, SAX events, MP3:-). Blessing XML notation > for these allows implementers to implement XML import/export > and allows integrators to join things together using their > XML toolbox for the glue. Notations alone do not provide for XML 'import' of non-XML data. Notations are similar to MIME content-types, they simply provide for names of external, perhaps binary, datatypes. A grove parser, on the other hand, is what allows integration of non-XML data as defined by either a notation or MIME content-type. Since EBNF is the most common and standardized format for describing syntaxes I have suggested that a set of EBNF productions form the property set for a grove for a given notation/content-type. An explanation of such uses of groves in the healthcare field is available in the slides from my XML Healthcare talk (see http://www.openhealth.org/talks ). A description of the grove for XML itself (using the XML 1.0 productions) is available at http://www.openhealth.org/XSet Jonathan Borden The Open Healthcare Group http://www.openhealth.org 
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