[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: [SML] Whether to support Attribute or not?
On Mon, 29 Nov 1999, Pavel Velikhov wrote: > > If you have to "dig" into the contents to figure > > out which "processing pipeline" the content is > > placed on then you have effectively elminated > > all hope of sequential processing. Thus, you > > need random access to the information stream. > > And hence, "large" memory requiremens, thus > > undermining the apparant "simplicity" of SML. > > > > Well, I don't agree with you on this point. I have been working > on a streaming query processor for XML for some time, and the > problem is just not there. Why is it a problem going into the > element one or two levels deep? Besides the chances that you will > encode all the information relevant to the query processor into > attributes is very small. Consider the example above with the > local schools: what if I want to select all homes that have > some specific school in their neighborhood? This information > cannot be encoded in the attributes, since its nested. But I > can still stream such queries, all I have to do is descend one > level into each element and the find the school that satisfies > the condition. In the case you have mentioned, if the <home> to be presented exceeds the capacity of the input buffer, then it must be copied elsewhere until enough information is gathered to accept or reject it. If the element in question is a top-level element, and if its children are numerous or large, then a large portion of the XML stream need be held in storage. In any case, a large number of allocations/deallocations would occur if the input buffer could not be leveraged. What I would do in this case, is make hash values for the possible schools, and put the hash values in the attributes -- as this information is intended for the processor of the information and not for the end-user. With this information, the memory requirements could be dramatically reduced since only a small fraction of the stream would have to be held in memory. Best yet, the attribute stream can now be discarded even if it exceeds the input buffer. I hope this explains where I'm coming from. ;) Clark 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/ and on CD-ROM/ISBN 981-02-3594-1 To unsubscribe, mailto:majordomo@i... the following message; unsubscribe 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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