[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Services-based automation (WAS RE: Realistic proposals to the W3C?)
Jonathan Borden wrote - > > The XML model defines a node labelled directed graph. In this model, arcs or > edges have the type "element" "attribute" "CDATA section" "comment" etc. > > The RDF model defines an edge labelled directed graph, for example arcs may > be labelled "color", "type.of.cheese" "type.of.sauce" "topping". This may > not seem a radical difference but understand that software which makes > inferences regarding the properties of a pizza, as represented in an RDF > graph, may be totally unconcerned about whether the "type.of.cheese" is an > attribute or an element and whether this property is serialized before or > after the "type.of.sauce" property. > A basic edge-labeled graph defines its structure mainly by edges, keeping its values or data in the nodes. The node model for xml uses nodes to delineate the structure as well as to hold data. The edge-labeled model has a cleaner separation of structure and data. I happen to like working with a edge-labeled model better, the DOM uses a node model. Do the two models really represent anything different? Not really. But if connections - a form of structure - are the most important thing to you, edge-labeled models might seem more attractive or "natural". In either case, we are looking to the labels to give us clues as to the "meaning", or at least to the "use". In a csv file, this would be equivalent to having a first row with the column headers. What do those labels really "mean"? The labels can't tell us that by themselves. They are only precise in a well-defined domain where there are interfaces or schemas or some other kind of agreement about how to ***use*** them. That's Len's "services". In that domain, we can know to look for label "ABC" and we can predict how to use it to get the results we want. We can trade precision for a wider range of use by developing ontologies. An ontology says what terms are related to what other ones, at least in an more-general/less-general sense. This gives us a more compl ex, structured set of labels. But we're still in the same area of "services". Cheers, Tom Passin
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