Friday, December 09, 2005
The VO and the SW
The VO and the SW: "What does an identifier identify?
This question is a fairly reliable way to start a fight, in the right company. Does an identifier identify a particular set of bytes, or might it represent only the current version of a resource, so that the contents returned when it is dereferenced (if indeed it ever is) could potentially change each time? Does a homepage URL refer to a person or to a web page? Are identifiers still useful (and not just in theory) if they are not dereferencable? Should identifiers have a `meaning', and if so, who gets to specify it? Is there an important practical difference between a locator (a URL) and an identifier (a URI)? Oh yes, and what about persistence?
While it's possible to have quite enjoyably sophisticated arguments about all of these questions, and to reasonably take all of the possible implied positions, and probably several of them simultaneously in different contexts, there is no consensus on any of them, and the only stable resolution is to avoid giving a technical answer to a fundamentally social problem. This position is blessed also in the recent Web Architecture document [std:webarch] (or rather, in the rdfURIMeaning-39 TAG `issue', related to the WebArch document), which seems to conclude that `meaning is use', and tries to leave it at that. Thus only the creator or owner of a binding (of identifier to resource) can identify the boundaries and invariants of the resource in question (Henry Thomson), and so if homepage URLs end up being used to identify people, then that is therefore what they mean."
This question is a fairly reliable way to start a fight, in the right company. Does an identifier identify a particular set of bytes, or might it represent only the current version of a resource, so that the contents returned when it is dereferenced (if indeed it ever is) could potentially change each time? Does a homepage URL refer to a person or to a web page? Are identifiers still useful (and not just in theory) if they are not dereferencable? Should identifiers have a `meaning', and if so, who gets to specify it? Is there an important practical difference between a locator (a URL) and an identifier (a URI)? Oh yes, and what about persistence?
While it's possible to have quite enjoyably sophisticated arguments about all of these questions, and to reasonably take all of the possible implied positions, and probably several of them simultaneously in different contexts, there is no consensus on any of them, and the only stable resolution is to avoid giving a technical answer to a fundamentally social problem. This position is blessed also in the recent Web Architecture document [std:webarch] (or rather, in the rdfURIMeaning-39 TAG `issue', related to the WebArch document), which seems to conclude that `meaning is use', and tries to leave it at that. Thus only the creator or owner of a binding (of identifier to resource) can identify the boundaries and invariants of the resource in question (Henry Thomson), and so if homepage URLs end up being used to identify people, then that is therefore what they mean."
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