Re: [CODE4LIB] XML Schema vs Library APIs (OAI-PMH/SRU/unAPI)
Hi Rob, This is just a rehash of a previous discussion on this list, between us: http://www.mail-archive.com/code4lib@listserv.nd.edu/msg05309.html So I guess I'm wasting my time ;) Thanks, I added a link to the previous discussion. You wrote: Referring to your blog post, you can say how the four inter-relate: Schema Identifier uniquely identifies the format. Schema Location is a non-unique description of the format. Schema Name is a short, human readable, non-unique name for the format and Namespace is a non-unique namespace used by the format. These definitions can help to clarify things, but they are of little practical value. The practical question is how to refer to a particular format. If you have to manually look at each particular server and collection to find out what format is *actually* served, then names and identifiers are of little help to code against. Both schema identifiers and schema names only help you to guess a format. A precise format needs an authoritative reference that you can validate against. If there exists an official XML Schema, this and only this schema defines the format (or the commonly agreed upon subset that you can work with without manually adopting each single data source). A single schema may contain multiple namespaces, and there isn't a unique identifier for a schema. For example, any simple Dublin Core based syntax must have at least two Namespaces, Dublin Core and the wrapper element. SchemaLocation is not unique as there can be many copies of the same schema. A single schema may define multiple root elements, such as MODS does with both item and collection level elements. A unique identifier for a schema is helpful because you do not need to actually look up a schema that you already know by its identifier. But it's not a must. If there is no single root namespace, you just should not use a namespace to point to a particular format. Ok, enough :-) Jakob -- Jakob Voß jakob.v...@gbv.de, skype: nichtich Verbundzentrale des GBV (VZG) / Common Library Network Platz der Goettinger Sieben 1, 37073 Göttingen, Germany +49 (0)551 39-10242, http://www.gbv.de
Re: [CODE4LIB] XML Schema vs Library APIs (OAI-PMH/SRU/unAPI)
That is (still) incorrect. A single schema may contain multiple namespaces, and there isn't a unique identifier for a schema. For example, any simple Dublin Core based syntax must have at least two Namespaces, Dublin Core and the wrapper element. SchemaLocation is not unique as there can be many copies of the same schema. A single schema may define multiple root elements, such as MODS does with both item and collection level elements. Referring to your blog post, you can say how the four inter-relate: Schema Identifier uniquely identifies the format. Schema Location is a non-unique description of the format. Schema Name is a short, human readable, non-unique name for the format and Namespace is a non-unique namespace used by the format. This is just a rehash of a previous discussion on this list, between us: http://www.mail-archive.com/code4lib@listserv.nd.edu/msg05309.html So I guess I'm wasting my time ;) Rob Sanderson On Thu, Feb 24, 2011 at 9:44 AM, Jakob Voss jakob.v...@gbv.de wrote: Hi, We are developing a general API management tool to provide different APIs (unAPI, SRU, OAI-PMH...) with different record formats (MARC, MODS, DC...) to our databases. We now stumbled upon some confusion regarding XML formats. The basic question is what is a format and how do you refer to it? I came to the conclusion that at least SRU schema identifiers are useless. In addition you can extract XML namespace URIs from XML Schemas, so all you need to identify a format is a link to its XML Schema. I wrote a more detailed blog posting about this at http://jakoblog.de/2011/02/24/xml-schema-vs-library-apis-oai-pmhsruunapi/ Does anyone of you relies on SRU schema identifiers when consuming SRU? I think at least for XML-based formats we should only use the XML Schema as authoritative reference. Sure there are different applications of variants of one schema, but then it makes no sense to use global identifiers in addition to local names. Jakob -- Jakob Voß jakob.v...@gbv.de, skype: nichtich Verbundzentrale des GBV (VZG) / Common Library Network Platz der Goettinger Sieben 1, 37073 Göttingen, Germany +49 (0)551 39-10242, http://www.gbv.de
Re: [CODE4LIB] XML Schema vs Library APIs (OAI-PMH/SRU/unAPI)
I've thought about/messed with this stuff before, and come up with no good elegant solution. It is indeed kind of a mess. On 2/24/2011 12:03 PM, Robert Sanderson wrote: That is (still) incorrect. A single schema may contain multiple namespaces, and there isn't a unique identifier for a schema. For example, any simple Dublin Core based syntax must have at least two Namespaces, Dublin Core and the wrapper element. SchemaLocation is not unique as there can be many copies of the same schema. A single schema may define multiple root elements, such as MODS does with both item and collection level elements. Referring to your blog post, you can say how the four inter-relate: Schema Identifier uniquely identifies the format. Schema Location is a non-unique description of the format. Schema Name is a short, human readable, non-unique name for the format and Namespace is a non-unique namespace used by the format. This is just a rehash of a previous discussion on this list, between us: http://www.mail-archive.com/code4lib@listserv.nd.edu/msg05309.html So I guess I'm wasting my time ;) Rob Sanderson On Thu, Feb 24, 2011 at 9:44 AM, Jakob Vossjakob.v...@gbv.de wrote: Hi, We are developing a general API management tool to provide different APIs (unAPI, SRU, OAI-PMH...) with different record formats (MARC, MODS, DC...) to our databases. We now stumbled upon some confusion regarding XML formats. The basic question is what is a format and how do you refer to it? I came to the conclusion that at least SRU schema identifiers are useless. In addition you can extract XML namespace URIs from XML Schemas, so all you need to identify a format is a link to its XML Schema. I wrote a more detailed blog posting about this at http://jakoblog.de/2011/02/24/xml-schema-vs-library-apis-oai-pmhsruunapi/ Does anyone of you relies on SRU schema identifiers when consuming SRU? I think at least for XML-based formats we should only use the XML Schema as authoritative reference. Sure there are different applications of variants of one schema, but then it makes no sense to use global identifiers in addition to local names. Jakob -- Jakob Voßjakob.v...@gbv.de, skype: nichtich Verbundzentrale des GBV (VZG) / Common Library Network Platz der Goettinger Sieben 1, 37073 Göttingen, Germany +49 (0)551 39-10242, http://www.gbv.de
