Re: [CODE4LIB] SRU/ZeeRex explain question : record schemas
Thanks Ray, I believe it is! A schema listed there is available for requesting with the recordSchema= parameter, yes? Cool, that's exactly what I was looking for. Another question though. I note when looking up schemaInfo... I'm a bit confused by the sort attribute. How could you sort by a schema? What is this attribute actually for? Jonathan Ray Denenberg, Library of Congress wrote: schemaInfo is what you're looking for I think. Look at http://z3950.loc.gov:7090/voyager. Line 74, for example, schemaInfo schema identifier=info:srw/schema/1/marcxml-v1.1 sort=false name=marcxml titleMARCXML/title /schema Is this what you're looking for? --Ray - Original Message - From: Jonathan Rochkind rochk...@jhu.edu To: CODE4LIB@LISTSERV.ND.EDU Sent: Friday, April 30, 2010 3:57 PM Subject: [CODE4LIB] SRU/ZeeRex explain question : record schemas This page: http://www.loc.gov/standards/sru/resources/schemas.html says: The Explain document lists the XML schemas for a given database in which records may be transferred. Every schemas is unambiguously identified by a URI and a server may assign a short name, which may or may not be the same as the short name listed in the table below (and may differ from the short name that another server assigns). But perusing the SRU/ZeeRex Explain documentation I've been able to find, I've been unable to find WHERE in the Explain document this information is listed/advertised. Can anyone clue me in?
Re: [CODE4LIB] SRU/ZeeRex explain question : record schemas
From: Jonathan Rochkind rochk...@jhu.edu Another question though. I note when looking up schemaInfo... I'm a bit confused by the sort attribute. How could you sort by a schema? What is this attribute actually for? Well indulge me, this is best explained by the current OASIS SRU draft. (The current and earlier specs don't do a good job here. But for background if interested: sorting as an SRU function was supported in SRU 1.1 and taken out of version 1.2, replaced by sorting as a function of the query language rather than the protocol. For the OASIS work it's in both. For the current spec at LC, which reflects 1.2, the attribute doesn't even make sense. If you go back to the 1.1 archive it does. Still, the OASIS document treats it more clearly.) See http://www.loc.gov/standards/sru/oasis/sru-2-0-draft-most-current.doc See section 9.1. So essentially, when you sort in SRU, you provide an XPath expression. The XPath expression is meaningful in the context of a schema, but the *record schema* may not be the most meaningful schema for purposes of sorting, there may be another schema more meaningful. So, you have the capability to specify not only a record schema but an auxiliary sort schema. A given schema that an Explain file lists will usually be one that is used as a record schema, but it may also be usable as a sort schema. That's what the sort attribute tells you. --Ray
Re: [CODE4LIB] SRU/ZeeRex explain question : record schemas
This makes some amount of sense, thanks. I actually kind of liked the sorting as part of CQL in SRU 1.2. I see how XPath sorting can be convenient too. But you will leave sorting as part of CQL too in any changes to CQL specs, I hope? I think CQL has a lot of use even outside of SRU proper, so I encourage you to leave it's spec not too tightly coupled to SRU. I think there are at least three ways to sort as part of (different versions of?) SRU now! 1) An actual separate sortKeys query paramater 2) Included in the CQL expression in query, using the sortBy keyword. 3) In draft not finalized, OASIS/SRU 2.0 methods of specifying XPaths for sorting. [Thanks for including the link to the current SRU 2.0 draft, I didn't know that was publically available anywhere, it's not really googlable]. Do I have this right? As SRU 1.2 is the only actual spec I have to work with... am I right that either top-level sortKeys, or embedded in CQL with sortBy would both be legal in SRU 1.2 (whether a given server supports one or both of them is a different question -- but they are both legal to spec, yes?). I'd actually strongly encourage you to leave both of them as legal to spec in SRU 2.0, they make things much simpler to work with (although also less flexible; that's generally the trade-off) then requiring XPath's to be specified. Especially when a corpus being searched may include records in diverse and varied and inconsistent record schemas. Jonathan Ray Denenberg, Library of Congress wrote: From: Jonathan Rochkind rochk...@jhu.edu Another question though. I note when looking up schemaInfo... I'm a bit confused by the sort attribute. How could you sort by a schema? What is this attribute actually for? Well indulge me, this is best explained by the current OASIS SRU draft. (The current and earlier specs don't do a good job here. But for background if interested: sorting as an SRU function was supported in SRU 1.1 and taken out of version 1.2, replaced by sorting as a function of the query language rather than the protocol. For the OASIS work it's in both. For the current spec at LC, which reflects 1.2, the attribute doesn't even make sense. If you go back to the 1.1 archive it does. Still, the OASIS document treats it more clearly.) See http://www.loc.gov/standards/sru/oasis/sru-2-0-draft-most-current.doc See section 9.1. So essentially, when you sort in SRU, you provide an XPath expression. The XPath expression is meaningful in the context of a schema, but the *record schema* may not be the most meaningful schema for purposes of sorting, there may be another schema more meaningful. So, you have the capability to specify not only a record schema but an auxiliary sort schema. A given schema that an Explain file lists will usually be one that is used as a record schema, but it may also be usable as a sort schema. That's what the sort attribute tells you. --Ray
Re: [CODE4LIB] SRU/ZeeRex explain question : record schemas
From: Jonathan Rochkind rochk...@jhu.edu But you will leave sorting as part of CQL too in any changes to CQL specs, I hope? I think CQL has a lot of use even outside of SRU proper, so I encourage you to leave it's spec not too tightly coupled to SRU. The OASIS TC firmly supports this approach (and by firmly I mean 100%) so the only way this could get changed is via public comment. I think there are at least three ways to sort as part of (different versions of?) SRU now! 1) An actual separate sortKeys query paramater 2) Included in the CQL expression in query, using the sortBy keyword. 3) In draft not finalized, OASIS/SRU 2.0 methods of specifying XPaths for sorting. [Thanks for including the link to the current SRU 2.0 draft, I didn't know that was publically available anywhere, it's not really googlable]. As you corrected yourself in a subsequent message: Ah, I think I was wrong below. I must have been looking at different versions of the SRU spec without realizing it. SRU 1.1 includes a sortKeys parameter, and CQL 1.1 does not include a sortBy clause. SRU 1.2 does NOT include a sortKeys parameter, and CQL 1.2 does include a sortBy clause. Yes, that's correct. Do I have this right? As SRU 1.2 is the only actual spec I have to work with... am I right that either top-level sortKeys, or embedded in CQL with sortBy would both be legal in SRU 1.2 No. Legal in 2.0 - the OASIS version, not legal in 1.2. In 1.2 it is not legal to have a sort parameter in the request. OASIS is standardizing SRU and CQL loosely coupled that is, SRU can use other query languages and CQL may be invoked by other protocols, but they are generally oriented towards being used together. But since SRU may be used with a query language that might not have sort capability, the TC felt it necessary to include sorting as part of the protocol. Conversely since CQL may be used by a protocol that doesn't support sorting, similarly CQL should support sorting. There is a section in the draft standard that discusses what to do if a request has conflicting sort specifications. --Ray
[CODE4LIB] SRU/ZeeRex explain question : record schemas
This page: http://www.loc.gov/standards/sru/resources/schemas.html says: The Explain document lists the XML schemas for a given database in which records may be transferred. Every schemas is unambiguously identified by a URI and a server may assign a short name, which may or may not be the same as the short name listed in the table below (and may differ from the short name that another server assigns). But perusing the SRU/ZeeRex Explain documentation I've been able to find, I've been unable to find WHERE in the Explain document this information is listed/advertised. Can anyone clue me in?
Re: [CODE4LIB] SRU/ZeeRex explain question : record schemas
schemaInfo is what you're looking for I think. Look at http://z3950.loc.gov:7090/voyager. Line 74, for example, schemaInfo schema identifier=info:srw/schema/1/marcxml-v1.1 sort=false name=marcxml titleMARCXML/title /schema Is this what you're looking for? --Ray - Original Message - From: Jonathan Rochkind rochk...@jhu.edu To: CODE4LIB@LISTSERV.ND.EDU Sent: Friday, April 30, 2010 3:57 PM Subject: [CODE4LIB] SRU/ZeeRex explain question : record schemas This page: http://www.loc.gov/standards/sru/resources/schemas.html says: The Explain document lists the XML schemas for a given database in which records may be transferred. Every schemas is unambiguously identified by a URI and a server may assign a short name, which may or may not be the same as the short name listed in the table below (and may differ from the short name that another server assigns). But perusing the SRU/ZeeRex Explain documentation I've been able to find, I've been unable to find WHERE in the Explain document this information is listed/advertised. Can anyone clue me in?
Re: [CODE4LIB] SRU/ZeeRex explain question : record schemas
There's a schemaInfo element right under the explain element that carries that data. Here's a pointer to the Explain record for my LCNAF database. http://alcme.oclc.org/srw/search/lcnaf Don't let the browser fool you! View the source and you'll see the actual XML that was returned. The schemaInfo element is towards the bottom. Ralph p.s. For my LCNAF friends on the list, note the change to the database element in the serverInfo section. It now include the update date and number of records in the database! That's being automatically generated by the SRW server. -Original Message- From: Code for Libraries [mailto:code4...@listserv.nd.edu] On Behalf Of Jonathan Rochkind Sent: Friday, April 30, 2010 3:58 PM To: CODE4LIB@LISTSERV.ND.EDU Subject: [CODE4LIB] SRU/ZeeRex explain question : record schemas This page: http://www.loc.gov/standards/sru/resources/schemas.html says: The Explain document lists the XML schemas for a given database in which records may be transferred. Every schemas is unambiguously identified by a URI and a server may assign a short name, which may or may not be the same as the short name listed in the table below (and may differ from the short name that another server assigns). But perusing the SRU/ZeeRex Explain documentation I've been able to find, I've been unable to find WHERE in the Explain document this information is listed/advertised. Can anyone clue me in?
