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Re: inelegant but working pipeline seeks elegance

From: Conal Tuohy <conal.tuohy@versi.edu.au>
Date: Wed, 23 May 2012 11:00:22 +1000
Message-ID: <4FBC36A6.1020205@versi.edu.au>
To: mozer <xmlizer@gmail.com>
CC: XProc Dev <xproc-dev@w3.org>
Yes I did get a satisfactory answer, thanks.

My mistake was to implement conditional processing using <p:choose> and 
<p:when>. Instead I should have used <p:for-each>, and expressed the 
conditional as a predicate in the <p:iteration-source>.

Using <p:choose> really only makes sense when choosing from a set (n>1) 
of pipelines. If there's only 1 pipeline (to be either run or not run), 
then <p:for-each> is better.

Thanks!

Conal


On 20/05/12 21:35, mozer wrote:
> Hi Conal,
>
> Since you truncated the last result, it's not clear to me if you found 
> the answer you were looking for at the time
>
> Xmlizer
>
> 2012/3/12 Conal Tuohy <conal.tuohy@versi.edu.au 
> <mailto:conal.tuohy@versi.edu.au>>
>
>     Embarrassing isn't it, when you ask for help and then immediately
>     see a better alternative yourself?
>
>     I managed to remove the p:choose[@name='whether-to-save-record']
>     within the p:viewport moving the conditional into a predicate in
>     the p:viewport's select statement (see below).
>
>     I guess I could also convert the resumptionToken handling to use a
>     p:viewport rather than a p:choose. The sub-pipeline of the
>     p:viewport would run either once (if there were a resumptionToken)
>     or not at all.
>
>     Perhaps the rule of thumb I'm looking for is:
>
>     To implement a simple "if", always use a p:viewport rather than a
>     p:choose (because the  p:otherwise would be a pain).
>
>         <?xml version="1.0"?>
>         <p:declare-step
>            version="1.0"
>            xmlns:p="http://www.w3.org/ns/xproc"
>            xmlns:fn="http://www.w3.org/2005/xpath-functions"
>            xmlns:harvester="tag:conal.tuohy@versi.edu.au
>         <mailto:tag%3Aconal.tuohy@versi.edu.au>,2012:oai-pmh"
>            xmlns:oai="http://www.openarchives.org/OAI/2.0/"
>            xmlns:tdar="http://www.tdar.org/namespace"
>
>         >
>
>         <harvester:list-records
>                name="harvest"
>                base-uri="http://ahad.edu.au/oai-pmh/oai"
>                base-storage-uri="/tmp/harvest/"
>                metadata-prefix="tdar"/>
>
>         <p:declare-step type="harvester:list-records" name="list-records">
>         <p:option name="base-uri" required="true"/>
>         <p:option name="base-storage-uri" required="true"/>
>         <p:option name="metadata-prefix"/>
>         <p:option name="resumption-token"/>
>         <p:variable name="uri" select="concat($base-uri,
>         '?verb=ListRecords&amp;')"/>
>         <!-- query the OAI-PMH server -->
>         <p:choose name="resumption-token-or-metadata-prefix">
>         <p:when test="p:value-available('resumption-token')">
>         <p:load name="query-with-resumption-token">
>         <p:with-option name="href" select="concat($uri,
>         'resumptionToken=', $resumption-token)"/>
>         </p:load>
>         </p:when>
>         <p:otherwise>
>         <p:load name="query-with-metadata-prefix">
>         <p:with-option name="href" select="concat($uri,
>         'metadataPrefix=', $metadata-prefix)"/>
>         </p:load>
>         </p:otherwise>
>         </p:choose>
>         <p:identity name="query-results"/>
>         <p:viewport name="record"
>         match="oai:OAI-PMH/oai:ListRecords/oai:record[oai:metadata[tdar:dataset
>         | tdar:project | tdar:person | tdar:institution | tdar:image |
>         tdar:sensoryData]]">
>
>         <!-- double-encode the record identifier so as to produce
>         URI-encoded file name -->
>         <p:variable name="file-name"
>         select="concat(fn:encode-for-uri(fn:encode-for-uri(/oai:record/oai:header/oai:identifier)),
>         '.xml')"/>
>         <!-- save the record -->
>         <p:store name="save-record" indent="true">
>         <p:input port="source" select="oai:record/oai:metadata/*"/>
>         <p:with-option name="href" select="concat($base-storage-uri,
>         $file-name)"/>
>         </p:store>
>         <p:identity>
>         <p:input port="source">
>         <p:pipe step="save-record" port="result"/>
>         </p:input>
>         </p:identity>
>         </p:viewport>
>
>         <!-- query again (recursively) if a resumptionToken was
>         returned in the query results -->
>         <p:choose name="whether-to-resume-query">
>         <p:variable name="resumption-token-returned"
>         select="/oai:OAI-PMH/oai:ListRecords/oai:resumptionToken"/>
>         <p:when test="normalize-space($resumption-token-returned)">
>         <harvester:list-records>
>         <p:with-option name="base-uri" select="$base-uri"/>
>         <p:with-option name="base-storage-uri"
>         select="$base-storage-uri"/>
>         <p:with-option name="resumption-token"
>         select="$resumption-token-returned"/>
>         </harvester:list-records>
>         </p:when>
>         <p:otherwise>
>         <!-- no resumption token (or empty resumption token) returned;
>         nothing to do -->
>         <p:identity name="dummy1"/>
>         <p:sink name="dummy2"/>
>         </p:otherwise>
>         </p:choose>
>
>         </p:declare-step>
>
>         </p:declare-step>
>
>
>
>
>     -- 
>     Conal Tuohy
>     eResearch Business Analyst
>     Victorian eResearch Strategic Initiative
>     +61-466324297 <tel:%2B61-466324297>
>
>
>


-- 
Conal Tuohy
eResearch Business Analyst
Victorian eResearch Strategic Initiative
+61-466324297
Received on Wednesday, 23 May 2012 01:01:18 GMT

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