xquery functions reusing xquery code date: september, 2008 dan mccreary president dan mccreary &...

XQuery FunctionsReusing XQuery CodeDate: September, 2008

Dan McCrearyPresidentDan McCreary & [email protected](952) 931-9198

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Metadata Solutions

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D Copyright 2007 Dan McCreary & Associates2

Overview

• Why use functions?• XQuery Built-in functions• eXist-specific functions• How to define functions• Passing parameters• Function signatures• Recursive functions

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Why Use Functions?

• To reuse snippets of your code

• To make code easier to maintain

• To make code easier to read

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Function Layers

Base XQuery 1.0 Functions

eXistUpdate

XQueryUpdate 1.0

eXist built-inFunctions

PublicFunctions

Your Custom Functions

eXist Extensions

future

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eXist Function Documentation

• eXist has around 384 functions

• tools for searching built in to each installation

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D Copyright 2007 Dan McCreary & Associates 6

eXist Function Documentation Tool

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Common XQuery Built-in Functions• functions for getting data

– doc, collection• numeric functions

– abs, avg, ceiling, floor, max, min, number, round, round-half-to-even, sum• date and time functions

– current-dateTime, current-date, current-time, implicit-timezone• set functions

– distinct-values, starts-with, deep-equal, empty, subsequence• common string functions:

– concat, lower-case, substring, substring-before, substring-after, string-join, upper-case

• logic– boolean, not, false, true

• uri-functions– base-uri, document-uri, namespace-uri, namespace-uri-for-prefix

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Common eXist Built-in Extensions

• request – processing incoming HTTP requests– create-session, get-parameter, get-data, get-session, get-context-path, get –

cookie-names, get-cookie-value, get-header, get-hostname, get-method, get-server-port

• response – Setting outgoing HTTP responses– redirect, set-cookie, set-header, set-status-code

• xmldb– create collection, store, move, copy, change permissions, created, get-child-

collections, remove, rename• update

– insert, update, replace, rename, delete• session

– manage session variables• system

– get system status like build number, memory-free or index data• text – filter, fuzzy-match-all, fuzzy-match-any, highlight-matches, kwic-

display, match-all, match-any• ngram – full-text indexing contains, starts-with, ends-with, matches• util – call, binary-doc, complie, eval, exclusive-lock, index-keys, log-system-

out, random

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Other eXist Extension Modules

• E-mail – send an e-mail to a person from the result of an XQuery

• Scheduler – schedule reports to run at intervals• Compression – compress files• Math – advanced math functions• Image Management – generate thumbnail images

etc.• XML Differences – report on how XML files differ• GML – Geography Markup Language

Note: These need to be configured by the eXist systems administrator.

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URI functions

• base-uri, document-uri, static-base-uri, document-uri, iri-to-uri

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Math and Set Functions

• floor

• exists

• insert-before

• insert-after

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NGram

• contains – does a full-text string contain a specific string?

• starts-with, ends-with – does a full-text string start or end start with a string?

• filter-matches – exclude specific results from a match

http://exist-db.org/xquery/ngram

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How to Define a Function

declare function local:my-function() as return-type {

…your code here

return

<result/>

};

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Hello World Function

declare function local:hello-world() as xs:string {

let $message := 'Hello World'

return

$message

};

• The "local" namespace• Can not be called outside of this XQuery file

• No input parameters• A single string as an output parameter

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How to Call a Function

xquery version "1.0";

declare function local:hello-world() as xs:string { let $message := 'Hello World' return $message};

let $my-variable := local:hello-world()

You must use the "local:" prefix.

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String Processing Example

Copyright 2011 Dan McCreary & Associates16

• Write a function that returns the "database path" to your current location.

• Input:– '/exist/rest/db/apps/faqs/views/my-query.xq

• Output:– '/db/apps/faqs'

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Input and Output Parameters

xquery version "1.0";

declare function local:app-base-collection($uri as xs:string) as xs:string { let $app-base := substring-before(substring-after($uri, '/exist/rest'), '/views/') return $app-base};

let $uri := '/exist/rest/db/apps/faqs/views/my-query.xq'

return<results> <app-base-collection>{local:app-base-collection($uri)}</app-base-collection></results>

<results> <app-base-collection>/db/apps/faqs</app-base-collection></results>

Use a string as input and get a string as output.

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D Copyright 2007 Dan McCreary & Associates 18

Get the Base Collectionxquery version "1.0";

declare function local:app-base-collection() as xs:string { let $app-base := concat('/db/', substring-before(substring-after(request:get-uri(), '/exist/rest/db/'), '/')) return $app-base};

return<results> <uri>{request:get-uri()}</uri> <app-base-collection>{local:app-base-collection()}</app-base-collection></results>

Note that this will not work from within oXygen, only from the web browser.

<results> <uri>/exist/rest/db/xrx-training/labs/02-functions/app-base-collection.xq </uri> <app-base-collection>/db/xrx-training</app-base-collection></results>

Output:

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Passing Parameters

• You can pass many parameters into any function but functions usually return only a simple type or a complex element

• Each parameter has a “cardinality” that describes if it is an optional parameter (may be null), or has more then one value.

Note: checking parameters is a great way to test the data for your functions

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Cardinality Specifiiers

• The following notation is used to describe the cardinality of each parameter:

none a single required parameter? an optional single parameter

* zero to many parameter

+ One to many parameters

Also called the "arity" of a function


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Labs

• Create your own function that will capitalize the first letter of a word– Use the substring($in, 1, 1) function to get the

first character– Use the upper-case() function to convert to

upper case

• Create a second function to capitalize all the first letter in a sentence– Use the tokenize() function to separate a

sentence into a sequence of words


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Lab Description:

• Create an XQuery function that will return the “title case” of a string.

Input:

the quick brown fox jumps over the lazy dog

Output:

The Quick Brown Fox Jumps Over The Lazy Dog


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Labs

• Title Case Lab• https://docs.google.com/document/pub?id=15_CZ8sHjd_yGC2B83oKGCIQtXQJtqyowy7v3KtSzbvc


xquery functions reusing xquery code date: september, 2008 dan mccreary president dan mccreary &...

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