Editing XML data with XForms

Multimedia Document
Editing XML data with XForms
Stéphane Sire (speaking)

Framework
IC > IIF > MEDIA : http://media.epfl.ch
Models &
Environments for
Document related
Interaction &
Authoring
MEDIA
XML based technologies
19.02.2009
1
Introduction

Editing XML Data ?
Classical approach with text editors
requires knowledge of XML
not for non expert end-users
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Introduction
2

Editing XML Data ?
What they say ?
http://www.ibm.com/developerworks/library/x-xml2008prevw.html
The end of markup-centric editors
“In the early days, a lot of vendors released markup-centric editors that made embedded documents in tree controls. This had the advantage of being incredibly easy to code using numerous preexisting tree components like JTree on Swing. But they had the distinct disadvantage that nobody wanted to read, write, or edit their XML documents as trees. The marketplace has mostly swept these tools away to an unlamented grave.”
Elliotte Rusty Harold
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Introduction
3

Editing XML Data ?
Classical approach with form based user interfaces
no knowledge of XML required
can be deployed in Web browsers
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Introduction
4

What Forms Standards are Available ?
Web Forms in HTML
not XML output but key/value pairs (flat data model)
no automatic validation (dependent on scripting in Javascript)
Propietary formats
Adobe XML Forms, Microsoft InfoPath, etc.
W3C XForms
open standard (free)
XForms 1.0 appeared in 2001, became a Recommendation in 2007
XForms 1.1 now a Candidate Recommendation
based on XML for editing XML data
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Introduction
5

XForms builtin Features
Input Validation and Calculation
Declarative Actions and Events (no scripting)
Accessibility
Device Independence
abstract forms controls that may be rendered with different devices
Data persistence
communication layer compliant with REST principles
Initial data insertion as XML
no need for template languages as with JSP or RoR
Compatible with any XML host language (XHTML, SVG, …)
this allows to “borrow” user interface elements from a foreign language
Model View Controller MVC
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XForms overview
6

MVC in XForms
Each XForms document has three parts
a model that contains the data to be edited and submitted
one or more views
forms controls (presentation part)
elements from a host presentation document (XHTML, SVG, …)
each view is bound to a particular element in the model via an XPath expression
some controllers
forms controls (logical part)
bindings that control data input value space
actions triggered by events to update the model and/or the views
submissions that control model downloading from and offloading to server(s)
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XForms overview
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Anatomy of an XForms document
<?xml version="1.0"?>
<html xmlns="http://www.w3.org/1999/xhtml” xmlns:xf="http://www.w3.org/2002/xforms"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<head>
<model xmlns="http://www.w3.org/2002/xforms" id="order-model">
<instance>
<doughnuts xmlns="">
<quantity/>
</doughnuts>
</instance>
<bind nodeset="quantity" type="xsd:nonNegativeInteger"/>
<submission action=”http://doughnuts.org/order" method="post" id="order-submit" />
</model>
</head>
<body>
<h2>Order Doughnuts</h2>
<xf:input ref="quantity">
<xf:label>Quantity</xf:label>
</xf:input>
<xf:submit submission="order-submit">
<xf:label>Order</xf:label>
</xf:submit>
</body>
</html>
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XForms overview
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Legend
xml declarations
Model
Views (incl. host language)
Controllers
XPath
expression

XForms Modules
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XForms overview
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Data Declaration <xforms:instance>
one or more <xforms:instance> inside an <xforms:model>
case 1: linked to external data
with an src attribute : <xforms:instance src=“my-data-source.xml”/>
case 2: inline instance data
with an XML skeleton empty of data or not
optional link to an XML Schema file
with a schema attribute on the model element
optional id attribute
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XForms data declaration
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<xforms:instance id="credit-card-instance">
<credit-card>
<type/>
<number/>
<expiration-month/>
<expiration-year/>
<verification-code/>
<valid>false</false>
</credit-card>
</xforms:instance>

What’s the need for several data instances ?
Data can be loaded from different data sources
one data instance per source
Data can be saved to different data sinks
one data instance per sink
This is the basis for supporting Ajax patterns in XForms
we will detail this with the <xforms:submission> element
Data instances can also be used to represent non-user data
application data (e.g. a list of city to display in selection lists)
the state of some user interface elements, the value of the data instance control the visibility of the user interface elements
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XForms data declaration
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Data Vaildation with Model Item Properties <xforms:bind>
Model item properties define rules that constrain the elements and attributes of the instances
They are defined on <xforms:bind> elements placed within an <xforms:model>
They apply to a nodeset through a nodeset attribute (implicit iteration)
which is defined by an XPath expression
Each property is associated with an attribute applying to different facets
e.g. check that <age> is a positive integer
with the type attribute
<xforms:bind nodeset=“user/age” type=“xsd:nonNegativeInteger”/>
XPath expressions in <xforms:bind> are by default relative to the root element of the first XForms instance
except when starting with instance(“instance-id”)
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XForms data bindings
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List Of Model Item Properties on <xforms:bind>
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Examples of XPath expressions in Data Bindings
imagine what each model item property does ?
nodeset="year" constraint=". > 1970”
ref="volume" calculate="../height * ../width * ../depth”
nodeset="quantity" type="xsd:integer" required="true()
nodeset="state" required="../country='USA'"
nodeset="verification-code” relevant="../type = 'visa' or ../type = 'mastercard’”
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Data Editing with Forms Controls
They bind a user interface “widget” with an instance data model element or attribute
they “control” user inputs
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XForms forms controls
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<model id="order-model"
xmlns="http://www.w3.org/2002/xforms" >
<instance>
<doughnuts xmlns="">
<quantity>20</quantity>
</doughnuts>
</instance>
</model>
XPath expression
<xf:input ref="quantity">
<xf:label>Quantity</xf:label>
</xf:input>

Several Kinds Of Forms Controls
To control the edition of instance data
input: a basic text field
textarea: a multiline text field
secret: passwords and the like
upload: upload a file or data stream
range: choose from a range of values
selection among a list of items
select: choose any number of items from a list
select1: choose one item from a list
To present data (non editable)
output: display non-editable value
To generate events which can be used to trigger actions
submit: send the form data as specified in the model's submission
trigger: forge an event
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Some Possible Forms Controls Representation
Would you recognize the forms controls ?
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Forms Control Look and Feel
Some attributes control the appearance of forms control
id, class, style: styling with CSS
appearance : choose between “full”, “compact” or “minimal” display
this augments the number of forms widgets available with the same vocabulary
incremental update behaviour
with the incremental attribute
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select1 appearance =“minimal”
appearance =“compact”
appearance =“full”
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Forms Control Edited Content
Some attributes control the content of forms control
ref: bind the content of the control with one instance data in the model
nodeset: bind an itemset in a selection control with a list of instance data in the model
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<instance id="order">
<Order xmlns="">
<Grape>Chardonnay</Grape>
</Order>
</instance>
<instance id="grapes">
<Grape xmlns="">
<Name>Cabernet Franc</Name>
<Name>Carignan</Name>
<Name>Cinsault</Name>
… etc … <Name>Ugni Blanc</Name>
<Name>Viognier</Name>
</Grape>
</instance>
<xf:select1 ref="instance('order')/Grape" appearance=”compact">
<xf:label>Grape type: </xf:label>
<xf:itemset nodeset="instance('grapes')/Name">
<xf:label ref="."/>
<xf:value ref="."/>
</xf:itemset>
</xf:select1>

Forms Control Feedback
Forms Controls allow 4 child elements to give feedback to the user
<xforms:label>: mandatory label
<xforms:alert>: error message to show in case of validation error
<xforms:hint>: hint to show when users mouse over the control
<xforms:help>: help dialog displayed on demand
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alert
hint
help

User Interface Generation With Repetitions
<xforms:repeat> allows to “iterate” over a collection of instance data and to generate repetitive user interface elements
the attribute nodeset points to the collection with an XPath
the enclosed block (XForms and Host language constructs) is repeated
this is an easy way to generate tables rows, lists, etc.
Each <xforms:repeat> defines an implicit index
users can manually change the selected index
the user interface highlights the item at the index
it can be used in XPath expressions with index(‘repeat-id’) function
the index is used with insert / delete actions (see infra)
<xforms:repeat> can be nested
inner nodeset expressions are interpreted relatively to the nodeset of the parent’s repetition
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XForms repetition
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User Interface Generation Basic Example
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XForms repetition
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<model xmlns="http://www.w3.org/2002/xforms”>
<instance id="grapes">
<Grape xmlns="">
<Name>Cabernet Franc</Name>
<Name>Cabernet Sauvignon</Name>
<Name>Carignan</Name>
… etc …
<Name>Semillon Blanc</Name>
<Name>Ugni Blanc</Name>
<Name>Viognier</Name>
</Grape>
</instance>
</model>
<table>
<tr><th>Grapes</th></tr>
<xf:repeat nodeset="instance('grapes')/Name">
<tr><td><xf:output ref="."/></td></tr>
</xf:repeat>
</table>

Actions and Events
Programming side effects with no scripting language
Actions can be invoked in response to events
events declarations follow the XML Events recommendation
event defined by an event, an observer, a target and a handler
in XForms the handler is an Action
Actions can be used in isolation
with an ev:event attribute to subscribe to an event whose observer/target is the parent of the action
with an ev:observer attribute to subscrive to an event whose observer is different than the parent of the action
e.g. <xforms:toggle ev:event=“DOMActivate” case=“noshow”/>
Actions can be grouped into sequences in a <xforms:action>
equivalent to a declarative script
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XForms user interaction
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Different Kinds of Actions
There are actions to
set focus to a form control
display a message to the user
navigate to a new URI (in the same or a new window)
change the value of an instance data node
<xforms:setvalue ref=“XPath expr.” value=“XPath expr.”/>
variant with copy instead of value
variant with inline content
force a recalculation, revalidation, or screen refresh
submit or reset all or a portion of the instance data
perform other actions to deal with scrolling and manipulating repeating line item tables
insert or delete instance data nodes (see next slide)
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Data Mutation with Actions and Events (insertion)
<xforms:insert> action
inserts an item inside a nodeset at the index specified by an at XPath expression and in position “before” or “after”
e.g. <xf:insert nodeset="instance('grapes')/Name" at="1" position="before"/>
by default duplicates the last node of the set
This allows to interactively edit repeated data when used in conjunction with a <xforms:repeat>
The common pattern is to observe a <xforms:trigger>
e.g.
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<xf:trigger>
<xf:label>Add grape at 1</xf:label>
<xf:actionev:event="DOMActivate">
<xf:insert nodeset="instance('grapes')/Name" at="1" position="before"/>
<xf:setvalue ref="instance('grapes')/Name[1]" value="instance('admin')/Name"/>
</xf:action>
</xf:trigger>

Data Mutation with Actions and Events (Deletion)
<xforms:delete> action
deletes an item inside a nodeset at the index specified by an at XPath expression
e.g. <xf:insert nodeset="instance(’diary')/Person" at="index(‘my-repeat’)"/>
This allows to interactively edit repeated data when used in conjunction with a <xforms:repeat>
The common pattern is to observe a <xforms:trigger>
e.g. delete an item in a repetition
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<xf:repeat nodeset="instance('grapes')/Name" id="grape-repetition">
<tr><td>
<xf:output ref="." class="editable"/>
<xf:trigger appearance="minimal" class="edit-button">
<xf:label><img src="../apps/coursmd/cancel.png" alt="Delete" /></xf:label>
<xf:delete ev:event="DOMActivate" nodeset="." at="1"/>
</xf:trigger>
<tr><td>
</x:repeat>

Dynamical User Interface with <xforms:switch>
<xforms:swith> introduces several alternatives in the rendering of a page
each <xforms:case> child of a switch is an alternative
identified with an id attribute
the <xforms:toggle> action can be used anywhere to react to an event and to select which alternative is currently visible in a switch with a case attribute
e.g. <toggle case="products" ev:event="DOMActivate"/>
Applications
show / hide details on demand
the first case contains a Show button
the second case contains a Hide button and the details
tabbed browsing (each panel is a case in a switch)
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Grouping with <xforms:group>
<xforms:group> sets the context to a current node in the data model with a ref attribute
all relative XPath expressions in descendants forms controls are relative to the <xforms:group> context
e.g.
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<group ref=”instance(‘order’)/client/address">
<label>Shipping Address</label>
<input ref="line_1">
<label>Address line 1</label>
</input>
<input ref="line_2">
<label>Address line 2</label>
</input>
<input ref="postcode">
<label>Postcode</label>
</input>
</group>
<instance id=”order”>
<order xmlns="">
<client>
<name/>
<address>
<line_1/>
<line_2>
<postcode/>
</client>
<cart>
…
</cart>
</customers>
</instance>

Model Based Switching with <xforms:group>
an <xforms:group> can be dynamically hidden
by using a relevant model item property on its bound node
this also applies to any other forms control
the node bound to an <xforms:group> can be changed dynamically
by using a conditional XPath expression
this will change the content of the full group each time the conditional XPath expression is reevaluated
e.g.
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<instance id="members">
<Members xmlns="">
<Person><id>1</id><Name>Eva</Name><Age>20</Age></Person> …
<instance id=”admin">
<Admin xmlns="">
<Selection>2</Selection>…
<xf:group ref="instance('members')/Person[child::id = instance(’admin')/Selection]">
<xf:output ref="Name"/> is <xf:output ref="Age"/> years old
</xf:group>

Submitting Data with an <xforms:submission>
The purpose of XForms is to submit data to a server !
Submissions also work to upload data from a server
XForms is Ajax ready
you can define multiple submissions to load / save different parts of the data model within the same forms document
one or more <xforms:submission> elements are declared in the model in the head
action attribute defines the destination URI (deprecated for a resource attribute in XForms 1.1 which can be dynamical)
method attribute defines the protocol (get, post, etc.)
ref attribute defines which instance / node(s) to submit
replace attribute defines what to do with the result
instance attribute defines which instance to replace
many more attributes…
don’t forget the id attribute to control when to submit
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XForms submission
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Submission Example
Sends the content of instance(‘order’) to the /order URL using the POST method
<xforms:submission id="save-submission" ref="instance(’order')" method=”post" replace="none" action="/order" />
“post” data is serialized as an XML document with a content type “application/xml” within the HTTP request body
“get” data is URL encoded and appended to the URI using the separator defined in an optional separator attribute (default to &)
NB: absolute paths in action are relative to the servlet context
Retrieves the list of countries at countries.xml and replaces the content of the instance ‘countries’
<xforms:submission id=”get-countries” method="get” instance=“countries” action=“countries.xml" serialize=“false”/>
serialize attribute is set to none to avoid submitting data
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XForms submission
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Controlling Submissions
<xforms:submit> forms controls trigger the submissions in the body of the document
e.g. basic Search button
<xforms:send> actions can be used to react to events by triggering a submission
e.g. same as above with a send action
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XForms submission
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<xforms:submit submission=”search-submission">
<xforms:label>Search</xforms:label>
</xforms:submit>
<xforms:trigger>
<xforms:label>Search</xforms:label>
<xforms:action ev:event="DOMActivate">
<xforms:send submission="save-submission" />
</xforms:action>
</xforms:submit>

Submissions and XML databases
XML databases (such as Exist) have REST APIs
CRUD functionalities exposed through HTTP methods
create (PUT)
read (GET)
update (POST)
delete (DELETE)
<xforms:submission> can direcly talk with the Exist database
by using a URI is of the form (Exist database)
/exist/rest/db/orbeon/{database}/{collection}/{resource}…
try http://localhost:8080/orbeon/exist/rest/db/orbeon/in your browser
XML database can also store XQuery scripts which are executed when accessed through REST APIs
This allows to develop XRX applications
XForms + REST + XQuery
no middleware (direct client-to-database applications, except for Orbeon Forms server)
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XRX framework
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How to Test XForms with Orbeon Forms
With the XForms sandbox provided with Orbeon Forms
On the public Orbeon Forms demonstration server
http://www.orbeon.com/ops/xforms-sandbox/
On your own local installation of Orbeon Forms under Tomcat
http://localhost:8080/orbeon/xforms-sandbox/
Make your own Orbeon Forms application
Write an XHTML file (my-forms.xhtml)
Place this file into your Orbeon Forms deployed server
under WEB-INF/resources/my-forms.xhtml
add a page flow entry into WEB-INF/resources/page-flow.xml that uses this file as its view
<page path-info="/hello" view="my-forms.xhtml"/>
open it with your browser (do not forget to start Tomcat)
http://localhost:8080/orbeon/hello
change config/epilogue-servet.xpl to use theme-plain.xsl transformation for your page if you do not want Orbeon menus (this is more tricky)
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Orbeon Forms
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Debugging XForms with Orbeon Forms
Activate the data instance inspector widget
add this line at the end of your XHTML XForms file to debug :
<span class="inspector-widget-class”>
<widget:xforms-instance-inspector xmlns:widget="http://orbeon.org/oxf/xml/widget"/>
</span>
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Orbeon Forms
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Summary of XForms in XHTML documents
In the <head> section
declare the model(s)
declare the instance(s) and their initial values
empty / inline / from file
declare submission(s) that allow to save / reload the instance
bind the instance data model to item properties
data types, constraints, etc.
In the <body>
bind controls to the instances
declare repetitive parts of the user interface
hard wire actions to events
repetitive parts insertion and deletion
user interface visual state change
submissions
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Summary
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Summary of main XPath use in XForms
Bind a model item property to one or more instance nodes
nodeset attribute
Compute dynamical expressions for model item properties
readonly, required, relevant, calculate, constraint attributes
Bind a form control to instance data
ref attribute (single node binding)
nodeset attribute (node set binding)
Specify the node or node set for operation by some action
e.g. at attribute (in node insertion or removal)
e.g. value attribute (in setvalue)
Make some calculation in some actions
e.g. index attribute (in <xforms:setindex> for a repetition)
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Summary
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Summary Of XForms Companion Recommendations
XPath + Namespaces in XML
used everywhere
XML Schemas
to define your own data types including with patterns (RegExp)
support is optional in an XForms user agent
XForms has equivalent facilities to define data types
XML Events
in XForms <script> handlers are replaced with <action> handlers
CSS
Forms Controls can be styled
with Orbeon Forms you can use the class attribute of forms controls and then declare their style
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Summary
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Useful Namespaces to Remember
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Summary
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XForms References
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References
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Orbeon Forms References
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References
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