I am trying to apply pattern for an element in xsd.
Element is of type XHTML.
I want to apply pattern like this.
<a attributes="some set of attributes"><img attributes="some set of attribtes"/></a>
Rules:
<a> tag with attributes followed by <img> with attributes.
Sample Valid Data:
<a xlink:href="some link" title="Image" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/1999/xhtml">
<img alt="No Image" title="No Image" xlink:href="soem path for image" xlink:title="Image" xmlns="http://www.w3.org/1999/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" />
</a>
Invalid:
<a>data<img/></a>--Data Present, no attributes
<a><img>abcd</img></a>--data Present, No attributes
<a><img/></a>---No attributes
Can any one suggest how to write pattern for this.
<xsd:restriction base="xs:string">
<xs:pattern value="Need help"/>
</xsd:restriction>
Thank you.
The XSD pattern facet is used to constrain the 'lexical space' of a simple type (that is, the set of literal strings that denote instances of the type) using regular expressions. It won't help you to require that certain elements must have attributes.
If you want specific attributes to be present (e.g. title and xlink:href on the a element, title and alt on the img element), the simplest way to do so in a schema is by declaring those attributes as required. The schema for XHTML 1.0 strict, for example (at http://www.w3.org/TR/xhtml1-schema/#xhtml1-strict) declares both src and alt as being required on img:
<xs:element name="img">
<xs:complexType>
<xs:attributeGroup ref="attrs"/>
<xs:attribute name="src" use="required" type="URI"/>
<xs:attribute name="alt" use="required" type="Text"/>
...
</xs:complexType>
</xs:element>
If what you want is just to require that some attributes be used, but you don't care which, XSD doesn't make the task easy: in XSD 1.0 there is no convenient way to say "I don't care which attribute appears, but there has to be one". You can enforce such a constraint (even if some observers like me find it a bit odd) by using assertions in XSD 1.1, or by using a Schematron schema in addition to your XSD schema.
Related
Given a schema that defines an element of a certain type, is it possible to allow that type to be extended, but still have that extension element be strongly typed? In other words, add some kind of extension point that can be used from an external schema to add elements that can only be used in this location?
Let's say the schema looks kinda like:
<xs:schema …>
<xs:element name="Match" type="tns:TNodeConstraint" />
<xs:complexType name="TNodeConstraint">
<xs:group ref="tns:Expression" />
</xs:complexType>
<xs:group name="Expression">
<xs:choice>
<xs:element name="And">
<xs:complexType … />
</xs:element>
<xs:element name="Or">
<xs:complexType … />
</xs:element>
<xs:element name="IsAbstract">
<xs:element name="IsExtern">
<!-- Some kind of extension point? -->
</xs:choice>
</xs:group>
</xs>
Is it possible to extend the Expression group so that a second, external schema could say that I can accept IsMyCustomConstraint here, but not IsMyCustomSortOrder? So this will be valid:
<Match>
<IsAbstract />
<IsExtern />
<IsMyCustomConstraint />
</Match>
But this would be invalid?
<Match>
<IsAbstract />
<IsExtern />
<IsMyCustomSortOrder />
</Match>
I don't want to use xs:any as that would allow putting a "sort order" where a constraint can go.
I can modify the original schema
I'm in control of what the namespaces of IsMyCustomConstraint and IsMyCustomSortOrder would be, and it's not important if they match the original schema or not.
is it possible to allow that type to be extended, but still have that extension element be strongly typed?
Definitely - this is described in detail, with examples, here: https://www.w3.org/TR/2000/WD-xmlschema-0-20000225/#DerivExt. As far as I can tell, you just need to declare one or more complex types that are extensions of your base type 'TNodeConstraint'.
XML schema has a rich set of facilities to support type inheritance including:
abstract base types (base type must be extended or restricted before use)
extension (new type allows more values than the base type)
restriction (new type allows fewer values than the base type)
control of whether further extensions/restrictions are allowed (final/block attributes)
I don't see any need to use a separate XSD for the extensions, although you can if you want to. You may find it useful to know about xsi:type, abstract types and the block/final attributes - all are described the XML Schema Part 0 - Primer mentioned above.
I am a new comer to JaxB World and I am facing one problem w.r.t. unmarshalling of the stored xml content into java class object. Problem description is as follows. Let me know if this is solvable
I have my xsd file which contains following content(this is just a example)
Student info
<xs:complexType name="specialization" abstract="true">
</xs:complexType>
<xs:complexType name="Engineering">
<xs:complexContent>
<xs:extension base="specialization">
<xs:sequence>
<xs:element name="percentage" type="xs:int" minOccurs="0"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="Medical">
<xs:complexContent>
<xs:extension base="specialization">
<xs:sequence>
<xs:element name="grade" type="xs:string" minOccurs="0"/>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
Now all the corresponding java classes are generated by compiling the xsd. Now lets assume in my application i will set the specialization attribute of Student info by constructing Engineering class instance. So after all the operation when i save
the xml file that get saved will have the entry like below
<Student>
<Name>Name1</Name>
<Specialization>
<percentage>78<percentage>
</Specialization>
</Student>
Now when the above content goes for unmarshalling, unmarshalling fails saying unexpected element . I guess this is b'cos Specialization element is of type specialization it calls unmarshalling on itself rather than derived object which is stored.
I hope my explanation is clear. Is there any way that we can unmarshall based on derived class instanse type. The xsd and bindings.xjb file is completely in my control so i can add or modify any entries/info which conveys to unmarshalling rules to unmarshall on derived class.
Thanks for your Suggestion but the it still not working for me.
Here is what I tried
Option #1 - xsi:type
My xsd looks same as what is explained in the example but still the Xsi:type doesn't come in the resulted xml. Do i need to add any other setting while compiling? Which JaxB version should i use for this?
Option#2 - Substitution Groups
When i added the substitution entry part in my xsd, XSD compilation failed saying duplicate names "Engineering" and "Medical". I guess element name and type Name being same compilation cribs(All engineering, Medical,specialization being same both in type definition and element Name)
I can't modify the generated classes as we are using Model driven Architecture. Only thing that is in hand is xsd. Any modification to the xsd is allowed. Ideally First option should have worked. But can't figure out why it is not working. Let me know if you have some suggestion to narrow down the problem.
There are different ways of representing Java inheritance in XML when using JAXB:
Option #1 - xsi:type
In this representation an attribute is used to indicate the subtype being used to populate this element.
<Student>
<Name>Name1</Name>
<Specialization xsi:type="Engineering">
<percentage>78<percentage>
</Specialization>
</Student>
For a detailed example see:
http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-xsitype.htmlhtml
Option #2 - Substitution Groups
Here an element name is used to indicate the subtype. This corresponds to the schema concept of substitution groups and leverages JAXB's #XmlElementRef annotation:
<Student>
<Name>Name1</Name>
<Engineering>
<percentage>78<percentage>
</Engineering>
</Student>
For a detailed example see:
http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-substitution.html
I need to specify a XSD for validating XML documents. The XSD will be used for a JAXB generation of Java bindings.
My problem is specifying optional elements which I do not know the names of and which I in general am not interested in parsing.
The structure of the XML documents is like:
<TRADE>
<TIME>12:12</TIME>
<MJELLO>12345</MJELLO>
<OPTIONAL>12:12</OPTIONAL>
<DATE>25-10-2011</DATE>
<HELLO>hello should be ignored</HELLO>
</TRADE>
The important thing is, that:
I can not assume any order, and the next XML document instance migtht have tags in a different order
I am only interested in parsing some of the tags, some are mandatory and some are optional
The XML documents can be extended with new elements which I am not interested in parsing
The structure of my XSD is like (not a valid xsd):
<?xml version="1.0" encoding="ISO-8859-1"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<!-- *********************************************** -->
<!-- Trade element definitions for the XML Documents -->
<!-- *********************************************** -->
<xs:complexType name="Trade">
<!-- Using the all construction ensures that the order does not matter -->
<xs:all>
<xs:element name="DATE" type="xs:string" minOccurs="1" maxOccurs="1" />
<xs:element name="TIME" type="xs:string" minOccurs="1" maxOccurs="1" />
<xs:element name="OPTIONAL" type="xs:string" minOccurs="0" maxOccurs="1" />
<xs:any minOccurs="0"/>
</xs:all>
</xs:complexType>
<!-- TRADE is the mandatory top-level tag -->
<xs:element name="TRADE" type="Trade"/>
</xs:schema>
So, in this example: DATE and TIME are mandatory (they must be in the XML exactly once), OPTIONAL might be present once and then I would like to specify, that all other tags are allowed. The order does not matter.
How do I specify a valid XSD for this?
This is a classic parser problem.
Basically, your BNF is:
Trade = whatever whatever*
whatever = "DATE" | "TIME" | anything
anything = a-z a-z*
But this is ambigous. The string "DATE" can both be accepted under the whatever rule as "DATE" and as anything.
So if you have
<TRADE>
<TIME>12:12</TIME>
<DATE>25-10-2011</DATE>
<DATE>25-12-2011</DATE>
</TRADE>
it is unclear whether that should be accepted or not.
It could be interpreted either one of
"TIME", "DATE", anything
anything, anything, "DATE"
anything, anything, anything
"TIME", "DATE", anything
"TIME", "DATE", "DATE"
etc.
It all boils down to: If you have a wildcard combined with random sequence, you cannot meaningfully decide which token matches which rule.
It especially does not make sense to have optional elements together with a wilcard.
You have two options:
use xs:sequence instead of xs:all
do not use wildcard
As I understand it, both options are in conflict with your wishes.
Perhaps you can construct a wildcard that matches everything except DATE, TIME etc.
Is it a hard requirement to have JAXB bindings to your "known" elements?
If not, you can basically have just <any maxoccurs="unbounded" processContents="skip"/> as your xsd, and then pick out the elements you are interested in from the DOM tree.
(See here how to use JAXB without data binding.)
I have been working on learning XML Schema for the past few years now, off and on. I have a pretty good handle on the basics but one thing still eludes me:
I want to be able to create an XML document similar to the following:
<itemList xmlns="http://mydomain.com/namespaceA">
<item>
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:nsB="http://mydomain.com/namespaceB">
<body>
<p>Any HTML code here but I want to be able to mark up
<nsB:myBTag><strong>some</strong> of the text</nsB:myBTag>
with tags from namespaceB even if those tags are nested within
standard HTML tags and even if there are then more HTML tags
nested within my namespaceB tags.</p>
</body>
</html>
</item>
</itemList>
Note that inside the <html> element the xhtml namespace is the default namespace. This is because I want document authors to be able to use a standard HTML editor and then simply insert the special namespaceB tags where they need them. There will be far more XHTML tags than namespaceB tags in any one instance document.
So, from what I have tentatively learned so far, I think my two schemas will need to look something like this:
namespaceA
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:nsA="http://mydomain.com/namespaceA"
targetNamespace="http://mydomain.com/namespaceA">
<xs:element name="itemList">
<xs:complexType>
<xs:sequence>
<xs:element name="item" maxOccurs="unbounded" minOccurs="1">
<xs:complexType>
<xs:any namespace="http://www.w3.org/1999/xhtml"
minOccurs="1" maxOccurs="1"
processContents="strict">
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
(I think the only namespace I need to declare for the content model within the <item> tag is the XHTML namespace because then the <html> tag in the instance document declares the namespaceB namespace, but I am in no way positive.)
namespaceB
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:nsB="http://mydomain.com/namespaceB"
targetNamespace="http://mydomain.com/namespaceB">
<xs:element name="myBTag">
<!-- I am clueless here -->
<!-- I have no idea how to make sure that additional HTML tags
can go in here without screwing everything up -->
</xs:element>
</xs:schema>
The big question is: Do I need to do anything to make sure that XHTML and namespaceB tags can be freely intermixed or is that just part and partial of the operation of the <xs:any> tag?
Naturally, my schemas and documents will be far more complicated than this. I have simplified them down for easy discussion. Thanks in advance for any help you can provide. If I can get over this one hurdle I can create a really powerful system for educational content that will help educate the whole world for free.
According to the XS spec, the <xs:any> element can have a namespace attribute which can have the value ##any - this means that the corresponding element in the document can have any namespace.
The namespace attribute being absent has the same effect - so you can just omit it. i.e. the answer to the "big question" is:
Do I need to do anything to make sure that XHTML and namespaceB tags can be freely intermixed? No, you don't
Or is that just part and partial of the operation of the tag? Yes, it is
Disclaimer: I haven't tested this, only read the spec above. If I were you, I'd try validating some example XML documents with your simplified XSDs above, using a popular XSD validator, to determine under what conditions it validates.
I'm new to XSD, and I'm quite confused as to when to use attribute, and when to use element?
Why cant we specify minOccurs and maxOccurs in attribute?
Also, why is it we cannot specify use="required" in element?
An element is an XML element - a opening tag, some content, a closing tag - they are the building blocks of your XML document:
<test>someValue</test>
Here, "test" would be an element.
Attributes is an additional info on a tag - it's an "add-on" or an extra info on an element, but can never exist alone:
<test id="5">somevalue</test>
"id" is an attribute.
You cannot have multiple attributes of the same name on a single tag --> minOccurs/maxOccurs makes no sense. You can define required (or not) for an attribute - anything else doesn't make sense.
The elements are defined by their occurrence inside complex types - e.g. if you have a complex type with a <xs:sequence> inside - you are defining that all elements must be present and must the in this particular order:
<xs:complexType name="SomeType">
<xs:sequence>
<xs:element name="Element1" type="xs:string" />
<xs:element name="Element2" type="xs:string" />
</xs:sequence>
</xs:complexType>
Inside an element of that type, the sub-elements "Element1" and "Element2" are required and must appear in this order - there's no need for "required" or not (like with attributes). Whether or not an element is required is defined by the use of minOccurs and maxOccurs; both are =1 by default, e.g. the element must occur, and can only occur once. By tweaking those settings, you can define an element to be optional (minOccurs=0), or allow it to show up several times (maxOccurs > 1).
I'd strongly recommend you check out the W3Schools Tutorial on XML Schema and learn some more about XML schema.
Marc
Example: XSD Format
<xs:complexType name="contactInformation">
<xs:all>
<xs:element name="firstName" type="xs:string" minOccurs="0"/>
<xs:element name="workCountryId" type="xs:long" minOccurs="0"/>
</xs:all>
<xs:attribute name="id" type="xs:long"/>
</xs:complexType>
XML Format
<contactInformation id=100>
<firstname>VELU</firstname>
<workCountryId>120</workCountryId>
</contactInformation>
attribute is optional by default. To specify that the attribute is required, use the use attribute:
e.g. <xs:attribute name="id" type="xs:long" use="required"/>
More about attributes and elements.
A complexType element is an XML element that contains other elements and/or attributes.
The all element specifies that the child elements can appear in any order and that each child element can occur zero or one time.
maxOccurs Optional. Specifies the maximum number of times the element can occur. The value must be 1.
minOccurs Optional. Specifies the minimum number of times the element can occur. The value can be 0 or 1. Default value is 1
An element is an XML node - and it can contain other nodes, or attributes. It can be a simple type or a complex type. It is an XML entity.
An attribute is a descriptor. It can't contain anything and can only be a simple type.
Have a look at this. Of course, you can just google something like "XML element vs attribute"
<element myAttribute="value">
<subElement />
<subElement anotherAttribute="this is an attribute's value">Element value</subElement>
</element>
You can't have more than one attribute with the same name in XML, therefore you can't use minOccurs and maxOccurs for attributes.
You don't need use="required" for elements because you can have minOccurs="1" instead.
It is your choice when to use attributes and when to use elements. Here are some guidelines: http://www.ibm.com/developerworks/xml/library/x-eleatt.html