XML Schema - Lecture Slides | Distributed Software Development | CS 682, Study notes of Software Engineering

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Distributed Software Development

XML Schema

Chris Brooks

Department of Computer ScienceUniversity of San Francisco

Department of Computer Science — University of San Francisco – p. 1/

Modifying XML programmatically • Last week we saw how to use the DOM parser to read an XMLdocument. • The DOM parser can also be used to create and modify nodes.

Department of Computer Science — University of San Francisco – p. 2/

Adding nodes • We then insert nodes by attaching them to existing nodes.^ ◦^

node.appendChild(newNode) ◦ node.insertBefore(newNode, childAfter) ◦ node.replaceChild(newNode, oldNode)

-^ We can also remove nodes:

◦^ node.removeChild(nodename)

Department of Computer Science — University of San Francisco – p. 4/

7-5:

Example def changeRating(artist,

newrating)

cds

=^

doc.getElementsByTagName(’cd’) for item

in cds

a^ = item.getElementsByTagName(’artist’) if^ a[0].firstChild.data.strip()

artist.strip()

r = item.getElementsByTagName(’rating’) r[0].replaceChild(doc.createTextNode(newrating),

r[0].firstChild

return

doc

Department of Computer Science — University of San Francisco – p. 5/

Defining XML documents • Recall that, unlike HTML, an XML author can declare any tagshe or she wants. • If you’re just making your own simple documents, an ad hocapproach can work fine. • If you’re building more complex applications, need toincorporate legacy data, or need to exchange data with others,this may not be suitable. • XML Schema are a way to formally define legal XMLdocuments.

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Data Interchange • A challenge in exchanging data between heterogenoussystems is ensuring that all participants agree on the meaningand representation of the data.^ ◦^

Is author a sub-element of book, or the other way around? ◦ Do all books have to have an ISBN tag, or is it optional?What is the format of a valid ISBN number? ◦ Must price be a float? ◦ Is there an order that elements must occur in?

-^ XML allows users of data to validate this data against a^ schema

.

Department of Computer Science — University of San Francisco – p. 8/

DTDs • A Document Type Definition is information about the legalstructure of an XML document. • A DTD allows you to specify the set of allowable elements (thevocabulary), how they fit together (the grammar), and the legalvalues that can be assigned to them (their semantics).

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7-11:

DTD example