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5. Documents and document models
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5.0 Document model formal expressions
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A UBL document is an XML instance that satisfies constraints chosen by the UBL TC
[[1] - structural and lexical constraints are described by a document model
 [1] - value constraints are described through supplemental declarative files
[[2] - see [Chapter 8.] for overview
][1] - instance constraints are described in the specification
]
A document model is a syntax formalism
[[1] - for machine processing of the constraints of information model components in a physical expression of a sequence of characters
 [1] - two different expressions of the document model based on the form of the documents
[[2] - determined by the kinds of networks across which the documents are transmitted
][1] - compact binary-encoded documents
[[2] - ASN.1 ISO 8825
][1] - marked-up text-based documents
[[2] - W3C Schema XSD
][1] - note that the XML constraints are normative while the ASN.1 constraints are not normative
]
The document model constrains the interchange of information, not the application data model
[[1] - a popular misconception in XML-based system design is to equate the document model with the application data model
 [1] - XML provides independence between the two data models of the applications performing an interchange
 [1] - an application translates information from its data model to and from the interchange model
]
One of two normative components of UBL is the W3C Schema XSD expression of XML document constraints
[[1] - formal expression of document constraints expressed for automated processing
 [1] - two instantiations of the document constraints:
[[2] - one with comments
[[3] - spreadsheet model information copied for reference purposes
][2] - one without comments
[[3] - streamlined file may be processed more quickly by some applications
 [3] - referenced as the "run time versions" of the schemas
]][1] - the other normative component is the definitions in the spreadsheets
[[2] - recall the discussion on [Chapter 3. Information items]
]]
The UBL TC has mandated additional normative instance-oriented constraints that go beyond the formal document model
[[1] - this promotes interoperability and blind interchange of XML documents
 [1] - some of these constraints are difficult or impossible to be checked using XML-based tools
]

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+//ISBN 1-894049::CSL::Presentation::UBL//DOCUMENT Practical Universal Business Language Deployment 2009-02-12 13:50UTC//EN
Practical Universal Business Language Deployment
Third Edition - 2009-02-12
ISBN 978-1-894049-23-8
Copyright © Crane Softwrights Ltd.