Extensible Markup Language

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Extensible Markup Language
XML
XML
2
General Advantages of XML for KR
XML offers new general possibilities, from
which AI knowledge representation (KR) can profit
(1) Definition of self-describing data in
worldwide standardized, non-proprietary
format (2) Structured data and knowledge
exchange for enterprises in various
industries (3) Integration of information from
different sources (into uniform documents)
XML
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Specific Advantages of XML for KR
XML provides the most suitable infrastructure for
knowledge bases on the Web (incl. for W3C
languages such as RDF) Additional special KR
uses of XML are

• Uniform storage of knowledge bases
• Interchange of knowledge bases between different
  AI languages
• Exchange between knowledge bases and databases,
  application systems, etc.

XML
Even transformation/compilation of AI source
programs using XML markup and annotations is
possible
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Address Example External to HTML
External Presentation
Xaver M. Linde Wikingerufer 7 10555 Berlin
HTML tags are still presentation-oriented
XML
HTML Markup
ltemgtXaver M. Lindelt/emgt ltbrgt Wikingerufer
7 ltbrgt ltstronggt10555 Berlinlt/stronggt
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Address Example HTML to XML
HTML Markup
While not conveying any formal semantics
ltemgtXaver M. Lindelt/emgt ltbrgt Wikingerufer
7 ltbrgt ltstronggt10555 Berlinlt/stronggt
XML tags are chosen for content-structuring needs
XML
XML Markup
ltaddressgt ltnamegtXaver M. Lindelt/namegt
ltstreetgtWikingerufer 7lt/streetgt lttowngt10555
Berlinlt/towngt lt/addressgt
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Address Example XML to External
XML Markup
ltaddressgt ltnamegtXaver M. Lindelt/namegt
ltstreetgtWikingerufer 7lt/streetgt lttowngt10555
Berlinlt/towngt lt/addressgt
XML
XML stylesheets are, e.g., usable to
generate different presentations
External Presentations
Xaver M. Linde Wikingerufer 7 10555 Berlin
Xaver M. Linde Wikingerufer 7 10555 Berlin
. . .
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Address Example XML to XML
XML Markup 1
ltaddressgt ltnamegtXaver M. Lindelt/namegt
ltstreetgtWikingerufer 7lt/streetgt lttowngt10555
Berlinlt/towngt lt/addressgt
XML stylesheets are also usable to transform XML
representations
XML
XML Markup 2
ltaddressgt ltnamegtXaver M. Lindelt/namegt
ltplacegt ltstreetgtWikingerufer 7lt/streetgt
lttowngt10555 Berlinlt/towngt
lt/placegt lt/addressgt
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Address Example Some Stylesheets Will Contain
Term-(Tree-)Rewriting Rules
address
name
street
town
T
S
N
XML
address
name
place
street
town
N
T
S
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Address Example XML Queries
XML Markup
subelements
element
ltaddressgt ltnamegtXaver M. Lindelt/namegt
ltstreetgtWikingerufer 7lt/streetgt lttowngt10555
Berlinlt/towngt lt/addressgt
s
XML Query (XML-QL)
WHERE ltaddressgt ltnamegtXaver M.
Lindelt/namegt ltstreetgtslt/streetgt
lttowngttlt/towngt lt/addressgt CONSTRUCT
ltbindinggt ltsgtslt/sgt lttgttlt/tgt
lt/bindinggt
XML
XML queries can select subelements of XML elements
ltbindinggt ltsgtWikingerufer 7lt/sgt
lttgt10555 Berlinlt/tgt lt/bindinggt
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Address Example Prolog Queries
Prolog Term
substructures
address( name("Xaver M. Linde"),
street("Wikingerufer 7"), town("10555
Berlin") )
s
structure
XML
Prolog Query
Prolog queries can select substructures of Prolog
structures
address( name("Xaver M. Linde"),
street(S), town(T) )
S "Wikingerufer 7" T "10555 Berlin"
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Address Example The Element Tree
XML
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Address ExampleDocument Type Definition and
Tree (1)
Document Type Definition (DTD)
Extended Backus-Naur Form (EBNF)
lt!ELEMENT address (name, street, town)
gt lt!ELEMENT name (PCDATA) gt lt!ELEMENT
street (PCDATA) gt lt!ELEMENT town (PCDATA) gt
address name street town name
PCDATA street PCDATA town PCDATA
XML
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Address ExampleDocument Type Definition and
Tree (2)
Document Type Definition (DTD)
lt!ELEMENT address (name, place) gt lt!ELEMENT place
(street, town) gt lt!ELEMENT name (PCDATA)
gt lt!ELEMENT street (PCDATA) gt lt!ELEMENT
town (PCDATA) gt
Document Type Tree
XML
address
name
place
street
town
PCDATA
PCDATA
PCDATA
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Well-Formedness and Validity
XML principles for a document being
well-formed
XML principle for a document
being valid with respect to (w.r.t.) a DTD

• Open and close all tags
• Empty tags end with /gt
• There is a unique root element
• Elements may not overlap
• Attribute values are quoted
• lt and are only used to start tags and entities
• Only the five predefined entity references are
  used

• Match the constraints listed in the DTD (or,
  generate from DTD as linearized derivation tree,
  as shown later)

XML
Checked by validators such as http//www.stg.brown
.edu/service/xmlvalid/
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Mail-Box Example Address Variant
XML
Node-Labeled, (Left-to-Right-)Ordered Element
Tree
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""-Disjoined Street/Mail-Box ExampleDocument
Type Definition and Tree
Document Type Definition (DTD)
lt!ELEMENT address (name, (street box), town)
gt lt!ELEMENT name (PCDATA) gt lt!ELEMENT
street (PCDATA) gt lt!ELEMENT box (PCDATA)
gt lt!ELEMENT town (PCDATA) gt
"" Choice The above box address and the
original street address are valid w.r.t. this
""-DTD
XML
Document Type Tree
address
name
street
town
box
PCDATA
PCDATA
PCDATA
PCDATA
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Phone Fax Example Address Variant
Prolog Term
address( name("Xaver M. Linde"),
street("Wikingerufer 7"), town("10555
Berlin"), phone("030/1234567"),
phone("030/1234568"), fax("030/1234569") )
XML
Node-Labeled, (Left-to-Right-)Ordered Element
Tree
address
town
name
fax
phone
phone
street
Xaver M. Linde
Wikingerufer 7
10555 Berlin
030/1234567
030/1234569
030/1234568
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""/""-Repetitive-Phone -Fax ExampleDocument
Type Definition and Tree
Document Type Definition (DTD)
lt!ELEMENT address (name, street, town, phone,
fax) gt lt!ELEMENT name (PCDATA) gt lt!ELEMENT
street (PCDATA) gt lt!ELEMENT town (PCDATA)
gt lt!ELEMENT phone (PCDATA) gt lt!ELEMENT
fax (PCDATA) gt
""/"" One/Zero or More The above
two-phone/one-fax address is valid w.r.t. this
""/""-DTD but the original no-phone/no-fax
address is not (?1 phone!)
XML
Document Type Tree
address
name
street
phone
fax
town
PCDATA
PCDATA
PCDATA
PCDATA
PCDATA
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Country Example Address Variant
Prolog Term
address( name("Xaver M. Linde"),
street("Wikingerufer 7"), town("10555
Berlin"), country("Germany") )
XML
Node-Labeled, (Left-to-Right-)Ordered Element
Tree
address
name
street
town
country
Xaver M. Linde
Wikingerufer 7
10555 Berlin
Germany
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"?"-Optional-Country ExampleDocument Type
Definition and Tree
Document Type Definition (DTD)
lt!ELEMENT address (name, street, town, country?)
gt lt!ELEMENT name (PCDATA) gt lt!ELEMENT
street (PCDATA) gt lt!ELEMENT town (PCDATA)
gt lt!ELEMENT country (PCDATA) gt
"?" One or Zero The above country address and
the original countriless address are valid
w.r.t. this "?"-DTD
XML
Document Type Tree
address
country
name
street
town
PCDATA
PCDATA
PCDATA
PCDATA
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Country Address A Complete XML Document
Referring to an External DTD
XML Document (just ASCII, e.g. stored in a file)
lt?xml version"1.0" standalone"no"?gt lt!DOCTYPE
address SYSTEM "country-address.dtd"gt ltaddressgt
ltnamegtXaver M. Lindelt/namegt
ltstreetgtWikingerufer 7lt/streetgt lttowngt10555
Berlinlt/towngt ltcountrygtGermanylt/countrygt lt/addr
essgt
XML
The XML declaration uses standalone attribute
with "no" value DTD import The DOCument TYPE
declaration names the root element address and,
after the SYSTEM keyword, refers to an external
DTD "country-address.dtd" (or, at some
absolute URL, to an "http//www.test.org/country-a
ddress.dtd")
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"minOccurs"-Optional-Country ExampleXML Schema
Definition
Equivalent XML Schema Definition (XSD)
lt?xml version"1.0"?gt ltxsdschema
xmlnsxsd"http//www.w3.org/2001/XMLSchema"gt
ltxsdelement name"address"gt
ltxsdcomplexTypegt ltxsdsequencegt
ltxsdelement name"name" type"xsdstring"/gt
ltxsdelement name"street" type"xsdstring"/gt
ltxsdelement name"town"
type"xsdstring"/gt ltxsdelement
name"country" type"xsdstring" minOccurs"0"/gt
lt/xsdsequencegt lt/xsdcomplexTypegt
lt/xsdelementgt lt/xsdschemagt
XML
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"minOccurs"-Optional-Country ExampleXML Schema
Tree
Equivalent Document Schema Tree
XML
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Country Address A Complete XML Document
Referring to an External XSD
Equivalent XML Document (just ASCII, e.g. stored
in a file)
lt?xml version"1.0"?gt ltaddress
xsinoNamespaceSchemaLocation"country-address.xsd
" xmlnsxsi"http//www.w3.org/2001/XMLSchema
-instance" gt ltnamegtXaver M. Lindelt/namegt
ltstreetgtWikingerufer 7lt/streetgt lttowngt10555
Berlinlt/towngt ltcountrygtGermanylt/countrygt lt/addr
essgt
XML
The xsinoNamespaceSchemaLocation attribute is
embedded in the root element address and refers
to an external XSD "country-address.xsd" (or, at
some absolute URL, to an "http//www.test.org/coun
try-address.xsd")