Σημασιολογικός Ιστός (Semantic Web) - XML

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1 Πανεπιστήμιο Πειραιώς Τμήμα Ψηφιακών Συστημάτων Σημασιολογικός Ιστός (Semantic Web) - XML Δρ. Ανδριάνα Πρέντζα Αναπληρώτρια Καθηγήτρια aprentza@unipi.gr

2 Πανεπιστήμιο Πειραιά Τμήμα Ψηφιακών Συστημάτων XML Schema

3 Let s create the XML Schema!!!!

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6 <?xml version="1.0" encoding="iso "?> <xs:schema xmlns:xs=" <xs:element name="shiporder"> <xs:complextype> <xs:sequence> <xs:element name="orderperson" type="xs:string"/> <xs:element name="shipto"> <xs:complextype> <xs:sequence> <xs:element name="name" type="xs:string"/> <xs:element name="address" type="xs:string"/> <xs:element name="city" type="xs:string"/> <xs:element name="country" type="xs:string"/> </xs:sequence> </xs:complextype> </xs:element> <xs:element name="item" maxoccurs="unbounded"> <xs:complextype> <xs:sequence> <xs:element name="title" type="xs:string"/> <xs:element name="note" type="xs:string" minoccurs="0"/> <xs:element name="quantity" type="xs:positiveinteger"/> <xs:element name="price" type="xs:decimal"/> </xs:sequence> </xs:complextype> </xs:element> </xs:sequence> <xs:attribute name="orderid" type="xs:string" use="required"/> </xs:complextype> </xs:element> </xs:schema> This design method is very simple, but can be difficult to read and maintain when documents are complex. The next design method is based on defining all elements and attributes first, and then referring to them using the ref attribute.

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8 Άσκηση Να καθοριστεί νέος τύπος δεδομένων σε ένα XML Schema ο οποίος να διαδέχεται τις ακέραιες τιμές από -100 έως το 500.

9 Άσκηση Tο XML Schema φαίνεται παρακάτω.

10 Επεξήγηση... complextype: ορίζει σύνθετο τύπο που υποστηρίζει ιδιότητες και περιεχόμενα στοιχείων simpletype: ορίζει απλό τύπο complexcontent: περιέχει επεκτάσεις ή περιορισμούς για ένα σύνθετο τύπο που περιέχει μεικτά περιεχόμενα ή στοιχεία μόνο simplecontent: περιέχει επεκτάσεις ή περιορισμούς σε ένα στοιχείο complextype με δεδομένα χαρακτήρα ή ένα στοιχείο simpletype ως content και δεν περιέχει στοιχεία

11 Πανεπιστήμιο Πειραιά Τμήμα Ψηφιακών Συστημάτων XML Schema Παραδείγματα

12 1) Select which of the following correctly explain the value that can be described in the ItemPrice element content. <xs:element name="itemprice" type="itempricetype" /> <xs:simpletype name="itempricetype"> <xs:restriction base="xs:int"> <xs:mininclusive value="500" /> <xs:maxinclusive value=" " /> </xs:restriction> </xs:simpletype> a.the value can be described, but the value cannot be described b.the value can be described, but the value cannot be described c. The value 501 can be described, but the value 500 cannot be described d. The value 500 can be described, but the value 499 cannot be described

13 The extension element extends an existing simpletype or complextype element.

14 2) Select which of the following is a valid XML document with respect to XML Schema Document below. <?xml version="1.0" encoding="utf-8"?> <xs:schema xmlns:xs=" <xs:element name="personal_information" type="newpersonalinfotype" /> <xs:complextype name="newpersonalinfotype"> <xs:complexcontent> <xs:extension base="personalinfotype"> <xs:sequence> <xs:element ref="birth_date" /> <xs:element ref="hobbies" maxoccurs="30" /> </xs:sequence> </xs:extension> </xs:complexcontent> </xs:complextype> <xs:complextype name="personalinfotype"> <xs:sequence> <xs:element ref="name"/> <xs:element ref=" _address" /> </xs:sequence> </xs:complextype> <xs:element name="name" type="xs:string" /> <xs:element name=" _address" type="xs:string" /> <xs:element name="birth_date" type="xs:string" /> <xs:element name="hobbies" type="xs:string" /> </xs:schema>

15 2) Select which of the following is a valid XML document with respect to XML Schema Document below. a. <?xml version="1.0" encoding="utf-8"?> <Personal_Information> <Name>Taro Yamada</Name> < _Address>tyamada@aaa.com</ _Address> <Birth_Date> </Birth_Date> </Personal_Information> b. <?xml version="1.0" encoding="utf-8"?> <Personal_Information> <Name>Taro Yamada</Name> < _Address>tyamada@aaa.com</ _Address> <Birth_Date> </Birth_Date> <Hobbies>Listening to music</hobbies> <Hobbies>Watching movies</hobbies> </Personal_Information>

16 2) Select which of the following is a valid XML document with respect to XML Schema Document below. c. <?xml version="1.0" encoding="utf-8"?> <Personal_Information> <Birth_Date> </Birth_Date> <Hobbies>Listening to music</hobbies> <Hobbies>Watching movies</hobbies> <Name>Taro Yamada</Name> < _Address>tyamada@aaa.com</ _Address> </Personal_Information> d. <?xml version="1.0" encoding="utf-8"?> <Personal_Information> <Hobbies>Listening to music</hobbies> <Hobbies>Watching movies</hobbies> <Birth_Date> </Birth_Date> < _Address>tyamada@aaa.com</ _Address> <Name>Taro Yamada</Name> </Personal_Information>

17 Guidelines An element is added to the complex type personalinfotype defined in the complextype element. This is called a complex type derived by extension. The following illustrates the procedures for a complex type derived by extension: 1. Designate a new data type name for the name attribute of the complextype element. <xs:complextype name="newpersonalinfotype"> </xs:complextype> 2. Clearly indicate that the content of the complexcontent element is a complex type, and designate the name of the data type serving as the base attribute of the extension element. <xs:complexcontent> <xs:extension base="personalinfotype"> </xs:extension> </xs:complexcontent> 3. Define the order of occurrence (model group) of the added element and the element as descendant elements of the extension element. Use the sequence element to make the occurrence in the defined order. <xs:sequence> <xs:element ref="birth_date" /> <xs:element ref="hobbies" maxoccurs="30" /> </xs:sequence> When the complex type is derived by extension, the position for the added element is after the element last defined with the original data type.

18 3) Select which of the following is a correct XML Schema definition if you must designate an integer less than or equal to 0 as the content of the Discount_Amount element. Assume that the XML Schema namespace prefix is xs. a. <xs:element name="discount_amount" type="xs:negativeinteger /> b. <xs:element name="discount_amount" type="xs:positiveinteger /> c. <xs:element name="discount_amount" type="xs:nonnegativeinteger /> d. <xs:element name="discount_amount" type="xs:nonpositiveinteger />

19 4) The following sentences describe characteristics of XML schema as compared to DTD. Select which of the following is NOT correct. a. Since the specification is simple, using XML schema rather than DTD allows for shorter XML statements when defining the same schema structure. b. XML schema is a well-formed XML document. c. XML schema provides for various data types, including date type, integer type, etc. d. XML schema is compatible with XML namespace.

20 5) Select which of the following is correct as a definition adding a Mobile element to the Personal_Information element defined in the given XML Schema Document. <xs:element name="personal_information" type="personalinfotype" /> <xs:complextype name="personalinfotype"> <xs:sequence> <xs:element ref="name" /> <xs:element ref="date_of_birth" /> <xs:element ref="hobbies" minoccurs="1" maxoccurs="30" /> </xs:sequence> </xs:complextype> <xs:element name="name" type="xs:string" /> <xs:element name="date_of_birth" type="xs:string" /> <xs:element name="hobbies" type="xs:string" /> a. <xs:element name="personal_information" type="newpersonalinfotype" /> <xs:complextype name="newpersonalinfotype"> <xs:complexcontent> <xs:restriction base="personalinfotype"> <xs:sequence> <xs:element ref="mobile" /> </xs:sequence> </xs:restriction> </xs:complexcontent> </xs:complextype> <xs:element name="mobile" type="xs:string" />

21 5) Select which of the following is correct as a definition adding a Mobile element to the Personal_Information element defined in the given XML Schema Document. <xs:element name="personal_information" type="personalinfotype" /> <xs:complextype name="personalinfotype"> <xs:sequence> <xs:element ref="name" /> <xs:element ref="date_of_birth" /> <xs:element ref="hobbies" minoccurs="1" maxoccurs="30" /> </xs:sequence> </xs:complextype> <xs:element name="name" type="xs:string" /> <xs:element name="date_of_birth" type="xs:string" /> <xs:element name="hobbies" type="xs:string" /> b. <xs:element name="personal_information" type="newpersonalinfotype" /> <xs:complextype name="newpersonalinfotype"> <xs:complexcontent> <xs:restriction base="personalinfotype"> <xs:sequence> <xs:element ref="name" /> <xs:element ref="date_of_birth" /> <xs:element ref="hobbies" minoccurs="1" maxoccurs="30" /> <xs:element ref="mobile" /> </xs:sequence> </xs:restriction> </xs:complexcontent> </xs:complextype> <xs:element name="mobile" type="xs:string" />

22 5) Select which of the following is correct as a definition adding a Mobile element to the Personal_Information element defined in the given XML Schema Document. <xs:element name="personal_information" type="personalinfotype" /> <xs:complextype name="personalinfotype"> <xs:sequence> <xs:element ref="name" /> <xs:element ref="date_of_birth" /> <xs:element ref="hobbies" minoccurs="1" maxoccurs="30" /> </xs:sequence> </xs:complextype> <xs:element name="name" type="xs:string" /> <xs:element name="date_of_birth" type="xs:string" /> <xs:element name="hobbies" type="xs:string" /> c. <xs:element name="personal_information" type="newpersonalinfotype" /> <xs:complextype name="newpersonalinfotype"> <xs:complexcontent> <xs:extension base="personalinfotype"> <xs:sequence> <xs:element ref="mobile" /> </xs:sequence> </xs:extension> </xs:complexcontent> </xs:complextype> <xs:element name="mobile" type="xs:string" />

23 5) Select which of the following is correct as a definition adding a Mobile element to the Personal_Information element defined in the given XML Schema Document. <xs:element name="personal_information" type="personalinfotype" /> <xs:complextype name="personalinfotype"> <xs:sequence> <xs:element ref="name" /> <xs:element ref="date_of_birth" /> <xs:element ref="hobbies" minoccurs="1" maxoccurs="30" /> </xs:sequence> </xs:complextype> <xs:element name="name" type="xs:string" /> <xs:element name="date_of_birth" type="xs:string" /> <xs:element name="hobbies" type="xs:string" /> d. <xs:element name="personal_information" type="newpersonalinfotype" /> <xs:complextype name="newpersonalinfotype"> <xs:complexcontent> <xs:extension base="personalinfotype"> <xs:sequence> <xs:element ref="name" /> <xs:element ref="date_of_birth" /> <xs:element ref="hobbies" minoccurs="1" maxoccurs="30" /> <xs:element ref="mobile" /> </xs:sequence> </xs:extension> </xs:complexcontent> </xs:complextype> <xs:element name="mobile" type="xs:string" />

24 6) The element WidgetDesc begins with descriptive text and is followed by Size and Shape descriptions. The Size and Shape description are each optional and may occur in any order. Which of the following is the correct content model for WidgetDesc? a) <xsd:element name="widgetdesc" content="mixed"> <xsd:complexcontent> <xsd:node type="#pcdata"/> <xsd:element name="size" use="optional"/> <xsd:element name="shape" use="optional"/> </xsd:complexcontent> < /xsd:element> b) <xsd:element name="widgetdesc" type="xsd:string"> <xsd:complexcontent> <xsd:any> <xsd:element name="size" minoccurs="0"/> <xsd:element name="shape" minoccurs="0"/> </xsd:any> </xsd:complexcontent> < /xsd:element>

25 6) The element WidgetDesc begins with descriptive text and is followed by Size and Shape descriptions. The Size and Shape description are each optional and may occur in any order. Which of the following is the correct content model for WidgetDesc? c) <xsd:element name="widgetdesc"> <xsd:complextype> <xsd:node type="#pcdata" use="optional"/> <xsd:element name="size" use="optional"/> <xsd:element name="shape" use="optional"/> </xsd:complextype> < /xsd:element> d) <xsd:element name="widgetdesc"> <xsd:complextype mixed="true"> <xsd:all> <xsd:element name="size" type="xsd:string" minoccurs="0" /> <xsd:element name="shape" type="xsd:string" minoccurs="0" /> </xsd:all> </xsd:complextype> < /xsd:element>

26 Schema Namespaces Ισοδύναμα με XML namespaces Χρησιμοποιείται για τον προσδιορισμό των schema elements Το <schema> πρέπει να προσδιοριστεί με το schema namespace <schema xmlns = > Το namespace μπορεί να έχει ένα namespace prefix για το schema Το πρόθεμα prefix προσδιορίζει τα elements που ανήκουν στο targetnamespace <schema xmlns = xmlns:co =

27 <schema> targetnamespace Attribute <schema> targetnamespace attribute Δηλώνει το namespace του τρέχοντος schema Αυτό πρέπει να είναι ένα μοναδικό Παγκόσμιο Αναγνωριστικό Πόρου Universal Resource Identifier (URI) Διευκολύνει τον parser στη διαφοροποίηση ορισμών τύπων Χρησιμοποιείται κατά την επικύρωση του schema Διευκολύνει το διαχωρισμό διαφορετικών λεξιλογίων στο schema targetnamespace:namespace_prefix = some_uri... Θα πρέπει να ταιριάζει με τη δήλωση του schema namespace

28 Παράδειγμα XML <schema> <?xml version="1.0" encoding="utf-8"?> <xsd:schema targetnamespace = xmlns:co= xmlns:xsd=" elementformdefault="qualified attributeformdefault="qualified elementformdefault="qualified"> <!-- Declare the root element of our schema --> <xsd:element name="customerorder type="co:customerorder"/> <!-- Further Definitions & declarations not shown --> </xsd:schema>

29 7) Μία εταιρεία βρίσκεται στη διαδικασία ορισμού του καταλόγου προϊόντων. Οι απαιτήσεις απαιτούν το κάθε προϊόν να προσδιορίζεται μοναδικά από το SKU (Stock Keeping Unit) και περιέχει όνομα προϊόντος, περιγραφή και τιμή. Επιπρόσθετα, κάποια προϊόντα μπορούν να έχουν μέχρι πέντε αξεσουάρ. Κάθε αξεσουάρ είναι κι αυτό προϊόν. Για να συσχετιστεί ένα αξεσουάρ με ένα προϊόν απαιτείται μόνο ο κωδικός SKU του αξεσουάρ. Τέλος, είναι επίσης απαίτηση να μπορεί να προστεθεί ένας κωδικός προώθησης ο οποίος θα είναι αποτελεσματικός για μία συγκεκριμένη χρονική περίοδο. Ένας προγραμματιστής ορίζει το παρακάτω XML Schema για το προϊόν: <schema targetnamespace= xmlns=' xmlns:acc= ' <complextype name="product"> <sequence> <element name="sku" type="integer"/> <element name="name" type="string"/> <element name="description" type="string"/> <element name="unitprice" type="decimal"/> <element name="accessory" minoccurs="0 maxoccurs="unbounded" type="acc:product"/> </sequence> </complextype>

30 Ποια/ες από τις παρακάτω απαντήσεις είναι σωστή? A) Η αντικατάσταση της τιμής ιδιότητας maxoccurs="unbounded" με την maxoccurs="5" θα κάνει τον ορισμό του XML schema να ταιριάζει με τις απαιτήσεις. B)Η τιμή ιδιότητας maxoccurs="unbounded" μπορεί να διαγραφεί, δεδομένου ότι η συγκεκριμένη ιδιότητα και τιμή προστίθεται by default σε οποιοδήποτε ορισμό XML Schema που περιέχει ήδη τον ορισμό της ιδιότητας minoccurs="0". Γ) Ο τύπος του ορισμού του SKU πρέπει να γραφτεί ως type="sku" Δ) Ο τύπος του ορισμού του UnitPrice πρέπει να γραφτεί ως type="amount"

31 8) Select which of the following is a correct XML Schema description matching the conditions below. Select all that apply. Assume the XML Schema Namespace prefix is "xs." Conditions: The "Address" attribute is defined as a string type that may be omitted. a) <xs:attribute name="address" type="xs:string" use="optional"/> b) <xs:attribute name="address" type="xs:string" optional="true"/> c) <xs:attribute name="address" type="xs:string" required="optional"/> d) <xs:attribute name="address" type="xs:string" use="required"/>

32 9) Select which of the following is a valid XML document with respect to the following XML Schema Document. <?xml version="1.0"?> <xs:schema xmlns:xs=" > <xs:element name="employee" type="employeetype" /> <xs:complextype name="employeetype"> <xs:sequence maxoccurs="unbounded"> <xs:element ref="name" /> <xs:element ref="department" /> </xs:sequence> </xs:complextype> <xs:element name="name" type="xs:string" /> <xs:element name="department" type="xs:string" /> </xs:schema>

33 a) <Employee></Employee> b) <Employee> < Name>Masashi Tanaka</Name> < Name>Makiko Okamura</Name> < /Employee> c) <Employee> < Name>Masashi Tanaka</Name> < Name>Makiko Okamura</Name> < Department>Sales Department</Department> < Department>Accounting Department</Department> < /Employee> d) Κανένα από τα παραπάνω δεν ακολουθεί τους κανόνες στο XML Schema

34 10) Select which of the following is INCORRECT as an XML Schema description. Assume that the namespace prefix xs is declared as " <xs:simpletype name="data_type"> <xs:restriction base="xs:int"> <xs:minexclusive value="20"/> <xs:maxinclusive value="200"/> </xs:restriction> < /xs:simpletype> < xs:element name="price" type="data_type"/> a) A value of 20 is allowed under the Price element b) A value of 23.4 is not allowed under the Price element c) A value of 200 is allowed under the Price element d) A value of 99 is allowed under the Price element

35 11) Select which of the following is an XML Schema document that correctly defines the Unit Price element as either 3500 or a) <xs:simpletype name="pricetype"> <xs:restriction base="xs:int"> <xs:mininclusive value="3500"/> <xs:maxinclusive value="4500"/> </xs:restriction> < /xs:simpletype> < xs:element name="unit Price" type="pricetype"/> b) <xs:simpletype name="pricetype"> <xs:restriction base="xs:int"> <xs:minexclusive value="3500"/> <xs:maxexclusive value="4500"/> </xs:restriction> < /xs:simpletype> < xs:element name="unit Price" type="pricetype"/>

36 11) Select which of the following is an XML Schema document that correctly defines the Unit Price element as either 3500 or c) <xs:simpletype name="pricetype"> <xs:restriction base="xs:int"> <xs:enumeration value="3500"/> <xs:enumeration value="4500"/> </xs:restriction> < /xs:simpletype> < xs:element name="unit Price" type="pricetype"/> d) <xs:simpletype name="pricetype"> <xs:restriction base="xs:int"> <xs:minlength value="3500"/> <xs:maxlength value="4500"/> </xs:restriction> < /xs:simpletype> < xs:element name="unit Price" type="pricetype"/>

37 12) Select which of the following represent valid XML documents with respect to the XML Schema document below: <?xml version="1.0"?> < xs:schema xmlns:xs=" <xs:element name="customer_information" type="customertype" /> <xs:complextype name="infotype"> <xs:sequence> <xs:choice> <xs:sequence> <xs:element ref="company" /> <xs:element ref="address" /> </xs:sequence> <xs:sequence> <xs:element ref="lastname" /> <xs:element ref="firstname" /> </xs:sequence> </xs:choice> </xs:sequence> < /xs:complextype>

38 <xs:complextype name="customertype"> <xs:complexcontent> <xs:extension base="infotype"> <xs:choice> <xs:element ref="telephone" /> <xs:element ref="mobile" /> </xs:choice> </xs:extension> </xs:complexcontent> </xs:complextype> <xs:element name="company" type="xs:string" /> <xs:element name="address" type="xs:string" /> <xs:element name="lastname" type="xs:string" /> <xs:element name="firstname" type="xs:string" /> <xs:element name="telephone" type="xs:string" /> <xs:element name="mobile" type="xs:string" /> < /xs:schema>

39 a) <?xml version="1.0"?> <Customer_Information> < Company>masashi</Company> < Address>okamura</Address> < Mobile> </Mobile> < Mobile> </Mobile> < /Customer_Information> b) <?xml version="1.0"?> < Customer_Information> < Company>masashi</Company> < Address>okamura</Address> < Mobile> </Mobile> < /Customer_Information> c) <?xml version="1.0"?> < Customer_Information> < Company>Okamura</Company> < Address>Masashi</Address> < Telephone> </Telephone> < /Customer_Information> d) <?xml version="1.0"?> < Customer_Information> < Company>Okamura</Company> < Address>Masashi</Address> < LastName>masashi</LastName> < FirstName>okamura</FirstName> < Telephone> </Telephone> < Mobile> </Mobile> < /Customer_Information>

40 13) Select which of the following correctly represents what should be described in (1) of the XML Schema document in order to correctly define the following XML Document (the Location_of_Origin attribute of Fruit element is mandatory): [XML Document] <?xml version="1.0"?> <Fruit Location_of_Origin="Aomori"> <Name>Apple</Name> <Price>350</Price> </Fruit> [XML Schema Document] <?xml version="1.0"?> <xs:schema xmlns:xs=" <xs:element name="fruit" type="fruittype" /> <xs:complextype name="basetype"> <xs:sequence> <xs:element ref="name" /> </xs:sequence> </xs:complextype> (1) <xs:element name="name" type="xs:string" /> <xs:element name="price" type="xs:integer" /> </xs:schema>

41 a) <xs:complextype name="fruittype"> <xs:complexcontent> <xs:restriction base="basetype"> <xs:sequence> <xs:element ref="price" /> </xs:sequence> <xs:attribute name="location_of_origin" type="xs:string" use="required" /> </xs:restriction> </xs:complexcontent> < /xs:complextype> b) <xs:complextype name="fruittype"> <xs:complexcontent> <xs:extension base="basetype"> <xs:sequence> <xs:element ref="price" /> </xs:sequence> <xs:attribute name="location_of_origin" type="xs:string" use="required" /> </xs:extension> </xs:complexcontent> < /xs:complextype> c) <xs:complextype name="fruittype"> <xs:simplecontent> <xs:extension base="basetype"> <xs:sequence> <xs:element ref="price" /> </xs:sequence> <xs:attribute name="location_of_origin" type="xs:string" use="required" /> </xs:extension> </xs:simplecontent> < /xs:complextype> d) <xs:complextype name="fruittype"> <xs:simplecontent> <xs:restriction base="basetype"> <xs:sequence> <xs:element ref="price" /> </xs:sequence> <xs:attribute name="location_of_origin" type="xs:string" use="required" /> </xs:restriction> </xs:simplecontent> < /xs:complextype>

42 14) Select which of the following are incorrect when extending the definition of a simple type element that has been defined using XML Schema. a. < xs:element name="bookinformation" type="bookinfotype" /> < xs:simpletype name="newbookinfotype"> <xs:simplecontent> <xs:extension base="bookinfotype"> <xs:attribute name="isbn" type="xs:string" use="required" /> </xs:extension> </xs:simplecontent> < /xs:simpletype> b. < xs:element name="bookinformation" type="bookinfotype" /> < xs:simpletype name="newbookinfotype"> <xs:simplecontent> <xs:restriction base="bookinfotype"> <xs:attribute name="isbn" type="xs:string" use="required" /> </xs:restriction> </xs:simplecontent> < /xs:simpletype>

43 14) Select which of the following are incorrect when extending the definition of a simple type element that has been defined using XML Schema. c. < xs:element name="bookinformation" type="bookinfotype" /> < xs:complextype name="newbookinfotype"> <xs:simplecontent> <xs:extension base="bookinfotype"> <xs:attribute name="isbn" type="xs:string" use="required" /> </xs:extension> </xs:simplecontent> < /xs:complextype> d. < xs:element name="bookinformation" type="bookinfotype" /> < xs:complextype name="newbookinfotype"> <xs:simplecontent> <xs:restriction base="bookinfotype"> <xs:attribute name="isbn" type="xs:string" use="required" /> </xs:restriction> </xs:simplecontent> < /xs:complextype>

44 Note A simple type extension does not increase the scope of the value for the value of the type forming a base, but rather adds an attribute definition to the simple type element. Adding an attribute to a simple type element results in a complextype element; However, the content of the element is still simple type, so a simplecontent element is designated as the child element of the complextype element. Next, an extension element is designated, with an attribute definition described for that child element.

45 15) Select which of the following XML Schema documents correctly defines the following: Use an integer value for the Quantity element content, the Quantity element has a Unit attribute, which must be described (may not be omitted). Use a text type value for the Unit attribute a. <?xml version="1.0" encoding="utf-8"?> < xs:schema xmlns:xs=" <xs:element name="quantity" type="quantitytype"/> <xs:complextype name="quantitytype"><xs:simplecontent> <xs:extension base="xs:int" > <xs:attribute name="unit" type="xs:string" use="required" /> </xs:extension> </xs:simplecontent></xs:complextype> </xs:schema> b. <?xml version="1.0" encoding="utf-8"?> <xs:schema xmlns:xs=" <xs:element name="quantity" type="quantitytype" /> <xs:complextype name="quantitytype"> <xs:attribute name="unit" type="xs:string" use="required" /> </xs:complextype> </xs:schema>

46 c. <?xml version="1.0" encoding="utf-8"?> < xs:schema xmlns:xs=" <xs:element name="quantity"> <xs:complextype> <xs:simplecontent> <xs:extension base="xs:int" > <xs:attribute name="unit" type="xs:string" use="required" /> </xs:extension> </xs:simplecontent> </xs:complextype> </xs:element> </xs:schema> d. <?xml version="1.0" encoding="utf-8"?> < xs:schema xmlns:xs=" <xs:element name="quantity"> <xs:complextype> <xs:attribute name="unit" type="xs:string" use="required" /> </xs:complextype> </xs:element> </xs:schema>