ICE1341 Programming Languages Spring 2005 Lecture #8 Lecture #8 In-Young Ko iko.AT. icu.ac.kr iko.AT. icu.ac.kr Information and Communications University

ICE1341 ICE1341 Programming LanguagesProgramming Languages

Spring 2005Spring 2005

Lecture #8Lecture #8

In-Young Koiko .AT. icu.ac.kr

Information and Communications University (ICU)

Spring 2005 2 ICE 1341 – Programming Languages © In-Young Ko, Information and Communications University

AnnouncementsAnnouncements

The due date of the midterm project is The due date of the midterm project is postponed to postponed to Thursday April 14Thursday April 14thth (a (a week after the midterm exam)week after the midterm exam)

There will be the There will be the project presentationproject presentation session on the due datesession on the due date


Axiomatic Semantics (cont.)Axiomatic Semantics (cont.) NamesNames VariablesVariables BindingsBindings Binding LifetimesBinding Lifetimes

Last LectureLast Lecture


This LectureThis Lecture

Binding Lifetimes (cont.)Binding Lifetimes (cont.) WWW ConceptsWWW Concepts WWW LanguagesWWW Languages

XML (Extended Markup Language)XML (Extended Markup Language)


Program Memory StructureProgram Memory Structure

Static AreaStatic Area Program codeProgram code Non-local variablesNon-local variables Static variablesStatic variables

Dynamic StorageDynamic Storage Stack AreaStack Area

Local variablesLocal variables Parameters and return valuesParameters and return values

Heap AreaHeap Area Dynamically allocated memory Dynamically allocated memory

blocksblocks

Dynamic storage controlDynamic storage controle.g., e.g., java java –xm1024m–xm1024m MyProgram MyProgram

Stack AreaStack Area

Static AreaStatic Area

Heap AreaHeap Area

……

Dyn

amic

Sto

rage

Dyn

amic

Sto

rage


Binding LifetimesBinding Lifetimes

StaticStatic: Storage bindings remain throughout execution: Storage bindings remain throughout executione.g. e.g. all FORTRAN 77 variables, Java static variablesall FORTRAN 77 variables, Java static variables

AdvantagesAdvantages: efficiency (direct addressing); : efficiency (direct addressing); history-sensitivehistory-sensitive subprogram supportsubprogram support

DisadvantageDisadvantage: lack of flexibility (no recursion): lack of flexibility (no recursion)

Stack-DynamicStack-Dynamic: Storage bindings are created when : Storage bindings are created when their declaration statements are elaboratedtheir declaration statements are elaborated

e.g. e.g. local variables in C subprograms and Java methodslocal variables in C subprograms and Java methods Advantage: allows recursion; conserves storageAdvantage: allows recursion; conserves storage Disadvantages: overhead of allocation and deallocation; Disadvantages: overhead of allocation and deallocation;

subprograms cannot be history sensitive; slower accesses subprograms cannot be history sensitive; slower accesses ((indirect addressingindirect addressing))

* AW Lecture Notes


Binding Lifetimes Binding Lifetimes – cont.– cont.

Explicit Heap-DynamicExplicit Heap-Dynamic: Storages are allocated and deallocated : Storages are allocated and deallocated by explicit directives, specified by the programmer, which take by explicit directives, specified by the programmer, which take effect during executioneffect during execution

e.g. e.g. dynamic objects in C++ (via new and delete)dynamic objects in C++ (via new and delete)

all objects in Java (new int[100])all objects in Java (new int[100]) AdvantageAdvantage: provides for dynamic storage management: provides for dynamic storage management DisadvantageDisadvantage: inefficient and unreliable: inefficient and unreliable

Implicit Heap-DynamicImplicit Heap-Dynamic: Storages are allocation and deallocation : Storages are allocation and deallocation caused by assignment statementscaused by assignment statements

e.g. e.g. all variables in APL; all strings and arrays in Perl and JavaScriptall variables in APL; all strings and arrays in Perl and JavaScript AdvantageAdvantage: flexibility: flexibility DisadvantagesDisadvantages: inefficient, because all attributes are dynamic; loss of : inefficient, because all attributes are dynamic; loss of

error detection by the compilererror detection by the compiler

* AW Lecture Notes


Type CheckingType Checking

Type CheckingType Checking: the activity of ensuring that the : the activity of ensuring that the operands of an operator are of compatible typesoperands of an operator are of compatible types

Compatible TypeCompatible Type: a type that is either legal for : a type that is either legal for an operator, or is allowed under language rules to an operator, or is allowed under language rules to be implicitly converted to a legal type (be implicitly converted to a legal type (coercioncoercion))

Type ErrorType Error: the application of an operator to an : the application of an operator to an operand of an inappropriate typeoperand of an inappropriate type

A programming language is A programming language is strongly typedstrongly typed if if type errors are always detectedtype errors are always detected

* AW Lecture Notes


Type CompatibilityType Compatibility

Name Type CompatibilityName Type Compatibility: two variables have : two variables have compatible types if they are in either the same declaration compatible types if they are in either the same declaration or in declarations that use the same type nameor in declarations that use the same type name Easy to implement but highly restrictiveEasy to implement but highly restrictive

Subranges of integer types are not compatible with integer typesSubranges of integer types are not compatible with integer types

e.g.,e.g., type Indextype is 1..100;type Indextype is 1..100;

count: Integer;count: Integer;

index: Indextype;index: Indextype; Formal parameters must be the same type as their corresponding Formal parameters must be the same type as their corresponding

actual parameters (Pascal)actual parameters (Pascal)

Structure Type CompatibilityStructure Type Compatibility: : two variables have two variables have compatible types if their types have identical structurescompatible types if their types have identical structures More flexible, but harder to implementMore flexible, but harder to implement

Spring 2005 10

ICE 1341 – Programming Languages © In-Young Ko, Information and Communications University

Type Compatibility Type Compatibility – cont.– cont.

Derived TypeDerived Type: a new type that is based on some : a new type that is based on some previously defined typepreviously defined type Derive types inherit all the properties of their parent typesDerive types inherit all the properties of their parent types Derived types allow types with the same structure to be differentDerived types allow types with the same structure to be different

e.g., type celsius is new Float;e.g., type celsius is new Float;

type fahrenheit is new Float;type fahrenheit is new Float;

SubtypeSubtype: a range-constrained version of an existing type: a range-constrained version of an existing type A subtype is compatible with its parent typeA subtype is compatible with its parent type

e.g., subtype Small_type is Integer range 0..99;e.g., subtype Small_type is Integer range 0..99;

Anonymous TypeAnonymous Type: Unnamed type: Unnamed type Anonymous types are all unique, even inAnonymous types are all unique, even in

e.g., C, D : array (1..10) of Integer;e.g., C, D : array (1..10) of Integer;

Spring 2005 11


The World Wide Web (WWW)The World Wide Web (WWW)

““Information Management: Information Management: A Proposal”, A Proposal”, Tim Berners-Tim Berners-LeeLee, , CERNCERN, March 1989, March 1989

A proposal to build a A proposal to build a global global hypertext systemhypertext system for CERNfor CERN

www.w3.org/History/1989/www.w3.org/History/1989/proposal.htmlproposal.html

The original proposal of the WWWThe original proposal of the WWW

Spring 2005 12


WWW ConceptsWWW Concepts

HypertextHypertext

Universal ReadershipUniversal Readership

SearchingSearching Client-Server ModelClient-Server Model

FormatFormatNegotiationNegotiation• Image formatsImage formats• Text fontsText fonts• FramesFrames

www.w3.org/Talks/General/Concepts.htmlwww.w3.org/Talks/General/Concepts.html

Spring 2005 13


Languages for WWWLanguages for WWW

HTMLHTML (Hypertext Markup Language) (Hypertext Markup Language) Scripting Languages (e.g., Perl, JavaScript)Scripting Languages (e.g., Perl, JavaScript) XMLXML (Extended Markup Language) (Extended Markup Language) RDFRDF (Resource Description Framework) (Resource Description Framework) DAMLDAML (DARPA Agent Markup Language) (DARPA Agent Markup Language) SOAPSOAP (Simple Object Access Protocol) (Simple Object Access Protocol) WSDLWSDL (Web Services Description Language) (Web Services Description Language) WSFLWSFL (Web Services Flow Language) (Web Services Flow Language) ……

Spring 2005 14


SGML (Standard Generalized Markup SGML (Standard Generalized Markup Language)Language)

SGML is SGML is a a metameta-markup language-markup language developed in developed in the early 1980s (ISO 8879, 1986)the early 1980s (ISO 8879, 1986)

HTMLHTML was developed was developed using SGMLusing SGML in the early in the early 1990s - 1990s - specifically for Web documentsspecifically for Web documents

Problems with HTML:Problems with HTML:1. 1. Fixed set of tags and attributesFixed set of tags and attributes

User cannot define new tags or attributesUser cannot define new tags or attributes So, the tags cannot connote any particular meaningSo, the tags cannot connote any particular meaning

2. 2. No restrictions on arrangement or order of tagNo restrictions on arrangement or order of tag appearanceappearance

SGML is SGML is too large and complextoo large and complex to use, and it is to use, and it is very very difficult to build a parserdifficult to build a parser for it for it

AW lecture notes

Spring 2005 15


XML (Extended Markup Language)XML (Extended Markup Language)

XML is XML is a light version of SGMLa light version of SGML that provides a that provides a way of way of storing and transferring data of any kindstoring and transferring data of any kind

XML vs. HTMLXML vs. HTML HTML is a markup language used to describe the HTML is a markup language used to describe the

layoutlayout of any kind of information of any kind of information XML is a meta-markup language that can be used to XML is a meta-markup language that can be used to

define markup languages that can define markup languages that can define the meaningdefine the meaning of specific kinds of informationof specific kinds of information

XML does XML does not predefine any tagsnot predefine any tags All documents described with an XML-derived All documents described with an XML-derived

markup language can be markup language can be parsed with a single parsed with a single parserparser

AW lecture notes

Spring 2005 16


A Sample XML DocumentA Sample XML Document<?xml version = "1.0“?><?xml version = "1.0“?>

<class><class><name><name>Prog. Lang.Prog. Lang.</name></name><code><code>ICE1341ICE1341</code></code><students><students>

<student <student id=“20041233”id=“20041233”>> <name><name>K.D. KoK.D. Ko</name></name> <bday><bday>820304820304</bday></bday></student></student><student <student id=“20041234”id=“20041234”>> <name><name>C.S. C.S.

LeeLee</name></name> <bday><bday>830512830512</bday></bday></student></student>

</students></students></class></class>

Spring 2005 17


XML SyntaxXML Syntax A flexible text format that is originally designed for A flexible text format that is originally designed for

large-scale electronic publishing of documentslarge-scale electronic publishing of documents An An XML documentXML document is a is a hierarchical organizationhierarchical organization

of one or more named elementsof one or more named elements An An elementelement is composed of an opening-tag, data is composed of an opening-tag, data

(string or another element), and a closing-tag(string or another element), and a closing-tag An An opening-tagopening-tag is an element name surrounded by is an element name surrounded by

‘<’ and ‘>’‘<’ and ‘>’ A A closing-tagclosing-tag is an element name surrounded by ‘<’ is an element name surrounded by ‘<’

and ‘/>’and ‘/>’ An element may have zero or more An element may have zero or more attributesattributes An An attributeattribute is a name-value pair that specifies a is a name-value pair that specifies a

property of the elementproperty of the element

Spring 2005 18


XML Syntax XML Syntax – cont.– cont.

All XML documents begin with an XML declaration:All XML documents begin with an XML declaration:<?xml version = "1.0"?><?xml version = "1.0"?> XML comments are just like HTML commentsXML comments are just like HTML comments

XML names: XML names: Must begin with a letter or an underscoreMust begin with a letter or an underscore They can include digits, They can include digits, hyphenshyphens, and , and periodsperiods There is There is no length limitationno length limitation They are They are case sensitivecase sensitive (unlike HTML names) (unlike HTML names)

Syntax rules for XML:Syntax rules for XML: Every XML document defines Every XML document defines a single root elementa single root element, whose , whose

opening tag must appear as the first line of the documentopening tag must appear as the first line of the document Every element that has content must have a Every element that has content must have a closing tagclosing tag Tags must be properly nestedTags must be properly nested All All attribute values must be quotedattribute values must be quoted

AW lecture notes

Spring 2005 19


A Sample XML DocumentA Sample XML Document

<?xml version = "1.0“?><?xml version = "1.0“?>





An opening-tagAn opening-tag

A closing-tagA closing-tag

An elementAn element

An attributeAn attribute

The root elementThe root element

A valueA value

Spring 2005 20


The XML GrammarThe XML Grammar

document ::= document ::= prologprolog elementelement MiscMisc** element ::= element ::= EmptyElemTagEmptyElemTag | | STagSTag contentcontent ETagETag EmptyElemTag ::= 'EmptyElemTag ::= '<<' ' NameName ( (SS AttributeAttribute)* )* SS? '? '/>/>'' STag ::= 'STag ::= '<<' ' NameName ( (SS AttributeAttribute)* )* SS? '? '>>'' content ::= content ::= CharDataCharData? ((? ((elementelement | | ReferenceReference | |

CDSectCDSect | | PIPI | | CommentComment) ) CharDataCharData?)*?)* ETag ::= 'ETag ::= '</</' ' NameName SS? '? '>>'' S ::= (S ::= (#x20 #x20 | | #x9#x9 | | #xD#xD | | #xA#xA)+)+ Attribute ::= Attribute ::= NameName ' '==' ' AttValueAttValue Name ::= (Name ::= (LetterLetter | ' | '__' | '' | '::') (') (NameCharNameChar)*)* Comment ::= 'Comment ::= '-->''

XML Spec: http://www.w3.org/TR/2004/REC-xml-20040204/XML Spec: http://www.w3.org/TR/2004/REC-xml-20040204/

Spring 2005 21


An XML Document GrammarAn XML Document Grammar





class class “<class>” node “</class> “<class>” node “</class>

node node name code students name code students

name name “<name>” string “</name>” “<name>” string “</name>”

code code “<code>” string “</code>” “<code>” string “</code>”

students students “<students>” student* “<students>” student* “</students>”“</students>”

student student “<student” S “id=\”” num “<student” S “id=\”” num “\”” S “/>” name birthday “\”” S “/>” name birthday “</student>”“</student>”

birthday birthday “<bday>” num “</bday>” “<bday>” num “</bday>”

Spring 2005 22


XML APIsXML APIs

SAX (Simple API for XML)SAX (Simple API for XML) – – XML-DEVXML-DEV Stream-based Access InterfaceStream-based Access Interface (Sequential Access) (Sequential Access) Notifies an application of a stream of Notifies an application of a stream of parsing eventsparsing events Needs a Needs a Content HandlerContent Handler to handle the parsing to handle the parsing

events (e.g., start and end of an element)events (e.g., start and end of an element) Appropriate to handle a large XML document Appropriate to handle a large XML document

DOM (Document Object Model)DOM (Document Object Model) – – W3CW3C Object-oriented Access Interface Object-oriented Access Interface (Random Access)(Random Access) Builds a Builds a tree of nodestree of nodes based on the structure and based on the structure and

information in an XML documentinformation in an XML document Types of nodes: Types of nodes: DocumentDocument, , ElementElement, , AttrAttr, …, …

Spring 2005 23


DOM RepresentationDOM Representation

classclass

namename codecode studentsstudents

ProgProg. Lang. Lang ICE1341ICE1341 studentstudent studentstudent

namename bdaybday namename bdaybday

Y.K. KoY.K. Ko 820304820304 D.W. KimD.W. Kim 830512830512

classclass





<class><class> <name><name>Prog. Lang.Prog. Lang.</name></name> <code><code>ICE1341ICE1341</code></code> <students><students>

<student <student id=“20037001”id=“20037001”>> <name><name>Y.K. KoY.K. Ko</name></name> <bday><bday>820304820304</bday></bday> </student></student> <student <student id=“20037002”id=“20037002”>> <name><name>D.W. KimD.W. Kim</name></name> <bday><bday>830512830512</bday></bday> </student></student>


XML DocumentXML Document DOM RepresentationDOM Representation

Document Document (Root Node)(Root Node)

Elements Elements (Child Nodes)(Child Nodes)

Node Values Node Values (Text Nodes)(Text Nodes)

Spring 2005 24


XML ProcessorsXML Processors

XML ParsersXML Parsers: read XML documents and : read XML documents and provide access to their content and structure via provide access to their content and structure via DOM (e.g., Xerces, Sun’s Java XML Parser)DOM (e.g., Xerces, Sun’s Java XML Parser)

Document Filtering (Validation)Document Filtering (Validation) Document Type Declaration (DTD)Document Type Declaration (DTD): a : a grammargrammar for for

a class of XML documents a class of XML documents XML Schema (XSD)XML Schema (XSD): a successor of DTD. : a successor of DTD.

Describes the structure of an XML documentDescribes the structure of an XML document XML PresentationXML Presentation

eXtensible Stylesheet Language (XSL)eXtensible Stylesheet Language (XSL): a : a language to define the transformation and language to define the transformation and presentation of an XML documentpresentation of an XML document

Spring 2005 25


XML ProcessorsXML Processors

XML XML DocumentDocument

DatabasesDatabases

XML ParserXML Parser

DTD/ DTD/ XMLSchemaXMLSchema

XSL XSL DescriptionDescription

XSL ProcessorXSL Processor

XML Grammar XML Grammar (Structure) Validation(Structure) Validation

DOM ObjectsDOM Objects

HTML HTML PresentationPresentation

classclass





classclass





Parsing EventsParsing Events

DOM APIDOM API SAX APISAX API

Spring 2005 26


XML Logical Structure ExamplesXML Logical Structure Examples

<patient name = "Maggie Dee <patient name = "Maggie Dee

Magpie">Magpie"> ......</patient></patient>

AW lecture notes



<patient><patient>

<name><name>

<first> Maggie </first><first> Maggie </first>

<middle> Dee </middle><middle> Dee </middle>

<last> Magpie </last><last> Magpie </last>

</name></name>

......

</patient></patient>



<patient><patient>

<name> Maggie Dee Magpie <name> Maggie Dee Magpie

</name></name>

......

</patient></patient>

Spring 2005 27


Logical Structure of an XML DocumentLogical Structure of an XML Document

A new A new nested tagnested tag needs to be defined to needs to be defined to provide more info about the content of a provide more info about the content of a tagtag

Nested tags are better than attributes, Nested tags are better than attributes, because because attributes cannot describe attributes cannot describe structurestructure and the structural complexity and the structural complexity may growmay grow

AttributesAttributes should always be used should always be used to to identify numbers or namesidentify numbers or names of elements of elements (like HTML id and name attributes)(like HTML id and name attributes)

AW lecture noteshttp://tech.irt.org/articles/js212/

Spring 2005 28


Related MaterialsRelated Materials

W3C’s XML Web Site: http://www.w3.org/XML/W3C’s XML Web Site: http://www.w3.org/XML/ XML Specification: http://www.w3.org/TR/2004/REC-XML Specification: http://www.w3.org/TR/2004/REC-

xml-20040204/xml-20040204/ XML Concepts: XML Concepts:

http://www.w3.org/Talks/General/Concepts.htmlhttp://www.w3.org/Talks/General/Concepts.html DTD Tutorial: http://www.w3schools.com/dtd/DTD Tutorial: http://www.w3schools.com/dtd/ XML Schema Tutorial: XML Schema Tutorial:

http://www.w3schools.com/schema/default.asphttp://www.w3schools.com/schema/default.asp W3C’s XSL Site: http://www.w3.org/Style/XSL/W3C’s XSL Site: http://www.w3.org/Style/XSL/ Other XML-related Notes: Other XML-related Notes:

http://www.w3.org/XML/notes.htmlhttp://www.w3.org/XML/notes.html

Spring 2005 29


Midterm Term ProjectMidterm Term Project Design a Design a structured programming languagestructured programming language that includes the that includes the

following language componentsfollowing language components Type declaration statements for Type declaration statements for int, float, char, arrayint, float, char, array Operations: Operations: +, -, *, /, and, or, not+, -, *, /, and, or, not Assignment statementAssignment statement Conditional statement (Conditional statement (ifif statement) statement) Loop (Loop (whilewhile statement) statement) Program blocks (Program blocks (beginbegin … … endend))

Develop an Develop an XML-based syntaxXML-based syntax of the language of the language Write the Write the grammargrammar of the language in EBNF of the language in EBNF Write a Write a sample programsample program by using the language that you defined by using the language that you defined Display the sample program on MS Internet Explorer to validate Display the sample program on MS Internet Explorer to validate

its XML syntaxits XML syntax Explain the Explain the language design decisionslanguage design decisions such as application such as application

domains, and naming, binding, type compatibility, scoping rulesdomains, and naming, binding, type compatibility, scoping rules

Due by April 14thDue by April 14th

Documents

ICE1341 Programming Languages Spring 2005 Lecture #8 Lecture #8 In-Young Ko iko.AT. icu.ac.kr iko.AT. icu.ac.kr Information and Communications University