Color: A Modern Web Development Language Mark J. Stahl Advised By: Dr. Mark Burge Department of Computer Science Undergraduate Project

Introduction Color is a prototyped object-oriented language designed specifically for the development of the World Wide Web. The core of the language is based on the message-passing semantics of Self and SmallTalk. Color’s evaluator was inspired by a declarative, logic programming language called Prolog. And the syntax of Color is taken directly from JavaScript, providing the familiarity and syntactic structures of the C family of languages. Current Web Language Problems Attempt to be everything to everyone URI’s (Universal Resource Identifiers) are not linguistically considered Relational database access is still reliant upon antiquated standards (i.e. SQL) No linguistic support for markup languages (XML, HTML, etc) Color Addresses These Problems Color is not a all-purpose language, and is specific to the Web domain URI’s are used for both local and remote resource (daemon, and file) access Color uses declarative (Prolog-like) expressions for database querying Markup languages are treated the same as other Objects within Color

XML / HTML Querying The following examples illustrate the using of declarative statements and predicate logic to query XML documents var xmlFamily = Mary Joseph Joseph Eleanor Mark Joseph ; // Define an ancestor predicate ‘ancestor(?c, ?p) <- ‘parent(?c, ?p); ‘ancestor(?c, ?p) <- ‘parent(?c, ?g) && ancestor( ?g, ?p); The first statement says that ‘p’ is an ancestor of ‘c’ if ‘p’ is a parent of ‘c’. The second statement says ‘p’ is an ancestor of ‘c’ if ‘c’ has some parent ‘g’ and if ‘p’ is an ancestor of ‘g’; The second line provides a recursive definition while the first line provides the simplest definition on an ancestor. // Is Joseph an ancestor of Mark’s? ancestor(“Mark”, “Joseph”); » true // Who are Mary’s ancestors? ancestor(“Mary”, ?tree); » tree = [“Joseph”, “Eleanor”)

Relational Database Querying The following examples illustrate the using of declarative statements and predicate logic to query relational database without SQL // Define an ancestor predicate ‘ancestor(?c, ?p) <- ‘parent(?c, ?p); ‘ancestor(?c, ?p) <- ‘parent(?c, ?g) && ancestor( ?g, ?p); The first statement says that ‘p’ is an ancestor of ‘c’ if ‘p’ is a parent of ‘c’. The second statement says ‘p’ is an ancestor of ‘c’ if ‘c’ has some parent ‘g’ and if ‘p’ is an ancestor of ‘g’; The second line provides a recursive definition while the first line provides the simplest definition on an ancestor. // Is Joseph an ancestor of Mark’s? ancestor(“Mark”, “Joseph”); » true // Who are Mary’s ancestors? tree = ancestor(“Mary”, ?tree); » [“Joseph”, “Eleanor”] firstname 1 2 parent index 3 Mary Joseph Mark Joseph Eleanor The members table within the stahlfamily database.

XML / HTML Element Access The following examples illustrate using the. operators in order to return or change a single value or the entirety of an XML element var xmlFamily = Mary Joseph Joseph Eleanor Mark Joseph ; // Return the first name of the first child in the list. // Returns an XMLList object containing “Mary”. var name = xmlFamily.stahlfamily.member[0].firstname; // Change Joseph’s name to Walter xmlFamily.stahlfamily.member[1].firstname = “Walter”; // Return the parent of the third child in the list. // Returns an XML object contain: // Joseph. var parent = xmlFamily.stahlfamily.member[2][1]; // Assign a variable with Joseph’s position. // Return a String object containing “father”. var familyPos =

Relational Database Access The following examples illustrate using the. operators in order to return or change a single value or the entirety of a relational database // Obtain a database resource and assign it to xmlFamily var xmlFamily = ; // Return the first name of the first child in the list. // Returns an XMLList object containing “Mary”. var name = xmlFamily.stahlfamily.member[0].firstname; // Change Joseph’s name to Walter xmlFamily.stahlfamily.member[1].firstname = “Walter”; // Return the parent of the third child in the list. // Returns an XML object contain: // Joseph. var parent = xmlFamily.stahlfamily.member[2][1]; // Assign a variable with Joseph’s position. // Return a String object containing “father”. var familyPos = firstname 1 2 parent index 3 Mary Joseph Mark Joseph Eleanor The members table within the stahlfamily database.

The Linguistic Ancestry of Color Self( –Self provided Color with its prototyped object semantics. Color also used Self’s message-passing semantics as its core syntactic structure. Color:3 + 4» 3.add(4)» 7 Self:3 + 4or 3 add: 4» 7 JavaScript( –In order to remain familiar to the majority of programmers, JavaScript was chosen to used as the main syntactic structure Color. –With JavaScript’s infix notation and the dot operator (used for object slot access), the learning curve to become proficient with Color would be heavily decreased.

Color Objects and Object Inheritance print how to print objects proto +how to add points proto x3 x: y y: 5 proto x7 x: y y: 9 clone point how to clone an object proto x0 x: y y: 0 Each Color point intrinsically describes its own format, but appeals to another object for any behavior that is shared amount points. To create a new object in Color, the ‘clone’ message is sent to the prototypical point. The ‘clone’ method copies its receiver.

Color Syntax and Objects Identifiers and Function int x = 5;// integer object with the value of 5 x = 5; // variable of type ‘variant’ containing and // integer object fun hypo(a, b) { // function can be nested fun square(x) { return x * x; } // functions can act as data as well fun square (x) { return x * x;) a = square(4); b = square; c = b(5); Objects fun Rectangle(w, h) {// Rectangle constructor this.width = w; this.height = h; } page = new Rectangle(8, 11); // assuming a function computer_area page.area = computer_area; // assuming and object Circle // we can define a property available to all Cirlcs Circle.proto.pi = ; // or change an objects prototype at runtime page.proto = new Circle();