Semantic and Declarative Technologies AIT Budapest Péter Szeredi http://cs.bme.hu/~szeredi/ait/

Semantic? Declarative? What the hell…? According to the Merriam-Webster dictionary: Semantic (adjective): relating to the meanings of words and phrases Declarative (adjective): having the form of a statement rather than a question or a command And in conjunction with technology? Semantic web: let search engines understand the web, not just read it Declarative programming: solve tasks by just describing the desired solution Why together in the same course? Common foundation: (mathematical) logic

Question: X? Answer: X?

A puzzle scheme from the book … Imagine an island on which every native is either a knight – who always tells the truth; or a knave – who always lies But they cannot be distinguished otherwise… If you hear Alf saying: “1+1=2”, he is a … If you hear Bob saying “1+1=3”, he is a … What if Cecil says: “I am a knight”? Can Cecil be a knight? Can he be a knave? Can it happen that Dan says: “I am a knave”?

Puzzle # 28 from the book In this problem, there are two natives, A and B. A makes the following statement: “At least one of us is a knave.” (*) What are A and B? Think of writing a program in your favorite programming language, which takes (*) or some similar text as input, and returns the solution(s)…

Let’s use “controlled English” input <person> ::= A | B | C | … <native> ::= knight | knave <statement> ::= <person> is a <native> | <person> says <statement> | <statement> and <statement> | <statement> or <statement> “A says: at least one of us is a knave.” becomes: A says A is a knave or B is a knave Given this input format, how many lines of code would the puzzle solver require in your favorite programming language?

Prolog - Programming in logic (or English?) Prolog is a simple, yet very flexible programming language based on a subset of First Order Logic Examples (use syntax extensions, additional operators, etc.) statements of a knight have truth value 1. % truth(knight, 1). statements of a knave have truth value 0. % truth(knave, 0).    statement (Native1 is a Native2) evaluates to B  if      statements of a Native1 have truth value B1 and     statements of a Native2 have truth value B2 and     B is 1-abs(B1-B2). % is is a built in for arithmetic, here B = 1 iff B1==B2 statement (Native1 says S) evaluates to B  if              statements of a Native1 have truth value B1 and      statement S evaluates to B2 and B is 1-abs(B1-B2). statement (S1 or S2) evaluates to B if     statement S1 evaluates to B1 and      statement S2 evaluates to B2 and     B is B1 \/ B2.  % B is the disjunction of B1 and B2

SWISH: a web environment for Prolog

Adding constraints to Prolog Constraint Logic Programming (CLP) – what is it? It extends Prolog with much stronger reasoning capabilities for a limited data domain (e.g. integers, Booleans, etc.) CLPFD (CLP for Finite Domain) – very efficient solution of combinatorial problems, e.g. Sudoku puzzles 7 4 2 1 9 3 5 8 6 7 4 2 1 9 3 5 8 6

The Semantic Web (SW) part of the course Description Logics (DL) – the maths behind SW DL variants with different complexity Transforming human knowledge to DL format Reasoning algorithms (outline) The practical side of the Semantic Web OWL 2 (Web Ontology Language) The Protégé editor and reasoning framework

Course summary Rough course layout: Requirements: Course webpage: Introduction to (First Order) Logic Weeks 1-2 Prolog programming Weeks 2-7 Constraint programming Weeks 8-12 Logics for the Semantic Web Weeks 12-14 Requirements: 2 assignments (15% each) 30% total 2 tests (mid-term & final, 20% each) 40% total Many small exercises + class activity 30% Course webpage: http://cs.bme.hu/~szeredi/ait/

Abilities helpful for this course The ability of clean, logical formulation of one’s expectations of a function or a procedure The ability to write recursive programs The acceptance of the single assignment principle: a variable can be assigned a value only once

Why should you attend this course? Learn a very different programming paradigm, which you can also use in other languages such as C, Java, etc. Learn techniques to quickly and concisely solve difficult algorithmic problems Learn Description Logics – the maths behind the next generation „intelligent" Web 3.0 It’s a niche market – experts of declarative and semantic technologies enjoy high-paying jobs

Some real-life applications Clarissa: natural voice processing used in systems on the International Space Station NRM: network management system for configuring multi-vendor IP backbone networks ContractExpress: intelligent contract creation system for law firms COPLEX: real-time logistics optimization Watson: cognitive system that defeated former human champions in the Jeopardy! quiz show SecuritEase: the dominant stock broking system in New Zealand