Constraint programming is an area of Artificial Intelligence which has many applications. This thesis applies its techniques to a new kind of problem - the rendering of online retailer websites.
First, in-depth introductions to constraint programming and the problem of
rendering a shop website will be given. A prototypical implementation of a
constraint problem solver and a system to solve and illustrate the problem will
be described.
The architecture of the prototypical implementation and specific features, algorithms, and design decisions will be detailed, analysed, and illustrated. An overview of related work both in the fields of constraint programming and website generation will be presented and existing technologies evaluated.
Features and concepts unique to this thesis, like real-time constraint satisfaction, will be introduced and discussed.
Finally, a comprehensive example will illustrate the problem, means of modelling it, and possible solutions. An outlook to future work and a summary conclude the
thesis.
Constraint Programming ist ein Teilgebiet der künstlichen Intelligenz mit vielen praktischen Anwendungen. Diese Diplomarbeit wendet die Techniken auf eine neue Art von Problem an - das Rendern von Webseiten von Internetshops.
Zuerst wird eine detaillierte Einführung zu Constraint Programming und dem Problem die Webseite eines Online-Shops zu rendern gegeben werden. Eine Beispielimplementierung eines Constraint Problem Solvers und eines Systems um das Problem zu lösen und illustrieren werden beschrieben werden.
Die Architektur der Beispielimplementierung und spezielle Eigenschaften, Algorithmen und Implementierungsentscheidungen werden genau beschrieben, analysiert und illustriert werden. Ein Überblick von ähnlichen Arbeiten sowohl im Bereich des Constraint Programming als auch im Bereich des Generierens von Webseiten wird dargestellt und vorhandene Technologien bewertet werden.
Besonderheiten und Konzepte, die in dieser Diplomarbeit erarbeitet wurden, wie Echtzeit-Constraint Satisfaction, werden eingeführt und diskutiert werden.
Schließlich wird ein ausführliches Beispiel das Problem, Arten der Modellierung und mögliche Lösungen veranschaulichen. Ein Ausblick auf zukünftige Forschung und eine Zusammenfassung beschließen diese Diplomarbeit.
Contents
Introduction
Motivation
Aim and Scope
Related Work
I Modelling of the Problem
1 Description of the Problem
1.1 Personalised Content
1.2 Generating Personalised Content
1.3 Constraints to consider
2 Constraints
2.1 Introduction
2.2 Constraint Satisfaction Problems
2.3 Solution Process
2.3.1 Arc Consistency
2.4 Constrained Optimisation Problems
2.4.1 Extended Constrained Optimisation Problems
2.5 Soft Constraints
2.6 Real-time Constraint Satisfaction
2.6.1 Analysis of the Function ψ
3 Constraint Problem Model
3.1 Slots and Campaigns
3.2 Values of Campaigns
3.3 Values of Slots
3.3.1 Example
3.4 Relaxation of Constraints
3.5 Duplicate Content
3.5.1 Example
3.6 Forced Promotions
3.6.1 Example
3.7 Real-time Problem Solution
II Prototypical Implementation
4 Overview
4.1 System Architecture
4.1.1 Distributed Approach
4.1.2 Web Interface
4.1.3 Web Service
4.2 Implementation Language
4.2.1 Documentation
4.2.2 Testing
4.2.3 Packaging
4.3 Version Control System
4.4 Test Machine Setup
5 Constraint Problem Solver Library
5.1 Overview of existing Constraint Problem Solvers
5.2 Architecture
5.2.1 Domain
5.2.2 Variable
5.2.3 AbstractConstraint
5.2.4 BinaryConstraint
5.2.5 BinaryRelation
5.2.6 AllDifferentConstraint
5.2.7 TupleConstraint
5.2.8 OneOfEqualsConstraint
5.2.9 ConstraintList
5.2.10 Problem
5.2.11 Solution
5.2.12 ConstraintSolver
5.2.13 Ruby Extensions
5.3 Constraint Problem Solution
5.3.1 Solution Process
5.3.2 Modifications for Soft Constraints
5.3.3 Constraint Satisfaction with Time Limit
5.3.4 Variable and Value Ordering
5.4 Constraint Revision
5.4.1 Binary Constraints
5.4.2 All Different Constraints
5.4.3 Tuple Constraints
5.4.4 One-of-equals Constraint
5.5 Tests and Package Management
5.6 Limitations
6 Constraint Problem Solver SOAP Wrapper
6.1 Architecture
6.1.1 Library Script
6.1.2 WSDL
6.1.3 Control Scripts
6.2 Tests and Package Management
6.3 Limitations
6.4 Use of the Interface
7 Web User Interface
7.1 Architecture
7.1.1 Data Model
7.1.2 Controller
7.1.3 View
7.2 Interface to Amazon.com
7.3 Tests and Package Management
7.4 Full Example
8 Summary
8.1 Future Work
8.1.1 Constraint Model
8.1.2 Constraint Solver
8.2 Conclusion
III Appendix
A Performance Evaluation of Consistency Algorithms
A.1 Binary Constraints
A.1.1 Methodology
A.1.2 Results
A.2 All Different Constraints
A.2.1 Methodology
A.2.2 Results
A.3 The Difference All Different makes
B Effectiveness of Real-time Constraint Satisfaction
B.1 Methodology
B.2 Results
B.2.1 Time Limit after first Solution
B.2.2 Time Limit before first Solution
C Installation Instructions and Software Versions
C.1 General
C.2 Constraint Problem Solver Library
C.3 Constraint Problem Solver SOAP Wrapper
C.4 Web User Interface
Research Objective and Core Topics
The primary research objective of this thesis is to demonstrate the feasibility of using constraint programming to generate personalised websites dynamically. The work addresses the increasing complexity of website design by modelling the rendering process as a constraint satisfaction and optimisation problem, ensuring that tailored content is delivered to customers efficiently within real-time constraints.
- Application of Artificial Intelligence techniques to dynamic web content generation.
- Modelling of complex constraints such as duplicate content prevention, page value maximisation, and real-time response requirements.
- Development of a prototypical constraint solver library implemented in Ruby.
- Integration of the solver with web services via SOAP for distributed architecture.
- Performance evaluation of consistency algorithms and real-time constraint satisfaction effectiveness.
Excerpt from the Publication
1.3. Constraints to consider
The most important constraints are summarised below. Depending on the specific retailer and web site there might be many more to consider. It is not meant to be an exhaustive and accurate model.
no duplicate content Any content shown on a page must be free of duplicates. Not only does this create a bad impression with the customer, but also uses space which might instead be used to promote different products and increase the chances of showing something the user is interested in.
no bad recommendations Bad recommendations are promotions for products the customer has already bought or is not interested in. The chances of selling the promoted item are very small, and maybe the customer will be annoyed and lose interest in the page.
maximisation of page value The value of a page is determined by the content shown and how it is shown. Personalised content is more valuable than non-personalised content. Showing something valuable on top of the page is better than showing it at the bottom, such that the customer has to scroll down to notice it. Further difficulties arise because the value of content is not known or not known exactly. Different customers prefer different types of content and therefore the content does not have an intrinsic value.
limited time The page must be presented to the customer before he loses interest – the time which can be spent generating it is limited. This does not only include the time to compute what to show, but also the time the page fragments need to render themselves.
available data Depending on the data available, the content which can be generated is different. The value of the page has to be maximised regardless of this. There always has to be something to display, even if there is no data available at all.
Summary of Chapters
1. Description of the Problem: This chapter introduces the challenges of website personalisation and the necessity for dynamic content generation, defining key constraints for online retail environments.
2. Constraints: This section establishes the theoretical foundations of constraint satisfaction and optimisation problems, including formal definitions and algorithms for consistency.
3. Constraint Problem Model: This chapter translates the identified web-rendering requirements into a formal constraint model, introducing concepts like slot-campaign associations and duplicate content prevention.
4. Overview: This chapter details the architectural design of the prototypical implementation, focusing on the integration of the solver, the SOAP wrapper, and the web interface.
5. Constraint Problem Solver Library: This chapter explains the internal logic and object-oriented implementation of the custom constraint solver library in Ruby.
6. Constraint Problem Solver SOAP Wrapper: This chapter describes the technical implementation of the SOAP-based web service that exposes the solver's functionality to external clients.
7. Web User Interface: This chapter introduces the front-end application built with the Camping framework, which demonstrates the end-to-end rendering of personalised website components.
8. Summary: This concluding chapter reviews the achievements of the thesis, discusses limitations, and suggests directions for future research in real-time constraint satisfaction.
Keywords
Constraint Programming, Artificial Intelligence, E-Commerce, Website Personalisation, Constraint Satisfaction, Optimisation, Dynamic Web Rendering, SOAP, Ruby, Real-time Systems, Consistency Algorithms, Constraint Modelling, User Interface, Web Services, Software Architecture
Frequently Asked Questions
What is the core focus of this research?
The research focuses on applying Artificial Intelligence techniques, specifically constraint programming, to solve the complex problem of generating personalised content for online retailer websites in real-time.
What are the primary challenges addressed by this work?
The work addresses challenges such as ensuring content variety (no duplicates), improving recommendation relevance, maximising the business value of displayed content, and adhering to strict real-time rendering constraints.
What is the primary goal of the system presented?
The goal is to provide a proof-of-concept and prototypical implementation of a system capable of assembling web content dynamically based on specific constraints relevant to each individual user session.
Which methodologies were employed?
The author developed a custom constraint solver library from scratch in Ruby, employing algorithms for constraint propagation, arc consistency, and soft constraints to handle optimisation tasks.
What does the main body of the thesis cover?
The body covers problem modelling, theoretical background of constraint satisfaction, implementation details of a dedicated solver library, development of a SOAP-based wrapper, and a web-based user interface for demonstration.
What define the main keywords of this work?
Key terms include Constraint Programming, E-Commerce, Personalisation, Optimisation, Real-time Satisfaction, and Web Service Architecture.
How is the performance of the implemented solver evaluated?
The performance is evaluated through extensive benchmarking in the appendix, comparing different consistency algorithms (like binary decomposition vs. hyper-arc consistency) across various problem sizes and types.
How does the system handle time-critical website rendering?
The system incorporates a "real-time constraint satisfaction" mechanism that drops constraints based on their priority and cost as the available computing time nears its limit, ensuring a result is always produced.
- Citation du texte
- Lars Kotthoff (Auteur), 2007, Using constraints to render websites, Munich, GRIN Verlag, https://www.grin.com/document/83438
