Design of a Graphics Interface for Linear Programming

Information Systems Working Papers Serie

THE SCIENCE AND ART OF FORMULATING LINEAR PROGRAMS

This paper describes the philosophy underlying the development of an intelligent system to assist in the formulation of large linear programs. The LPFORM system allows users to state their problem using a graphical rather than an algebraic representation. A major objective of the system is to automate the bookkeeping involved in the development of large systems. It has expertise related to the structure of many of the common forms of linear programs (e.g. transportation, product-mix and blending problems) and of how these prototypes may be combined into more complex systems. Our approach involves characterizing the common forms of LP problems according to whether they are transformations in place, time or form. We show how LPFORM uses knowledge about the structure and meaning of linear programs to construct a correct tableau. Using the symbolic capabilities of artificial intelligence languages, we can manipulate and analyze some properties of the LP prior to actually generating a matrix.Information Systems Working Papers Serie

HYPER MODEL MANAGEMENT SYSTEMS

In this paper we study the integration of Model Management and Hypertext systems to produce a Hyper Model Management System (HMMS). Model Management Systems constitute a class of software that is designed to support the construction, storage, retrieval, and use of models in the context of decision support systems (DSS). Hypertext systems allow users to split information into data fragments which the user cart browse to find information by taking non-linear paths in computer based texts. It has been suggested that DSSs should be conceived as environments which support decision making. We support the view that such environments can be readily provided for the subtask of model management by hypertext systems. The different kinds of model knowledge can be captured within different types of hypertext nodes and the relationships among these can be maintained by hypertext links. In this paper we describe some aspects of model management where hypertext will have a significant impact. However, plain hypertext is ineffective in dealing with the dynamic nature of information in model management tasks where data is revised, models executed, and reports are created on the fly. Dynamic domains require dynamic hypertexts. In this paper we also study the requirements for dynamic hypertexts. These can be satisfied within the class of generalized hypertext systems by using special hypertext nodes and links which we describe. We explore different architectures to integrate MMS and Hypertext systems to obtain HMMSs. This paper emphasizes the need for a shift to integrating Model Management and hypertext technologies.Information Systems Working Papers Serie

LPBlocks: a block-based language for linear programming

Dissertação de mestrado em Informatics EngineeringLinear programming is a mathematical optimization technique used in numerous fields including mathematics, economics, and computer science, with numerous industrial contexts, including solving optimization problems such as planning routes, allocating resources, and creating schedules. As a result of its wide breadth of applications, a considerable amount of its user base lacks programming knowledge and experience and thus often resorts to using graphical software such as Microsoft Excel. However, despite its popularity amongst less technical users, the methodologies used by these tools are often ad-hoc and prone to errors. Block-based languages have been successfully used to aid novice programmers and even children in programming. Thus, we created a block-based programming language termed LPBlocks that allows users to create linear programming models using data contained in spreadsheets. This language guides the users to write syntactically and semantically correct programs and thus aids them in a way that current languages do not. We have also implemented a web application where users can define linear programming models, reactively see their mathematical representation and execute them to obtain the optimization values for the variables defined by the users. To assess the applicability of LPBlocks we used it to successfully express numerous and varied linear programming problems. Furthermore, we designed and ran a qualitative empirical study to understand the experience our tool and language brings to users from various backgrounds. Although we see differences amongst the users, most of them were able to model several problems using LPBlocks.Programação linear é um conjunto de técnicas de otimização matemática utilizada em várias áreas estas incluem matemática, economia, ciências da computação e usos em contextos industriais, incluindo planear rotas, alocar recursos e planear horários. Como resulta das suas aplicações variadas uma grande quantidade dos seus utilizadores não possuem conhecimentos de programação e por isso utilizam software gráfico como o Microsoft Excel. Apesar da sua popularidade este software utiliza metodologias ad-hoc e propicias a erros. As linguagem de programação por blocos tem surgido nos últimos anos com o intuito de ajudar programadores iniciantes, tendo mesmo aplicações no ensino de crianças. Sendo assim nos criamos uma linguagem de programação pro blocos que utiliza dados contidos em folhas de calculo para criar modelos de programação linear chamada LPBlocks. Esta linguagem guia utilizadores na criação de modelos semanticamente e sintaticamente corretos. Para avaliar a validade de LPBlocks nos implementamos vários problemas utilizando a mesma. Posteriormente implementamos esta linguagem e utilizamo-la num estudo com utilizadores de vários níveis de experiência. Depois utilizamos a informação recolhida durante o estudo para avaliar LPBlocks e propor melhorias

HYPERTEXT-BASED RELATIONSHIP MANAGEMENT FOR DSS

There is a need for integrated access to a wide range of information related to the development and use of DSS in organizations. This information comes in many forms, both formal and informal, and is highly interrelated. To handle this complex information base, we argue that a separate relationship management component should be added to the three traditional components of a DSS (namely, the database, user interface and model management systems). The role of the relationship management component is to relieve DSS application programs of the need to maintain and provide access to the complex set of relationships that can exist between elements in the application domain. We discuss the kinds of information and relationships that arise during the development and use of a DSS, outline the requirements for an independent subsystem to manage this information base, and propose the use of an extended hypertext software system, H+, to simultaneously handle relationship management and provide an interesting and useful interface to users.Information Systems Working Papers Serie

LPSPEC: A Language for Representing Linear Programs

Information Systems Working Papers Serie

HYPER MODEL MANAGEMENT SYSTEMS

In this paper we study the integration of Model Management and Hypertext systems to produce a Hyper Model Management System (HMMS). Model Management Systems constitute a class of software that is designed to support the construction, storage, retrieval, and use of models in the context of decision support systems (DSS). Hypertext systems allow users to split information into data fragments which the user cart browse to find information by taking non-linear paths in computer based texts. It has been suggested that DSSs should be conceived as environments which support decision making. We support the view that such environments can be readily provided for the subtask of model management by hypertext systems. The different kinds of model knowledge can be captured within different types of hypertext nodes and the relationships among these can be maintained by hypertext links. In this paper we describe some aspects of model management where hypertext will have a significant impact. However, plain hypertext is ineffective in dealing with the dynamic nature of information in model management tasks where data is revised, models executed, and reports are created on the fly. Dynamic domains require dynamic hypertexts. In this paper we also study the requirements for dynamic hypertexts. These can be satisfied within the class of generalized hypertext systems by using special hypertext nodes and links which we describe. We explore different architectures to integrate MMS and Hypertext systems to obtain HMMSs. This paper emphasizes the need for a shift to integrating Model Management and hypertext technologies.Information Systems Working Papers Serie

HYPERTEXT-BASED RELATIONSHIP MANAGEMENT FOR DSS

There is a need for integrated access to a wide range of information related to the development and use of DSS in organizations. This information comes in many forms, both formal and informal, and is highly interrelated. To handle this complex information base, we argue that a separate relationship management component should be added to the three traditional components of a DSS (namely, the database, user interface and model management systems). The role of the relationship management component is to relieve DSS application programs of the need to maintain and provide access to the complex set of relationships that can exist between elements in the application domain. We discuss the kinds of information and relationships that arise during the development and use of a DSS, outline the requirements for an independent subsystem to manage this information base, and propose the use of an extended hypertext software system, H+, to simultaneously handle relationship management and provide an interesting and useful interface to users.Information Systems Working Papers Serie