This chapter discusses how to engineer the criteria from Chapters 2 through 5 to be used with several different types of technologies. These technologies have come to prominence after much of the research literature in software testing, but are now very common and account for a large percentage of new applications being built. Sometimes we modify the criteria, and sometimes simply discuss how to build the models that the existing criteria can be applied to. Some of these technologies, such as Web applications and embedded software, tend to have extremely high reliability requirements. So testing is crucial to the success of the applications. The chapter explains what is different about these technologies from a testing viewpoint, and summarizes some of the existing approaches to testing software that uses the technologies.

Object-oriented technologies became prominent in the mid-1990s and researchers have spent quite a bit of time studying their unique problems. A number of issues with object-oriented software have been discussed in previous chapters, including various aspects of applying graph criteria in Chapter 2, integration mutation in Chapter 5 and the CITO problem in Chapter 6. This chapter looks into how the use of classes affects testing, and focuses on some challenges that researchers have only started addressing. Most of these solutions that have not yet made their way into automated tools. The most important of these challenges is testing for problems in the use of inheritance, polymorphism, and dynamic binding.

We end this book with a discussion of three challenging areas in testing software. Although researchers have been interested in emergent properties for many years, the area, far from being “solved,” continues to escalate in terms of importance for industry. Likewise, testability is attracting renewed attention due to characteristics of some of the newer software technologies. Finally, we suggest some directions for software testing in practice and in the research arena.

TESTING FOR EMERGENT PROPERTIES: SAFETY AND SECURITY

Testing for emergent properties presents special challenges. This section offers high level guidance for engineers faced with testing systems where safety and/or security play an important role.

Emergent properties arise as a result of collecting components together into a single system. They do not exist independently in any particular component. Safety and security are classic emergent properties in system design. For example, the overall safety of an airplane is not determined by the control software by itself, or the engines by themselves, or by any other component by itself. Certainly, the individual behavior of a given component may be extremely important with respect to overall safety, but, even so, the overall safety is determined by the interactions of all of these components when assembled into a complete airplane. In other words, an airplane engine is neither safe nor unsafe considered by itself because an airplane engine doesn't fly by itself.

Formal fuzzy logic has developed into an extensive, rigorous, and exciting discipline since it was first proposed by Joseph Goguen and Lotfi Zadeh in the midtwentieth century, and it is a wonderful topic for introducing students to the richness and fascination of formal logic and the philosophy thereof. This textbook grew out of an interdisciplinary course on fuzzy logic that I've taught at Smith College, a course that attracts philosophy, computer science, and mathematics majors. I taught the course for several years with only a course reader because the few existing texts devoted to fuzzy logic were too advanced for my undergraduate audience (and probably for some graduate audiences as well). Finally, after writing voluminous supplements for the course, I decided to write an accessible introductory textbook on many-valued and fuzzy logic. It is my hope that after working through this textbook, students will have the necessary background to tackle more advanced texts, such as Gottwald (2001), Hájek (1998b), and Novák, Perfilieva, and Močkoř (1999), along with the rest of the vast fuzzy literature.

This book opens with a discussion of the philosophical issues that give rise to fuzzy logic – problems and paradoxes arising from vague language – and returns to those issues as new logical systems are presented. There is a two-chapter review of classical logic to familiarize students and instructors with my terminology and notation, and to introduce formal logic to those who have no prior background.

It's time to face two problems that we sidestepped while exploring three-valued logical systems for vagueness.

Although the Sorites argument is valid in all of the systems we've presented, we claimed that the paradox can nevertheless be dissolved in three-valued logic because the Principle of Charity premise is not true on any reasonable interpretation. The first problem concerns the exact nature of the principle's nontruth. Our sample interpretations rendered the premise false in Bochvar's external system, which didn't sound right because its negation – which states that 1/8″ does make a difference – must then be true. However, the situation looked more promising in the other three systems, where the Principle of Charity and its negation were neither true nor false. But now let us recall that the Principle of Charity is so called by virtue of the colloquial reading, One-eighth of an inch doesn't make a difference. Put that way, the Principle of Charity seems true, or close to it, doesn't it? If you shrink a tall person by 1/8″, surely that person will still be tall. (If you disagree, change the shrinking to 1/100″ – we'll still get the paradox, but surely 1/100″ doesn't make a difference.) Three-valued accounts can avoid the paradox by claiming that the Principle of Charity is either false or neither true nor false, but that leaves another puzzle: why does the principle seem to be true?

We can expect, within a fairly short time frame, that each research-based institution in Europe will have a repository and that the research outputs from each institution will be collected in and disseminated through the repository. Within the scope of this publication, a digital repository is being defined as

• 1. Containing research results,

• 2. Institutional and/or thematic, and

• 3. OAI-PMH compliant.

Institutional repositories contain scholarly publications (reports, working papers, preprints, post prints and published versions of articles and books) produced by universities or research institutions. Thematic repositories are usually organised around a specific discipline or research domain. All digital repositories, either institutional or thematic, comply with the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH), which enables their contents to be widely shared. Digital repositories contribute to the open access movement by providing platforms for researchers to make research results freely available on the web. They contribute to improving the visibility of research results, typically scientific articles, and are as such an important part of the digital repositories infrastructure vision for European research (DRIVER).

This DRIVER's Guide to Repositories aims to motivate and promote the creation, development and networking of digital repositories. The guide does not provide strict directions on how to construct a repository, or network of repositories. It contains comprehensive and current information on digital repository-related issues in the research community and is particularly relevant to repository managers, decision makers, funding agencies and infrastructure services as stakeholders. This guide not only supports the institutions that already participate in the current EU-funded DRIVER network, it also reaches out to institutions that are about to get started with repositories or aim to further extend their current services or impact.

DRIVER has identified five specific, complex and longer-term issues which are essential to either the establishment, development or sustainability of a digital repository:

• – the business of digital repositories

• – the population of repositories

• – intellectual property rights

• – data curation

• – long-term preservation

The success of a repository depends on having addressed these five issues sufficiently. Good practices and lessons learned as part of this report will assist stakeholders in both their day-to-day and long-term challenges, and can help them avoid reinventing the wheel. These issues will be addressed in five chapters, which all focus on inter- and transnational approaches.

Kleene's “strong” three-valued logic

We began Chapter 1 by noting that sentences concerning borderline cases of vague predicates pose counterexamples to the Principle of Bivalence. For example, the sentence Mary Middleford is tall appears to be neither true nor false. We begin our exploration of logics for vagueness by dropping the Principle of Bivalence and allowing sentences to be either true (T), false (F), or neither true nor false (N – if you like, you may also say that N is neutral). This gives rise to three-valued (trivalent) systems of logic. We use the same language as classical propositional logic. Truth-value assignments can now assign N (as well as T or F) to atomic formulas, and we'll use this value to signal the application of a vague predicate to a borderline case.

How are the truth-functions for the standard propositional connectives defined over the three values? There are several plausible choices, and the set of truth-functions we choose will define a specific system of three-valued logic. In this chapter we present four well-known systems of three-valued logic. Many others have been developed, but these four systems are sufficient to explore the flavor of three-valued logics and how they might be used to tackle problems associated with vagueness.

Overview

It will be surprising if there are any tertiary-level research-based or teaching institutions in Europe that do not have a digital repository within a few years. Worldwide, repositories have been increasing at an average rate of about one per day over the last year or so and this can be expected to gather pace further. The reasons for having a repository are so compelling, the advantages so obvious, the payoff so potentially large, that no institution seriously intent upon its mission, and upon enhancing its profile and internal functioning, will want to disadvantage itself badly by not having one (or more).

Digital repositories can also be developed and maintained by a subject community (or entity acting on behalf of a subject community). These are more usually established by harvesting content from institutional repositories, but there are a few exceptions where subject community repositories attract content from the creators directly. Institutional and subject repositories have many purposes in common, but institutions find additional, institution- specific advantages in having a repository, too. Digital repositories have a number of functions or foci:

• – to open up and offer the outputs of the institution or community to the World

• – to impact on and influence developments by maximising the visibility of outputs and providing the greatest possible chance of enhanced impact as a result

• – to showcase and sell the institution to interested constituencies – prospective staff, prospective students and other stakeholders

• – to collect and curate digital outputs (or inputs, in the case of special collections)

• – to manage and measure research and teaching activities

• – to provide and promote a workspace for work-in-progress, and for collaborative or large-scale projects

• – to facilitate and further the development and sharing of digital teaching materials and aids

• – to support and sustain student endeavours, including providing access to theses and dissertations and providing a location for the development of e-portfolios

This chapter covers the business issues around digital repositories – their raisons d’être, putting forth a business case for repositories, the costs and resources associated with them, and the things managers must think about and plan for in sustaining and developing them. Repositories can cost a lot to establish, or very little.

Issues of vagueness

Some people, like 6′ 7″ Gina Biggerly, are just plain tall. Other people, like 4′ 7″ Tina Littleton, are just as plainly not tall. But now consider Mary Middleford, who is 5′ 7″. Is she tall? Well, kind of, but not really – certainly not as clearly as Gina is tall. If Mary Middleford is kind of but not really tall, is the sentence Mary Middleford is tall true? No. Nor is the sentence false. The sentence Mary Middleford is tall is neither true nor false. This is a counterexample to the Principle of Bivalence, which states that every declarative sentence is either true, like the sentence Gina Biggerly is tall, or false, like the sentence Tina Littleton is tall (bivalence means having two values). The counterexample arises because the predicate tall is vague: in addition to the people to whom the predicate (clearly) applies or (clearly) fails to apply, there are people like Mary Middleford to whom the predicate neither clearly applies nor clearly fails to apply. Thus the predicate is true of some people, false of some other people, and neither true nor false of yet others. We call the latter people (or, perhaps more strictly, their heights) borderline or fringe cases of tallness.

Vague predicates contrast with precise ones, which admit of no borderline cases in their domain of application. The predicates that mathematicians typically use to classify numbers are precise.