Disclaimer: The definitions below are intended for tracing the long road of defining what databases are about, therefore the value of the quotes should be regarded from the historical perspective.
"Historically, data base systems evolved as generalized access methods [...] As a result, most data base systems emphasize the question of how data may be stored or accessed, but they ignore the question of what the data means to the people who use it." (John F Sowa, "Conceptual Graphs for a Data Base Interface", 1976)
"A database is a set of data whose structure can be described by a connected graph, and whose instances can be accessed simultaneously." (Rob Gerritsen et al, "On Some Metrics for Databases or What is a Very Large Database?", 1977)
"Data […] that is stored more-or-less permanently in a computer we term a database." (Jeffrey D Ullman, "Principles of Database Systems", 1980)
"When we talk informally about a database, we refer to a collection of mutually related data, to the computer hardware that is used to store it, and to the programs used to manipulate it. […] A database is a collection of related data. The data storage for a database is accomplished by the use of one or more files. All files of one database are accessible from one computer or from any interconnected computer if the database is distributed over several computers." (Gio Wiederhold, "Database Design" 2nd Ed., 1983)
"[...] there is a class of methodologies - really more of an environment - for storing, accessing, and in general, managing data which can form the foundation for survival in a world which is going to become ever more data oriented as time goes on. That class of methodologies or environment has come to be known as database." (Mark L Gillenson, "Database: Step by Step", 1985)
"A database is a self-describing collection of integrated records. […] A database is self-describing in that it contains, in addition to application data, a description of its own structure. […] A database is more than a collection of files. A database includes not only files, but also a data dictionary and a description of the relationships among the records in the files. These relationship descriptions are stored and recalled during database. […] A database is a data model of an organization." (David M Kroenke & Kathleen Dolan, , "Database Processing: Fundamentals, design, implementation" 3rd Ed., 1988)
"A database is not a technology. Rather, it is an expression of organization, clarity, and precision. It may or may not be computerized. If it is, it may exist on a microcomputer, a minicomputer, or a large mainframe. Finally, a database may or may not be centralized. However a database is implemented and operated, success is impossible without the codification of and adherence to data semantics, which are the rules for meaning, validity, and usage." (Michael M Gorman, "Database Management Systems: Understanding and Applying Database Technology", 1991)
"What is a database? It's a file - that's an electronic version of information sheets and binders. It enables you to efficiently use your information. […] Just as a binder contains information sheets, a database holds records. […] First, a database enables you to store larger amounts of information than a binder. […] Second, a database enables you to retrieve your information more efficiently, more flexibly, and more creatively. […] Third, a database can manipulate the information it contains. […] Fourth, a database enables you to print your information on Information envelopes, labels, fax cover sheets, reports, and letters." (Guy Kawasaki, "Database 101", 1991)
"When a database is computerized, it represents the automation of the knowledge component of a business, which is manifest through the business's quality operation, planning, and management With a successful database, the managers of a business can research the past, organize the present, and plan for the future." (Michael M Gorman, "Database Management Systems: Understanding and Applying Database Technology", 1991)
"Conceptually, the database is a set of sentences expressing propositions asserted to be true of the UoD [Universe of Discourse]. Since sentences may be added to or deleted from the database, the database may undergo transitions from one state to another. However, at any particular time, the sentences populating the database must individually and collectively conform to the application specific grammar or design plan which is the conceptual schema." (Terry Halpin, "Conceptual Schema & Relational Database Design" 2nd Ed., 1995)
"In using a data base, first look at the metadata, then look at the data. [...] The old computer acronym GIGO (Garbage In, Garbage Out) applies to the use of large databases. The issue is whether the data from the database will answer the research question. In order to determine this, the investigator must have some idea about the nature of the data in the database - that is, the metadata." (Gerald van Belle, "Statistical Rules of Thumb", 2002)
"To be worthy of being called a database, a system must have two essential properties. 1. It holds data as an integrated system of records. 2. It contains self-describing information." (Colin Ritchie, "Relational Database Principles" 2nd Ed., 2002)
"A database can be considered as an organised collection of data which is meant to represent some UoD [Universe of Discourse]. […] A database is made up of two parts: an intensional part and an extensional part. The intension of a database is a set of definitions which describe the structure or organisation of a given database. The extension of a database is the total set of data in the database. The intension of a database is also referred to as its schema." (Paul Beynon-Davies, "Database Systems" 3rd Ed. 2004)
"A database in manual terms is analogous to a filing cabinet, or more accurately to a series of filing cabinets. A database is a structured repository for data. The overall purpose of such a repository is to maintain data for some set of organisational objectives. Traditionally, such objectives fall within the domain of administration. Most database systems are built to retain the data required for the running of the day-to-day activities of an organisation. […] Structure normally implies some logical division, usually hierarchical. Hence we speak of a database as being a collection of data structures. […] Each data structure in a database is in turn also a hierarchical collection of data. In manual terms, such data structures would be folders hung in a filing cabinet." (Paul Beynon-Davies, "Database Systems" 3rd Ed. 2004)
"Databases rarely begin their life empty. More often the starting point in their lifecycle is a data conversion from some previously exiting data source. And by a cruel twist of fate, it is usually a rather violent beginning. Data conversion usually takes the better half of new system implementation effort and almost never goes smoothly." (Arkady Maydanchik, "Data Quality Assessment", 2007)
"[...] data conversion is the most difficult part of any system implementation. The error rate in a freshly populated new database is often an order of magnitude above that of the old system from which the data is converted. As a major source of the data problems, data conversion must be treated with the utmost respect it deserves." (Arkady Maydanchik, "Data Quality Assessment", 2007)
"The corporate data universe consists of numerous databases linked by countless real-time and batch data feeds. The data continuously move about and change. The databases are endlessly redesigned and upgraded, as are the programs responsible for data exchange. The typical result of this dynamic is that information systems get better, while data deteriorates. This is very unfortunate since it is the data quality that determines the intrinsic value of the data to the business and consumers. Information technology serves only as a magnifier for this intrinsic value. Thus, high quality data combined with effective technology is a great asset, but poor quality data combined with effective technology is an equally great liability." (Arkady Maydanchik, "Data Quality Assessment", 2007)
"As we know, every action produces an equal and opposite reaction. Adding security reduces performance. Sharding and partitioning the database affords greater performance and distribution but creates complexity that is difficult to manage. Adding robust monitoring can generate huge volumes of log data to be stored, rotated, secured, and cleansed. Keeping the design “simple” often defers the interests of flexibility until later, where it becomes very expensive." (Eben Hewitt, "Technology Strategy Patterns: Architecture as strategy" 2nd Ed., 2019)
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