A personal knowledge base (PKB) is an electronic tool used to express, capture, and later retrieve the personal knowledge of an individual. It differs from a traditional

database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases ...

in that it contains subjective material particular to the owner, that others may not agree with nor care about. Importantly, a PKB consists primarily of knowledge, rather than

information Information is an abstract concept that refers to that which has the power to inform. At the most fundamental level information pertains to the interpretation of that which may be sensed. Any natural process that is not completely random, ...

; in other words, it is not a collection of documents or other sources an individual has encountered, but rather an expression of the distilled knowledge the owner has extracted from those sources or from elsewhere.See also the dissertation of Max Völkel, which examined personal knowledge data models, and proposed a meta-model called "Conceptual Data Structures": The term was mentioned as early as the 1980s, but the term came to prominence in the 2000s when it was described at length in publications by computer scientist Stephen Davies and colleagues, who compared PKBs on a number of different dimensions, the most important of which is the

data model A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to the properties of real-world entities. For instance, a data model may specify that the data element representing a car be c ...

that each PKB uses to organize knowledge.

Data models

Davies and colleagues examined three aspects of the data models of PKBs: * their , which prescribes rules about how knowledge elements can be structured and interrelated (as a

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

graph Graph may refer to: Mathematics *Graph (discrete mathematics), a structure made of vertices and edges **Graph theory, the study of such graphs and their properties *Graph (topology), a topological space resembling a graph in the sense of discre ...

, tree plus graph, spatially, categorically, as n-ary links, chronologically, or

ZigZag A zigzag is a pattern made up of small corners at variable angles, though constant within the zigzag, tracing a path between two parallel lines; it can be described as both jagged and fairly regular. In geometry, this pattern is described as ...

); * their , or basic building blocks of information that a user creates and works with, and the level of

granularity Granularity (also called graininess), the condition of existing in granules or grains, refers to the extent to which a material or system is composed of distinguishable pieces. It can either refer to the extent to which a larger entity is sub ...

of those knowledge elements (such as word/concept, phrase/proposition, free text notes, links to information sources, or composite); and * their , which involves the level of formal semantics introduced into the data model (such as a

type system In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type to every "term" (a word, phrase, or other set of symbols). Usually the terms are various constructs of a computer progra ...

and related

schema The word schema comes from the Greek word ('), which means ''shape'', or more generally, ''plan''. The plural is ('). In English, both ''schemas'' and ''schemata'' are used as plural forms. Schema may refer to: Science and technology * SCHEMA ...

s, keywords, attribute–value pairs, etc.). Davies and colleagues also emphasized the principle of transclusion, "the ability to view the same knowledge element (not a copy) in multiple contexts", which they considered to be "pivotal" to an ideal PKB. They concluded, after reviewing many design goals, that the ideal PKB was still to come in the future.

Personal knowledge graph

In their publications on PKBs, Davies and colleagues discussed

knowledge graph The Google Knowledge Graph is a knowledge base from which Google serves relevant information in an infobox beside its search results. This allows the user to see the answer in a glance. The data is generated automatically from a variety of sou ...

s as they were implemented in some software of the time. Later, other writers used the term personal knowledge graph (PKG) to refer to a PKB featuring a graph structure and

graph visualization Graph drawing is an area of mathematics and computer science combining methods from geometric graph theory and information visualization to derive two-dimensional depictions of graphs arising from applications such as social network analysis ...

. However, the term is also used by software engineers to refer to the different subject of a knowledge graph a person, in contrast to a knowledge graph a person in a PKB.

Software architecture

Davies and colleagues also differentiated PKBs according to their

software architecture Software architecture is the fundamental structure of a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements and relations. ...

: file-based, database-based, or client–server systems (including Internet-based systems accessed through desktop computers and/or handheld mobile devices).

History

Non-electronic personal knowledge bases have probably existed in some form for centuries: Leonardo da Vinci's journals and notes are a famous example of the use of

notebook A notebook (also known as a notepad, writing pad, drawing pad, or legal pad) is a book or stack of paper pages that are often ruled and used for purposes such as note-taking, journaling or other writing, drawing, or scrapbooking. History ...

s. Commonplace books, , annotated

private libraries A private library is a library that is privately owned. Private libraries are usually intended for the use of a small number of people, or even a single person. As with public libraries, some people use bookplates – stamps, stickers or ...

, and card files (in German, ) of

index card An index card (or record card in British English and system cards in Australian English) consists of card stock (heavy paper) cut to a standard size, used for recording and storing small amounts of discrete data. A collection of such cards e ...

s and edge-notched cards are examples of formats that have served this function in the pre-electronic age. Undoubtedly the most famous early formulation of an electronic PKB was

Vannevar Bush Vannevar Bush ( ; March 11, 1890 – June 28, 1974) was an American engineer, inventor and science administrator, who during World War II headed the U.S. Office of Scientific Research and Development (OSRD), through which almost all warti ...

's description of the "

memex Memex is a hypothetical electromechanical device for interacting with microform documents and described in Vannevar Bush's 1945 article "As We May Think". Bush envisioned the memex as a device in which individuals would compress and store all of ...

" in 1945. In a 1962 technical report,

human–computer interaction Human–computer interaction (HCI) is research in the design and the use of computer technology, which focuses on the interfaces between people (users) and computers. HCI researchers observe the ways humans interact with computers and design te ...

pioneer

Douglas Engelbart Douglas Carl Engelbart (January 30, 1925 – July 2, 2013) was an American engineer and inventor, and an early computer and Internet pioneer. He is best known for his work on founding the field of human–computer interaction, particularl ...

(who would later become famous for his 1968 "

Mother of All Demos "The Mother of All Demos" is a name retroactively applied to a landmark computer demonstration, given at the Association for Computing Machinery / Institute of Electrical and Electronics Engineers (ACM/IEEE)—Computer Society's Fall Joint Comp ...

" that demonstrated almost all the fundamental elements of modern personal computing) described his use of edge-notched cards to partially model Bush's memex.

Examples

In their 2005 paper, Davies and colleagues mentioned the following, among others, as examples of

software application Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

s that had been used to build PKBs using various data models and architectures: ;

Open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized so ...

* Compendium (software) * Haystack (MIT project) ;Closed source *

MyLifeBits MyLifeBits is a life-logging experiment begun in 2001. It is a Microsoft Research project inspired by Vannevar Bush's hypothetical Memex computer system. The project includes full-text search, text and audio annotations, and hyperlinks. The "exper ...

* NoteCards * Personal Knowbase * PersonalBrain * Tinderbox (application software)

References

{{Computable knowledge Knowledge representation