# Personal knowledge base

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{{short description|Knowledge management software}}
{{about|knowledge management software|the general concept|Personal knowledge management}}
{{InfoMaps}}
A '''personal knowledge base''' ('''PKB''') is an electronic tool used by an individual to express, capture, and later retrieve personal knowledge. It differs from a traditional [database](/source/database) 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](/source/information); 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.<ref name="Davies 2005">{{Cite tech report |last1=Davies |first1=Stephen |last2=Velez-Morales |first2=Javier |last3=King |first3=Roger |date=August 2005 |title=Building the memex sixty years later: trends and directions in personal knowledge bases |number=CU-CS-997-05 |location=Boulder, Colo. |institution=Department of Computer Science, [University of Colorado at Boulder](/source/University_of_Colorado_at_Boulder) |url=https://scholar.colorado.edu/concern/reports/t722h9830}}</ref><ref name="Davies 2011">{{Cite journal |last=Davies |first=Stephen |date=February 2011 |title=Still building the memex |journal=[Communications of the ACM](/source/Communications_of_the_ACM) |volume=54 |issue=2 |pages=80–88 |doi=10.1145/1897816.1897840 |s2cid=9551946 |url=https://cacm.acm.org/magazines/2011/2/104378-still-building-the-memex/fulltext |archive-url=https://web.archive.org/web/20210624161048/https://cacm.acm.org/magazines/2011/2/104378-still-building-the-memex/fulltext |archive-date=2021-06-24 |url-status=live}}</ref><ref name="Völkel 2010">See also the dissertation of Max Völkel, which examined personal knowledge data models, and proposed a meta-model called "Conceptual Data Structures": {{Cite thesis |last=Völkel |first=Max |title=Personal knowledge models with semantic technologies |date=January 2010 |publisher=Faculty of Economics, [Karlsruhe Institute of Technology](/source/Karlsruhe_Institute_of_Technology), University of the State of Baden-Württemberg, and National Laboratory of the Helmholtz Association |url=https://publikationen.bibliothek.kit.edu/1000019641 |doi=10.5445/IR/1000019641 |oclc=837821583 |type=Ph.D. thesis |location=Karlsruhe}}</ref>

The term {{em|personal knowledge base}} was mentioned as early as the 1980s,<ref name="Brooks 1985">{{Cite journal |last=Brooks |first=Tom |date=April 1985 |title=New technologies and their implications for local area networks |journal=Computer Communications |volume=8 |issue=2 |pages=82–87 |doi=10.1016/0140-3664(85)90218-X }}</ref><ref name="Kruger 1986">{{Cite book |last=Krüger |first=Gerhard |title=Employment and the transfer of technology |date=1986 |publisher=[Springer-Verlag](/source/Springer-Verlag) |isbn=3540166394 |editor-last=Henn |editor-first=Rudolf |location=Berlin; New York |pages=39–52 |chapter=Future information technology—motor of the 'information society' |doi=10.1007/978-3-642-71292-0_4 |oclc=14108228 }}</ref><ref name="Forman 1988">{{Cite book |last=Forman |first=George E. |title=Constructivism in the computer age |date=1988 |publisher=[Lawrence Erlbaum Associates](/source/Lawrence_Erlbaum_Associates) |isbn=0805801014 |editor-last=Forman |editor-first=George E. |series=The Jean Piaget Symposium series |location=Hillsdale, NJ |pages=[https://archive.org/details/constructivismin0000unse/page/83 83–101] |chapter=Making intuitive knowledge explicit through future technology |oclc=16922453 |editor-last2=Pufall |editor-first2=Peter B. |chapter-url=https://archive.org/details/constructivismin0000unse/page/83 |chapter-url-access=registration}}</ref><ref name="Smith 1991">{{Cite book |last=Smith |first=Catherine F. |title=Evolving perspectives on computers and composition studies: questions for the 1990s |date=1991 |publisher=[National Council of Teachers of English](/source/National_Council_of_Teachers_of_English) |isbn=0814111661 |editor-last=Hawisher |editor-first=Gail E. |location=Urbana, IL |pages=[https://archive.org/details/evolvingperspect00gail/page/224 224–252] |chapter=Reconceiving hypertext |oclc=23462809 |editor-last2=Selfe |editor-first2=Cynthia L. |chapter-url=https://archive.org/details/evolvingperspect00gail/page/224 |chapter-url-access=registration}}</ref> but the term came to prominence in the 2000s when it was described at length in publications by computer scientist Stephen Davies and colleagues,<ref name="Davies 2005" /><ref name="Davies 2011" /> who compared PKBs on a number of different dimensions, the most important of which is the [data model](/source/data_model) that each PKB uses to organize knowledge.<ref name="Davies 2005" />{{rp|18}}<ref name="Völkel 2010" />

==Data models==
Davies and colleagues examined three aspects of the data models of PKBs:<ref name="Davies 2005" />{{rp|19–36}}

* their {{em|structural framework}}, which prescribes rules about how knowledge elements can be structured and interrelated (as a [tree](/source/Tree_(data_structure)), [graph](/source/Graph_(discrete_mathematics)), tree plus graph, spatially, categorically, as n-ary links, chronologically, or [ZigZag](/source/ZigZag_(software)));
* their {{em|knowledge elements}}, or basic building blocks of information that a user creates and works with, and the level of [granularity](/source/granularity) of those knowledge elements (such as word/concept, phrase/proposition, free text notes, links to information sources, or composite); and
* their {{em|schema}}, which involves the level of [formal semantics](/source/Formal_semantics_(logic)) introduced into the data model (such as a [type system](/source/type_system) and related [schema](/source/Database_schema)s, keywords, [attribute–value pair](/source/attribute%E2%80%93value_pair)s, etc.).

Davies and colleagues also emphasized the principle of [transclusion](/source/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.<ref name="Davies 2005" /><ref name="Davies 2011" /> They concluded, after reviewing many design goals, that the ideal PKB was still to come in the future.<ref name="Davies 2005" /><ref name="Davies 2011" />

===Personal knowledge graph===
In their publications on PKBs, Davies and colleagues discussed [knowledge graph](/source/knowledge_graph)s as they were implemented in some software of the time.<ref name="Davies 2005" /><ref name="Davies 2011" /> Later, other writers used the term '''personal knowledge graph''' (PKG) to refer to a PKB featuring a graph structure and [graph visualization](/source/graph_visualization).<ref name="Pyne & Stewart 2022">{{cite journal |last1=Pyne |first1=Yvette |last2=Stewart |first2=Stuart |date=March 2022 |title=Meta-work: how we research is as important as what we research |journal=[British Journal of General Practice](/source/British_Journal_of_General_Practice) |volume=72 |issue=716 |pages=130–131 |pmid=35210247 |pmc=8884432 |doi=10.3399/bjgp22X718757}}</ref> However, the term {{em|personal knowledge graph}} is also used by software engineers to refer to the different subject of a knowledge graph {{em|about}} a person,<ref>For example: {{cite book |last1=Li |first1=Xiang |last2=Tur |first2=Gokhan |last3=Hakkani-Tür|author3-link=Dilek Hakkani-Tür |first3=Dilek |last4=Li |first4=Qi |date=December 2014 |chapter=Personal knowledge graph population from user utterances in conversational understanding |title=SLT 2014: 2014 IEEE Workshop on Spoken Language Technology: proceedings: December 7–10, 2014, South Lake Tahoe, Nevada, U.S.A. |publisher=[IEEE](/source/IEEE) |location=Piscataway, NJ |pages=224–229 |isbn=9781479971305 |oclc=945951970 |doi=10.1109/SLT.2014.7078578 |s2cid=6428777 |chapter-url=https://www.researchgate.net/publication/282177475}} And: {{cite journal |last1=Cao |first1=Lei |last2=Zhang |first2=Huijun |last3=Feng |first3=Ling |date=January 2022 |title=Building and using personal knowledge graph to improve suicidal ideation detection on social media |journal=[IEEE Transactions on Multimedia](/source/IEEE_Transactions_on_Multimedia) |volume=24 |pages=87–102 |doi=10.1109/TMM.2020.3046867|arxiv=2012.09123 |bibcode=2022ITMm...24...87C |s2cid=229210559 }}</ref> in contrast to a knowledge graph {{em|created by}} a person in a PKB.<ref>{{cite journal |last1=Balog |first1=Krisztian |last2=Mirza |first2=Paramita |last3=Skjæveland |first3=Martin G. |last4=Wang |first4=Zhilin |date=June 2022 |title=Report on the Workshop on Personal Knowledge Graphs (PKG 2021) at AKBC 2021 |journal=ACM SIGIR Forum |volume=56 |issue=1 |pages=1–11 (8) |quote=What does 'personal' in PKG mean? It could be taken to mean (objective) facts about the user (''I ate lunch at restaurant X on date Y. I like fish.''), subjective beliefs of the user (''[I believe that] Pineapple pizza is just wrong. The Earth is flat.''), or objective facts that are of particular interest to the user (''Pineapple pizza is also often called Hawaiian Pizza''). |url=https://www.sigir.org/wp-content/uploads/2022/07/p04.pdf |archive-url=https://web.archive.org/web/20220711210242/https://www.sigir.org/wp-content/uploads/2022/07/p04.pdf |archive-date=2022-07-11 |url-status=live}}</ref>

== Software architecture ==
Davies and colleagues also differentiated PKBs according to their [software architecture](/source/software_architecture): [file](/source/Computer_file)-based, database-based, or [client–server](/source/client%E2%80%93server) systems (including Internet-based systems accessed through desktop computers and/or handheld mobile devices).<ref name="Davies 2005" />{{rp|37–41}}

== History ==
Non-electronic personal knowledge bases have probably existed in some form for centuries: [Leonardo da Vinci's journals and notes](/source/Leonardo_da_Vinci) are a famous example of the use of [notebook](/source/notebook)s. [Commonplace books](/source/Commonplace_books), {{em|[florilegia](/source/florilegia)}}, annotated [private libraries](/source/private_libraries), and [card file](/source/card_file)s (in German, {{lang|de|Zettelkästen}}) of [index card](/source/index_card)s and [edge-notched card](/source/edge-notched_card)s are examples of formats that have served this function in the pre-electronic age.<ref>For example, two articles that describe the use of [edge-notched card](/source/edge-notched_card)s as a personal knowledge base in health and medicine are: {{cite journal |last=Hoff |first=Wilbur |date=May 1967 |title=A health information retrieval system for personal use |journal=[Journal of School Health](/source/Journal_of_School_Health) |volume=37 |issue=5 |pages=251–254 |doi=10.1111/j.1746-1561.1967.tb00505.x |pmid=5182183 }} And: {{Cite book |last1=Manning |first1=Phil R. |title=Medicine, preserving the passion |last2=DeBakey |first2=Lois |date=1987 |publisher=[Springer-Verlag](/source/Springer-Verlag) |isbn=0387963618 |edition=1st |location=New York |pages=[https://archive.org/details/medicinepreservi00mann/page/57 57–71 (59)] |chapter=The personal information center |doi=10.1007/978-1-4757-1954-3_3 |oclc=13580831 |chapter-url=https://archive.org/details/medicinepreservi00mann/page/57 |chapter-url-access=registration}} Another mention of its use by a writer is: {{cite book |last=Piercy |first=Marge |author-link=Marge Piercy |date=1982 |title=Parti-colored blocks for a quilt |location=Ann Arbor |publisher=[University of Michigan Press](/source/University_of_Michigan_Press) |pages=[https://archive.org/details/particoloredbloc00pier/page/27 27] |isbn=0472063383 |oclc=8476006 |url=https://archive.org/details/particoloredbloc00pier/page/27 |url-access=registration |doi=10.3998/mpub.7442 |quote=I have a memory annex which serves my purposes. It uses edge-notched cards.}}</ref>

Undoubtedly the most famous early formulation of an electronic PKB was [Vannevar Bush](/source/Vannevar_Bush)'s description of the "[memex](/source/memex)" in 1945.<ref name="Davies 2005" /><ref name="Davies 2011" /><ref name="Bush 1945">{{Cite journal |last=Bush |first=Vannevar |date=July 1945 |title=As we may think |url=https://www.theatlantic.com/magazine/archive/1945/07/as-we-may-think/303881/ |journal=[Atlantic Monthly](/source/Atlantic_Monthly) |volume=176 |issue=1 |pages=101–108 }}</ref> In a 1962 technical report, [human–computer interaction](/source/human%E2%80%93computer_interaction) pioneer [Douglas Engelbart](/source/Douglas_Engelbart) (who would later become famous for his 1968 "[Mother of All Demos](/source/Mother_of_All_Demos)" that demonstrated almost all the fundamental elements of modern personal computing) described his use of edge-notched cards to partially model Bush's memex.<ref>{{Cite book |last=Engelbart |first=Douglas C. |url=http://www.dougengelbart.org/pubs/augment-3906.html |title=Augmenting human intellect: a conceptual framework |date=1962 |publisher=[Stanford Research Institute](/source/Stanford_Research_Institute) |location=Menlo Park, CA |chapter=Some possibilities with cards and relatively simple equipment |oclc=8671016 |access-date=2018-08-12 |archive-url=https://web.archive.org/web/20110504035147/http://www.dougengelbart.org/pubs/augment-3906.html |archive-date=2011-05-04 |url-status=dead}}</ref>

==Examples==
The following [software application](/source/software_application)s have been used to build PKBs using various data models and architectures. The list includes software mentioned by Davies and colleagues in their 2005 paper,<ref name="Davies 2005" /> and additional software.

;[Open source](/source/Open_source)
* [Compendium](/source/Compendium_(software))<ref name="Davies 2005" />
* [Haystack (MIT project)](/source/Haystack_(MIT_project))<ref name="Davies 2005" />
* [Joplin](/source/Joplin_(software))<ref name="Das 2024">{{cite web |last=Das |first=Ankush |date=2024-07-03 |title=9 open source second brain knowledge base tools |url=https://itsfoss.com/open-source-second-brain-apps/ |website=ItsFOSS |access-date=2026-02-23}}</ref>
* [Logseq](/source/Logseq)<ref name="Das 2024" />
* [NoteCards](/source/NoteCards)<ref name="Davies 2005" />
* [Org-mode](/source/Org-mode)<ref>{{cite web |last=Chavan |first=Abhijeet |date=2007-12-01 |title=Get organized with Emacs Org-mode |url=https://www.linuxjournal.com/article/9116 |website=[Linux Journal](/source/Linux_Journal) |access-date=2026-02-23}}</ref>
* [QOwnNotes](/source/QOwnNotes)<ref name="Das 2024" />
* [TiddlyWiki](/source/TiddlyWiki)<ref>{{cite web |last=Kasiya |first=Chifundo |date=2025-12-10 |title=I built a personal knowledge base without using Notion or Obsidian |url=https://www.makeuseof.com/i-built-personal-knowledge-base-without-using-notion-or-obsidian/ |website=[MakeUseOf](/source/MakeUseOf) |access-date=2026-02-23}}</ref>

;Closed source
* [Evernote](/source/Evernote)<ref>{{cite book |last1=Tsui |first1=Eric |last2=Wang |first2=Wai Ming |last3=Sabetzadeh |first3=Farzad |date=November 2014 |chapter=Enacting personal knowledge management & learning with web services interoperability tools |title=2014 IEEE 3rd International Conference on Cloud Computing and Intelligence Systems |location=Piscataway, NJ |publisher=[IEEE](/source/IEEE) |pages=491–494 |doi=10.1109/CCIS.2014.7175785}}</ref>
* [Microsoft OneNote](/source/Microsoft_OneNote)<ref name="Davies 2005" />
* [MindManager](/source/MindManager)<ref name="Davies 2005" />
* [MyLifeBits](/source/MyLifeBits)<ref name="Davies 2005" />
* [Notion](/source/Notion_(productivity_software))<ref name="Pyne & Stewart 2022" />
* [Obsidian](/source/Obsidian_(software))<ref name="Pyne & Stewart 2022" />
* [Personal Knowbase](/source/Personal_Knowbase)<ref name="Davies 2005" />
* [PersonalBrain](/source/PersonalBrain)<ref name="Davies 2005" />
* [Roam](/source/Roam_(software))<ref name="Pyne & Stewart 2022" />
* [Tinderbox](/source/Tinderbox_(application_software))<ref name="Davies 2005" />

==See also==
{{Div col|colwidth=22em}}
* {{annotated link|Computer-assisted qualitative data analysis software}}
* {{annotated link|Information system}}
* {{annotated link|Issue-based information system}}
* {{annotated link|Lifelog}}
* {{annotated link|Notetaking}}
** [Comparison of notetaking software](/source/Comparison_of_notetaking_software)
* {{annotated link|Outliner}}
* {{annotated link|Personal knowledge management}}
* {{annotated link|Personal wiki}}
** {{slink|List of wiki software#Personal wiki software}}
* {{slink|Tag (metadata)#Knowledge tags}}
{{Div col end}}

==References==
{{Reflist}}

Category:Knowledge representation

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Adapted from the Wikipedia article [Personal knowledge base](https://en.wikipedia.org/wiki/Personal_knowledge_base) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Personal_knowledge_base?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.