Deme Presentation at Stanford Open Source (un)conference '08

1. Motivation Architecture Implementation Demo Deme Architecture Todd Davies Mike Mintz Stanford University Stanford Open Source (un)conference ’08 Davies, Mintz Deme Architecture

2. Motivation Architecture Implementation Demo Outline 1 Motivation 2 Architecture Item Structure Item Ontology Viewers 3 Implementation 4 Demo Davies, Mintz Deme Architecture

6. Motivation Architecture Implementation Demo Objectives Hierarchy of item types with shared functionality Versioning for every item type Not just documents Highly collaborative Every item type supports discussion Very granular permissions Easily Extensible Embedded views Davies, Mintz Deme Architecture

12. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Outline 1 Motivation 2 Architecture Item Structure Item Ontology Viewers 3 Implementation 4 Demo Davies, Mintz Deme Architecture

13. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo What is an item? All persistent data abstracted as items E.g., documents, users, settings, etc. Items are instances of “item types” Item types specify structure of ﬁelds Items provide values for ﬁelds E.g. “Person” is item type, “Mike” and “Todd” are items of that type First Name Last Name Mike Mintz Todd Davies Davies, Mintz Deme Architecture

16. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Item inheritance Item types can inherit from other item types “Item” is at top of the hierarchy E.g., Item -> Document -> Comment Item types inherit existing ﬁelds, add additional ﬁelds Item: name, description Document: name, description, body Comment: name, description, body, commented_item Davies, Mintz Deme Architecture

17. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Item inheritance Item types can inherit from other item types “Item” is at top of the hierarchy E.g., Item -> Document -> Comment Item types inherit existing ﬁelds, add additional ﬁelds Item: name, description Document: name, description, body Comment: name, description, body, commented_item Davies, Mintz Deme Architecture

19. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Overview Agents Collections Documents Relationships Permissions URLs Davies, Mintz Deme Architecture

20. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo All Items All items share metadata structure: Unique ID Name Description Creator / Create Time Updater / Update Time Versions Trashed? Davies, Mintz Deme Architecture

21. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Agents Agents Item that can “do” things (Given permissions, can appear as creator/updater) Application user is always a speciﬁc Agent Subclasses: Person, AnonymousAgent, Group Groups Collection of Agents Members can share common permissions Accounts Channel of authentication Subclasses: PasswordAccount, OpenId Davies, Mintz Deme Architecture

24. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Collections ItemSets Arbitrary collection of items Subclasses: Folio Folio Every group has one folio Contains items shared among all members Davies, Mintz Deme Architecture

25. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Collections ItemSets Arbitrary collection of items Subclasses: Folio Folio Every group has one folio Contains items shared among all members Davies, Mintz Deme Architecture

26. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Documents Main unit of collaborative work Different item types for different formats Subclasses TextDocument HtmlDocument DjangoTemplateDocument Comment FileDocument ImageDocument Comments refer to other Items Sometimes speciﬁc versions and locations Davies, Mintz Deme Architecture

29. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Relationships Explicit items for relationships between items Subclasses: GroupMembership, ItemsetMembership Davies, Mintz Deme Architecture

30. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Permissions Speciﬁes who can do what to which items Agent Ability Item Three levels Direct Groupwide Default Roles Customizable sets of abilities Davies, Mintz Deme Architecture

33. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Custom URLs Users can create custom URLs to point to items Each domain can have separate namespace of URLs Davies, Mintz Deme Architecture

34. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Custom URLs Users can create custom URLs to point to items Each domain can have separate namespace of URLs Davies, Mintz Deme Architecture

36. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo What is a viewer? A Django class that processes browser or API requests URLs that begin with /resource/ are routed to viewers Viewers handle items of speciﬁc type Viewers inherit from other viewers Everything ultimately inherits from ItemViewer ItemViewer is about 80% of view code Davies, Mintz Deme Architecture

40. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo RESTful URLs Entry actions /resource/<viewer>/<id>/<action> E.g., /resource/person/5/edit E.g., /resource/person/5 Collection actions /resource/<viewer>/<action> E.g., /resource/person/new E.g., /resource/person E.g., /resource/person.json Davies, Mintz Deme Architecture

41. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo RESTful URLs Entry actions /resource/<viewer>/<id>/<action> E.g., /resource/person/5/edit E.g., /resource/person/5 Collection actions /resource/<viewer>/<action> E.g., /resource/person/new E.g., /resource/person E.g., /resource/person.json Davies, Mintz Deme Architecture

42. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Authentication There is always an authenticated agent in a viewer (If user does not log in, it is AnonymousAgent.) Viewer takes care of checking permissions for authenticated agent Davies, Mintz Deme Architecture

43. Motivation Item Structure Architecture Item Ontology Implementation Viewers Demo Authentication There is always an authenticated agent in a viewer (If user does not log in, it is AnonymousAgent.) Viewer takes care of checking permissions for authenticated agent Davies, Mintz Deme Architecture

44. Motivation Architecture Implementation Demo Deme is written in Django Deme is: A collection of Django models A system of hierarchical viewers that use Django templates Additional components that handle Deme-speciﬁc features Versioning Permissions Commenting Davies, Mintz Deme Architecture

45. Motivation Architecture Implementation Demo Why Django? Big developer community Now supports multi-table inheritance Davies, Mintz Deme Architecture

46. Motivation Architecture Implementation Demo Models –> Item types A Django model corresponds to an item type An item is: A Django model instance A row in a table Davies, Mintz Deme Architecture

47. Motivation Architecture Implementation Demo Models –> Item types A Django model corresponds to an item type An item is: A Django model instance A row in a table Davies, Mintz Deme Architecture

48. Motivation Architecture Implementation Demo Database Visual Davies, Mintz Deme Architecture

49. Motivation Architecture Implementation Demo Versioning Every table has a dual version-table Person ID First Name Last Name 1 Mike Mintz PersonVersion ID Version First Name Last Name 1 1 Michael Mintz 1 2 Mike Mintz Davies, Mintz Deme Architecture

50. Motivation Architecture Implementation Demo Demo time! Davies, Mintz Deme Architecture

Deme Presentation at Stanford Open Source (un)conference '08

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