Lively Object Groups

Tim Felgentreff, Philipp Tessenow, Lauritz Thamsen Jens Lincke, Prof. Robert Hirschfeld Software Architecture Group Hasso-Plattner-Institut Potsdam www.hpi.uni-potsdam.de/swa 2012-07-25

The Lively Kernel

■ Browser-based development platform - written in HTML and JavaScript - self-sufficient system and tools - module systems, Morphic architecture, visual connections ■ Classical development - classes, traits, layers - Smalltalk-inspired tools ■ Explorative development - composition of visible morphs - per-object scripting - object serialization ■ PartsBin objects repository - share created objects and applications

Freedom Of Speech

■ Debating adventure - characters find paths through the world - characters interact with each other - player insults other characters to defeat them ■ Explorative development - created parts instead of classes - exchanged parts through the parts bin - reused parts by delegating instead of building class hierarchies

Hey, look over there!

He must have taught you everything you know.

things that don't talk, don't taste good

Explorative Development

■ Direct manipulation ■ Immediate feedback ■ Morph compositions

// this.doitContext = this.get('Boy') // ... if (correctAnswer === answer) { asker.nextTurn(this, asker) } else { this.getHit(); if (!this.isDead()) { asker.nextTurn(asker, this) } } // ...

I have never lost a melee!

Change Propagation

■ Object manipulation only works one object at a time

this.selectedMorphs.forEach(function (ea) { ea.setScale(2) })

Code Re-use in Similar Objects

■ No object-centric way for shared behavior

this.selectedMorphs.forEach(function (ea) { ea.addScript(function isObstacle() { return false; }) })

Scene-Graph

■ No mechanisms for browsing part compositions

this.owner.owner.owner // Parts Bin

Workspace

X

M

–

Association between Tools and Morphs

■ Ambiguous connection from code editors to objects

-- ALL --soliloquize

Scripts

+

-

undefined

OgreCharacter3

Target:

Tag:

all

ObjectEditor

X

M

–

Explorative Development - Conclusions

■ Pros - Fast development - direct manipulation - immediate feedback - morph composition ■ Cons - Difficult maintenance - change propagation to similar objects is often manual - code-reuse between logical "classes" is hard - behavior is hidden within the scene graph - connection between tool and object is ambiguous

Enhanced ObjectEditor

■ Scene graph - explore scene-graph - direct element selection ■ Change propagation - changes propagate to all group elements ■ Code re-use - view / edit common scripts on all group members ■ Usability - shortcut to edit objects / groups - select groups visually: magnifier or selection - evaluate do-its on every group member - name and save groups for later use

Limitations

■ Persistent Groups - no explicit group objects - group membership saved on morphs - group selection only incorporates visible morphs ■ Group Scripts - tools do not distinguish between individual and group scripts

-- ALL --

Scripts

+

-

undefined

Tag:

all

run

Name group

Villains [2]

ObjectEditor (WebDev'12)

X

M

–

Conclusions

■ Explorative development problems - change propagation to similar objects is often manual - code-reuse between logical "classes" is hard - behavior is hidden within the scene graph - connection between tool and object is ambiguous ■ We improved working on multiple morphs - multiple live objects can be edited simultaneously - groups enable trait-like, object-centric views - scene graph is visually explorable - magnifier links morphs and code

Sources

■ Hopscotch: Towards User Interface Composition, Bykov, WASDeTT, 2007 ■ The Lively PartsBin: A Cloud-based Repository for Collaborative Development of Active Web Content, Lincke, Krahn, Ingalls, Röder, and Hirschfeld, HICSS, 2012 ■ Method and apparatus for enhancing computer-user selection of computer-displayed objects through dynamic selection area and constant visual feedback, Osga, Glenn, US Patent No 5757358 ■ Bret Victor - Inventing on Principle, CUSEC, 2012 http://vimeo.com/36579366, retrieved on May 14, 2012 ■ Do We Really Need to Extend Syntax for Advanced Modularity? Shigeru Chiba, Michihiro Horie, Kei Kanazawa, Fuminobu Takeyama, Yuuki Teramoto, AOSD, 2012