Group:
data type
Group:
mathematics
Topic:
abstract data type
Topic:
consistency testing
Topic:
database consistency and reliability
Topic:
declarative vs. procedural representation
Topic:
dependency analysis
Topic:
error safe systems
Topic:
implementation of user interfaces
Topic:
range checking
Topic:
run-time assertions
Topic:
simulation
Topic:
user interface tool kits
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Summary
A constraint is a predicate on dynamic behavior. For example, setting the width of a column to 50% constrains the column to half the width of the table.
Constraints are a declarative description. They are useful for type declaration. A constraint solver takes a system of constraints and finds a satisfying assignment of
free variables. Constraint solvers may be difficult to use. (cbb 4/06)
Subtopic: constraints as types 
| Quote: a robust library expresses constraints as types, reports errors relative to user, and does not cause application errors [»fricA4_2000]
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Subtopic: constraints
| Quote: a one-way constraint determines the value of a variable from an expression; e.g., label.left = frame.left+10 [»zandBT11_2005]
| | Quote: constraints make applications more modular; define at point of use, automatically adjusting to other objects; avoids change/delete notification [»zandBT11_2005]
| | Quote: extend UML with stereotypes (new elements), tagged values (new attributes), and constraints (new semantics) [»boocG_1999]
| | Quote: constraints for which operations for an entity, static and dynamic invariants, and pre-/ post-conditions [»smitJM1_1981]
| | Quote: in paper solutions to programming problems, 18% used constraints, 16% used declarations; 12% used imperative programming; children without programming experience
| | Quote: spreadsheet formulas are like constraints; fits business mental model, but not programmer's mental model [»myerB3_2000]
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Subtopic: constraints as satisfiability
| Quote: survey of propositional satisfiability (SAT) and constraint programming (CP); similarities and differences [»bordL12_2006]
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Subtopic: constrained movement
| Quote: Fitts' law also applies to constrained movement: speed of movement is linearly related to the normal constraint [»accoJ3_1997]
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Subtopic: incremental constraint solver
| Quote: efficient, incremental algorithm for solving user interface, constraint systems of linear equations and inequalities; based dual simplex method [»bardGJ12_2001]
| | Quote: DeltaBlue algorithm allows incremental updates to a constraint hierarchy; gives applications [»freeBN1_1990]
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Subtopic: constraint solver
| Quote: straight-line code for repeated solutions of linear constraints; uses projection-based algorithm for constraint compilation [»bornA11_1997]
| | Quote: algorithm to compile straight-line code to solve a system constraints; convert constraints to hierarchical normal form; for equality, inequality, boolean, integer linear, and partial order constraints [»harvW10_1997]
| | Quote: one pass method for constraint satisfaction; recursively locate free variables that are easily satisfied; re-evaluate in reverse order [»suthIE5_1963]
| | Quote: analyze escape constraints with types and static single assignment (SSA); linear time and space
| | Quote: a constraint is a subroutine yielding a scalar that should be zero; use one pass method or relaxation; e.g., can analyze force distribution of a pin connected truss [»suthIE5_1963]
| | Quote: constraint enforcement may be too expensive; if so, associate with a block of operations; e.g., database transactions [»tarrP4_1998]
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Subtopic: user interface constraints
| Quote: survey of one-way constraints in two user interface development tookkits, Garnet and Amulet [»zandBT11_2005]
| | Quote: efficient, incremental algorithms to solve constraints for user interfaces; e.g., to place a pane in the left third of a window [»bornA10_1997]
| | Quote: constraints useful for user interfaces; e.g., state consistency, view consistency, formatting requirements, animation [»freeBN1_1990]
| | Quote: with Gilt, specify filter expressions for user interface widgets by demonstration or icon selection; filters implemented by constraints [»myerBA11_1991]
| | Quote: Sketchpad maintains constraints for vertical lines, parallel/perpendicular lines, points on circle, upright symbols, equal size symbols; specialized constraints as needed [»suthIE5_1963]
| | Quote: Sketchpad stores how a drawing is tied together; a hexagon stays closed despite being moved [»suthIE5_1963]
| | Quote: Sketchpad stores the structure of subpictures
| | Quote: when merge objects of the same type, a single object results with dependencies updated recursively; e.g., merging lines merges their endpoints [»suthIE5_1963]
|
Subtopic: layout by constraint
| Quote: for graphical interfaces, one-way constraints will only be used for layout; students prefer a procedural approach [»zandBT11_2005]
| | Quote: primarily used constraints for graphical layout; preferred a layout manager for simple layouts [»zandBT11_2005]
| | Quote: document layout by negotiation between viewer constraints and designer constraints; about 110 constraints per style sheet [»bornA11_1997]
| | Quote: constraint solvers are useful for graphical layout with springs and struts
| | Quote: allow arbitrary code in constraints; constraints are difficult to debug; easily used for graphical layout; difficult to use for other purposes
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Subtopic: alternatives to constraints
| Quote: can register an 'interest' in an object to be called on any update;e.g., to resize a button when its label changes; simpler than constraints [»pausR10_1992]
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Subtopic: problems with constraints
| Quote: allow arbitrary code in constraints; constraints are difficult to debug; easily used for graphical layout; difficult to use for other purposes
| | Quote: constraints are hard to debug -- cyclical constraints, bugs appear far from source, spaghetti code, slot errors, evaluation misunderstood [»zandBT11_2005]
| | Quote: constraint solvers can be unpredictable, difficult to debug, and difficult to master [»myerB3_2000]
| Quote: avoid using annotations to guide the constraint solver; error-prone
[»zandBT11_2005]
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Related Topics
Group: data type (34 topics, 730 quotes)
Group: mathematics (23 topics, 560 quotes)
Topic: abstract data type (64 items)
Topic: consistency testing (60 items)
Topic: database consistency and reliability (15 items)
Topic: declarative vs. procedural representation (54 items)
Topic: dependency analysis (34 items)
Topic: error safe systems (76 items)
Topic: implementation of user interfaces (18 items)
Topic: range checking (20 items)
Topic: run-time assertions (25 items)
Topic: simulation (35 items)
Topic: user interface tool kits
(31 items)
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