Topic: temporal relationships

topics > computer science > programming > program control > Group: conditional control


conditional statement
event time
path expression
persistent data structure
temporal database
safety, liveness, and system properties
state machine
version control


Adams (QuoteRef: adamEN1_1973) has proposed conditional tenses for describing time relationships. For instance, "if A was true the last time B was true", or "if A will be true tomorrow". Such statements are difficult or impossible to implement using a state machine. They illustrate a fundamental difficulty with state machines: determining the current state depends on previously determined states, but determining previous states does not depend on saving current information. The current state must assume that time relationships have already been saved in state indicators. (cbb 5/80)
Subtopic: dynamic behavior as temporal relations up

Quote: present the dynamic behavior of a monitored program by a collection of temporal relations [»snodR5_1984]
Quote: report monitored information as event relations (where:new state:time) and interval relations (condition:start time:end time) [»snodR5_1984]
Quote: compile TQuel queries for the incremental update of temporal relations from a monitored program [»snodR5_1984]
Quote: semiautomatically derive sample behavioral models from the TRIO specification of a system [»ciapE1_1999]
Quote: in paper solutions that referred to past events, 50% used the present tense to mention a past event, 20% used the word 'after', 10% used a state variable [»paneJF2_2001]

Subtopic: time vs. information up

Quote: the interaction between time and information is not straightforward nor well understood [»theoCI3_1991]
Quote: an information management system needs a unique id or key for objects; time-invariant [»theoCI3_1991]
Quote: multiple relationships between time and information; e.g., time of event and time of database transaction [»theoCI3_1991]
Quote: the conceptual schema of an information system varies over time [»theoCI3_1991]

Subtopic: temporal relationship vs. state up

Quote: in paper solutions that referred to past events, 50% used the present tense to mention a past event, 20% used the word 'after', 10% used a state variable [»paneJF2_2001]
Quote: in paper solutions, participants used future and past tense instead of state variables; but most programming languages require state variables [»paneJF2_2001]

Subtopic: temporal relationships up

Quote: assumes that the temporal network contains all temporal relations and their consequences [»alleJF11_1983]
Quote: the temporal relations are before, equal, meets, overlaps, during, starts, finishes, containment and their complements [»alleJF11_1983, OK]
Quote: defines a hierarchy of reference intervals with NOW a variable bound to a particular reference interval; easy to track the present moment [»alleJF11_1983]
Quote: only disjunctive relationships between reference intervals (before, after); simplifies constraint propagation for temporal constraints [»alleJF11_1983]
Quote: store temporal intervals within reference intervals; complete relationships within a reference interval; inter-interval relationships outside [»alleJF11_1983]
Quote: conceptual modeling language uses time intervals and the predicate 'meets'; includes a full set of temporal relationships [»theoCI3_1991]
Quote: every CML object includes time intervals for model time (system's knowledge) and system time (system's belief about its knowledge) [»theoCI3_1991]
Quote: the priority ceiling protocol may be extended to real-time databases with transactions; allows schedule analysis and temporally consistent views [»rajkR_1991]

Subtopic: temporal flow up

Quote: for any flow x, pre(x) is the previous value; a- >x is initially a then x; e.g., count of rising edges [»benvA1_2003]
Quote: flows can follow slower clocks; e.g., 'x when c' is x's values when c is true; most flow operators use the same clock [»benvA1_2003]
Quote: properties can be constant over time, time-varying, or themselves times [»theoCI3_1991]
Quote: Scade requires a pre operator for feedback values; enables separate compilation; i.e., execution order within a node is independent of the node's caller

Subtopic: time series analysis up

Quote: time series analysis should be linear in time and sublinear in space; use data reduction/transformation, indexing methods, and flexible similarity searching [»shasD_2004]

Subtopic: temporal logic up

Quote: specify liveness axioms by temporal logic; uses box for henceforth and diamond for eventually; defines leads_to [»lampL1_1989]
Quote: Esterel's formal semantics is based on constructive causality [»benvA1_2003]
Quote: formulas in temporal logic easier to read than first-order logic and decidable; useful for reactive systems; e.g., P will hold eventually [»thomS4_2000]
Quote: model checking is automated, symbolic testing for properties expressed in temporal logic; can handle 10^100 states [»thomS4_2000]
Quote: the TimeLine graphical editor simplifies the specification of basic temporal properties for SPIN model checkers; linear temporal logic is difficult to use [»holzGJ11_2002]
Quote: TRIO--a first-order temporal logic language with a linear notion of time [»ciapE1_1999]

Subtopic: tense operators up

Quote: derive future, past, always, sometimes, lasts, lasted, withinFuture from Dist(F,t)--F holds at t time units from the current instant
Quote: though we can refer to times as points or intervals, most temporal references are implicitly stated by tense and event relationships [»alleJF11_1983]
Quote: Kamp extended L with tense operators, 'until' and 'since'; allows definition of any first-order tense [»nishH_1980]
Quote: tense operator 'until'; q1 U q2 iff q2 will be true at some future moment and q1 is true until then
Quote: tense operator 'since'; q1 S q2 iff q2 was true at some past moment and q1 has been true since then [»nishH_1980]
Quote: past tense is useful in conditionals, e.g., if x happened yesterday; could implement by setting flags [»adamEN1_1973]
Quote: people are expected to remember past values of attributes [»adamEN1_1973]
Quote: allow past conditionals, e.g., if b1 was true the last time b2 became true then [»adamEN1_1973, OK]
Quote: although future time is not practical as conditions, it is a typical feature of imperatives [»adamEN1_1973]
QuoteRef: adamEN1_1973 ;;19 implements when and whenever clause by pre-processor and flag generation. only partially successful.

Related Topics up

Group: formalism   (9 topics, 478 quotes)

Topic: conditional statement (8 items)
Topic: event time (45 items)
Topic: logic (84 items)
Topic: path expression (14 items)
Topic: persistent data structure (37 items)
Topic: temporal database (25 items)
Topic: time (49 items)
Topic: timestamps (19 items)
Topic: safety, liveness, and system properties (22 items)
Topic: state (35 items)
Topic: state machine (67 items)
Topic: version control
(34 items)

Updated barberCB 7/05
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