6894 · workshop in software design lecture 2 · september 14, 1998 · CTAS write on board in advance: handouts, names, Hoare quote do first 6 slides quickly remember to leave time for students to fill in info sheet: 5m? don't dwell on first abstraction slide might not have time for last two abstraction slides

the arrival scheduling problem a resource allocation problem aircraft arriving at an airport need to be sequenced for landing can’t let them land in same order as they arrive in terminal area runway may not be available when they get there faster aircraft would overtake slower ones current manual solution aircraft pass through ‘meter gates’ on border of terminal area arrivals at meter gate are delayed, and aircraft may be reordered currently, controllers use judgment & experience to make these decisions an opportunity for automation better scheduling can increase airport throughput and minimize delays (but cannot be optimal because of unpredictable weather, etc) reduce controller workload, and thus improve safety 1/17/2019 daniel jackson

what is CTAS? basics Center/TRACON Automation System set of tools to help controllers manage air traffic flow at large airports developed at NASA by Erzberger and colleagues chosen in 1991 by FAA as future automation system for terminal area technical innovations algorithms for trajectory synthesis and runway allocation user interface: “human-centered automation” a suite of tools TMA (Traffic Management Advisor) provides advisories on sequencing incoming aircraft to controllers in Center FAST (Final Approach Spacing Tool) provides advisories on sequencing for landing to controllers in TRACON DA (Descent Advisor), EDP (Expedite Departure Path), UPR (User Preferred Routing) exploit CTAS’s trajectory info for analyzing arrival/departure paths CAP (Collaborative Arrival Planning) pass scheduling info to airlines to optimize planning at hubs 1/17/2019 daniel jackson

what TMA does (roughly) from rapidly changing info (seconds) radar information giving aircraft positions and velocities flight plan info received from host computers and entered by controllers availability of runways slowly changing info (hours) weather data very slowly changing info (weeks) map of airspace static info characteristics of different kinds of aircraft computes suggested arrival times at meter gates for incoming aircraft so CTAS’s function is to provide advisories not safety-critical in a narrow technical sense but obviously reliability is of paramount concern CTAS especially useful during ‘rushes’ 1/17/2019 daniel jackson

organization of TMA software INPUT SOURCE MANAGER COMMUNICATIONS MANAGER USER INTERFACE (TGUI, PGUI) ROUTE ANALYZER DYNAMIC PLANNER 1/17/2019 daniel jackson

our project what Erzberger told me (June 98) algorithmic components (eg, DP, RA/TS) well understood mostly reliable concerned about two areas of software TGUI, PGUI code CM (communications manager) CM a much harder problem because we’d need to learn domain why i chose CM a more interesting problem large-scale engineering issues more about software design, less about algorithms, GUIs, etc CM is a vital component of TMA and FAST CM shapes the entire CTAS system 1/17/2019 daniel jackson

CM (Communication Manager) main functions maintains ‘aircraft tree’ (database of aircraft states) calls algorithmic components periodically to process entire tree maintains GUIs, handles user requests basic stats all in C connected only by sockets to other processes; no shared memory about 70kloc (including headers) but only about 20kloc of essential stuff history of development algorithmic components are focus of NASA research, startingin 1980’s dynamic planner was designed with OMT, an OO method route analyzer translated from Fortran CM was first written in 1991; most of current code from 1997-98 1/17/2019 daniel jackson

basic control loop of CM cm_motif.c main_loop (every 300ms) cm_sock_util.c select_active_sockets ism_socket.c ism_socket_read cm_read.c read_ra update_aircraft.c ism_socket.c:ism_socket_check handle_weather_update find_and_send_fps (1) request_etas_for_new_fps (2) distribute_ac.c: distribute_aircaft_to_ras (3) update_active_aircraft update_aircraft.c update_aircraft cm_send.c (1) forward_flight_plan_add (2) send_request_for_flight_plan (3) handoff_aircraft_to_ra 1/17/2019 daniel jackson

project goals & structure experiment with new technology design notions & tools evaluate: pitfalls & successes invent refinements, new approaches improve CTAS help NASA/CSC improve design of CM explain existing problems and propose solutions uncover problems a research project be willing to adjust plans as we learn more lots of cooperation, between teams too can change goals to more exciting ones 1/17/2019 daniel jackson