ALMA Software Glossary

2000-September-20

This glossary defines those terms (single words or phrases) concerning Software Engineering, Telescope Control and Interferometry. The meaning of each term is explained, focusing on its usage in the context of documentation. Entries are arranged alphabetically.

Abbreviations and Acronyms

Many documents employ abbreviations and acronyms to refer concisely to an item, after it has been introduced. The following list is aimed to help the reader in recalling the extended meaning of each short expression.

ABM	“Antenna Bus Master” A real-time computer located at the antenna that is responsible for the control and monitor of all hardware devices at the antenna. There is an identical copy of this computer at every antenna, each running identical software.
ACC	“Array Control Computer” The computer located at the central control area and responsible for coordinating all instrument activities. It is an ordinary Unix workstation.
ACE	“Adaptive Communication Environment” An open-source, object-oriented (OO), C++ framework that implements core design patterns for concurrent communication software across a range of OS platforms. (http://www.cs.wustl.edu/~schmidt/ACE.html)
ACK	“Acknowledge ” The bit in transmitted CAN frames that is set by a successful receiver of the frame.
ACS	“ALMA Common Software” ACS is the kernel software located between the application (on top) and other commercial and shared software over the operating systems. It supplies certain services such as messaging, logging, error and alarm handling, configuration database, etc.
ACU	“Antenna Control Unit” The system provided by the antenna manufacturer through which the antenna is monitored and controlled. The ACU primary access is through a CAN bus.
AIPS++	“Astronomical Information Processing System” AIPS++ supplies post-processing software for calibration, editing, image formation, image enhancement, and analysis of images and other data streams. A consortium of radio observatories developed the system with about 40 people contributing to the first release in 1999. (http://aips2.nrao.edu/docs/aips++.html)
ALMA	“Atacama Large Millimeter Array” A connected interferometer telescope array expected to consist of 64 millimeter-wave antennas each 12-meters in diameter. (http://www.alma.nrao.edu)
AMS	“Antenna Mount System” The software system that controls the movement of the antenna elevation and azimuth axes. The AMS receives commands from the high-level control system and implements them by directly interacting the ACU.
ANKA	ANKA (Angström Quelle Karlsruhe) is a synchrotron radiation source being constructed in southwestern Germany. It will be controlled using software from the KGB project. (http://www.fzk.de/anka/english/welcome.html)
API	“Application Programming Interface”
ARTM	“Array Real Time Machine” A real-time computer located at the central control area and responsible for the control and monitor of certain hardware (LO reference generation, fiber optic control, etc.) located only at the array center. Its function may be combined with ACC or CCC.
ATM	“Asynchronous Transfer Mode” ATM is a cell relay technology designed for high-speed transfer of data, voice and video across networks. It supports data transfer rates from 1.544 Mbps to 622 Mbps. Through LAN Emulation (LANE), ATM works with existing Ethernet and token ring networks.
AU	“Astronomical Unit” The average distance from the Earth to the Sun, i.e. 149,597,870 kilometers.
AUI	“Attachment Unit Interface” A 15-pin connector used with an Ethernet interface.
AZ	Azimuth, the horizontal angle measured clockwise (as viewed from above) from an arbitrary reference direction in the horizon coordinate system. For ALMA the reference point (zero azimuth) is defined as due north.
CAN	“Controller Area Network” A serial multi-drop bus originally developed by Bosch for automotive applications. In ALMA it is used to connect the ABM to most hardware devices located at the antenna. It will also be used with the correlator and in other places.
CASE	“Computer Aided Software Engineering”
CCC	“Correlator Control Computer” A real-time computer located at the central control area and responsible for the control and monitor of the correlator.
CCD	“Charge Coupled Device” In ALMA this is the digital camera located on the antenna and used for optical imaging. It is a data producer, and is also known as the Video Camera.
CDP	“Central Data Processor” A high performance computer (Beowulf?) to process the data from the ALMA correlator in quasi-realtime. It is located at the central control area and is controlled by the CCC.
CDR	“Critical Design Review” Sometimes called the “Final Design Review”.
COCOS	A commercial distributed system being developed by KGB to control devices at a petrol station, e.g. credit card readers, tank gauges, and point-of-sale applications. It will run on a number of LAN connected PCs using the PharLap RTOS or WinNT OS. It is a generalization and evolution of the ANKA system.
CORBA	“Common Object Request Broker Architecture” CORBA is an emerging open distributed object computing infrastructure being standardized by OMG. CORBA automates many common network programming tasks such as object registration, location, and activation; request de-multiplexing; framing and error-handling; parameter marshalling and de-marshalling; and operation dispatching.
CPU	“Central Processing Unit”
DBMS	“Data Base Management System”
EL	Elevation, the vertical angle measured upward from the horizon in the horizon coordinate system.
ESO	“European Southern Observatory” ESO and other agencies are building ALMA. (http://www.eso.org)
FITS	“Flexible Image Transport Format” FITS is the data format most commonly used within the astronomy community. FITS is primarily designed to store scientific data sets consisting of multidimensional arrays (1-D spectra, 2-D images or 3-D data cubes) and 2-dimensional tables containing rows and columns of data. (http://fits.gsfc.nasa.gov/)
FPDP	“Front Panel Data Port” A high-speed 32-bit parallel synchronous interface whereby VME boards are interconnected using ribbon cables routed across the front panels. It is the VITA-17 standard.
FPGA	Field Programmable Gate Array
GPS	"Global Positioning System" GPS is a satellite-based radio navigation system developed and operated by the U.S. Department of Defense (DOD). Important to ALMA is that the system permits users to determine the time with high precision and accuracy.
GUI	“Graphical User Interface”
HW	Hardware
ICD	“Interface Control Document” A document specifying a software or hardware interface.
IDL	“Interface Definition Language” IDL is part of the CORBA standard and permits interfaces to objects to be defined independent of an object’s implementation. IDL is used as input to an IDL compiler that produces source code that can be compiled and linked with an object implementation and its clients.
IF	"Intermediate Frequency"
IIOP	“Internet Inter-ORB Protocol” IIOP is part of the CORBA standard and is an object-oriented protocol that makes it possible for distributed programs written in different programming languages to communicate over the Internet.
IRAM	"Institut de RadioAstronomie Millimétrique" (French) IRAM and other agencies are building ALMA. (http://iram.fr/)
ISO	International Organization for Standardization ISO is a voluntary, non-treaty organization founded in 1946, responsible for creating international standards in many areas, including computers and communications. Its members are the national standards organizations of 89 countries, including the American National Standards Institute. The term "ISO" is not actually an acronym; rather it is a pun on the Greek prefix "iso-", meaning "same".
KGB	“Kontrol Gruppe für Beschleuniger” (German) The KGB project is working to provide software used to control remote hardware over a network. It part of the Jozef Stefan Institute in Ljubljana, Slovenia. The first application of the system is ANKA. (http://kgb.ijs.si/KGB/)
LAN	“Local Area Network” A network which is geographically limited, typically to a 1 km radius. Ethernet and FDDI are examples of standard LANs.
LO	"Local Oscillator"
LST
LTA	Long Term Accumulator
M&C	“Monitor and Control”
MPG	Max-Planck-Gesellschaft (German) Max-Planck-Society (http://www.mpg.de)
MPIfR	Max-Planck-Institut fuer Radioastronomie (German) Max-Planck-Institute for Radio Astronomy (http://www.mpifr-bonn.mpg.de)
N/A	“Not Applicable”
NRAO	“National Radio Astronomy Observatory” NRAO and other agencies are building ALMA. (http://www.nrao.edu/)
OCL	“Object Constraint Language” A modeling language that is part of the UML. It is used to specify all kinds of constraints, pre- and post-conditions, guards, etc. over the objects in the different models. (http://www-4.ibm.com/software/ad/standards/ocl.html)
OMG	“Object Management Group” The OMG was founded as a consortium in 1989 to promote the adoption of standards for managing distributed objects. It is the developer of the CORBA standard. (http://www.omg.org/)
OO	“Object Oriented” Object-oriented programming (OOP) refers to a type of programming that combines data structures with functions to create re-usable objects.
ORB	“Object Request Broker” The ORB is the part of the CORBA specification that manages the interaction between clients and servers. The specification defines the architecture of interfaces and services that must be provided by the ORB.
OS	“Operating System”
OSI	“Open Systems Interconnection” The 7-layer ISO standard for how messages are transmitted between two points in a network.
OTF	“On-The-Fly” An observing mode where the antenna motion follows a specified Pattern without stopping. At the same time the antenna actual and commanded positions are recorded. The position data are later used in the calibration of the science data.
OVRO	“Owens Valley Radio Observatory” (http://www.ovro.caltech.edu/)
PDR	“Preliminary Design Review” A design review that occurs before the CDR.
PPC	“PowerPC” A range of processors developed by an alliance of Apple, IBM and Motorola. For ALMA it is the processor embedded on a SBC.
RDBMS	“Relational Data Base Management System”
RF	"Radio Frequency"
RFP	“Request for Proposal”
RPC	“Remote Procedure Call” A protocol used by a program to request a service from a program located in another computer in a network. RPC uses the client/server model.
RT	“Real-Time”
RTR	“Remote Transmission Request” A type of CAN frame requesting transmission of a particular frame.
SBC	“Single Board Computer” A complete computer system on a single board. For ALMA this generally means a computer board mounted in a VME chassis.
SI	“Système International d'unités” (French) The international system of units of measurement.
SLALIB	SLALIB is a software library used by writers of positional-astronomy applications. (http://star-www.rl.ac.uk/star/docs/sun67.htx/sun67.html)
SNMP	“Simple Network Management Protocol” A protocol governing network management and the monitoring of network devices and their functions. It is generally used with TCP/IP networks.
SRS	“Software Requirements Specification”
SSLO	"Signed Sum of Local Oscillators” The effective total LO frequency. For the sum a negative sign indicates a reversal of the signal spectrum that occurs when the mixer output is from the lower sideband.
SW	Software
TAI	“International Atomic Time” TAI is a laboratory timescale. Though TAI shares the same second as UTC, UTC noticeably separates the two timescales in epoch because of the build-up of leap seconds. At the time of this writing UTC lags about half a minute behind TAI.
TAO	The ACE ORB (http://www.cs.wustl.edu/~schmidt/TAO.html)
TBC	“To Be Confirmed”
TBD	“To Be Determined”
TCL	“Tool Command Language” An interpreted script language developed by Dr. John Ousterhout at the University of California, Berkeley, and now developed and maintained by Scriptics (http://www.scriptics.com/resource/)
TPOINT	Telescope Pointing Analysis System An interactive modeling tool that analyses pointing observations to discover and measure telescope mechanical misalignments and flexures. (http://www.tpsoft.demon.co.uk)
UML	“Unified Modeling Language” The UML is a language for specifying, constructing, visualizing, and documenting the artifacts of a software-intensive system.
URI	“Uniform Resource Identifier” The generic set of all names/addresses that are short strings that refer to resources. (http://www.w3.org/addressing)
URL	“Uniform Resource Locator” The set of URI schemes that has explicit instructions on how to access the resource, typically a web page, on the internet. (http://www.w3.org/addressing)
UTC	“Universal Time Coordinated” UTC is the basis of civil timekeeping. Most time zones differ from UTC by an integer number of hours, though a few differ by n+0.5 hours. The UTC second is the same as the TAI second. In the long term, UTC keeps in step with the Sun. It does so even though the Earth's rotation is slightly variable by occasionally introducing a leap second.
UV	Visibilities
VLT	“Very Large Telescope” (http://www.eso.org/projects/vlt/)
VME	“Versa Module Europa” VME is a computer backplane bus system which makes use of the Eurocard standard. It is defined by the IEEE 1014-1987 standard.
WAN	“Wide Area Network” A data communications network usually constructed with serial lines, extending over distances greater than one kilometer.
WS	Workstation
XML	“eXtensible Markup Language” (http://www.w3.org/XML/)

Definitions

From observing program to correlator dump:

· An observing program is a set of observing sessions,

· an observing session is a set of time-contiguous schedule blocks,

· an schedule block is an un-interruptible set of scans,

· a scan is a set of observations,

· an observation is a set of integrations,

· and, an integration is a set of dumps.

actor	Actors are used when writing use cases. Actors are a role of an entity external to the system, and can be humans, machines, or devices. Actors are divided into primary and secondary. A primary actor is one having a goal requiring the assistance of the system, while a secondary actor is one from which the system needs assistance to satisfy its goal. (see The Unified Modeling Language Reference Manual, Rumbaugh, Jacobson, and Booch, p.144)
alarm	Alarms are asynchronous anomalous conditions discovered by the system.
array	The entire set of all ALMA antennas.
attribute	Attributes are changeable data associated with a device property. Attributes are writable and readable. Examples are values used to determine whether a new property value is valid (normally done with limits). Attributes are set to their default value upon Enable Device.
boresight	The actual orientation of the axis of symmetry of the main reflector with respect to established local coordinates (zenith direction and nominal azimuth zero).
CAN ID	The CAN message identification. A 29 bit identifier transmitted at the start of a CAN frame which also determines the frame’s priority
characteristic	Characteristics are non-changeable (static) data associated with a device property. Characteristics differ from attributes in that they read-only and rarely change (are compiled in). Examples of characteristics are the property’s default values, print format and human-readable descriptions.
command	An expression that can be input to a computer system or a software module to initiate an action or affect the execution of a function.
control point	The smallest atomic quantity used when setting a hardware value. Control points are writable and readable; the read returns the last value written. Control points are implemented as properties. An example control point would be used to set a voltage using a Digital to Analog Converter (DAC).
data set	All data belonging to a particular observation block including UV data, astronomical information (sources, coordinates, frequencies, etc.), raw observing and reduction scripts, system data, logs, warnings, environmental data, etc.
delay tracking	The continuous adjustment of the instrumental delay to match the geometric delay as a source is tracked.
delay tracking center	The direction on the sky for which the total delay to each antenna is a constant. When the compensating delay is implemented after a down Conversion (the usual case in radio interferometers) a fringe results that is a function of the down conversion local oscillator frequency. By changing the phase of this local oscillator (with the fringe rotator), the fringes may be reduced in frequency or stopped, as desired by the correlation system. Any errors in the total delay due to transmission or compensating delay imprecision result in a phase shift to the visibilities that is a function of IF frequency.
device	A device generally corresponds to the model of a physical device, for example, a receiver. It is a software concept used for control, and is a collection of properties. Devices are implemented as distributed objects.
distributed object	System components with which other components need to interact. In particular, the control system uses distributed objects to represent devices. Distributed objects are the smallest directly addressable entities in the system, and are generally composed of properties.
dump	The acquisition of data from the correlator corresponding to a dump time (see below).
dump time	The smallest interval of time for which a set of correlated data can be accumulated and output from the correlator.
engineer	A person who uses scientific knowledge to solve practical problems. For ALMA an engineer's principle assignment will be to build and maintain the hardware.
error	Errors occur as the result of command failure, for example, when a property is set. Usually they are a response to writing an inappropriate value or a hardware problem, but they can be any error condition that can be reported in the return of an operation.
fringe rotator	A mechanism to introduce a time-varying phase shift into the local oscillator signal to reduce the frequency of the oscillations of the correlator output. Fringe rotation allows the correlator output (whose amplitude is proportional to visibility amplitude) to be sampled at a lower rate. The fringe rotation is chosen so the fringe frequency for a point source located at the fringe stopping center would be reduced to zero (or very nearly zero). Usually the fringe-stopping center and the delay-tracking center coincide; both then are called the visibility phase tracking center.
function	A defined objective or characteristic action of a system or component.
functional requirement	A requirement that specifies a function that a system or component must be able to perform.
functional specification	A document that specifies the functions that a system or component must perform.
integration	A set of dumps, all identical in configuration (except for the antenna motion and some others), that is accumulated and forms the basic recorded unit.
interactive command	An interactive command can be used to specify table parameters for the next observation, start the next observation, cancel the current observation, etc.
mode	A condition in which a system, subsystem, or component may exist. Normally it comprises a set of possible states.
module	A relatively large subdivision of the implementation items in a software package. In most cases a software package corresponds to a single software module, but complex software packages can be split across more software modules. A software module is handled as a single configuration control unit and follows a standardized directory structure. Software modules correspond to components in UML terminology.
monitor point	The smallest atomic quantity read from hardware. Monitor points are always read-only. The read produces the actual value of a hardware measurement. Monitor points are implemented as properties. An example monitor point would return the reading from a module’s temperature probe.
observation	A set of integrations while the antennas complete an elemental pattern across the source, and possibly while frequency switching, nutator switching, etc.
observation block	Obsolescent synonym for schedule block
observation table	The hierarchical set of parameters that define the current observation.
observer	The person who prepared, or is otherwise responsible for an approved observing program. The observer is usually an astronomer.
observing program	A set of observing sessions to fulfil a formalized astronomy proposal with a particular scientific goal. A synonym for observing project.
observing script	The procedural representation of an observing session. It may contain loops and conditional tests using environmental parameters, pipeline results, and current scheduling status.
observing session	A time-contiguous set of schedule blocks in the same observing program. Note that sessions are defined post facto, as the scheduler only schedules schedule blocks.
observing tool	A GUI tool used by astronomers to prepare observations, usually from a template. The observing tool will produce an observing script, or may be used to directly control the instrument.
operational mode	The mode of a system, subsystem, or component that is installed in its intended environment.
operational requirement	A requirement that is applicable to a system or component that is installed in its intended environment.
operational state	The state of a system, subsystem, or component that is installed in its intended environment.
operator	The person in immediate control of the array. The operator is not usually an astronomer.
package	A major subdivision of a software project that collects a set of associated functions that are designed, developed, and tested together and independently from other packages. Software packages can be recursively defined as containing other software packages.
pattern	An antenna movement that is superimposed on (added to) the tracking of the target. Example patterns are a simple offset, a raster, and a spiral. A pattern is composed of one or more “strokes”.
phase tracking	An adjustment of the LO phase needed because delay tracking is done at the IF and not RF frequency.
phase tracking center	Usually the fringe stopping and the delay tracking centers coincide. When this is the case, both are referred to as the visibility phase tracking center, sometimes called the phase referencing center.
process	A program in execution. It consists of the executable program, the program's data and stack, its program counter, stack pointer and other registers, any support data stored in the database, and all the other information needed to run the program.
property	Properties are the smallest atomic quantities within a distributed object. Properties include real control and monitor points, and they are also virtual (software) variables with features similar to real control and monitor points.
regression test	A test performed on a modified program to instill confidence that changes are correct and have not adversely affected unchanged portions of the program.
scan	A set of observations with a common goal, for example, a pointing scan, a focus scan, or atmospheric amplitude calibrations scan.
schedule block	An un-interruptible scheduling unit, which may consist of a set of scans and logic to control their execution. The scans must be scheduled contiguously.
scheduler queue	The prioritized list of observation blocks produced by the dynamic scheduler.
serialized object
software device driver	A collection of subroutines and data that constitutes the software interface to an I/O device.
software life cycle	The period of time that begins when a software product is conceived and ends when the software is no longer used. The software life cycle typically includes concept, requirements, design, implementation, test, installation and checkout, operation and maintenance, and, sometimes, retirement. These phases may overlap or be performed iteratively.
state	The value assumed at a given instant by the variable used by the control software to represent the condition of a system, subsystem, or component. Normally it is a finer specification within a given mode.
status	The set of values of all the parameters (state, numeric read-outs, flags...) that define the condition of a system, subsystem, or component.
stereotype	A UML term for "a new kind of model element defined within the model based on an existing kind of model element". Stereotypes may extend the semantics but not the structure of pre-existing meta-model classes.
stroke	Patterns are composed of a series of separate strokes. For example, when a raster pattern is being performed a stroke is generally a single line in the raster.
subarray	A group of ALMA antennas. More explanation is needed here, as this is one of the most abused terms in radio astronomy.
subsystem	A secondary or subordinate system within a larger system. It usually refers to a physical device or a group of physical devices equipped with the control electronics and low level software.
system	A collection of components organized to accomplish a specific function or a set of functions. When no further characterized, it is generally used to refer to the whole of a complex piece of equipment made up by heterogeneous parts.
target	The central position being tracked by the antenna’s receiver beam. Normally this is a celestial object, but it can be anything able to be specified to the AMS.
timing event	Most ALMA computers and other hardware will receive a precise timing reference signal consisting of a periodic pulse with a period of 48 millisecond. The leading edge of each pulse marks a timing event.
turn	One turn of an antenna axis, or 360 degrees.
use case	A specific way of using the system by performing some part of the functionality. Each use case constitutes a complete course of action initiated by an actor, and it specifies the interaction that takes place between an actor and the system. The collected use cases specify all the existing ways of using the system.