OMG Document Number: dtc/2006-11-02 $Id: SpaceSystemV1.1.xsd 203 2006-11-14 03:34:58Z bkizzort $ This is the master schema for the OMG Space Domain Task Force XML Telemetric and Command data Exchange (XTCE) format. The ROOT Element This key ensures a unique parameter name at the system level. This key ensures a unique parameter type name at the system level. This key ensures a unique metaCommand name at the system level. This key ensures a unique algorithm name at the system level. This key ensures a unique stream name at the system level. This key ensures a unique service name at the system level. This key ensures a container stream name at the system level. SpaceSystem is a collection of SpaceSystem(s) including space assets, ground assets, multi-satellite systems and sub-systems. A SpaceSystem is the root element for the set of data necessary to monitor and command an arbitrary space device - this includes the binary decomposition the data streams going into and out of a device. A service is a logical grouping of container and/or messages. Command Meta Data contains information about commands A list of parameter types Parameters referenced by MetaCommands. This Parameter Set is located here so that MetaCommand data can be built independently of TelemetryMetaData. A set of Command Definitions All commands to be sent on this mission are listed here. In addition this area has verification and validation information Used to include a MetaCommand defined in another sub-system in this sub-system. BlockMetaCommands are simply a list of individual MetaCommands that can be packaged up in a single BlockMetaCommand. The Command Container defines the construction of a Command. All the data about telemetry is contained in TelemetryMetaData A list of parameter types A list of Parameters for this Space System. Holds the list of all potential container definitions for telemetry. Containers may parts of packets or TDM, and then groups of the containers, and then an entire entity -- such as a packet. In order to maximize re-used for duplication, the pieces may defined once here, and then assembled as needed into larger structures, also here. Messages are an alternative method of uniquely identifying containers within a Service. A message provides a test in the form of MatchCriteria to match to a container. A simple example might be: [When minorframeID=21, the message is the 21st minorframe container. The collection of messages to search thru will be bound by a Service. The ContainerRef should point to ROOT container that will describe an entire packet/minor frame or chunk of telemetry. A reference to a Service An unordered collection of algorithms This schema defines the dictionary for containers, which in turn describe the physical composition of data in a communication system An abstract block of data; used as the base type for more specific container types RateInStream is used to: a) generate alarms when the Container is updated too frequently or too infrequently, b) provide some 'guidelines' for generating forward link containers, c) provide some guidelines for spacecraft simulators to generate telemetry containers. If necessary, these rates may be defined on a per stream basis. The software should check that any Stream names referenced in the RateInStreamSet actually exist. May be used to indicate error detection and correction, change byte order, provide the size (when it can't be derived), or perform some custom processing. A list of raw parameters, parameter segments, stream segments, containers, or container segments. Sequence containers may inherit from other sequence containers; when they do, the sequence in the parent SequenceContainer is 'inherited' and if the location of entries in the child sequence is not specified, it is assumed to start where the parent sequence ended. Parent sequence containers may be marked as "abstract". The idle pattern is part of any unallocated space in the Container. Given that this Container is the Base container type, RestrictionCriteria lists conditions that must be true for this Container to be 'this' subContainer type. May be a simple Comparison List, a Boolean Expression, and/or in a Graph of containers established by the NextContainer An abstract type used by sequence containers. An entry contains a location in the container. The location may be either fixed or dynamic, absolute (to the start or end of the enclosing container, or relative (to either the previous or subsequent entry). Entries may also repeat. If no LocationInContainer value is given, the entry is assumed to begin immediately after the previous entry. The location may be relative to the start of the container (containerStart), relative to the end of the previous entry (previousEntry), relative to the end of the container (containerEnd), or relative to the entry that follows this one (nextEntry). If going forward (containerStart and previousEntry) then the location refers to the start of the Entry. If going backwards (containerEnd and nextEntry) then, the location refers to the end of the entry. May be used when this entry repeats itself in the sequence container. If not supplied, the entry does not repeat. This entry will only be included in the sequence when this condition is true. If no IncludeCondition is given, then it is will be included. A parameter that is not included will be treated as if it did not exist in the sequence at all. Holds a reference to a container name of container Holds a reference to a message name of message Holds a set of services, logical groups of containers OR messages (not both). Unordered Set of Containers SequenceContainers define sequences of parameters or other containers. Contains an ordered list of Entries. Used in Sequence Container An entry that is a single Parameter An entry that is only a portion of a parameter value indicating that the entire parameter value must be assembled from other parameter segments. It is assumed that parameter segments happen sequentially in time, that is the first part if a telemetry parameter first, however (and there's always a however), if this is not the case the order of this parameter segment may be supplied with the order attribute where the first segment order="0". An entry that is simply a reference to another container. An entry that is only a portion of a container indicating that the entire container must be assembled from other container segments. It is assumed that container segments happen sequentially in time, that is the first part of a container is first, however (and there's always a however), if this is not the case the order of this container segment may be supplied with the order attribute where the first segment order="0". Each instance of a container cannot overlap in the overall sequence with another instance An entry that is a portion of a stream (streams are by definition, assumed continuous) It is assumed that stream segments happen sequentially in time, that is the first part if a steam first, however, if this is not the case the order of the stream segments may be supplied with the order attribute where the first segment order="0". An entry whose name is given by the value of a ParamameterInstance. This entry may be used to implement dwell telemetry streams. The value of the parameter in ParameterInstance must use either the name of the Parameter or its alias. If it's an alias name, the alias namespace is supplied as an attribute. An entry that is an array parameter. This entry is somewhat special because the entry may represent only a part of the Array and it's important to describe which dimensions of the array come first in the sequence as well as the size of the array. Where the Dimension list is in this form: Array[1stDim][2ndDim][lastDim]. The last dimension is assumed to be the least significant - that is this dimension will cycle through its combination before the next to last dimension changes. The order MUST ascend or the array will need to be broken out entry by entry. For partial entries of an array, the starting and ending index for each dimension, OR the Size must be specified. Indexes are zero based. For an ArrayParameterType of size N, their should be N Dimensions An array made up by multiple Entries should not have indexes that overlap, but should be continuous. zero based index Used in packaging to define the expected rate that any individual container will be in a Stream A wrapper for those properties that are unique to telemetry parameters. Optional. Normally used when the database is built in a flat, non-hierarchical format Optional condition that must be true for this Parameter to be valid One or more physical addresses may be associated with each Parameter. Examples of physical addresses include a location on the spacecraft or a location on a data collection bus. Contains the address (e.g., channel information) required to process the spacecraft telemetry streams. May be an onboard id, a mux address, or a physical location. Contains the address (channel information) required to process the spacecraft telemetry streams This time will override any Default value for TimeAssociation. A telemetered Parameter is one that will have values in telemetry. A derived Parameter is one that is calculated, usually be an Algorithm. A constant Parameter is one that is used as a constant in the system (e.g. a vehicle id). A local Parameter is one that is used purely on the ground (e.g. a ground command counter). A Parameter marked as 'readOnly' true is constant and non-settable Telemetry parameter instances are oftentimes "time-tagged" with a timing signal either provided on the ground or on the space system. This data element allows one to specify which of possibly many AbsoluteTimeParameters to use to "time-tag" parameter instances with. The parameter ref must be to an AbsoluteTime Parameter If true, then the current value of the AbsoluteTime will be projected to current time. In other words, if the value of the AbsoluteTime parameter was set 10 seconds ago, then 10 seconds will be added to its value before associating this time with the parameter. The offset is used to supply a relative time offset from the time association and to this parameter A reference to an instance of a Parameter. Used when the value of a parameter is required for a calculation or as an index value. A positive value for instance is forward in time, a negative value for count is backward in time, a 0 value for count means use the current value of the parameter or the first value in a container. A reference to a Parameter. Uses Unix ‘like’ naming across the SpaceSystem Tree (e.g., SimpleSat/Bus/EPDS/BatteryOne/Voltage). To reference an individual member of an array use the zero based bracket notation commonly used in languages like C, C++, and Java. When it's important to know the physical address(s) on the spacecraft that this parameter may be collected from, use this. Holds the list of parameter type definitions. A Parameter is a description of something that can have a value; it is not the value itself. An array type. Will be an array of parameters of the type referenced in 'arrayTypeRef' and have the number of array dimensions as specified in 'numberOfDimensions' AggegateParameters are analogous to a C struc, they are an aggregation of related data items. Each of these data items is defined here as a 'Member' Holds the list of argument type definitions. Numerical ranges that define the universe of valid values for this argument. Used to further bound argument values inside the ValidRange for the overall Data Type Numerical ranges that define the universe of valid values for this argument. Used to further bound argument values inside the ValidRange for the overall Data Type A type definition used as the base type for a CommandDefinition The MetaCommand is derived from this Base. Arguments of the base MetaCommand are further specified. Optional. Normally used when the database is built in a flat, non-hierarchical format Many commands have one or more options. These are called command arguments. Command arguments may be of any of the standard data types. MetaCommand arguments are local to the MetaCommand. Need to ensure that the named types actually exist Used to set the initial calibrated values of Arguments. Will overwrite an initial value defined for the ArgumentType. For integer types base 10 (decimal) form is assumed unless: if proceeded by a 0b or 0B, value is in base two (binary form, if proceeded by a 0o or 0O, values is in base 8 (octal) form, or if proceeded by a 0x or 0X, value is in base 16 (hex) form. Floating point types may be specified in normal (100.0) or scientific (1.0e2) form. Time types are specified using the ISO 8601 formats described for XTCE time data types. Initial values for string types, may include C language style (\n, \t, \", \\, etc.) escape sequences. Initial values for Array or Aggregate types may not be set. Tells how to package this command Appended to the TramsmissionConstraint List of the base command. Constraints are checked in order. A CommandTransmission constraint is used to check that the command can be run in the current operating mode and may block the transmission of the command if the constraint condition is true. Pause during timeOut, fail when the timeout passes Indicates whether the constraints for a Command may be suspended. Some Command and Control Systems may require special user access or confirmations before transmitting commands with certain levels. The level is inherited from the Base MetaCommand. Used when the significance (possible consequence) of a command varies by the operating context An Interlock is a type of Constraint, but not on Command instances of this MetaCommand; Interlocks apply instead to the next command. An Interlock will block successive commands until this command has reached a certain stage (through verifications). Interlocks are scoped to a SpaceSystem basis. The name of a SpaceSystem this Interlock applies to. By default, it only applies to the SpaceSystem that contains this MetaCommand. Only applies when the verificationToWaitFor attribute is 'queued' or 'executing'. A flag that indicates that under special circumstances, this Interlock can be suspended. A Command Verifier is a conditional check on the telemetry from a SpaceSystem that that provides positive indication on the processing state of a command. There are eight different verifiers each associated with difference states in command processing: TransferredToRange, TransferredFromRange, Received, Accepted, Queued, Execution, Complete, and Failed. There may be multiple ‘complete’ verifiers. ‘Complete’ verifiers are added to the Base MetaCommand ‘Complete’ verifier list. All others will overide a verifier defined in a Base MetaCommand. Transferred to range means the command has been received to the network that connects the ground system to the spacecraft. Obviously, this verifier must come from something other than the spacecraft. Sent from range means the command has been transmitted to the spacecraft by the network that connects the ground system to the spacecraft. Obviously, this verifier must come from something other than the spacecraft. A verifier that simply means the SpaceSystem has received the command. A verifier that means the SpaceSystem has accepted the command A verifer that means the command is scheduled for execution by the SpaceSystem. A verifier that indicates that the command is being executed. An optional Element indicates how far along the command has progressed either as a fixed value or an (possibly scaled) ParameterInstance value. A possible set of verifiers that all must be true for the command be considered completed. When true, indicates that the command failed. timeToWait is how long to wait for the FailedVerifier to test true. Parameters that are set with a new value after the command has been sent. Appended to the Base Command list Sets a Parameter to a new value (either from a derivation or explicitly) after the command has been verified (all verifications have passed) Value type must match Parameter type Result of the MathOperation will be the new Parameter value Sometimes it is necessary to suspend alarms - particularly 'change' alarms for commands that will change the value of a Parameter Will suspend all Alarms associated with this Parameter for the given suspense time after the given verifier Similar to an EntryList type but also may include command arguments or -as a convenience - fixed value entries. The Key = Command Op Code. Each MetaCommand may have one CommandContainer. The sequence may now contain command fields Given that this Container is the Base container type, RestrictionCriteria lists conditions that must be true for this Container to be 'this' subContainer type. May be a simple Comparison List, a Boolean Expression, and/or in a Graph of containers established by the NextContainer A command verifier is used to check that the command has been successfully executed. Command Verifiers may be either a Custom Algorithm or a Boolean Check or the presence of a Container for a relative change in the value of a Parameter. The CheckWindow is a time period where the verification must test true to pass. All comparisons must be true When verification is a new instance the referenced Container Used to look for relative change in a Parameter value. Only useful for numeric Parameters Used when times must be calculated Used by Meta Command to indicate ground Parameters that should be set after completion of a command. Contains an unordered Set of Command Containers Significance provides some cautionary information about the potential consequence of each MetaCommand. If none is supplied, then the current SpaceSystem is assumed to be the one at risk by the issuance of this command No specific meanings have been assigned to these different levels, but they mirror the Alarm levels of Telemetry. An enumerated list of verifier types This schema defines the structure for an Algorithm. An Algorithm may be one of a growing set of pre-defined algorithms or a named escape into a user defined algorithm where (depending on the system) the name of the algorithm may be a java class, a function in a shared library, an external program or some other reference to an outside algorithm. At some later date, this schema may also allow the logic of the user defined algorithm to be defined within the instance document itself (perhaps using MathML?). The simplest form of algorithm, a SimpleAlgorithmType contains an area for a free-form pseudo code description of the algorithm plus a Set of references to external algorithms. External algorithms are usually unique to a ground system type. Multiple external algorithms are possible because XTCE documents may be used across multiple ground systems. This optional element may be used to enter Pseudo or actual code for the algorithm. The language for the algorithm is specified with the language attribute This is the external algorithm. Multiple entries are provided so that the same database may be used for multiple implementation s A set of labeled inputs is added to the SimpleAlgorithmType Names an input parameter to the algorithm. There are two attributes to InputParm, inputName and parameterName. parameterName is a parameter reference name for a parameter that will be used in this algorithm. inputName is an optional "friendly" name for the input parameter. Names and provides a value for a constant input to the algorithm. There are two attributes to Constant, constantName and value. constantName is a variable name in the algorithm to be executed. value is the value of the constant to be used. A set of labeled outputs are added to the SimpleInputAlgorithmType Names an output parameter to the algorithm. There are two attributes to OutputParm, outputName and parameterName. parameterName is a parameter reference name for a parameter that will be updated by this algorithm. outputName is an optional "friendly" name for the output parameter. A set of labeled triggers is added to the SimpleInputOutputAlgorithmType First telemetry container from which the output parameter should be calculated. Algorithm processing priority. Calibrators are normally used to convert to and from bit compacted numerical data A calibration type where a segmented line in a raw vs calibrated plane is described using a set of points. Raw values are converted to calibrated values by finding a position on the line corresponding to the raw value. The algorithm triggers on the input parameter. A calibration type where a curve in a raw vs calibrated plane is described using a set of polynomial coefficients. Raw values are converted to calibrated values by finding a position on the curve corresponding to the raw value. The first coefficient belongs with the X^0 term, the next coefficient belongs to the X^1 term and so on. A simple mathematical operation A trigger is used to initiate the processing of some algorithm. A trigger may be based on an update of a Parameter or on a time basis. Triggers may also have a rate that limits their firing to a 1/rate basis. Names a parameter that upon change will start the execution of the algorithm. Holds a parameter reference name for a parameter that when it changes, will cause this algorithm to be executed. This schema provides a language for defining binary stream data. The top level type definition for all data streams that are frame based. This Container (usually abstract) is the container that is in the fixed frame stream. Normally, this is a general container type from which many specific containers are inherited. This is a reference to a connecting stream - say a custom stream. For streams that contain a series of frames with a fixed frame length where the frames are found by looking for a marker in the data. This marker is sometimes called the frame sync pattern and sometimes the Asynchronous Sync Marker (ASM). This marker need not be contiguous although it usually is. The pattern of bits used to look for frame synchronization. CCSDS ASM for non-turbocoded frames = 1acffc1d truncate the mask from the left truncate the pattern from the left Allowed slip (in bits) in either direction for the sync pattern For streams that contain a series of frames with a variable frame length where the frames are found by looking for a series of one's or zero's (usually one's). The series is called the flag. in the PCM stream that are usually made to be illegal in the PCM stream by zero or one bit insertion. The pattern of bits used to look for frame synchronization. A stream type where some level of custom processing (e.g. convolutional, encryption, compression) is performed. Has a reference to external algorithms for encoding and decoding algorithms. Must check to ensure that the attributes encodedStreamRef and decodedStreamRef point to valid Streams Algorithm outputs may be used to set decoding quality parameters. A PCM Stream Type is the high level definition for all Pulse Code Modulated (PCM) (i.e., binary) streams. Holds a reference to a stream name of reference stream Contains an unordered set of Streams. A Sync Strategy specifies the strategy on how to find frames within a stream of PCM data. The sync strategy is based upon a state machine that begins in the 'Search' state until the first sync marker is found. Then it goes into the 'Verify' state until a specified number of successive good sync markers are found. Then, the state machine goes into the 'Lock' state, in the 'Lock' state frames are considered good. Should a sync marker be missed in the 'Lock' state, the state machine will transition into the 'Check' state, if the next sync marker is where it's expected within a specified number of frames, then the state machine will transition back to the 'Lock' state, it not it will transition back to 'Search'. After searching for the frame sync marker for some number of bits, it may be desirable to invert the incoming data, and then look for frame sync. In some cases this will require an external algorithm Maximum number of bit errors in the sync pattern (marker). Used to contain an absolute time. Contains an absolute (to a known epoch) time. Use the [ISO 8601] extended format CCYY-MM-DDThh:mm:ss where "CC" represents the century, "YY" the year, "MM" the month and "DD" the day, preceded by an optional leading "-" sign to indicate a negative number. If the sign is omitted, "+" is assumed. The letter "T" is the date/time separator and "hh", "mm", "ss" represent hour, minute and second respectively. Additional digits can be used to increase the precision of fractional seconds if desired i.e. the format ss.ss... with any number of digits after the decimal point is supported. Contains multiple values (as members) of any type Order is important only if the name of the AggregateParameter or Aggregate Argument is directly referenced in SequenceContainers. In this case the members are assued to be added sequentially (in the order listed here) into the Container. Each member of the Aggregate Data has a name and a reference to another DataType. The other DataType may be any other DataType. Circular references are not allowed. ensure no circular references An array of values of the type referenced in 'arrayTypeRef' and have the number of array dimensions as specified in 'numberOfDimensions' An abstract type used by within the schema to derive other data types by the ground system. Used to derive one Data Type from another - will inherit all the attributes from the baseType any of which may be redefined in this type definition. Must be derived from a like type (e.g,, String from String). No circular derivations. An abstract type used by within the schema to describe derive other data types by the ground system. Scale and offset are used in a y =mx +b type relationship (m is the scale and b is the offset) to make adjustments to the encoded value to that it matches the time units. Binary Encoded time is typically used with a user supplied transform algorithm to convert time data formats that are too difficult to describe in XTCE. Contains an arbitrarily large binary value Extra bits are truncated from the MSB (leftmost) Contains a boolean value Initial value is always given in calibrated form. Initial value must match either the oneStringValue or the zeroStringValue Contains an enumerated value - a value that has both an integral and a string representation. Initial value is always given in calibrated form. Contains a floating point value The Valid Range bounds the universe of possible values this Parameter may have. Initial value is always given in calibrated form Contains an integral value The Valid Range bounds the universe of possible values this Parameter may have. Initial value is always given in calibrated form. Default is base 10 form; binary, octal, or hexadecimal values may be given by preceding value with 0[b|B], 0[o|O|, 0[x|X] respectively. An abstract type that is a super type of either an Integer or Float Data type. Used to contain a relative time value. Used to describe a relative time. Normally used for time offsets. A Relative time is expressed as PnYn MnDTnH nMnS, where nY represents the number of years, nM the number of months, nD the number of days, 'T' is the date/time separator, nH the number of hours, nM the number of minutes and nS the number of seconds. The number of seconds can include decimal digits to arbitrary precision. For example, to indicate a duration of 1 year, 2 months, 3 days, 10 hours, and 30 minutes, one would write: P1Y2M3DT10H30M. One could also indicate a duration of minus 120 days as: -P120D. An extension of Schema duration type. Contains a String Value Initial values for string types, may include C language style (\n, \t, \", \\, etc.) escape sequences. restriction pattern is a regular expression Describes how a particular piece of data is sent or received from some non-native, off-platform device. (e.g. a spacecraft) Used to describe an arbitrary byte order in multibyte parameters. First byte in list is the first in the stream. Byte significance is the highest for most significant bytes. If not included, it is assumed that the most significant byte is first, least significant byte last. For all major encodings of integer data Use when different calibrations must be used on the Parameter in different contexts. Use the first one that tests true For common encodings of floating point data Use when different calibrations must be used on the Parameter in different contexts. Use the first one that tests true For common encodings of string data Like C strings, they are terminated with a special string, usually a null character. Like PASCAL strings, the size of the string is given as an integer at the start of the string. SizeTag must be an unsigned Integer For binary data or for integer, float, string, or time data that is not in any of the known encoding formats. For any data that is not encoded in any of the known integer, float, string, or time data formats use a To/From transform algorithm. Used to convert binary data to an application data type Used to convert binary data from an application data type to binary data Epochs may be specified as a date or TAI (which correlates to 1 January 1958) Contains an unordered collection of Alias's Used to contain an alias (alternate) name or ID for the object. For example, a parameter may have a mnemonic, an on-board id, and special IDs used by various ground software applications; all of these are alias's. Some ground system processing equipment has some severe naming restrictions on parameters (e.g., names must less then 12 characters, single case or integral id's only); their alias's provide a means of capturing each name in a "nameSpace". A list of boolean comparisons, or boolean groups that are logically ANDed together. Any ORed conditions in the list are evaluated first. A simple restriction on string for hexadecimal numbers. Must be in 0b or 0B form. Holds an arbitrarily complex boolean expression An ordered list of bytes where the order of the bytes is in stream order. Each byte has an attribute giving its significance. The software must check to ensure that the significance of each byte is unique, and does not contain bytes of greater significance greater than the size of the object A ParameterInstanceRef to a value or another parameter instance Parameter is assumed to be of the same type as the comparison Parameter Value is assumed to be of the same type as the comparison Parameter A simple ParameterInstanceRef to value comparison. The string supplied in the value attribute needs to be converted to a type matching the Parameter being compared to. Numerical values are assumed to be base 10 unless proceeded by 0x (hexadecimal), 0o (octal), or 0b (binary). The value is truncated to use the least significant bits that match the bit size of the Parameter being compared to. Operators to use when testing a boolean condition for a validity check Context calibrations are applied when the ContextMatch is true. Context calibrators overide Default calibrators Contains a Numeric value; value may be provided directly or via the value in a parameter. Uses a parameter instance to obtain the value. The parameter value may be optionally adjusted by a Linear function or use a series of boolean expressions to lookup the value. Anything more complex and a DynamicValue with a CustomAlgorithm may be used A slope and intercept may be applied to scale or shift the value of the parameter in the dynamic value An abstract type definition used as the base for NameDescriptionType or OptionalNameDescriptionType. The short description is intended to be used for quick "memory jogger" descriptions of the object. The Long Description is intended to be used for explanatory descriptions of the object and may include HTML markup. Long Descriptions are of unbounded length Use for any other data associated with each named object. May be used to include administrative data (e.g., version, CM or tags) or potentially any MIME type. Data may be included or given as an href. It is strongly recommended that the short description be kept under 80 characters in length A simple element that provides for simple, but common error checking and detection. Bit position starts with 'zero'. Cyclic Redundancy Check (CRC) definition. Legal values for coefficient's are 0 or 1. Exponents must be integer values. A simple union type combining integer, octal, binary, and hexadecimal types Schema for a Header record. A header contains general information about the system or subsystem. A simple restriction on string for hexadecimal numbers. Must be in 0x or 0X form. Contains an Integer value; value may be provided directly or via the value in a parameter. Uses a parameter instance to obtain the value. The parameter value may be optionally adjusted by a Linear function or use a series of boolean expressions to lookup the value. Anything more complex and a DynamicValue with a CustomAlgorithm may be used A slope and intercept may be applied to scale or shift the value of the parameter in the dynamic value Lookup a value using the lookup list supplied. Use the first match found. Mathematical operators Contains either a simple Comparison, a ComparisonList, an arbitrarily complex BooleanExpression or an escape to an externally defined algorithm A simple comparison check All comparisons must be true An arbitrarily complex boolean expression An escape to an externally defined algorithm Postfix (aka Reverse Polish Notation (RPN)) notation is used to describe mathmatical equations. It uses a stack where operands (either fixed values or ParameterInstances) are pushed onto the stack from first to last in the XML. As the operators are specified, each pops off operands as it evaluates them, and pushes the result back onto the stack. In this case postfix is used to avoid having to specify parenthesis. To convert from infix to postfix, use Dijkstra's "shunting yard" algorithm. Use a constant in the calculation Use the value of this parameter in the calculation Use the value of another Parameter in the calculation Binary operators: +, -, *, /, %, ^ operate on the top two values in the stack, leaving the result on the top of the stack. Unary operators: 1/x, x!, e^x, ln, log, and trigonometric operators operate on the top member of the stack also leaving the result on the top of the stack. 'ln' is a natural log where 'log' is a base 10 logarithm. Trigonometric operators use degrees. 'swap' swaps the top two members of the stack. Used for "directory" style unique names. We need to preclude spaces, '.', '/', ':", "[" and "]". Only letters, digits, '_', ' ' and "-" are allowed The type definition used by most elements that require a name with optional descriptions. Used when referencing a directory style "NameType". All characters are legal. All name references use a Unix ‘like’ name referencing mechanism across the SpaceSystem Tree (e.g., SimpleSat/Bus/EPDS/BatteryOne/Voltage) where the '/', ‘..’ and ‘.’ are used to navigate through the hierarchy. The use of an unqualified name will search for an item in the current SpaceSystem first, then if none is found, in progressively higher SpaceSystems. A SpaceSystem is a name space (i.e., a named type declared in MetaCommandData is also declared in TelemetryMetaData - and vice versa). There are two ways numeric data can be changed to string data: using a Java style NumberFormat, or using an enumerated list. Enumerated lists can be assigned to a single value or a value range. A number or range assigned to a string. A string value associated with a numerical range.