Element coverage for pkg/xtce, XTCE 1.2 (OMG), CCSDS 660.1-G-2
Why a matrix and not a PICS
Every other package in this repository carries a PICS proforma, because CCSDS Blue Books publish one to fill in. XTCE has none to fill in: it is an OMG schema, and CCSDS 660.1-G-2 is a Green Book, a guide, not a Recommended Standard. So this file substitutes a coverage matrix, listing the schema's elements against what the package does with each. It lives beside the protocol page so the documentation triad stays uniform.
What the statuses mean
| Status | Meaning |
|---|---|
| Supported | Modeled as Go types, decoded, and reachable through the API. |
| Opaque | Parsed as far as the XML allows and kept as raw bytes, so a caller can handle it and a later version can model it without changing what Load accepts. |
| Ignored | Decoded past without error. The element does not appear in the model. A file using it still loads. |
| Unsupported | Same as ignored on the wire, but named here because something depends on it: a parameter whose type is an unsupported kind will fail Validate with an unresolved reference. |
The loader rejects malformed XML, a non-SpaceSystem root, documents past the
size or depth limits, and a document whose values cannot be read as their
schema types, such as a FixedValue that is not a number (ErrInvalidValue).
Element coverage never fails Load: every status in the tables below loads.
Values inside a covered element still have to parse.
Table A-1: Document structure
| Element | Status | Notes |
|---|---|---|
SpaceSystem | Supported | |
Root and recursive. Parent links are built during Load so references can resolve upwards. | ||
Space | Supported | |
Required by the schema. Load rejects a root without one. | ||
Space | Supported | |
Space | Supported | |
Carried, not interpreted. | ||
Long | Supported | |
Header | Supported | |
Version, date, classification, validation status. | ||
Header/, NoteSet, HistorySet | Ignored | |
AliasSet | Ignored | |
Alternate names for a thing. Nothing in this package resolves by alias. | ||
Ancillary | Ignored | |
Mission-defined key-value data. | ||
Telemetry | Supported | |
Parameter | ||
Command | Supported | |
Parameter | ||
ServiceSet | Ignored | |
Namespace http: | Supported | |
Both as a default namespace and with a prefix; tested both ways. Child elements are matched by namespace too, so a Telemetry from another vocabulary is ignored rather than decoded as XTCE's. | ||
Table A-2: Parameters
| Element | Status | Notes |
|---|---|---|
ParameterSet | Supported | Telemetry and command sides share one name space, matching the schema's parameterNameKey. |
Parameter | Supported | Name, parameterTypeRef, initial value, descriptions. |
ParameterRef | Ignored | The schema allows a reference in place of a definition. |
ParameterProperties | Ignored | Data source, persistence, read-only. |
Table A-3: Parameter types
| Element | Status | Notes |
|---|---|---|
Integer | Supported | |
Size, signedness, encoding, calibrator. | ||
Float | Supported | |
Size, encoding, calibrator. | ||
Enumerated | Supported | |
Full enumeration list including maxValue ranges. | ||
String | Supported | |
Encoding and restriction pattern. | ||
Binary | Supported | |
Boolean | Supported | |
Including the one and zero string values. | ||
Absolute | Supported | |
Encoding, units, scale, offset, reference epoch. Its encoding nests one level deeper than the others'. | ||
Relative | Opaque | |
The name is decoded so references resolve; the contents stay raw. TypeKind() reports "relative time (not modeled)", and Layout refuses a parameter of this type. | ||
Array | Opaque | |
Same treatment; the name and arrayTypeRef are decoded, the dimension list stays raw. | ||
Aggregate | Opaque | |
Same treatment; the member list stays raw. | ||
UnitSet, Unit | Supported | |
Carried, not converted. power defaults to 1 through Power. | ||
ValidRange | Ignored | |
ToString | Ignored | |
@baseType | Opaque | |
The attribute is decoded; type inheritance is not followed. | ||
Table A-4: Data encodings
| Element | Status | Notes |
|---|---|---|
Integer | Supported | |
Encoding, size, bit and byte order, default calibrator. | ||
Float | Supported | |
Same. | ||
String | Supported | |
Fixed size in Layout. Termination resolves through Resolve, with the terminator counted toward the field because it occupies packet space; a delimited string starting off an octet boundary is refused, since searching over octets would be meaningless. LeadingSize is refused by name: the width of the size field is an attribute of an element kept raw, so there is no way to know how far to skip. Variable is opaque. | ||
Binary | Supported | |
Fixed size in Layout; a DynamicValue size resolves through Resolve. A negative resolved width is refused rather than read as zero. | ||
@change | Supported | |
Carried on both numeric encodings, as a pointer so absent, meaning any change is significant, stays distinguishable from zero. | ||
@bitOrder, @byteOrder | Supported | |
Defaults applied through accessors. Validate checks that encoding, bitOrder and byteOrder are legal enumeration members (Err). | ||
Error | Ignored | |
Checksums and CRCs described in the database. This repository's own CRCs are in pkg/crc. | ||
From | Ignored | |
An algorithm, and algorithms are out of scope. | ||
To | Ignored | |
Same. | ||
Table A-5: Calibrators
| Element | Status | Notes |
|---|---|---|
Default | Supported | |
On integer and float encodings. | ||
Polynomial | Supported | |
All terms, with coefficient and exponent. | ||
Spline | Supported | |
All points, plus order and the extrapolate flag. | ||
Math | Supported | |
The postfix expression is modeled in document order and evaluated. 47 of the 49 operators in Math are implemented; ~ and div are refused because the schema's definitions of them contradict themselves. Parameter needs a value source, supplied through ApplyWith. | ||
Context | Opaque | |
Calibration that depends on another parameter's value, kept as raw XML. Data marks its presence, so a consumer knows the default curve alone may be wrong for a given packet. | ||
Table A-6: Containers
| Element | Status | Notes |
|---|---|---|
ContainerSet | Supported | |
Sequence | Supported | |
Name, abstract flag, idle pattern. | ||
EntryList | Supported | |
Ordered. Decoded by a hand-written unmarshaller because entry order is packet order and encoding/xml cannot preserve it across separate fields. | ||
Parameter | Supported | |
Container | Supported | |
Parameter | Opaque | |
Kept in the ordered list as EntryOther, so it still occupies its position. Its reference is not validated. | ||
Container | Opaque | |
Same. | ||
Stream | Opaque | |
Same. | ||
Indirect | Opaque | |
Same. | ||
Array | Opaque | |
Same. | ||
Location | Supported | |
Fixed values in every Fixed spelling: decimal, 0x, 0o, 0b. The reference location is carried, defaulting through Reference. DynamicValue resolves through Resolve; Discrete is opaque. containerEnd resolves against the packet length for the container being read, and is refused for a spliced inner container whose end is not yet known. nextEntry is refused: it positions the following entry, and treating it as previous would silently misplace the field. | ||
RepeatEntry | Supported | |
Fixed counts in every Fixed spelling, and DynamicValue counts through Resolve. Offset is refused: the gap between repetitions is not modeled, and packing them without it would place them wrongly. | ||
Include | Opaque | |
Raw XML. Layout places the entry regardless; a caller that needs the condition can parse it. | ||
Time | Ignored | |
Base | Supported | |
The reference is resolved and checked for cycles. | ||
Base | Yes | |
Comparison, Comparison and Boolean are modeled and evaluated by Match, which resolves a candidate container against the packet when its shape depends on the contents. | ||
Restriction | Supported | |
Condition, ANDed and ORed, nested to any depth, evaluated by Match. | ||
Condition | Supported | |
Both forms of right-hand side: a Value literal, or a second Parameter so two fields can be compared against each other. | ||
Condition/ | Yes | |
Defaults to true, per Parameter. | ||
Condition/ | Parsed | |
A value from another packet; Match reports a non-zero instance on either side rather than guessing. | ||
Restriction | Opaque | |
Raw XML. By definition outside the file. | ||
Restriction | Parsed | |
Deciding it needs the stream rather than one packet, so Match does not evaluate it. | ||
Comparison/ | Yes | |
Defaults to true, so a comparison is against the engineering value. | ||
Comparison/ | Parsed | |
A value from another packet; Match reports a non-zero instance rather than guessing. | ||
DynamicValue | Supported | |
Parameter plus an optional Linear. Resolved by Resolve, which decodes each field as it places it so a later one can be sized or positioned by an earlier one's value. A forward reference is refused rather than guessed. A non-zero instance reads another packet and is refused. | ||
Linear | Supported | |
Slope and intercept. An absent slope is one, not zero: the schema states no default, and zero would discard the parameter. | ||
Default, Rate | Ignored | |
Binary on a container | Ignored | |
Table A-7: Commands
| Element | Status | Notes |
|---|---|---|
Meta | Supported | |
All three member kinds are kept: MetaCommand, Meta, Block. | ||
MetaCommand | Supported | |
Skeleton only: name, abstract flag, descriptions. | ||
Meta | Supported | |
A command included by reference. The reference is kept but not resolved. | ||
Block | Opaque | |
The name and descriptions are decoded; the Meta stays raw. | ||
Base | Supported | |
The reference and the Argument, the name/value pairs that narrow the base command, are decoded. The reference is not resolved or cycle-checked. | ||
ArgumentList, Argument | Supported | |
Names and argument. | ||
Argument and its types | Unsupported | |
The argument-side mirror of the parameter types. | ||
Command | Unsupported | |
The uplink bit layout. | ||
Transmission | Unsupported | |
When a command may be sent. | ||
VerifierSet | Unsupported | |
How to tell a command worked. | ||
Default, Context | Unsupported | |
How dangerous a command is. | ||
Interlock | Unsupported | |
Parameter, Parameters | Unsupported | |
A warning about the command side. Everything that makes a command safe to send (verifiers, constraints, significance) is in the unsupported list. This package can tell you a command exists and what arguments it takes. It cannot tell you whether sending it is allowed or what it will do. Do not build an uplink path on this model.
Table A-8: Alarms
| Element | Status | Notes |
|---|---|---|
DefaultAlarm | Ignored | On numeric, enumerated and other types. |
ContextAlarmList | Ignored | |
StaticAlarmRanges, ChangePerSecondAlarmRanges | Ignored | |
AlarmConditions | Ignored |
Alarms are ignored rather than kept opaque. Half-modeled alarm limits are worse than none: a caller who found some of them present might reasonably assume all of them were.
Table A-9: Streams, messages, algorithms, services
| Element | Status | Notes |
|---|---|---|
StreamSet and every stream type | Ignored | |
Fixed and variable frame streams. This repository implements frames directly, in pkg/tmdl, pkg/tcdl, pkg/aos and pkg/usdl. | ||
MessageSet, Message | Ignored | |
AlgorithmSet and every algorithm type | Ignored | |
Out of scope by decision, not by effort. | ||
ServiceSet | Ignored | |
Table A-10: References and names
| Feature | Status | Notes |
|---|---|---|
Absolute references (/A/B/C) | Supported | |
Relative references (../B/C, ./C) | Supported | |
| Bare names | Supported | Searched in the referencing system, then each ancestor to the root. |
NameReferenceType pattern | Supported | Malformed references are rejected with ErrInvalidReference. |
| Alias-based resolution | Unsupported | AliasSet is ignored, so nothing resolves by alias. |
Table A-11: Validation
| Check | Status | Notes |
|---|---|---|
| XSD schema conformance | Unsupported | |
No validator in the standard library and no dependencies taken. Use xmllint for this. | ||
parameter resolves | Supported | |
Spanning both metadata sides. | ||
parameterRef in entries resolves | Supported | |
containerRef in entries resolves | Supported | |
Base resolves | Supported | |
| Container inheritance is acyclic | Supported | |
Linear graph colouring. Identity is by pointer, so two systems may each have a Common. | ||
| Duplicate names within a SpaceSystem | Supported | |
Parameters, types, containers, commands, and sibling systems. | ||
| Encoding enumerations are legal | Supported | |
encoding, bitOrder and byteOrder on every parameter type's data encoding are checked against the schema's members, including the arbitrary byte-list order. | ||
argument resolves | Unsupported | |
Argument types are not modeled. | ||
meta resolves | Unsupported | |
Limits
| Limit | Value | Why |
|---|---|---|
Max | 64 MiB | |
XTCE sets no ceiling. Real databases run to a few megabytes. | ||
MaxDepth | 100 levels | |
SpaceSystem is recursive, so deep nesting would recurse during decoding. The check is a token scan that runs before decoding. | ||
Growing the coverage
This matrix is the contract for scope. Anything moving out of Unsupported or Opaque lands with its model structs, a fixture exercising it, and a change to its row here, in the same commit. A status that drifts from the code is worse than a gap that is written down.
Wire test vectors
The octets backing this statement live in the vector corpus — 8 published corpus files. Each vector names the clause it comes from and carries the derivation that produced it.
| File | |
|---|---|
xtce/documents.json | 8 corpus files |
These are data files, so any implementation can check itself against the same octets. See CONTRACT.md for how, and how this is verified for what rests on a published vector versus a reading of the clause.