XTCE12 — TimeAssociation should be settable at the Container

Description Kevin Rice 2007-10-22 21:34:53 BST
Time Association needs to apply to any parameter in a Packet/Container. The
XTCE parameter/parameterproperties/timeassociation can be used to capture an
"offset" time from a packet time stamp. In CCSDS world, most telemetry
packets are time stamped – and sometimes those time stamps are adjusted by
some offset or delta for each telemetry parameter in the packet (in effect each
parameter is timetagged). Since the same parameter may exist in more than one
packet and have different offsets – the XTCE approach is limiting in this
regard since only one offset can captured per parameter, not at the
packet/container level. XTCE should modify its container entryList area so
that TimeAssociation can be captured per packet entry.

Propose to include the TimeAssociation proposal at SequenceEntry type

The working group created a proposal to include updates to the SequenceEntryType to incorporate TimeAssociation element options.

The existing TimeAssociationType gets some minor updates to the documentation. Replace the existing schema type:

<complexType name="TimeAssociationType">
<annotation>
<documentation xml:lang="en">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. </documentation>
<appinfo>The parameter ref must be to an AbsoluteTime Parameter</appinfo>
</annotation>
<complexContent>
<extension base="xtce:ParameterInstanceRefType">
<attribute name="interpolateTime" type="boolean" default="true">
<annotation>
<documentation xml:lang="en">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.</documentation>
</annotation>
</attribute>
<attribute name="offset" type="double">
<annotation>
<documentation xml:lang="en">The offset is used to supply a relative time offset from the time association and to this parameter</documentation>
</annotation>
</attribute>
<attribute name="unit" type="xtce:TimeAssociationUnitType" default="si_second">
<annotation>
<documentation>Specify the units the offset is in, the default is si_second.</documentation>
</annotation>
</attribute>
</extension>
</complexContent>
</complexType>

With the following new content for this schema type:

<complexType name="TimeAssociationType">
<annotation>
<documentation xml:lang="en">Describes a time association consisting of an instance of an absolute time parameter (parameterRef) and this entry. Because 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. See AbsoluteTimeParameterType.</documentation>
</annotation>
<complexContent>
<extension base="xtce:ParameterInstanceRefType">
<attribute name="interpolateTime" type="boolean" default="true">
<annotation>
<documentation xml:lang="en">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.</documentation>
</annotation>
</attribute>
<attribute name="offset" type="double">
<annotation>
<documentation xml:lang="en">The offset is used to supply a relative time offset from the time association and to this parameter</documentation>
</annotation>
</attribute>
<attribute name="unit" type="xtce:TimeAssociationUnitType" default="si_second">
<annotation>
<documentation xml:lang="en">Specify the units the offset is in, the default is si_second.</documentation>
</annotation>
</attribute>
</extension>
</complexContent>
</complexType>

Then update the existing SequenceEntryType content from:

<complexType name="SequenceEntryType" abstract="true">
<annotation>
<documentation xml:lang="en">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.</documentation>
</annotation>
<sequence>
<element name="LocationInContainerInBits" type="xtce:LocationInContainerInBitsType" minOccurs="0"/>
<element name="RepeatEntry" type="xtce:RepeatType" minOccurs="0">
<annotation>
<documentation xml:lang="en">
May be used when this entry repeats itself in
the sequence container. If not supplied, the
entry does not repeat.
</documentation>
</annotation>
</element>
<element name="IncludeCondition" type="xtce:MatchCriteriaType" minOccurs="0">
<annotation>
<documentation xml:lang="en">
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.
</documentation>
</annotation>
</element>
</sequence>
<attribute name="shortDescription" type="string" use="optional"/>
</complexType>

To the new definition that also incorporates annotation improvements to enhance clarity of the usage:

<complexType name="SequenceEntryType" abstract="true">
<annotation>
<documentation xml:lang="en">Defines an abstract schema type used to create other entry types. Describe an entry’s location in the container (See LocationInContainerInBitsType). The location may be fixed or dynamic, absolute or relative. Entries may be included depending on the value of a condition (See IncludeConditionType), and entries may also repeat (see RepeatEntryType). The entry’s IncludeCondition resolves to true, it is fully-resolved when its size is computable after RepeatEntry has been accounted for and then offset by LocationInContainer. See EntryListType, IncludeConditionType, RepeatEntryType and LocationInContainerInBitsType.</documentation>
</annotation>
<sequence>
<element name="LocationInContainerInBits" type="xtce:LocationInContainerInBitsType" minOccurs="0">
<annotation>
<documentation xml:lang="en">The start bit 0 position for each container is local to the container, but does include space occupied by inherited containers. When a container is "included", as opposed to inherited, then the interpreting implementation takes into account the start bit position of the referring container when finally assembling the start bits for the post-processed entry content. The default start bit for any entry is 0 bits from the previous entry, making the content contiguous when this element is not used.</documentation>
</annotation>
</element>
<element name="RepeatEntry" type="xtce:RepeatType" minOccurs="0">
<annotation>
<documentation xml:lang="en">May be used when this entry repeats itself in the sequence container. When an entry repeats, it effectively specifies that the same entry is reported more than once in the container and has the same physical meaning. This should not be construed to be equivalent to arrays.</documentation>
</annotation>
</element>
<element name="IncludeCondition" type="xtce:MatchCriteriaType" minOccurs="0">
<annotation>
<documentation xml:lang="en">This entry will only be included in the sequence when this condition is true, otherwise it is always included. When the include condition evaluates to false, it is as if the entry does not exist such that any start bit interpretations cannot take into account the space that would have been occupied if this included condition were true.</documentation>
</annotation>
</element>
<element name="TimeAssociation" type="xtce:TimeAssociationType" minOccurs="0">
<annotation>
<documentation xml:lang="en">Optional timing information associated with this entry.</documentation>
</annotation>
</element>
<element name="AncillaryDataSet" type="xtce:AncillaryDataSetType" minOccurs="0">
<annotation>
<documentation xml:lang="en">Optional ancillary data associated with this element.</documentation>
</annotation>
</element>
</sequence>
<attribute name="shortDescription" type="xtce:ShortDescriptionType" use="optional">
<annotation>
<documentation xml:lang="en">Optional short description for this entry element.</documentation>
</annotation>
</attribute>
</complexType>