Spacecraft Markup Language

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Spacecraft Markup Language
A Presentation to OMG 12/12/2000 www.interfacecont
rol.com/sml
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Problem Definition

• Space Program
• The Tower of Babel
• Contractors talking different languages
• Database Chaos Confusion
• Little Communication Interchange
• Nightmares
• Configuration Management
• Documentation

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FUSE Issues

• Database Management Across heterogeneous
  platforms (Unix,NT)
• ASIST RDL from GSFC
• http//rs733.gsfc.nasa.gov/ASIST/ASIST-home.html
• Extended RDL to RDL
• Developed parser and other tools
• Management in an object oriented database O2
• A lot of custom work
• An ASCII version is still a preferred method of
  data exchange

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RDL for FUSE Commanding

• DATABASE FUSE
• CLASS IDS
• CMDS SWB, DESC"SWB"
• UB USER_DATA DEFAULT 0
• UB OPCODE DEFAULT 0
• END ! CMDS SWB
• END
• CLASS SWB
• CMD IDS_CMDS APID 112
• END
• CLASS IDS_CMDS
• CMD BC_MGR ,FCTN 35, DESC "IDS IDB BUS
  CONTROLLER MANAGER TASK"
• END
• CLASS BC_MGR
• CMDS IDS_IDBCTRL, DESC "START/STOP IDB OR
  SET RETRY PARAMETERS"
• USER_DATA 0
• OPCODE 17
• BITFIELD PARAMETERS
• UI OP DEFAULT 0, MASK X0003,

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FUSION or Convergence

• Industry Standards
• XML, XSLT
• NASA Database Description Language
• RDL
• Object-Oriented Database
• O2, O2C

SML
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SML Goal

• To Provide the Space Community With a Common
  Definition of Spacecraft and Other Data Objects.
• A Space Ontology based on XML
• To provide a user-extensible framework that
  allows extensive flexibility while preserving
  cross-vendor compatibility within open XML
  standard.

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XML Benefits

• Standard ASCII Format for
• Data Description Definition
• Data Presentation
• Data Query
• Human Readable (friendly)
• Web/Computer Friendly
• Lots of freely available tools

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What Does XML Give Us?

• It is at least as readable as HTML
• Allows you to invent your own tags
• A lot of the programming is already done
• 3rd party parsers Apache Xerces , IBM,
  Microsoft
• 3rd party viewers - IE, Netscape
• It is directly reusable, Allows multiple views of
  the same data
• Tags dont have anything to do with how the data
  is displayed

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Is It Hype?

• XML finally offers the ability to create a
  globally accepted and cross-platform way of
  managing and communicating data and information.
• Intelligent Information Representation and
  Transfer
• Data Named Tags Type Information any other
  definable attributes

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Schema Vs. DTDs

• Document Type Definition (DTD)
• lt!DOCTYPE Book   
• lt!ELEMENT Book (Title, Chapter)gt   
• lt!ATTLIST Book Author CDATA REQUIREDgt   
• lt!ELEMENT Title (PCDATA)gt   
• lt!ELEMENT Chapter (PCDATA)gt   
• lt!ATTLIST Chapter id ID REQUIREDgt gt
• Why
• To check if the data conforms to its definition
• DTD Grammar for Data Validation during Parsing

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Schemas

• DTDs are not expressed in XML and cannot take
  advantage of existing tools.
• DTD limitation
• Which Schema?
• SOX
• Microsoft XML-Schema
• XML-Data
• W3C Schema
• http//www.w3.org/
• XML Schema has recently (2000-10-24) been
  advanced to Candidate Recommendation status

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Issues with Schemas

• Moving Standards
• Explicit
• Could be a good or bad thing
• Verbosity
• Not user friendly
• Multiple Inheritance

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SML

• Advantages
• Data Definitions based on legacy (RDL)
• User extensible Schema Definition
• Implicit Schema
• Compact representation
• KISS principle
• Object-Orientation
• Derivation of new data structures based on
  previously defined ones
• Object Oriented Commanding System
• Blends the notion of classes and objects
  (simpler)
• Mix data schema information
• A Schema can always be translated into another
  schema by applying the proper stylesheet

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SML So Far

• 10/26/99 First draft of Specification
• 11/99 Presented to
• GSFC NASA Code 580
• CCSDS Panel 2 Standards working group
• APL
• Ball Aerospace
• Used by Aerojet on SBIRS-High
• GE-Harris Harmon Railway Technology
• Version 1.6 released 9/20/2000

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SML Command Example

• ltCMDS NAMECCSDS DESCCCSDS ROOT Command gt
• ltUI NAMEAPID/gt
• ltUB NAMEFCTN/gt
• lt/CMDSgt
•  
• ltCCSDS NAMEIDS DESCIDS Commands gt
• ltAPIDgt 10 lt/APIDgt
• ltFCTNgt 2 lt/FCTNgt
• ltUB NAMEOPCODE DESCAdditional opcode
  parameter /gt
• lt/CCSDSgt
•  
• ltIDS NAMEDEV1 DESCDEV1 IDS Commands gt
• ltOPCODEgt 23 lt/OPCODEgt
• lt/IDSgt
•  

CCSDS IDS DEV1
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Protocol Definition

• Commanding implies a command protocol that has to
  be defined
• Protocol is usually layered
• Header
• Trailer
• Protocols can be nested

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Protocol Example

• ltCMDS NAME"CCSDS" DESC"CCSDS Root Command"gt
• ltHEADER MAXSIZE"240" DESC"CCSDS Header"gt
• ltRECORD NAME"HDR1"gt
• ltBITFIELD NAME"PKT"gt
• ltUI NAME"Version" MASK"0xE000" DEFAULT"0"
  MODE"STATIC"/gt
• ltUI NAME"Type" MASK"0x1000" DEFAULT"1"
  MODE"STATIC"/gt
• ltUI NAME"SecHdrFlag" MASK"0x800"
  DEFAULT"1" MODE"STATIC"/gt
• ltUI NAME"APID" MASK"0x7F"/gt
• lt/BITFIELDgt
• lt/RECORDgt
• ltRECORD NAME"HDR2"gt
• ltUB NAME"SEDS_RESERVED" DEFAULT"0"
  MODE"STATIC"/gt
• ltUB NAME"FCTN" DEFAULT"0"/gt
• lt/RECORDgt
• lt/HEADERgt
• ltTRAILERgt
• ltUB NAME"Checksum"gt
• ltMETHOD NAME"CCSDS_TRAILER"/gt

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SML Language Overview

• Tags
• Attributes
• Comments
• Namespaces

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SML File Structure

• lt?xml version"1.0" standalone"no"?gt
• ltDATABASE gt
• ltSECTION gt
• ltSPACEOBJECTS gt
• ltSPACEOBJECTS /gt
• lt/SECTIONgt
• lt/DATABASEgt
• Convenience containers tags to define has-a
  relationships. It does not imply an inheritance
  or is-a relationship.
• Note a ltSCHEMAgt tag has also been added for
  convenience

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SPACE OBJECTS

• COMMANDS
• TELEMETRY PACKETS
• DATABASE RECORDS
• MESSAGES

Objects can be derived from other objects Objects
have fields that can be optional or required
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Primitive Fields

• UB
• UI
• ULI
• SFP
• CHAR
• TIME

• SB
• SI
• SLI
• DFP
• STRING

Fields have various attributes implicit data
types
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Field Attributes

• Attributes
• Name (required)
• DESC
• MODE
• MASK
• MIN
• MAX
• BIGENDIAN
• UNITS

• VISIBLE
• RHIGH
• YHIGH
• YLOW
• RLOW
• DEFAULT
• AS
• DRANGE
• METHOD

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Grouping Constructs

• RECORD
• UNION
• BITFIELD
• ARRAY

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Other Space Objects

• PACKETS
• MESSAGES
• SCRIPTS

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Packets

• ltPACKET NAMEHDR
• DESCThis is the header information gt
• ltUB NAMEfield1/gt
• ltUI NAMEfield2/gt
• lt/PACKETgt

Telemetry Packets for instance
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Messages

• Support Concept of Software Bus
• Notification Messages
• Request/Replies Messages

ltMESSAGE NAMEmyMsg ltREQUESTgt ltSTRING
NAMEfilenamegt lt/REQUESTgt ltREPLYgt ltUB
NAMEstatus /gt ltSTRING NAMEerrstr /gt
lt/REPLYgt lt/MESSAGEgt
ltMESSAGE NAMEmyMsg gt ltNOTIFYgt ltSTRING
namefilename /gt lt/NOTIFYgt lt/MESSAGEgt
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SML Tools

• DBComp
• SML Builder
• SML Viewer
• SMLGENT
• JCMDGEN

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Putting it together
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SMLViewer
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Web Command to Spacecraft.

• The user sends a command from the SMLViewer.
  The GUI tool generates an SML message, and sends
  it to the Gateway (WEB Server).
• JCMDGEN parses and validates the SML message,
  then encodes the contents of the message to be
  transferred to the spacecraft.
• The Spacecraft receives the encoded message, and
  passes to the destination process.
• Onboard process operates on the message.

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Send a Command From Your Cell Phone
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Directions

• W3C Schema/XSLT Impact
• Namespaces
• Include,
• SML GUI Builder
• Drag Drop
• SML to W3C Schema Conversion Tool
• Automatic Message Validation
• Some SOAP Convergence
• SOAP Bridge