Advanced Synthetic Parameter Expression Language SPEL SCOS2000 Reference Implementation

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Advanced Synthetic Parameter Expression Language
- SPELSCOS-2000 Reference Implementation
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Background

• Ground systems and operations Monitoring and
  control data definition (ECSS-70-31- draft 18
  onwards) comprises
• Expression Language (EXPL)
• Synthetic Parameters Expression Language (SPEL)
• Interpretation Function Language (IFL)
• ? All these languages are consistent with the
  Procedure Language Standard (ECSS-70-32, PLUTO)
• Siemens contributed to ECSS-70-31, in particular
  to the SPEL language definition.

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Advanced SPEL Reference Implementation

• SCOS-2000 3.1 supports synthetic parameters
  defined in its operations language (OL).
• Objective of the SPEL Activity
• Provide an implementation of the SPEL standard
  language for the SCOS-2000 3.1 EGSE version.
• Identify the subset of SPEL that can be
  implemented within SCOS 3.1 (some limitations,
  e.g. No multi-domain capability, no variable
  packet parameters access, no SSM, no triggering
  on events)
• Verify the SPEL specification

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A brief tour of SPEL (1)

• Highlights of SPEL
• Type-safe SPEL uses a strict type system,
  emphasising consistency checks
• Powerful
• Exhaustive set of predefined functions including
  mathematical, string, date/time, and bit
  manipulation.
• Access to parameter properties (value,
  validity,..)
• Readable SPEL is closer to human language than
  many other languages
• Strictly block-oriented e.g. if .. then .. end
  if

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A brief tour of SPEL (2)

• Advanced features
• Advanced Operators for range check and set
  membership.
• Powerful case construct, eliminating need for
  complex if/else cascades.
• Triggers Control of the events triggering the
  synthetic parameters update cycle.
• Persistency Variables can be persistent.
• Engineering Units Variable declarations and
  constant expressions are augmented with an
  engineering unit, allowing consistency check and
  automatic conversion.

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A brief tour of SPEL (3)

• Large Set of Predefined Functions
• 25 arithmetic standard functions, e.g.
• abs, acos, asin,..ln, log,..tan, tanh, truncate
• Statistics functions taking n arguments average,
  min, max, e.g. min(P1, P2, P3)
• 13 time functions current_time, year, month,
  day_of_month,..
• 15 string functions for manipulation (e.g.
  capitalize, length_of) and conversion
  (to_integer, to_real,..).

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SPEL Examples (1)

• / Ex. 1 Simple /
• set raw value with G123 1 end with
• / Ex. 2 using if and local variable /
• declare
• x of type real
• end declare
• main
• x get engineering value of PE01
• if x between -1.0 and 1.0 then
• set raw value with arcsin(x)
• end if
• end main

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SPEL Examples (2)

• / Ex. 3 Check limit check state /
• declare
• lck of type limit check status
• end declare
• main
• lck get limit check status of P001
• in case lck
• is in (warning low, warning high)
• set raw value with warning
• or is in (danger low, danger high)
• set raw value with DANGER
• otherwise
• set raw value with nominal
• end case
• end main

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SPEL Examples (3)

• / Ex. 4 Using trigger /
• trigger on update of
• P001, P001
• end trigger
• main
• set raw value with P001P002P003 end with
• end main
• This SPEL parameters update will be triggered by
  P001 or P002, but not P003.
• By default (no trigger clause) all contributing
  (source) parameters will trigger the update.

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SPEL Implementation in SCOS

• Consistent extension of the SCOS TM parameter
  processing model (new class VIEWspel) ? existing
  applications run as before
• Technology
• SPEL parser uses Open Source tools (flex/bison)
  that are already adopted by SCOS (i.e. no new
  tools required!).
• SPEL parser builds Abstract Syntax Tree (AST).
  With every parameter update, the AST is executed.
• Online editing (edit/broadcast) supported?
  required for EGSE and nice for experimenting.

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Status Summary

• SPEL implementation is now part of the SCOS-2000
  3.1-based EGSE system at ESTEC.
• Envisaged future activities
• migrate to SCOS 3.1 H-P-Repatriation release.
• extend coverage of SPEL standard (delta check
  support, engineering units)
• implement IFL, EXPL inside SCOS-2000
• putback to SCOS-2000 mainline

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Conclusion

• Questions and Comments?
• ? Life demo

SCOS TQD showing SPEL parameter details