XASTRO XML based data exchange framework for space programs

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XASTRO - XML based data exchange framework for
space programs
Anthony Walsh, VEGA IT GmbH, awalsh_at_vega.de Niklas
Lindman, ESA/ESOC, nlindman_at_esa.int NASA-ESA
Workshop on Aerospace Product Data
Exchange ESA/ESTEC, Noordwijk, The
Netherlands April 9-12, 2002
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Presentation Outline

• XASTRO Study Introduction
• Motivation for Study
• Study Logic
• ASTROM/XASTRO Overview
• STEP and OMGs MDA
• Co-ordination with CCSDS/OMG XML Activities
• Critical Issues

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XASTRO Study Introduction

• ESA study to investigate the use of XML as the
  basis for a standard data exchange framework
  between customers, contractors and suppliers
  during the life-cycle of a space mission
• XASTRO is a study project being executed under
  ESAs Innovative Technology program as a
  potential solution to current data exchange
  problems
• XASTRO just being kicked off and will last 12
  months and is being managed from ESA/ESOC
• Address data exchange not just during the
  procurement phase, of a mission, but also though
  to integration of mission elements, mission
  operations, space product storage and retrieval
• Study will focus on space segment and information
  data exchange relevant from a operational
  perspective

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Motivation for XASTRO

• Data Exchange is difficult for many reasons
• Large quantity of information in a space mission
• Wide range of information types represented in a
  diverse range of formats, with little
  standardisation. Difficult to exchange data
  between stakeholders
• Many stakeholders geographically distributed
  (Space Organisations, Contractors, Scientists
  etc.)
• Information is generally document driven i.e. the
  information is tightly coupled to how it is
  presented
• Mission budgets are continually being tightened
  leading to greater need for efficiency while
  maintaining acceptable levels of risk
• Too many ad-hoc solutions to data exchange from
  one mission to the next

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Study Logic

• Review current data exchange frameworks and
  schemas (i.e. SML, IML, GSML, MDA, STEP) and
  related activities in CCSDS and OMG
• Propose a general data model framework to support
  space missions. Proposed framework has two main
  elements
• Astronautics reference Object Model (ASTROM)
  defined in UML
• XASTRO schemas (XASTRO is the XML based
  representation of the ASTROM UML model)
• Apply framework to candidate mission (CRYOSAT)
• High level analysis of whole mission
• Detailed analysis of most applicable domain
  candidates
• Develop prototype applications to test framework
• Summarise results and identify the way forward.
  For example, improvements to ASTROM,
  auto-generation of XASTRO from ASTROM,
  application of ASTROM to further domains.

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ASTROM/XASTRO Overview

• Is space system engineering framework, that
  allows a common way to describe, store and
  exchange data, consisting of
• Astronautics Reference Object Model (ASTROM) - a
  Unified Modelling Language (UML) data model that
  describes the entities within a space system.
• XML implementation of ASTROM (XASTRO) - a space
  data description and data interchange language.
• Most investment will go into design of a
  conceptual model in UML. This model gives context
  to the XASTRO schemas.
• XASTRO schemas directly generated from the ASTROM
  (using of XMI and XSLT)
• Above approach is aligned with OMGs Model Driven
  Architecture (MDA) - potential candidate for
  basic ASTROM framework

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ASTROM (as defined in proposal)

• Space system reference object model
• Described in UML
• Defines the standard entities in a space system
• Dictionary

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ASTROM - System Framework Model

• Defining the basic entities of a system
• components
• component connectivity
• data
• interchange formats
• archive formats

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ASTROM - Space Segment Model

• Bad Name!
• Defines the space system breakdown.
• Defines the basic entities of a space system.
• Shows the is-part-of relationship between the
  components

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ASTROM - Space Domain Model

• Defines the space application specific entities
  of the system
• Space engineering domain specific models
• Power Budget
• Link Budget
• TM/TC definition
• Flight Dynamics
• etc..

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ASTROM - Space Program Model

• Top - level model that defines
• Missions
• Mission domains
• Mission segments

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XASTRO (as defined in proposal)

• XML implementation of ASTROM as W3C XML Schema(s)
• Automated Generation of schema(s) from UML model
  (UML -gt XMI -gt XML Schemas) if feasible
• XASTRO Schemas
• XSP - Space Program Schema(s)
• XSS - Space Segment Schema (s)
• XSD - Space Domain Schema (s)
• XSF - System Framework Schema(s)

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OMGs Model Driven Architecture(1)

• UML replaces CORBA as core model in OMGs world
• Platform Independent Models (UML, MOF and CWM)
• Standard mappings to Platform Dependent Models
  (i.e. CORBA, EJB, .NET) which can include XML
  Schemas (XASTRO)

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OMGs Model Driven Architecture(2)
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The applicability of STEP to XASTRO

• Investigate the applicability of the AP-233
  information model to XASTRO
• An Application Protocol is the definition of an
  information and process model for an engineering
  model for the purpose of data exchange
• The structure of an Application Protocol
  Information Model and Integrated Resources that
  facilitate interoperability are defined in terms
  of a Description Method. In STEP the preferred
  description method is EXPRESS, while in XASTRO it
  is UML. However both appear to be analogous
  meta-models.
• Data exchange in XASTRO is facilitated through
  XML. In STEP there appears to be a large effort
  to map information models from Express to XML.
  One of the main activities in XASTRO is to map
  UML to XML schema.
• Perhaps STEP has already solved all our data
  exchange problems for space missions and we just
  dont know it!

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Collaboration with CCSDS/OMG

• The Consultative Committee for Space Data Systems
  (CCSDS) strives to establish a world-wide, open,
  CCSDS-compatible virtual space data system for
  international cross support, interoperability,
  and science information interchange.
• Participation in the CCSDS XML Technical Steering
  Group
• Provide useful input into the study
• Peer review
• Co-ordinate activities with other agencies, such
  as CNES and NASA
• Standards need to be adopted to avoid
  unstructured proliferation of schema
• Track developments in OMGs Space Task Force
  (i.e. proposals for Telemetry and Commanding Data
  Specification were recently submitted)

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Critical Issues

• Base XASTRO on open standards (UML, XML/XMI) with
  excellent tool support from many vendors running
  on many platforms
• Use existing frameworks when applicable (STEP,
  MDA, etc)
• Avoid duplication of existing work
• Work with standards organisations
• Keep it simple - however XASTRO must be
  expressive enough to capture the semantics of the
  problem domain
• Test framework with practical examples