Advantages of using XML for NCTRS Configuration Michael E. Dyck1, 1Anite Systems GmbH, Darmstadt, He

1
Advantages of using XML for NCTRS
ConfigurationMichael E. Dyck1,1Anite Systems
GmbH, Darmstadt, Hessen, 64293, Germany.

• Document Manipulation
• The following diagram illustrates the publication
  process used to extract information from XML
  configuration schema and instance documents.
• Publishing is a multi-step automated process
• Instance documents are converted into
  configuration reports through the use of XSLT
  stylesheets.
• The configuration schema is processed to extract
  the configuration content model and associated
  documentation converted into DocBook, HTML and
  PDF formats.

Abstract The Network Controller and Telemetry
Router System (NCTRS) is the ground station
network front end which provides a Mission
Control System (MCS) with the ability to
communicate with a variety of equipment in a
network of ground stations. Current
implementations of NCTRS use a proprietary
configuration file format to configure
communication with MCS clients and ground
stations. An XML based configuration format would
provide benefits in the areas of configuration
specification, validation, and system
interoperability.
Interoperability Configuration information
represented in XML documents which conform to
models defined in XML schemas are highly
interoperable. XML servers can provide access to
distributed configuration information. XSLT can
be used to extract specific information from
configuration databases and transform it into a
variety of formats. Mission Information Models
and mission instance data stored in a central
repository and served by XML servers can provide
a central point for communication of
configuration data between cooperating systems in
a network of ground system components.

• Requirements
• Support a variety of configuration data types
• Support both scalar and tabular configuration
  data
• Be easy to edit
• Support validation and error reporting
• Support multiple missions
• Maintain consistency with peer components
• Enhances interoperability
• Provides reporting of configuration details

• Content Model, Datatypes and Constraints
• XML Schema provides a mechanism to define a
  complex content model supporting
• scalar values
• tabular data
• hierarchical structures
• XML Schema provides support for a wide variety of
  datatypes including
• strings
• integers
• floating point numbers
• binary and boolean data
• enumerated types
• XML Schema provides support for defining content
  constraints including
• minimum and maximum lengths
• minimum and maximum values
• string patterns based on regular expressions
• required content and default values

Conclusions The development of a prototype XML
based configuration for NCTRS has demonstrated
that XML based configuration can be implemented
at low cost with immediate benefits to content
model specification, configuration validation and
system interoperability. The XML Schema
specification provides a standard to define
complex and detailed content model specifications
which exceed the requirements of NCTRS
configuration. XML schema provides improved
support for datatypes, data constraint
definitions, default value specifications, and
binding of content model to both implementation
and documentation. The availability of XML
parsers which support XML Schema enable more time
to be spent on defining and refining the content
model rather than dealing with the details of
parsing the configuration data from its
serialized form. Validating XML editors allow an
XML based configuration to be easily edited and
validated at the authoring stage. Validating XML
parsers allow the XML based configuration to be
revalidated at the time it is ingested into the
system. All this validation is achieved without
the need to develop complex constraint checking
software. The XSLT specification and freely
available XSLT processors allow interoperability
to be improved by providing a mechanism for
configuration data to be automatically filtered
and transformed into formats required by peer
systems. Future systems based on common domain
vocabularies defined in the XASTRO framework will
enable interoperability to be increased further
with the sharing of Mission Information Models
through XML servers.
Standardization One of the goals of the XASTRO
project being performed at ESOC by VEGA and Anite
is to produce a domain vocabulary with which the
configuration files of ground system components
can be conformant. These vocabularies will be
defined by XML Schemas derived from the ground
systems information models of the XASTRO
framework. Such vocabularies may then become the
standard for configuration files used by systems
like NCTRS.