XidML is an open standard XML

XML

Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....

 tailored for the aerospace

Aerospace

Aerospace comprises the atmosphere of Earth and surrounding space. Typically the term is used to refer to the industry that researches, designs, manufactures, operates, and maintains vehicles moving through air and space...

 industry . XidML describes how data is acquired, processed and packaged for transmission, storage or reproduction. The primary objective of XidML is to store and exchange complex instrumentation information between multiple vendors and user-groups gathering thousands of parameters.

Taxonomy

There are five major components within XidML – parameters, instruments, packages, links and algorithms – each with their own subset of metadata

Metadata

The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...

.

Parameters

Parameters describe all there is to know about a value being measured. Examples of the type of metadata associated with a parameter include

• Name: uniquely identifies the parameter
• DataFormat: format used to encode the sampled data - examples include Offset Binary and Binary Coded Decimal
• Unit: unit of measurement of the parameter (expressed relative to SI
  Si
  Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
  
   units)
• LongDescription: detailed description of a parameter
• ShortDescription: brief description of the parameter
• SizeInBits: number of bits used to encode the sampled data

It is also possible to decompose a parameter into sub-parameters and to describe the meaning of each sub-parameter. For example, a 48 bit IRIG

IRIG

The Inter Range Instrumentation Group is the standards body of the Range Commanders Council . They publish a number of standards through the RCC Secretariat at White Sands Missile Range ....

 Time parameter is typically broken up into High, Low and Micro time components.

Instruments

Instruments are the physical hardware used in data acquisition and describe how FTI devices are configured. All instruments share the following common metadata:

• Name: uniquely identifies the parameter
• Manufacturer: identifies the device manufacturer
• PartReference: uniquely identifies the type of device
• SerialNumber: uniquely identifies a specific device

Device configuration

Device configuration is described using zero or more settings. Settings are those values that affect the behavior of a device in an acquisition network. Settings consist of

• Name: This is the name of the setting. Device vendors publish the allowed values for settings using XdefML. Examples of settings include Filter Cutoff and Excitation Amplitude
• Value: This is the value associated with setting. Device vendors publish the allowed values and other value constraints using XdefML.

Packages

Packages describe how data is transmitted or stored. All packages must have globally unique names. Examples of transmission packages include IRIG-106 Chapter 4 PCM frame definitions, MIL-STD-1553

MIL-STD-1553

MIL-STD-1553 is a military standard published by the United States Department of Defense that defines the mechanical, electrical, and functional characteristics of a serial data bus. It was originally designed for use with military avionics, but has also become commonly used in spacecraft on-board...

message definitions and Ethernet packet descriptions. An example storage format is the IRIG Chapter 10 data storage description.
All packages share the same common structure:

• Properties: contains structural and other header information
• Content: describes the payload content of a package – specifically, what parameters are transmitted, how often they are transmitted and where they are located within the package
• Source: defines where a package originates
• Destination: describes the destination of a package

All packages also include the following data:

• Name: uniquely identifies a package
• PackageRate: number of times the a package is sent or received a second

Links

Links describe the physical connections between instruments. Examples of Links include an Ethernet connection between two networked devices and an RF link between an aircraft and a ground-station card in a PC. All links have a globally unique name.

• Name: uniquely identifies a link
• Type: defines the type of link e.g. Ethernet (an Ethernet connection) and ARINC-429 (a connection to an ARINC-429 bus)
• Packages: describes what packages are being transmitted on a link in addition to the sequencing of this data on a link (optional)

Algorithms

Algorithms describe how data is processed. Examples include polynomials used to linearize data and an algorithm used to extract a sub-set of bits from a parameter before transmission. All algorithms have a globally unique name.

• Name: uniquely identifies an algorithm
• Inputs: input parameters to an algorithm
• Outputs: parameters output by an algorithm

The semantics of how an algorithm processes and generates data is described in the body of the algorithm.

Origins

The use of XML has become increasingly common in the flight test industry as a means of automating translation tasks and facilitating interoperability between systems. XidML was created with the aim of addressing the specific requirements encountered in aerospace applications. A XidML committee ensure vendor independence and ensures XidML remains relevant into the future.

Revisions

XidML has undergone a number of revisions in response to community feedback and requirements. It is currently at version 3.0.0 which introduced several major changes since version 2.4. These include fewer schemas for simplification, to make it easier to process by software and reduce the likelihood of future changes to the schema. Additionally, an optional complementary schema called XdefML has been added that facilitates instrument set-up and validation.