xAcme

Organization of the xAcme extensions

Overview

xArch is an XML schema that defines how to represent instances of architectures in XML. xArch defines a namespace called archInstances that allows one to define a software architecture instance using:

Component Instances (computational entities in an architecture),
Connector Instances (communicational entities in an architecture),
Interface Instances (as part of components and connectors),
Link Instances (attachments between interfaces),
SubArchtiectures (for hierarchy), and
Groups (arbitrary groupings of components and connectors).

xArch was developed jointly by Carnegie Mellon University and the University of California, Irvine. For more information about xArch, see http://www.ics.uci.edu/pub/arch/xarch/. One of the motivations for the development of xArch was to allow it to be extensible, so that particular architecture description languages (ADLs), and related facilities (such as configuration management) can be encoded using xArch extensions,

The xAcme extensions extend xArch to provide facilities for encoding Acme architectural concepts. The Acme extensions are divided into five related extensions, each providing different Acme facilities. The organization of xAcme is illustrated above. The open arrows represent extension relationships. For example, the properties extension extends and uses types defined in the archInstances schema. The dotted line represents use only.

Additional Materials

A more detailed guide to xAcme, containing a brief introduction to XML Schema, rationale and examples, and a comparison between xAcme and ADML.
The xArch home page.

UCI xArch extensions

CMU ABLE Project pages

DASADA (Dynamic Assembly of Systems for Assurance, Dependability, and Adaptability) DARPA program pages.

Tool support

Tool support for xAcme has been added to AcmeStudio 1.6beta, allowing one to export xAcme descriptions. (Importing will be available soon.) AcmeStudio is available from http://www.cs.cmu.edu/~acme/AcmeStudio/AcmeStudio.html.

Comments and suggestions should be sent to Bradley Schmerl.

Properties extension

The properties extension adds simple properties to xArch instances. At this level, properties have no detailed structure; they simply consist of a name, a value and a type, each represented by uninterpreted strings. In addition, support for multiple subarchitectures is included in this extension.

View Schema (txt) | View Schema (xsd)
Additional Documentation: XMLSpy overview | Property diagram
Depends on: instances (core)

Properties adds to xArch:

Property instances: The ability to specify named properties with uninterpreted values
Subarchitectures: The ability to have multiple sub-architectures for component and connector instances, and also subarchitectures of architectural instances. This makes xArch compatible with Acme representations.

Families extension

The families extension adds to properties support for Acme style types of components, connectors, interfaces and properties, as well as the collection of all of these types into families. Instances defined in the properties schema are extended to refer to families as supertypes; in addition to this, instances may refer to a particular family used to define the default structure of the instance.

View Schema (txt) | View Schema (xsd)
Additional Documentation: XML Spy overview | Family diagram | TypedArchInstance diagram
Depends on: properties

Families adds to xArch:

component, connector and interface types, compatible with Acme types.
family definitions, as collections of types and structures
typed instances, which represent systems corresponding to a particular family (or style)

Constraints extension

The constraints extension extends families to add support for general constraints. At this level, constraints merely have a type and a description, both of which are uninterpreted strings.

View Schema (txt) | View Schema (xsd)
Additional Documentation: XML Spy Overview | Constraint diagram
Depends on: families

Acme Properties extension

The acmeProperties extension extends properties by adding structure to property types and values consistent with Acme property values and types. Structures for sets, sequences, records, and enumerated types are included.

View Schema (txt) | View Schema (xsd)
Additional Documentation: XML Spy Overview | PropertyValue diagram | PropertyType diagram

AcmeProperties adds to xArch:

Acme property types, such as int, float, etc., and sets, sequences and records.
Acme property values

Acme Constraints extension

The acmeConstraints extension extends constraints by defining additional structure corresponding to the abstract syntax of Armani constraints.

View Schema (txt) | View Schema (xsd)
Additional Documentation: XML Spy Overview | DesignRule diagram | DesignAnalysis diagram

AcmeConstraints adds to xArch:

the ability to define design analyses that can refer to functions defined outside of Acme (e.g., Java functions)
the ability to define invariant our heuristic constraints defined using a first-order predicate logic language
definition of architectural functions for use in constraints

Last modified: 30 March 2001. The development of xAcme was funded by the DARPA DASADA (Dynamic Assembly for Systems Adaptability, Dependability, and Assurance) program.