Architecture Description Languages (ADLs)

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Architecture Description Languages (ADLs)
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A Brief History of ADLs

• Software architecture emerged as a research
  discipline in the early 1990s
• Soon thereafter, many notations were either
  invented, recast, and/or argued for as
  architecture description languages
• Each provided modeling capabilities geared at
  software design
• Though not necessarily architecture!
• They saw varying degrees of adoption and use

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• What is an ADL?

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So, What Was the Answer?

• An ADL is a language that provides features for
  modeling a software systems conceptual
  architecture, distinguished from the systems
  implementation.
• An ADL must support the building blocks of an
  architectural description
• Components
• Interfaces
• Connectors
• Configurations

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What Happened to the ADLs?

• Some of the obvious reasons
• Often targeted at research environments
• Awkward syntax and/or semantics
• Modeling rigidity
• Limited and idiosyncratic analysis support
• Inadequate tool support
• UML
• Video killed the radio star

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Examples on ADL

• Early generations
• Darwin, Rapide, Wright
• Domain and style specific ADLs
• Koala, AADL
• Extensible ADLs
• Acme, ADML (an XML based ADL syntax derived from
  Acme), xADL

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What Does/Did an ADL Description Look Like?

• A Rapide component

type Application is interface extern action
Request(p params) public action Results(p
params) behavior (?M in String) Receive(?M) gt
Results(?M) end Application
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What Does/Did an ADL Description Look Like?

• A Wright connector

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What Does/Did an ADL Description Look Like?

• An Acme architecture

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Classifying ADLs

• Essential features
• Components
• Connectors
• Interfaces
• Configurations
• Desirable features
• Specific aspects of components, connectors, and
  configurations
• Tool support
• Approaches to modeling configurations
• Implicit configuration
• Explicit configuration
• Approaches to associating architecture with
  implementation
• Implementation constraining
• Implementation independent

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• Brilliant!
• So, what went wrong?

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Remember This?
Software Architecture
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Where 1G ADLs Lived
Software Architecture
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So, a Deeper Reason

• 1G ADLs focused exclusively on technology
• So did our study
• The broader context was completely missing
• Relation to system requirements
• Constraints imposed by implementation platforms
• Characteristics of application domains
• Organizational structure and politics
• Business model
• Position in the marketplace

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How Do We Define an ADL Then?

• An architectural model is an artifact or document
  that captures some or all of the design decisions
  that make up a systems architecture.
• Architectural modeling is the effort to capture
  and document the design decisions that make up a
  systems architecture.
• An architecture description language is a
  notation in which architecture models can be
  expressed.

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2G ADLs

• Only a handful of 1G ADLs have stuck around
• but, boy, have they changed
• They evolved into 2G ADLs
• UML 2.0 ? UML 1.x
• AADL ? MetaH
• Koala ? Darwin ? Conic
• xADL 2.0 ? xADL 1.0 ? C2
• All have strong technological foci
• Yet they are very different from each other

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UML 2.0

• De facto standard software design language
• Developed by OMG
• A Swiss Army Knife of notations
• Has a number of architectural constructs
• Ubiquitous
• Primary focus to conquer the world

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UML 2.0 in Action
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UML 2.0 in Action
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UML 2.0 in Action
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UML 2.0 Under the Lampposts
Software Architecture
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UML 2.0 Under the Lampposts
Software Architecture
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UML 2.0 Under the Lampposts
Software Architecture
Business
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UML 2.0 Under the Lampposts
Software Architecture
Business
Domain
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AADL

• Architecture Analysis and Design Language
• Initially stood for Avionics ADL
• Primarily textual
• Very detailed
• An AADL component runs on a processor, which runs
  one or more processes, each of which contains one
  or more threads of control, all of which can
  receive instructions through in ports and send
  data through out ports over a bus
• Primary focus embedded, real-time, hybrid
  systems

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AADL in Action
system implementation sensor_type.temperature subc
omponents the_sensor_processor
processor sensor_processor_type
the_sensor_process process
sensor_process_type.one_thread connections
bus access network -gt the_sensor_processor.networ
k event data port sensed -gt
the_sensor_process.sensed event data
port control -gt the_sensor_process.
control properties Actual_Processor_Bindin
g gt reference the_sensor_processor
applies to the_sensor_process end
sensor_type.temperature
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AADL Under the Lampposts
Software Architecture
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AADL Under the Lampposts
Software Architecture
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AADL Under the Lampposts
Software Architecture
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AADL Under the Lampposts
Software Architecture
Business
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Koala

• Developed at Philips
• In collaboration with Imperial College London
• Used in the consumer electronics domain
• Both graphical and textual
• Primary focus management of product populations
• Modeling
• Analysis
• Implementation generation
• Deployment

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Koala in Action
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Koala in Action
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Koala Under the Lampposts
Software Architecture
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Koala Under the Lampposts
Software Architecture
Technology
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Koala Under the Lampposts
Software Architecture
Technology
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Koala Under the Lampposts
Software Architecture
Technology
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xADL 2.0

• Developed at UC Irvine
• In use at Boeing
• XML substrate
• Both graphical and textual
• Primary focus extensibility

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xADL 2.0 in Action
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xADL 2.0 in Action
ltcomponent id"dbComp"gt ltdescriptiongtDatabaselt
/descriptiongt ltinterface id"sql-in"gt
ltdescriptiongtSQLlt/descriptiongt
ltdirectiongtinlt/directiongt lt/interfacegt
ltdatasourcegt ltvendorgtOracle
Corp.lt/vendorgt ltlocationgtdb.example.com12
34/db1lt/locationgt ltusernamegtwebUserlt/usern
amegt ltpasswordgtsecretlt/passwordgt
lt/datasourcegt lt/componentgt
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xADL 2.0 Under the Lampposts
Software Architecture
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xADL 2.0 Under the Lampposts
Software Architecture
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xADL 2.0 Under the Lampposts
Software Architecture
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xADL 2.0 Under the Lampposts
Software Architecture
Domain
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2G ADLs Side-by-Side
UML 2.0
AADL
Koala
xADL 2.0
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Some Observations

• Architecture embraces many concerns
• More mature and successful ADLs incorporate
  concerns from 3L
• Multiple views are a must
• No single set of modeling features is sufficient
  for every project
• Extensibility is a key property of ADLs
• Tools are often as important as notations