Modelbased Configuration Management for a Web Engineering Lifecycle

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Model-based Configuration Managementfor a Web
Engineering Lifecycle
Tien N. Nguyen Elect. and Computer Engineering
Department Iowa State University USA
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Web Engineering

• Web development has changed
• Initially seen as a form of authoring
• Now, also a form of application development
• A lot of efforts and time have been spent to
  maintain Web-based applications.
• Requires the same rigor as successful software
  development/maintenance
• Hence, Web engineering has emerged
• Promotes the use of sound technical and
  management principles for Web applications

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Web application development methods

• Several Web and hypermedia application
  development methods have been proposed.
• WebComposition, OOHDM, RMM, Model-driven Web
  development, HyperDE, WAM
• They introduce several models that address
  different aspects of Web development.
• Data, presentation, navigation, etc
• Each method introduces different set of logical
  abstractions and entities.

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Configuration Management

• Software configuration management (SCM)
• software engineering sub-discipline
• SCM is the discipline of organizing and managing
  the evolution of a software system.
• Web SCM has special challenges variety of object
  types, high rate of changes, continuous
  evolution, hyperlink structures,
• Various types of Web SCM tools
• Version control, change management, content
  management, configuration management

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Related work

• Version and configuration management tools
• Focus on files, not a Web project as a whole
• Change management based on files, text lines
• Inadequate to represent Web object structure
• Web application development environments
• File/directory-oriented versioning (commercial)
• Limited support for CM (research)
• Versioned hypermedia systems focus on hypermedia
  documents, limited support for programs
• Our previous work (Molhado ICSE 2005, SC WWW
  2004) focused on contents of Web artifacts.

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Example
v1
v2

Logical level
File representation level
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File-oriented SCM model
FILES/ DIRECTORIES (text or structured files)
File-based SCM system
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Configuration Management
Web Engineering Models

• Primary targets of SCM are files/directories.

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Model-based Web SCM

• All Web objects in models are versioned and saved
  persistently.
• Web objects do not need to be files or within
  files

SCM repository
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Model-based Web SCM framework
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Web SCM infrastructure

• An infrastructure for building SCM services into
  Web engineering environments
• The infrastructure provides
• Direct representation of Web object structure and
  structural changes, without need for analysis of
  file contents,
• SCM among entities, rather than among files,
• Structure-oriented versioning and SCM of Web
  entities in any models, and
• Versioned hypermedia between entities.

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Web SCM architecture (2)
THIRD-PARTY ENVIRONMENT
Web Engineering tools/editors
Calling API functions
New types of objects
Configuration Management Model
Versioned HypermediaModel
System Model
Structure Versioning Model
Generic Data Model
Version Model
Web SCM Infrastructure
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Web SCM architecture (3)
THIRD-PARTY ENVIRONMENT
Web tools/editors
Calling API functions
Existing Object types
Configuration Management Model
Versioned Hypermedia Model
Bridges/wrappers
System Model
Structure Versioning Model
Generic Data Model
Version Model
Web SCM Infrastructure
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Versioned Data Model

• Node a basic unit of identity (containing no
  values intrinsically other than itself)
• Slot a location that stores a value of any data
  type, possibly a reference.
• Can exist in isolation, but typically attached to
  nodes via attributes
• Attribute A mapping from nodes to slots

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Adding Version Control
Attribute table

• 3 kinds of slots constant, mutable, versioned

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Graph-based Structure Versioning
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version
1
2
3

• Graph can be nested.
• Attribute value can be in any data type, possibly
  a reference.

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Structure Versioning Scheme
Attributed trees and directed graphs
Tools/editors
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Fine-grained Structure Versioning
v1
v2
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Benefits

• Very flexible
• Nodes can participate in multiple graphs
• One mechanism for storing all information
• Graph structure and content
• Common structure shared among versions
• Fine-grained structure versioning of Web objects
  internal structure and other important structures
  such as navigational, compositional, and logical
  structures.

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Versions are points in time
Tree-structured discrete time
V1.0
V2.0
V3.0
V3.2
V3.1

• A version is a point in the systems lifetime.

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Product Versioning
Tree-structured discrete time
V1.0
V2.0
V3.0
V3.2
V3.1

• One global version space across entire project

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Editing and Versions
Tree-structured discrete time
V1.0
current gt V2.0
V3.0
Temporary version
V3.2
V3.1

• Users select a current version to work on.

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System Model

• Acts as a bridge to third-party environment
• Works at the model level, rather than files
• Allows for the description of a Web application
  via models with objects, compositions,
  structures, and relationships
• Provides an infrastructure for extensibility of
  new types of Web objects
• Atomic and composite component types
• User-defined object types derived from them
• Structure is represented via a directed graph

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Composite object

• A composite object contains a directed graph
  whose nodes have versioned references to objects.
• Nodes can have multiple user-defined attributes.
• This attributed digraph is used to represent the
  structure of a composite object.

A versioned reference to a member component
Composite object
component
component

component
component
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Configuration Management

• SCM supports via Molhado ICSE 2005
• set the current version (switching),
• discard or capture changes to a project,
• detect (structural) changes between two arbitrary
  versions,
• open and create a project,
• retrieve and modify meta-data of a project or of
  a version,
• manipulate structures,

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Hypertext Versioning

• HTML-style hyperlinks
• Each node can have an href slot.
• Using edges in a directed graph
• Create a composite component
• Use the digraph of the composite component to
  represent relationships among objects
• Versioned hypermedia model
• Hypermedia elements are first-class entities.

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Hypermedia entities

• Open hyperbase approach A relationship
  (hypertext) network is managed separately from
  object contents.
• A relationship network is defined as a set of
  links and anchors.
• A link, representing a relationship, is an
  association among a set of anchors.
• An anchor denotes a region of interest within an
  object, but is not part of it.
• A linkbase a container of hypertext networks

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Relationship network example
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Representation for hypermedia

• A linkbase is a composite component.
• A hypertext network is an atomic component, and
  has a digraph-based internal structure.
• Each link or anchor is represented as a logical
  unit (node) in that graph.
• The graph represents linking structure among
  anchors and links.
• Digraph versioning scheme enables fine-grained
  versioning for hypertexts and links.

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Benefits of this hypermedia

• Links are explicit and have variable arity.
• Both fine-grained and coarse-grained linking are
  supported.
• Relationship networks are separated from object
  contents.
• Fine-grained versioning for hypermedia structures
  and individual links

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WebSCM

• OO Hypermedia design model Schwabe et al
• Conceptual data model schema design
• Presentation model Web screen design
• Presentation design
• Screen composition design
• Navigational design
• Implementation model HTML, scripts,
• WebSCM manages configurations among objects in
  different models and versions of logical
  connections among them.

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Conceptual schema
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Implementation level

• Representing Web content
• Types of objects
• Data objects documents, images, audio, video
• Source code scripts, applets, controls
• Component libraries JavaBeans, MSF classes
• Textual vs. binary
• Textual objects are structurally versioned
• Markup documents (?ML), source code
• Binary objects are versioned as a whole

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Content change management

• Allows users to track history at any level
• Document node
• Web objects
• Web system as a whole
• Uses either the tree-based or digraph-based
  structure versioning algorithms
• The algorithms are generic for any node in a tree
  or a digraph
• Differencing and merging

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Differencing tools
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Versioning for an element
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HTML version comparison
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Conclusions

• A novel SCM approach model-based SCM
• An infrastructure for building SCM services into
  Web engineering environments
• Direct representation of Web object structure and
  structural changes
• Manage changes to Web objects at different levels
  of abstractions in a more meaningful manner
• Manage different structures (internal,
  navigational, compositional), and logical
  connections among Web objects

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Thank you

• Tien N. Nguyen
• Elect. and Computer Engineering Department
• Iowa State University
• www.eng.iastate.edu/tien/
• tien_at_iastate.edu

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Fine-grained tree versioning
Version v1
Version v2
2
2
(content is modified)
5
5
4
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Navigational structure
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Benefits of this hypermedia (2)

• Avoid complexity of version creation in
  versioning tasks for hypermedia structure
• Reduces cognitive overhead for users
• Avoid a serious UI problem version selection
  problem in link navigation
• Users traversal occurs at current version.
• Avoid problems in providing SCM for both
  hypermedia structure and individual links
• No more check in, check out individually for
  hypermedia entities

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Data records
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Model-to-model logical connections
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Web screen design

• Presentation design
• A screen basic unit of the presentation model
• Users specify presentation properties of a screen
  via CSS-like style sheets
• Composition of screens atomic composite

Frame A
Frame B
screen 3
screen 2
screen 4
screen 1
Frame B