Modelbased Configuration Management for a Web Engineering Lifecycle

Model-based Configuration Management for a Web Engineering Lifecycle Tien N. Nguyen Elect. and Computer Engineering Department Iowa State University USA 1

Web Engineering n Web development has changed u. Initially seen as a form of authoring u. Now, also a form of application development n n A lot of efforts and time have been spent to maintain Web-based applications. Requires the same rigor as successful software development/maintenance u. Hence, Web engineering has emerged u. Promotes the use of sound technical and management principles for Web applications 2

Web application development methods n Several Web and hypermedia application development methods have been proposed. u. Web. Composition, OOHDM, RMM, Modeldriven Web development, Hyper. DE, WAM… n They introduce several models that address different aspects of Web development. u. Data, n presentation, navigation, etc Each method introduces different set of logical abstractions and entities. 3

Configuration Management n Software configuration management (SCM) usoftware n n n 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 u. Version control, change management, content management, configuration management 4

Related work n Version and configuration management tools u Focus on files, not a Web project as a whole u Change management based on files, text lines u Inadequate to represent Web object structure n Web application development environments u File/directory-oriented n n versioning (commercial) u 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. 5

File-oriented SCM model <html>------------ FILES/ DIRECTORIES (text or structured files) File-based SCM system --------------------------------------------------------------------------------------------------------------------------------------------- Web Engineering Models Configuration Management §Primary targets of SCM are files/directories. 7

Model-based Web SCM n All Web objects in models are versioned and saved persistently. u Web objects do not need to be files or within files SCM repository <html>-------------------------------------------------------------------------------------------------------------------------------------------------------- 8

Web SCM infrastructure n n An infrastructure for building SCM services into Web engineering environments The infrastructure provides u. Direct representation of Web object structure and structural changes, without need for analysis of file contents, u. SCM among entities, rather than among files, u. Structure-oriented versioning and SCM of Web entities in any models, and u. Versioned hypermedia between entities. 10

Web SCM architecture (2) Web Engineering tools/editors Calling API functions Configuration Management Model New types THIRD-PARTY ENVIRONMENT Versioned Hypermedia Model of objects System Model Structure Versioning Model Generic Data Model Version Model Web SCM Infrastructure 11

Web SCM architecture (3) Web tools/editors Calling API functions Configuration Management Model Existing Object types Bridges/wrappers THIRD-PARTY ENVIRONMENT Versioned Hypermedia Model System Model Structure Versioning Model Generic Data Model Version Model Web SCM Infrastructure 12

Versioned Data Model n n 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. u. Can exist in isolation, but typically attached to nodes via attributes n Attribute: A mapping from nodes to slots 13

Adding Version Control Attribute table § 3 kinds of slots: constant, mutable, versioned 14

Graph-based Structure Versioning version Attr-name “a” “b” 5 “c” Attr-val 1 2 4 3 • Graph can be nested. • Attribute value can be in any data type, possibly a reference. 15

Fine-grained Structure Versioning v 1 v 2 17

Benefits n Very flexible u. Nodes n One mechanism for storing all information u. Graph n n can participate in multiple graphs structure and content Common structure shared among versions Fine-grained structure versioning of Web object’s internal structure and other important structures such as navigational, compositional, and logical structures. 18

Versions are points in time Tree-structured discrete time V 1. 0 V 2. 0 V 3. 1 n V 3. 2 A version is a point in the system’s lifetime. 19

Product Versioning Tree-structured discrete time V 1. 0 V 2. 0 V 3. 1 n V 3. 2 One global version space across entire project 20

Editing and Versions Tree-structured discrete time V 1. 0 current => V 2. 0 V 3. 1 n Temporary version V 3. 2 Users select a current version to work on. 21

System Model n n Acts as a bridge to third-party environment Works at the model level, rather than files u. Allows for the description of a Web application via models with objects, compositions, structures, and relationships n Provides an infrastructure for extensibility of new types of Web objects u. Atomic and composite component types u. User-defined object types derived from them u. Structure is represented via a directed graph 22

Composite object n n A composite object contains a directed graph whose nodes have versioned references to objects. u Nodes can have multiple user-defined attributes. This attributed digraph is used to represent the structure of a composite object. Composite object A versioned reference to a member component … component 23

Configuration Management n SCM supports via Molhado [ICSE 2005] uset the current version (switching), udiscard or capture changes to a project, udetect (structural) changes between two arbitrary versions, uopen and create a project, uretrieve and modify meta-data of a project or of a version, umanipulate structures, … 24

Hypertext Versioning n HTML-style hyperlinks u. Each n node can have an “href” slot. Using edges in a directed graph u. Create a composite component u. Use the digraph of the composite component to represent relationships among objects n Versioned hypermedia model u. Hypermedia elements are first-class entities. 25

Hypermedia entities n n n 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 26

Relationship network example 27

Representation for hypermedia n n n 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 finegrained versioning for hypertexts and links. 28

Benefits of this hypermedia n n 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 29

Web. SCM n n n OO Hypermedia design model [Schwabe et al] Conceptual data model: schema design Presentation model: Web screen design u Presentation design u Screen composition design u Navigational design n n Implementation model: HTML, scripts, … Web. SCM manages configurations among objects in different models and versions of logical connections among them. 30

Conceptual schema 31

Implementation level n n Representing Web content Types of objects u Data objects: documents, images, audio, video u Source code: scripts, applets, controls u Component libraries: Java. Beans, MSF classes n Textual vs. binary u Textual objects are structurally versioned F Markup u Binary documents (? ML), source code objects are versioned as a whole 32

Content change management n Allows users to track history at any level u. Document node u. Web objects u. Web system as a whole n n n 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 33

Differencing tools 34

Versioning for an element 35

HTML version comparison 36

Conclusions n n A novel SCM approach: model-based SCM An infrastructure for building SCM services into Web engineering environments u. Direct representation of Web object structure and structural changes u. Manage changes to Web objects at different levels of abstractions in a more meaningful manner u. Manage different structures (internal, navigational, compositional), and logical connections among Web objects 37

Thank you Tien N. Nguyen Elect. and Computer Engineering Department Iowa State University www. eng. iastate. edu/~tien/ tien@iastate. edu 38

Fine-grained tree versioning Version v 1 3 2 5 4 n 1 n 2 n 3 Version v 2 1 5 Content Children Parent “” “” “” [n 2, n 3] [n 5] null n 1 null n 2 Content Children Parent “” “” “” [n 2, n 3] [n 4, n 5] null n 1 n 1 n 2 n 3 null n 2 n 4 “” n 5 “new” n 4 “” n 5 “old” (content is modified) 39

Navigational structure 40

Benefits of this hypermedia (2) n Avoid complexity of version creation in versioning tasks for hypermedia structure u. Reduces n Avoid a serious UI problem: version selection problem in link navigation u. Users’ n n cognitive overhead for 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 41

Data records 42

Model-to-model logical connections 43

Web screen design n Presentation design u. A screen: basic unit of the presentation model u. Users specify presentation properties of a screen via CSS-like style sheets n Composition of screens: atomic & composite Frame A screen 2 screen 1 Frame B s c r e e n 3 Frame B screen 4 44