The document discusses 'ware', a reverse engineering tool for web applications which addresses challenges in understanding, maintaining, and evolving dynamic web applications due to their complexity and the variety of technologies used. It details the reverse engineering process, including static and dynamic analysis, and describes the tool's components designed for parsing source code, generating UML diagrams, and supporting user interactions with the application components. The experiments conducted demonstrate the tool's effectiveness in aiding the maintenance of undocumented web applications by automatically producing various UML representations and providing insights into system behavior.

1. WARE: a tool for the Reverse
Engineering of Web Applications
Anna Rita Fasolino
G. A. Di Lucca, F. Pace, P. Tramontana, U. De Carlini
Dipartimento di Informatica e Sistemistica
University of Naples Federico II, Italy
CSMR 2002, Budapest, Hungary
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2. Web Applications (WA):
problems and open issues
• The pressing market demand of web applications
– WAs developed in very short time
• The continuously changing needs of the evolving
application domains
– WAs frequently and rapidly modified with ad hoc approaches
• The lack of method in producing and maintaining
Web applications
– low quality software, with disordered architecture, and
inadequate and incomplete documentation
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3. Web applications: a recent classification
• Class 1: primarily static web sites
• Class 2: sites providing client-side interaction
– Based on an event model exploiting some script code
• Class 3: applications with dynamic content
– Pages are dynamically created on the fly, with the support of
various WWW rechnologies (CGI, JSP, PHP, Javascript,
XML, ODBC,…ASP,… )
Tilley and Huang, ICSE 2001
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4. Dynamic web applications
• Due to the large number of employed technologies,
understanding, maintaining and evolving a Class 3
application is a complex task
• The need for specific Reverse Engineering
techniques and processes to recover:
– Static and dynamic aspects of the applications
– Suitable representation models
• The need for reverse engineering tools that support
the extraction and the abstraction of the needed
information from a WA
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5. Reverse engineering Web Applications
• A reverse engineering process to recover the
following views:
– The static architecture of the WA
– The dynamic interactions between its components
– The final behavior offered
• Extended UML diagrams to represent these views
– Class diagrams to model the architecture
– Sequence and Collaboration diagrams to represent the
dynamic model
– Use case diagrams to describe the behavior of the WA
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6. The Reverse Engineering process
STATIC Components and
Web Application Direct Relations
ANALYSIS
Source Code between them
BEHAVIORAL Behavioral
ANALYSIS Model
DYNAMIC Dynamic Interactions
WA in ANALYSIS between Components
Execution
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7. Views obtainable by static analysis
• A coarse grained view:
– Web pages and Hypertextual links between pages :
– Pages are distinguished into server and client pages, static and
dynamic pages, simple and framed pages
• A finer grained view:
– inner page components and relationships
– input/output form, text box, anchors, scripts, applets, text, images,
multimedia objects (sounds, movies), …...
– Page components may be active components (e.g.,scripts or
applets)
– The relationships include: submit, build, redirect, include
• A UML class diagram representing both views
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8. The meta-model of a WA
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9. The WARE tool
• Designed to support the reverse engineering of a WA
– executes the static analysis of the WA source code
– populates a repository with the extracted information
– supports the user in abstracting the WA models
• Three main components:
– Interface Layer
– Service Layer
– Repository
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10. Interface layer
Graphical Visualizer
WARE
GUI VCG Dotty RIGI
WARE
Architecture
Service Layer
Parsers
IRF Translator
HTML JS
WA ASP Query Executor
Source ….
Files VBS
UML Diagram
PHP Abstractor
Extractor Abstractor
IRF Diagrams
DBR Repository
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11. The Service layer
• The Extractor component
– The Extractor parses the WA source code and produces an
Intermediate Representation Form (IRF)
– Several distinct parsers (for HTML, JavaScript, VBScript, ASP and
PHP technologies)
– New parsers can be added as the technology evolves
• The Abstractor component
– It implements abstraction operations necessary for reconstructing
the more abstract views of the WA
– It includes three main components
• A Translator that populates the relational database from the IRF
• A Query Executor that implements predefined queries over the
database
• The UML Diagram Abstractor that produces the class diagrams of a
WA at various degrees of detail and other relevant information
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12. The conceptual schema of the Repository
Java Applet Media Flash Object Mail Address Other Object
Web Object redirect Server Class
Server Function
Client Function
Static Page Built Page redirect Server Script
Web Page
Session Variable
Client Script Parameter
Modify Tag Client Page
Server Page include Server Cookie
event
Anchor
Client Module HTML Tag
Interface Object
Download Hyperlink
Submits
Form
DB Interface Mail Interface Server File Interface Other Interface
Frameset
Generic File
Field
Select Button Textarea
Frame
source
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13. The Interface Layer
• It provides the user interface for accessing the WARE
facilities:
– Reverse Engineering for parsing the WA and producing the
IRF
– Comprehension for executing comprehension-related
activities, such as exploring the inventory of the WA
components and their source code, computing the
reachability set of a component, creating clusters of related
components according to a given clustering criterion
– Query (Predefined query and Parametric query) for
activating the Abstractor’s functions, and graphically
visualizing the recovered information
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14. Computation of
the Reachability
set of a WA
component
Figure 4.4 – b: WA Components reachable starting from a selected
component
Grouping the WA
components into
cohesive clusters
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15. An experiment
• Carried out for assessing the adequacy of the tool functions in
supporting maintenance tasks
• The tool has been used to understand and redocument existing
WAs
• An example: A WA implementing a ‘Juridical Laboratory’
– 201 files, in 19 directories, sizing 4 Mbytes
– 55 Static Pages (55 HTML files in 10 directories)
– 19 Server Pages (19 ASP files in 4 directories)
– No design documentation available
• The WARE tool was preliminarly used to perform:
– The static analysis of the application, and for producing an
inventory of the WA components
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16. First step: the static analysis
• Main results:
– The population of the repository automatically produced by
the tool
– The inventory of the WA components
– Graphical representations of the class diagram of the WA at
various degrees of detail
• Coarse-grained representations (including just the pages)
• Fine-grained representation (including inner page components)
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17. The inventory of the WA components
Component type # Detected
Server page 19
Client Static page 55
Client Built page 14
External web page 3
Client script block 53
Function in Client script block 19
Form 11
Input/ output field 71
Submit Operation (POST method) 4
Submit Operation (GET method) 7
Anchor to files to be downloaded 111
Anchor to Hypertextual link 49
Data File 61
Server script block 76
Function in Server scripts 4
Database Interface Object 29
Mail Interface Object 3
Image file 65
Redirect operation in server 7
blocks
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18. The Class diagram of the WA
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19. The second phase: formulating and validating
hypotheses about the WA behavior
• Driven by the graphical representations, notable sub-graphs
were looked for (isolated sub-graphs, sub-trees, strongly
connected components, …)
• A tentative hypothesis about the behavior implemented by each
sub-graph was formulated with the support of:
– the names of the components, their source code analysis, and by
tracing the application execution
• Hypotheses were validated by the source code execution
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20. Results from the sub-graph analysis
• Four isolated sub-graphs
– Three small ones without static client pages
• Two of them implemented server-side functions for the web
administrator (management of the mailing list, and of the
registered users list)
• The third one resulted from an incorrectly made maintenance
operation
– A large one, rooted in the home page
• Nine user functions could be associated with nine notable sub-
graphs contained in it
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21. The sub-graphs in the WA class diagram
Professional Yellow Pages
Mailing List
Judicial
Proceedings
Judicial
Case
News Studies
Home
Web Searching
Chat
Forum
About
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22. Modeling the WA behavior
About
• A use case was defined and
associated with each notable
News
Home
sub-graph
Judicial Case Studies
• The scenarios describing the
use cases were defined with
User
Judicial Proceedings
the support of the tool (the
interactions between objects
Web Searching
Professionals Yellow Pages involved in the sub-graph
Registered User
WA Administrator were searched for and
Forum Mailing List analyzed)
Chat
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23. Modeling the WA dynamic view
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24. Conclusions
• The experiments we carried out showed that the
reverse engineering tool WARE can be used to
support the comprehension of Web Applications to be
maintained
• It supports the reconstruction of various UML
diagrams from undocumented applications:
– Static views are automatically produced by the tool
– Behavioral and dynamic views can be semi-automatically
obtained with the tool assistance
• A reverse engineering process based on the WARE
tool could be defined
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25. Future work
• Specific clustering criteria may support a more
effective analysis of the class diagrams recovered by
the tool
• A clustering approach should take into account both
the topology of the graphs, and the typology of the
connections in the graph
• The automatic clustering of Was will be investigated
in the context of large size web applications
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