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Constraining Software Evolution

Constraining Software Evolution. Steven P. Reiss Brown University. Software is Multidimensional. Documentation. Architecture. History. Patterns. DBMS Schema. Code. Test Cases. Module Structure. Component Structure. User Interface. Conventions. Design. Specifications.

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Constraining Software Evolution

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  1. Constraining Software Evolution Steven P. Reiss Brown University CLIME

  2. Software is Multidimensional Documentation Architecture History Patterns DBMS Schema Code Test Cases Module Structure Component Structure User Interface Conventions Design Specifications CLIME

  3. Software Artifacts • Dimensions are reflected in artifacts • Typically files, sometimes databases • Some artifacts are “paper only” • Generally one-to-one • But some artifacts have multiple dims • And some dims are spread over multiple artifacts • But it is the artifacts that are edited CLIME

  4. Evolution is One-dimensional • Artifacts evolve separately • Thus dimensions evolve independently • Different views become inconsistent • Design, documentation, etc. ignored • Software itself becomes inconsistent • Some dimensions don’t evolve • Some dimensions don’t have artifacts • These are totally ignored • Result is poor, unmaintainable software CLIME

  5. What is Needed • CONSISTENT EVOLUTION • OF ALL DIMENSIONS OF SOFTWARE • OVER THE LIFE OF THE SOFTWARE • This is our goal CLIME

  6. What We Propose • A tool to ensure artifacts consistency • Initially as the software is developed • During maintenance as the software evolves • The CLIME system CLIME

  7. Outline of Talk • Requirements for consistent evolution • Constraints as a mechanism • Implementing constraints in CLIME • On-going and future work CLIME

  8. Requirements for the Tool • Work with existing tools & artifacts • Handle a wide range of dimensions • Be extensible • Be bidirectional • Support partial & incomplete checking • Be able to locate points of inconsistency • Have low overhead and be unintrusive • Handle static and dynamic properties • Work incrementally CLIME

  9. Insight Yields Methodology • Artifacts are constraints on artifacts • Design • Constraints on the code • Constraints on the code’s behavior • Specifications • Constraints on the solution • In general • Software artifacts can be kept consistent by viewing each as constraints on other artifacts and checking these constraints. CLIME

  10. Basic Approach Software Artifacts Constraints Consistency Checker Inconsistency Report CLIME

  11. Problems with this Approach • Determining what artifacts are involved • How to extract the information needed for constraints from the artifacts • How to define constraints from this information • How to check constraints • What to report to the developer • Making it incremental and complete CLIME

  12. Related Work: XLinkIt • Constraining XML documents • Constraints are XLink/XPath queries • Documents can be dynamically generated • Has been applied to software engineering • Small number of dimensions • By dynamically generating from java code • Comparing to XML representation of UML • Problems • NOT incremental, complete, automatic, compatible, powerful enough, practical at large scales CLIME

  13. What are the Artifacts • Need to define the domain • Essentially the project being worked on • This concept already exists in environments • Need to identify artifacts • These are typically stored as files now • Identify artifacts using file types • We handle this using a project manager • Or from existing programming environment CLIME

  14. Project Manager: CLIP • Project determines the set of artifacts • Provides set of files to rest of system • Based on directory list (include + exclude) • Based on patterns • Based on artifact file types • Also specifies environment for files • Can be automatically generated • From existing environments (Eclipse, …) • Front end also available CLIME

  15. Project Interface CLIME

  16. Information From Artifacts • First we need to understand the artifacts • Artifacts alone are too varied and complex • We need specific information • To define the constraints • Different constraints need different info • Solution: abstract artifact information • Simpler than considering whole artifact • Tools to extract the needed information • This must be done incrementally • Store the result in a database CLIME

  17. Artifact Abstraction Software Artifacts Update Manager Abstractor Abstractor Abstractor Abstractor Update Information Database Manager Database CLIME

  18. Artifact Abstraction • Update Manager • Detects what has changed • Runs appropriate abstractor(s) for each artifact • Update Information • Commands to delete sets of tuples (patterns) • Commands to add tuples • Database Manager • Relational DBMS (JDBC/Postgresql) CLIME

  19. Current Abstractors • Source • Symbol table information (Modified Jikes) • Refs, defs, types, hierarchy, scopes, … • Semantic information (Using Soot) • Documentation information (CLAD: Doclet) • UML (Rose or any XMI-based tool) • Class & message interaction diagrams • CVS History • File version and revision history CLIME

  20. Test Case Abstraction • Desired information • What are the test cases • Test coverage of each test case • CITE: Test coverage tool • Extension of junit testing program • Use jikesbt to instrument code • Modified junit that uses cite • Produces coverage information when tests are run as well as the set of test cases • Line, branch, routine, call coverage CLIME

  21. Cite Coverage <TESTRUN DATE='1034344045851' PROJECT='onsets' USER='spr' NAME='spr.onsets.TestBitSet.testFirst' SIGNATURE='()V' STATUS='PASS' RUNID='17921'> <METHOD NAME='spr.onsets.OnsetBitSet.check' CALLED='35'> <BLOCK INDEX='18429' START='54' END='54' COUNT='35'> <BRANCH TOBLOCK='18431' COUNT='33' /> <BRANCH TOBLOCK='18430' COUNT='2' /> </BLOCK> <BLOCK INDEX='18430' START='54' END='54' COUNT='2'> <BRANCH TOBLOCK='18432' COUNT='2' /> </BLOCK> <BLOCK INDEX='18431' START='54' END='54' COUNT='33'> <BRANCH TOBLOCK='18432' COUNT='33' /> </BLOCK> <BLOCK INDEX='18432' START='54' END='54' COUNT='35' /> </METHOD> <METHOD NAME='spr.onsets.OnsetBitSet.firstBit' CALLED='3'> <CALLS NAME='spr.onsets.OnsetBitSet.check' COUNT='35' /> <BLOCK INDEX='18500' START='134' END='134' COUNT='3'> <BRANCH TOBLOCK='18504' COUNT='3' /> </BLOCK> <BLOCK INDEX='18501' START='135' END='135' COUNT='35'> <BRANCH TOBLOCK='18503' COUNT='33' /> <BRANCH TOBLOCK='18502' COUNT='2' /> </BLOCK> <BLOCK INDEX='18502' START='135' END='135' COUNT='2' /> <BLOCK INDEX='18503' START='134' END='134' COUNT='33'> <BRANCH TOBLOCK='18504' COUNT='33' /> </BLOCK> <BLOCK INDEX='18504' START='134' END='134' COUNT='36'> <BRANCH TOBLOCK='18501' COUNT='35' /> <BRANCH TOBLOCK='18505' COUNT='1' /> </BLOCK> <BLOCK INDEX='18505' START='138' END='138' COUNT='1' /> </METHOD> </TESTRUN> CLIME

  22. Database Manager: CLIDE • Maintains the database based on commands • First it finds all tuples that match remove patterns using queries • Matches new tuples to those to remove • Adds any really new tuples to the database • Updates any modified tuples • Removes tuples that are really deleted • Generates an update file • What was added, deleted, modified • Based on UIDs CLIME

  23. CLIDE: UIDs • Unique Ids are used to represent tuples • Each relevant tuple has one • Database manager maintains these • If tuple is only modified, it keeps its UID • Based on set of key fields • UIDs from abstractor => global UIDs • Provide pointers in the tuples • These provide low-level handles to the actual data CLIME

  24. CLIDE: Table Definition ?xml version="1.0"?> <!DOCTYPE CLIME:TABLES SYSTEM "file:/pro/clime/xml/schema/climetable.dtd" > <CLIME:TABLES xmlns:CLIME='file:/pro/clime/xml/schema/clime'> <CLIME:ENUM NAME="HistoryType"> <CLIME:CONST NAME="NONE" VALUE="0" /> <CLIME:CONST NAME="CVS" VALUE="1" /> </CLIME:ENUM> <CLIME:TABLE NAME="HistoryFile" > <CLIME:FIELD NAME="Id" TYPE="Id" KEY="1" /> <CLIME:FIELD NAME="FileName" TYPE="String" /> <CLIME:FIELD NAME="HistoryType" TYPE="HistoryType" /> <CLIME:FIELD NAME="RawFile" TYPE="String" /> <CLIME:FIELD NAME="CurrentVersion" TYPE="String" /> <CLIME:MATCH IDFIELD="Id" FIELDS="FileName RawFile" /> </CLIME:TABLE> <CLIME:TABLE NAME="HistoryVersion"> <CLIME:FIELD NAME="Id" TYPE="Id" KEY="1" /> <CLIME:FIELD NAME="ForFile" TYPE="Id" SOURCE="HistoryFile" /> <CLIME:FIELD NAME="FileName" TYPE="String" /> <CLIME:FIELD NAME="Version" TYPE="String" /> <CLIME:FIELD NAME="Author" TYPE="String" /> <CLIME:FIELD NAME="HasDesc" TYPE="Boolean" /> <CLIME:MATCH IDFIELD="Id" FIELDS="ForFile Version" /> </CLIME:TABLE> </CLIME:TABLES> CLIME

  25. CLIDE: Transitive Closure • Transitive closure is needed in software • Symbols available in scope • Subclass relationship • Control/data flow; type inference; … • TC is not a relational operation • CLIDE provides transitive relations • Automatically built and maintained • Update is done incrementally • Can be queried against directly CLIME

  26. Defining Constraints • Defined in terms of artifact abstractions • Multiple types of constraints are possible • Most constraints can be defined as relationships among the abstractions • Examples • This allows us to define metaconstraints • Issue: maintaining traceability • Source of the constraint; Point of violation • This leads to constraint instances CLIME

  27. Using Metaconstraints Metaconstraints Artifact Database Constraint Finder Constraint Instances CLIME

  28. Metaconstraints • Predicate equations (first order logic) • S is the base relation •  determines when x is applicable •  specifies what must be true • For this constraint to hold • Typically starts with for all or exists • These are general logic equations • With the full power of SQL available CLIME

  29. Example <CLIME:CONSTRAINT TYPE="QUERY" NAME="uml_source_class_correspondence" > <CLIME:EXPR OP="FORALL" VAR="x" TABLE="UmlClass"> <CLIME:EXPR OP="AND"> <CLIME:EXPR OP="NOTNULL"> <CLIME:EXPR OP="FIELD" FIELD="Name" VAR="x" /> </CLIME:EXPR> <CLIME:EXPR OP="EQL"> <CLIME:EXPR OP="FIELD" FIELD="ClassType" VAR="x" /> <CLIME:EXPR OP="INT" VALUE="0" /> </CLIME:EXPR> </CLIME:EXPR> <CLIME:EXPR OP="EXISTS" VAR="y" TABLE="SrcDefinition"> <CLIME:EXPR OP="AND"> <CLIME:EXPR OP="EQL"> <CLIME:EXPR OP="FIELD" FIELD="SymbolType" VAR="y" /> <CLIME:EXPR OP="INT" VALUE="3" /> </CLIME:EXPR> <CLIME:EXPR OP="EQL"> <CLIME:EXPR OP="FIELD" FIELD="Name" VAR="x" /> <CLIME:EXPR OP="FIELD" FIELD="Name" VAR="y" /> </CLIME:EXPR> </CLIME:EXPR> </CLIME:EXPR> </CLIME:EXPR> </CLIME:CONSTRAINT> CLIME

  30. Current Metaconstraints • UML Class Diagrams  Source • Every class has a corresponding source class • Interface matches a source interface • Class generalization matches hierarchy • Interface generalization matches hierarchy • UML operations correspond to methods • UML attributes correspond to fields • UML associations reflected in source CLIME

  31. Current Metaconstraints • Source  UML Class Diagrams • Public classes appear in UML model • Public interfaces appear in UML model • Generalizations among public classes • Generalizations using interfaces • Public methods appear in UML model • Associations using fields appear in UML • Test Cases  Source • Source covered by last test not changed CLIME

  32. Current Metaconstraints • Documentation => Source • Parameters, See Also, Throws correspond to source • Source => Documentation • Public classes and interfaces are documented CLIME

  33. Generic Constraints • Some constraints don’t have a source • Style constraints (e.g. naming conventions) • Usage constraints (e.g. language rules) • Some constraints have no artifact • Design patterns • Database manager allows explicit tuples • Generic (style constraints) • Project-specific (design patterns) • Constraints defined from these tuples CLIME

  34. Current Defined Constraints • Style Constraints • Class naming conventions • Method naming conventions • Field naming conventions • Local variable naming conventions • Constant naming conventions • Pattern Constraints • Façade patterns CLIME

  35. Current Defined Constraints • Language usage constraints • All parameters not starting with _ are used • All fields are read at least once • All fields are written at least once • All methods are called at least once • Fields are either private or protected • Any routine returning type X must return a new instance • Note this is specialized by the particular project CLIME

  36. Maintaining Constraints • Metaconstraints • Need to be translated into actual constraints • One for each matching item in the database • Several tasks need to be done • Look for new constraints to be added • Check new constraints for validity • Check prior constraints for applicability • Check prior constraints for validity • Remove dead constraints • This has to be done incrementally CLIME

  37. Constraint Instances • Basis for checking, updating, reporting • An instance contains • The meta constraint • The database object that is its source (UID) • Database objects that validate/invalidate it • Exists : The particular item that was found • For All : Any items that did not match • Any tables that affect the constraint • Current status of the instance (valid/invalid) • Stored in the database CLIME

  38. CLIC: Generating Constraints Metaconstraint Constraint Manager Item Query Test Query {UID,true|false} Assoc Tables Assoc UIDs Constraint Instance CLIME

  39. Test Query • XML metaconstraint mapped to SQL • Returns a set of UIDs and status • SELECT x.uid,true FROM … WHERE <holds> UNION SELECT x.uid,false FROM … WHERE <not-holds> • Restricted to UIDs that change • WHERE x.uid IN ... • Used for new constraints • Used for checking existing constraints CLIME

  40. Item Queries • Find UIDs for a constraint instance • Of those items that made is succeed or fail • XML metaconstraint mapped to SQL • Multiple queries generated for each instance • One for each level of nesting • Using information from prior level • Used to determine when to recheck constraint • Table associations determined directly • For cases which are NOT-based CLIME

  41. Showing Constraints: CLICUI • Constraint instances • Have enough information for traceability • UIDs of constraint mapped to database object • Database object has descriptive information • Have enough information for understanding • UIDs of exceptions or associated objects • Again can be mapped to database objects • What’s left is to report the results • In a meaningful way • Integrated with an environment CLIME

  42. Constraint User Interface CLIME

  43. CLICUI • User interface for browsing constraints • By type, by status, by source • Constraints kept up to date automatically • Details obtained from database • Relation-based user output • Location information from relation • Location information to the environment • “Goto” in the editor • Tell the environment to display something CLIME

  44. Eclipse-based Interface CLIME

  45. CLIME Experiences • CLIME used for several projects • On a game program (UML, source, tests, …) • On itself (43,500 LOC) • On SOOT (200KLOC), Eclipse (1.2MLOC) • CLIME on itself • Generates about 2300 constraints • Unobtrusively used • Bugs found through style and usage constraints CLIME

  46. CLIME: Summary • Integrating evolving software is the next step in development environments • This can be done by constructing and using constraints among the artifacts • A wide variety of artifacts and constraints can be managed cheaply and effectively CLIME

  47. CLIME: Summary • The constraint mechanism works with existing tools and artifacts • It extends to a variety of dimensions • It is extensible • It supports associating inconsistencies with artifacts • It has low overhead and is unobtrusive CLIME

  48. Current Research • Additional artifacts and constraints • Documentation, language usage, • Artifacts requiring complex constraints • UML interaction diagrams • Behavioral specifications and constraints • User-friendly front ends CLIME

  49. Complex Constraints • Queries can’t check all constraints • Language constraints (CCEL/Parasoft Jtest) require the abstract syntax tree • Dynamic constraints require static/dynamic analysis • The associated analysis is best done outside of queries CLIME

  50. Artifact Analysis Software Artifacts Update Manager Program Analysis Result Files Abstractor Update Information CLIME

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