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UT EE 382V - Study Notes

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Lecture 6 Architecture and Design Intent Lecture 6 Architecture and Design Intent Prototype Syntax system modspec preddef predname predpar wff primitive predpar opspec oppar type predparname opname oppar pre wff post wff obl wff modetype opparname impl opname oppar localdef opcall proppre proppost propobl localdef opcall Linkedwff type varname op oparg pre post obl known floor ceiling labelname wff label Experience Impact Dewayne E Perry ENS 623A Office Hours T Th 11 00 12 00 perry ece utexas edu www ece utexas edu perry education 382v s06 2006 Dewayne E Perry 1 EE 382V Lecture 6 Architecture and Design Intent modspec impl modname preddef typename opspec 2006 Dewayne E Perry EE 382V Lecture 6 Architecture and Design Intent Views 2 Specification Semantics Implemented 7 views for the prototype system overview specification overview detailed specification view implementation overview basic completeness view full completeness view interconnection view Symbol Table name nametype must be unique delete definition uses remain warning delete all uses def remains warning Type Checking of Arguments argument undefined warning parameter undefined warning arg type different from par type error Specification Consistency Specification Completeness wff inconsistent wrt list error check for metas IN par has at least on precondition OUT par has at least one postcondition 2006 Dewayne E Perry EE 382V 3 2006 Dewayne E Perry EE 382V 4 1 Lecture 6 Architecture and Design Intent Implementation Semantics Symbol Propagation Preliminaries Table Preconditions Op name must be defined ie the operation must have a specification in order to be called Type satisfied reaches ceiling propagated Checking of Arguments Postconditions Arg type must match par type Propagated Specification Consistency Propagated Specification Completeness Lecture 6 Architecture and Design Intent unknown until known known until contradicted while known satisfies pre obl known after last call is propagated Guaranteed by the construction semantics The same as for specs Obligations satisfied reaches floor propagated 2006 Dewayne E Perry EE 382V 5 Lecture 6 Architecture and Design Intent 2006 Dewayne E Perry Comments on Attributes Syntax got much bigger than originally thought because of slight differences in semantics Need more boolean attributes in order to remember the current state of affairs and reduce the amount of reprocessing Unparsing not too much of a problem but could not do formatting as would have liked Would like to be able to display an attribute grammar in a separate window Table structure is not quite right could then treat the interconnection and propagation information as an attribute not as part of the implementation language would get a clean separation of the specification implementation and program construction languages local tables for parameter def and usage better access for larger symbol tables Prototype is SLOW template build and arg fill especially propagation clip and attendant processing still not sure what underlying processing is entailed by the system 2006 Dewayne E Perry EE 382V 6 Lecture 6 Architecture and Design Intent Comments on Implementation Symbol EE 382V 7 2006 Dewayne E Perry EE 382V 8 2 Lecture 6 Architecture and Design Intent Comments on ARL No Needs for Real Implementation Enumerations Specialized many cases where boolean is not sufficient use of integers too archaic No Appropriate information as attributes windowing and multiple fonts Module Specifications in separate files Module Implementations in separate files Multiple only trees excess baggage eg a stack as a grammar problems with non connected subtrees and references No Collapsing of Cases General data base for browsing for predicates types and operations eg create and insert often identical No Clip facility Symbol Table organization Interconnection User Defined Data Structures Daemons Lecture 6 Architecture and Design Intent Debugging Facilities trace pause for each arl routine selectable trace inspection ie be able to use debug 2006 Dewayne E Perry EE 382V 9 Lecture 6 Architecture and Design Intent 2006 Dewayne E Perry EE 382V 10 Lecture 6 Architecture and Design Intent Motivation for Inscape Came from building systems Pieces often did not fit together informal interface descriptions incomplete interface descriptions often dependent on folklore Software Evolution and Light Semantics Changes resulted in surprises faults complexity inability to foresee consequences Three intertwined and essential problems complexity light semantics composition interface specifications designer intent evolution establish semantic dependencies user intent implications of interface and implementation changes ICSE 1999 Most Influential Paper Award from ICSE 1989 The Inscape Environment 2006 Dewayne E Perry EE 382V 11 2006 Dewayne E Perry EE 382V 12 3 Lecture 6 Architecture and Design Intent Complexity Complexity Complexity Invisibility semantic intricacy and wealth mostly implicit code is the desiccated product of a long intellectual process cope by attaching meaning to syntactic details Intricacy of detail analogies long logical proofs 4 voice fugues difficult to understand change is difficult and error prone difficult for creator compounded for others Wealth of detail analogies toccata Strauss symphonic poem details obscure real patterns individual detail of minor importance manage small details vs automate deep insights many small theorems vs few large theorems 13 2006 Dewayne E Perry type checking of full scale theorem proving Possible forms Lecture 6 Specifications obligations multiple results Short Construction and evolution constructive use of specifications structured exception handling propagation logic light semantic dependencies partial semantic information partial simple use of semantic information approximations explored aspects of the first two EE 382V 14 Inscape Contributions Beyond 2006 Dewayne E Perry EE 382V Architecture and Design Intent Light Semantics Inscape 80 faults fixed quickly prevention of problems via knowledge Wealth requires different strategy Lecture 6 Architecture and Design Intent support for this in fault studies 9 intricacy may be buried in the midst of wealth EE 382V Wealth is dominant in almost all software systems we build 9 complexity and scale interact growth by multiple distinct components not replication of a small set 2006 Dewayne E Perry comments suggestive names abstraction and encapsulation Claim sw often


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