12. Finding Components with Metadata in Component Repositoriesst.inf.tu-dresden.de/.../ss16/cbse/slides/12-cbse-finding-components.… · Component Search with Metadata 2. Searching

Fakultät Informatik - Institut Software- und Multimediatechnik - Softwaretechnologie – Prof. Aßmann - CBSE

12. Finding Components with Metadata in Component Repositories

Prof. Dr. Uwe Aßmann

Technische Universität Dresden

Institut für Software- und Multimediatechnik

http://st.inf.tu-dresden.de/teaching/cbse

Version 16-0.1, 29.03.16

1.  Component Search with Metadata

2.  Searching and Browsing with Faceted Classications

3.  Faceted Metadata

4.  UML Components

5.  Searching by Conformance to Protocols

Component-Based Software Engineering (CBSE)

Obligatory Literature

►  R. Prieto-Diaz. Implementing Faceted Classification for Software Reuse. CACM May 1991, vol 34(5). In the ACM digital library.

►  U. Aßmann. Reuse in Semantic Applications. REWERSE summer school 2005, La Valetta, Malta. Lecture Notes In Computer Science (LNCS) 3564.

■  http://www.springerlink.com/content/blx9yfthkq5xjtjg/


References

•  http://simile.mit.edu/wiki/Longwell •  http://simile.mit.edu/exhibit •  http://flamenco.berkeley.edu •  http://search.express.ebay.com •  http://base.google.com ►  FacetMap: Greg Smith, Mary Czerwinski, Brian Meyers, Daniel

Robbins, George Robertson, Desney S. Tan. FacetMap: A Scalable Search and Browse Visualization. IEEE Transactions on visualization and computer graphics, vol.12 , No. 5, september/october 2006.

►  Thorsten Teschke. Semantische Komponentensuche auf Basis von Geschäftsprozessmodellen. Dissertation. Universität Oldenburg, 2003.

►  Facet-based search of computer science literature in DBLP repository ►  http://dblp.l3s.de/?q=&newQuery=yes&resTableName=query_resultOsC5mC

Ø  Luca de Alfaro and Thomas A. Henzinger, Interface automata, ACM SIGSOFT FSE/ESEC, 2001

http://doi.acm.org/10.1145/503209.503226


12.1. Component Search in Component Repositories

•  It should be as easy to find good quality reusable software assets as it is to find a book on the internet

•  http://softwarereuse.nasa.gov/


Component Repositories

Ø  Components must be stored in component repositories with metadata (markup, attributes) to find them again

Ø  Description by Metadata: •  Attributes: Keywords, Author data •  Contracts (Usage protocols, behavioral specifications)

§  State machines §  Sequence diagrams §  Contracts (pre/post/invariants)

Ø  Examples of Component Repositories •  CORBA

§  implementation registry §  interface registry

•  COM+ registry •  Commercial Component Stores www.componentsource.com •  Debian Linux Component System (apt, dpkg) •  CTAN TeX Archive


Why Searching Components?

Ø  A public component repository is called a market, managed by a trader (broker) •  Distributing or selling components •  Companies can register components at the the trader •  Customers can search components in the markets and buy or rent them

Ø  Searching for functionality (interface, contract, protocol) •  Reuse instead of build •  Searching for components to replace own ones •  Semantic substituability (CM-S) should be ensured

Ø  Searching for quality features •  Performance, energy consumption, reliability


12.2 Searching and Browsing with Faceted Classifications

(thanks to Jan Polowinski)


Faceted Classification for Better Matchmaking

►  A facet is a dimension of a classification ■  Facets simplify search: Facet classification has been invented in library science to

simplify the description and search for books [Ranganathan]. ■  A component (or service) is described in several facets, dimensions, which are

orthogonal to each other ►  Matchmaking engines can look up a service by stating the desired properties

for all facets. ►  Classifications can be arranged in facets if several partitions of a group of

objects exist that are orthogonal ■  In domain modelling, this is often the case ■  Without facets, multiple inheritance hierarchies have to be specified, which are

often clumsy and error-prone ►  Idea: use facets for better matchmaking

Component-Based Software Engineering (CBSE) 9

Comparison

Standard Classification ►  V Vögel

■  V1 Atmung der Vögel ■  V2 Fortpflanzung der Vögel

►  F Fische ■  F1 Atmung der Fische ■  F2 Fortpflanzung der Fische

►  S Säugetiere ■  S1 Atmung der Säugetiere ■  S2 Fortpflanzung der Säugetiere

►  I Insekten ■  I1 Atmung der Insekten ■  I2 Fortpflanzung der Insekten

•  Kiemen: F1 Example: Wikipedia

Faceted Classification ►  Prozeßfacette

■  P Physiologie .  PA Atmung .  PF Fortpflanzung

►  Tierfacette ■  1 Vögel ■  2 Fische ■  3 Säugetiere ■  4 Insekten

•  Kiemen: PA 2


Facetted Browsing

►  Here Facet means: an interesting property of an object orthogonal to other properties

►  Incremental refinement of a set of results by restricting values of the data's facets

►  Empty result views impossible ►  Many application domains



Facet

Facet

Facet

Facet


Widget for Restriction of Facet Values


Sorting and Grouping

Mechanisms


Result Set


More Examples of Facetted Browsers

►  Flamenco ■  FLexible information Access using MEtadata in Novel

COmbinations ■  University of California, Berkeley ■  Browses DB

►  Longwell ■  SIMILE-Project ■  Browses RDF

►  Exhibit ■  SIMILE-Project

►  mSpace ■  University of Southampton

►  FacetMap ■  Microsoft Research


Facetted Browsing in e-Commerce






12.3 Faceted Metadata for Search in Component Repositories


Example: Service Facets in a UNIX System

►  To describe the services of a UNIX system, [Prieto-Diaz] employed a 4-faceted scheme ■  function ■  logical object ■  implementation object ■  tool

►  UNIX services can be described with appropriate facet values and looked up in a repository

►  Example: “append a line to a file with a text editor” ■  (function = append, logical class = line, implementation class = file, tool = text

editor):

Function Logical class

Implementation Class

Tool

edit Line File Text editor


Example: Services in a UNIX System

►  [Prieto-Diaz] already suggested to use controlled vocabulary (domain ontologies) to improve the effectiveness of the search: ■  If every facet is described by an ontology, the service descriptions are

standardized for a user group and improve understanding of service semantics. ►  Facets simplified the description of the components, improved the

understanding of their domain, and facilitated the search in component libraries.

Component-Based Software Engineering (CBSE) And for Components?

Component-Based Software Engineering (CBSE) And for Components?


Other Advantages

►  The facet classification is rather immune to extensions ■  Extending one facet leaves all others invariant ■  Example: If Europe is extended with a new member state, the matchmaking

algorithm can deliver new courses from the new member state, without affecting the rest of the semantic specifications at all

►  The accuracy can be improved by synonym lists (thesauri) ■  Synonyms increase the chances for a match ■  They permit to search not only for keywords, but also for their synonyms

(assembled in a thesaurus) ■  Beyond synonyms other refinement relations of concepts can be used to improve

the search

■  Example: Great Britain is used as a synonym for England, Scotland, and Wales. Synonyms allows for matchmaking on any of the keywords, so that students looking for a course need not bother about geographic and political details.


The Use of Ontologies in Faceted Matchmaking

►  Ontologies simplify matchmaking by standardization ■  Since they provide standardized terminology and standardized

ontological relations between the terms, queries can specify .  keywords with a precise, shared, and standardized meaning (semantic

search), .  contextual information for search in context, where the context is defined by

the ontological relations of the terms. ►  Example:

■  A web course on IT basics can be queried by the standardized word IT-basics (being semantic search)

■  also in context, by relating it to courses such as IT-advanced or IT-preparatory (contextual search)

.  “find me an IT basics course, which has a preceding preparatory IT course and has a follow-up advanced IT course“


Putting up a Component Repository for Your Company

►  Define facets for component metadata ■  If possible, reuse an ontology for a facet ■  Form a thesaurus for synonyms ■  Store the metadata as a tuple in the database

►  Realize a search algorithm that uses facets together with thesauri ►  Or use a faceted browser with the metadata


12.4 UML Components


Natural and Dependent Types

Ø  An object with a natural type (entity type) lives on its own and exists independent of context and collaborators (see DPF) ■  The type does not depend on other types (independent type) ■  Types that depend on others are called dependent types. ■  Role types, facet types, part types are dependent types.

.  Hotel vs. HotelRoom

.  Car vs. Screw or Motor

.  Book vs. Reader Ø  A big object (bob) is complex, hierarchical object with a natural type

•  Usually, it has subobjects with dependent types, role types and others. ►  A business object (domain object) is a bob with a natural type of the

domain model (business model) ►  Usually, business objects (domain objects) are large hierarchical objects ■  They can consist of thousands of smaller objects of dependent types (part-of

relation) ■  They can play many roles with context-based types


Component Specification with UML Components

•  A UML component is a hierarchical class for big objects with provided and required interfaces (roles)

•  Provided interfaces (provided roles) use „lollipop“ notation •  Required interfaces (required roles) use „plug“ notation

•  UML components can specify big objects with one natural core object and many dependent subobjects Some components are required to use specific other interfaces

<<comp spec>> CompanyMgr ICompanyMgt

<<comp spec>> CompanyMgr

ICompanyMgt

IAddressMgt

<<comp spec>> AdressMgr


Ports of UML Components

Ø  A port is a connection point of a UML component. •  A port has a set of roles (interfaces) •  It may be represented by a port object (gate)

System

Port Provided interfaces Required

interfaces


Lollipops und Plugs (Balls and Sockets)

►  For a UML component, provided and required interfaces can be distinguished n  A required interface specifies what the current class needs to execute.

<<provided>> Addresses

<<required>> Text AddressManager

listAdresses() listAdresses() sort()

Adresses

Text


Ports

►  Ports consist of port classes with interfaces and behavior in form of interface automata

n  provided: normal, offered interface n  required: used, necessary interface

Component

<<provided>> Port class

<<required>> Port class

Component

Port


Nesting of UML Components

►  UML components n  Ports are connected by links (connections) n  Delegation link: links outer and inner port

DocumentSystem Link/connection Delegator

Text Manager

Address Manager Adresses

email

email Manager

Text

Forms

Buffer

Lines TextRep

IText

IForm


Refinement of UML Components

►  UML components are nested, i.e., are bobs. ►  Nesting is indicated by aggregation and part-of relationship. ►  Nesting is introduced by an encapsulation operator encapsulate.

Document System

Document System

Text Manager


email email

Manager

Text

Forms

Buffer

Lines TextRep

IText

IForm

encapsulate

decompose


Encapsulation means Aggregation

►  Nesting means Aggregation n  A UML component is a package and a façade for all subcomponents

DocumentSystem

Text Manager


email

email Manager

Text

Forms

Buffer

Lines TextRep

IText

IForm

DocumentSystem

Text Manager

Address Manager

Adresses

email

email Manager

Text

Forms

Buffer

Lines

TextRep

IText

IForm


12.5 Searching in Component Repositories by Contract Conformance•  Contract Conformance means semantic substituability


Ports can be Equipped with Interface Automata Contracts

►  Ports consist of port classes with interfaces and behavior in form of interface automata (port automata, protocol automata)

n  provided: normal, offered interface n  required: used, necessary interface

Component



Component Port

Interface automaton

Interface automaton


Component Protocols with Operational Contracts

Ø  The port protocol automata can be composed to a component protocol automaton

Ø  Components may have a protocol automaton in which their ports, services, procedures should be called, invoked, or signalled

•  The provided protocol specifies in which order the services can be invoked (given by a provided interface automaton)

•  The required protocol specifies in which order the services can be invoked (given by a requried interface automaton)

Ø  The order of component invocation can be specified by a language over the alphabet of the ports, services, procedures (state-based protocol contract, operational contract)

•  Language contains sets of paths ofer the alphabet •  Finite state automaton (regular language) specify regular sets of paths

§  UML state chart (Hierarchical finite state machine, prococol machines) §  Data flow diagram

•  Stack machine (context-free language) •  Petri net (regular dialects, context-free and context-sensitive dialects)

Ø  The contract provides an abstraction of the implementation of the component

•  Implementations must be proven to be conformant to the procotol

Ø  The conformance checking is decidable if the protocol language is decidable

Ø  Sets of paths over states (words over state and edge alphabet)


The Golden Rules of Substitutability

Ø  Component A can replace component B if it offers more and requires less

Ø  Two conditions: •  A‘s provided protocol must be stronger (richer, larger) than B‘s – it must

guarantee more •  A‘s required protocol must be weaker (smaller) than B‘s – it must assume less

Ø  If those conditions hold for all component instances of two component types AT and BT, we say that AT can substitute BT in a program.


Subsumption of Single Interface/Port Protocols

Ø  A provided-port protocol Pr(P1) is-contained-in (is smaller than, is-weaker-than) a provided-port protocol Pr(P2), if Pr(P1) <= Pr(P2), i.e, if the set of guaranteed call sequences to P1 is smaller-equal than that to P2

Ø  A port protocol Pr(P1) subsumes (contains, is-stronger-than) a port protocol Pr(P2), if Pr(P1) > Pr(P2), i.e., if the set of guaranteed call sequences of P1 is larger than that of P2, i.e., it delivers more

•  Then, port P1 is conformant to P2 and P1 can substitute P2 in connections, because P1 delivers less paths of states than P2

•  Subsumption checking of ports, and thus, conformance checking, should be decidable (protocol language should be decidable)

Pr(P1) = a b b* c <= Pr(P2) = a b* c

P1:Component

<<provided>> Port Class

P1 a b

c b

P2:Component

<<provided>> Port Class

P2 a b c

<=

corrected


D:Component

r r r s t

<<provided>> Port Class 2

Subsumption of all Guarantees (Provided Protocols)

Ø  A component‘s guarantee (provided protocol) G(C1) is-contained-in (is-weaker-than, offers-less) a second component‘s guarantee G(C2), if forall ports P in C1.providedPorts: exists Q in C2.providedPorts: Pr(P) <= Pr(Q)

•  C1 offers/delivers on every port less than C2 on the corresponding port

Ø  A component‘s guarantee G(C1) subsumes (is-stronger-than, offers-more) a second component‘s guarantee G(C2), if for all ports P in C1.providedPorts: exists Q in C2.providedPorts: Pr(P) > Pr(Q)

•  Then, C1 is guarantee-conformant to C2 and can substitute it in output connections

a b b* c


<= E:Component

r* s t


a b* c


Pr(D.PortClass1) = a b b* c <= Pr(E.PortClass1) = a b* c Pr(D.PortClass2) = r r r s t <= Pr(E.PortClass2) = r* s t


Protocol Subsumption is Pairwise Port Subsumption

Ø  Every port of D must find a matching port of E, in whom it is contained

D:Component

r r r s t


a b b* c


<= E:Component

r* s t


a b* c


new


D:Component

r* s t

<<required>> Port Class 2

Subsumption of Assumptions (Required Protocols)

Ø  A component‘s assumption (required protocol) A(C1) contains (is-stronger-than, demands-more) a second component‘s assumption A(C2), if for all ports P in C1.requiredPorts holds:

•  Exists Q in C2.requiredPorts: Pr(P) > Pr(Q) (required ports of C2 have smaller or less assumptions) •  Q‘s required ports require less assumptions than P‘s required ports

Ø  A component‘s assumption A(C1) subsumes (is-contained-in, is-weaker-than, demands-less) a second component‘s assumption A(C2), if for all ports P in C1.requiredPorts holds:

•  Exists Q in C2.requiredPorts: Pr(P) <= Pr(Q) (required ports of C2 have larger and more assumptions) •  Then, C1 is assumption-conformant to C2 and can substitute it in input connections

a b* c


> E:Component

r s t


a b c


A(E.ReqPortClass1) = a b c <= G(D.ReqPortClass1) = a b* c A(E.ReqPortClass2) = r s t <= G(D.ReqPortClass2) = r* s t

corrected


Subsumption of Guarantees and Counterwise Subsumption of Assumptions

Ø  A component protocol Prot(C1) can subsume a component protocol Prot(C2) if G(C1) >= G(C2) and A(C2) <= A(C1)

•  If C1‘s assumptions are weaker than C2‘s •  And if C1‘s guarantees are stronger than C2‘s

Ø  Then, C1 is conformant to C2 and C1 can substitute C2 in input and output connections

Ø  C1 can be substituted for C2, if •  C1 delivers more or equal than C2 and (more performant, less guarantueeing) •  C1 demands less or equal than C2 (less demanding, less assuming)


Component

Subsumption of Protocols

Ø  A component protocol P(C1) can subsume a component protocol P(C2) •  P(C1) <= P(C2) •  For finite automata: P(C1) P(C2)

Ø  Then, C1 is conformant to C2 and C1 can substitute C2 Ø  Subsumption checking and thus, conformance checking, should be decidable

(protocol language should be decidable) •  Fortunately, automata can be decided on containment

⊆




Searching by Protocol

Ø  A component C can be found in a repository, if a query protocol Q is given with Q <= P(C)

Ø  Search consists of subsumption checking with all component protocols in the repository

Ø  Query protocols can be: •  Metadata about the component •  Provided protocols •  Required protocols •  Provided and required protocols


Declarative Protocols

Ø  A protocol can also be specified as predicates over the states of a component (declarative contract) •  Preconditions (assumptions) •  Postconditions (guarantees) •  Invariants

Ø  Then, the protocol consists of logic expressions. The logic should be decidable •  OCL •  Description logic •  Datalog •  Temporal logic (propositional logic with temporal quantifiers, such as LTL and

CTL) Ø  Subsumption checking of protocols and conformance can be done by

reasoning •  E.g., by subsumption checking of an OWL class hierarchy


The End - Acknowledgements

Ø  Faceted browsing slides are courtesy to Jan Polowinski.


Example: Finding Courses in Europe based on Ontologies

►  A course in the unified Bologna world of European education can be described by several facets: ■  topic area (computer science, music, literature, etc.), ■  level of advancement (undergraduate, graduate), ■  cost (free, non-free), ■  country (Germany, Italy, WesternEurope, EasternEurope, etc.)

►  Every facet can be described by an ontology, in this case on ■  topic area ■  level ■  cost ■  country

►  A semantic description of a course selects one value for each facet and forms a tuple ■  A free undergraduate music course could be described by the tuple (topic area =

music, advancement = undergraduate, cost = free, country = WesternEurope).


Ex. Finding Courses in Europe

►  Searching a course throughout the course databases in Europe consists of comparing the tuple point-wise to database entries.

►  The values need not match exactly, ■  Subsumption (inheritance) in the facet ontologies can be used to deliver

refinement of matchings. ■  Example: if free-course is subsumed by non-free-course, the matcher can yield a

free course, even if the client desired a non-free one. ■  Example: a matchmaker can return a (music, undergraduate, non-free, Germany)-

course which should fit the client's desires.

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12. Finding Components with Metadata in Component Repositoriesst.inf.tu-dresden.de/.../ss16/cbse/slides/12-cbse-finding-components.… · Component Search with Metadata 2. Searching