Function Interoperability George Athanasopoulos, Ed Fox, Yannis Ioannidis, George Kakaletris, Natalia Manola, Carlo Meghini, Andreas Rauber, Dagobert Soergel

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Layout What is interoperability? Why is it needed for? Pre-requisites Interoperability Cases Function Interoperability Levels Interoperability Issues –Issues –Solutions 2010 Odyssey Topics for discussion/exercise 2

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability What is Interoperability ? “ability of a system to work with or use the parts or equipment of another system” [Merriam-Webster dictionary] “Interoperability is a property of a product or system, whose interfaces are completely understood, to work with other products or systems, present or future, without any restricted access or implementation” [Wikipedia] “The ability of two or more systems or components to exchange information and to use the information that has been exchanged” [IEEE definition] 3

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability DL Function Interoperability – Part 1 Can be though of as …. 4 DL ADL B Functions

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Compatibility 5

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Product Compatibility as Interoperability From a user perspective product compatibility allows the user to adapt to a new system quickly 6

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability What if interoperability was possible.. Then we could: Provide users of one DL access to the content and functionality of other DLs Harmonize the user experience provided by different DLs so that the user who has learned to use one DL can use easily other DLs Save effort in creating new DLs, or adding functionality to an existing DL, by reusing existing software components 7

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Are we missing something ? A template for the description of functions A catalog/registry of existing functions 8

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Interoperability Cases: A process-based point of view Function Fa can use the functionality offered by Fb, by –Fa can use Fb as a plug-in (static) –Fa can call Fb as a service (dynamic) 9

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Interoperability Cases: A process-based point of view (cont) Replaceability: –If Function Fa can operate in environment E and Fb can also operate in E, then Fb can replace Fa, or a user can be given a choice between Fa and Fb 10

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Interoperability Cases: A data-based point of view If Function Fa can operate on the output of Fb then Fa and Fb are interoperable –Fa and Fb may also exchange data (possibly back and forth) as they run concurrently Function Fa is interoperable with a given data set D or a given data format DF if Fa can make use of the data in data set D or of data formatted according to DF If function Fa is interoperable with a given data set D or data format DF and function Fb is also compatible with D or DF, respectively, then Fb can replace Fa, or a user can be given a choice between Fa and Fb 11

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Interoperability Cases: A user-based point of view Functions Fa and Fb are (cross-) product- compatible if a user who has learned to use Fa can also use Fb 12

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Interoperability Dimensions the static vs dynamic dimension, which deals with the degree of dynamicity of the interaction between the functions: –static, if the interaction must be implemented at development time –dynamic, if the interaction can happen at run time 13

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Interoperability Dimensions (cont) the form of interaction: –composition: the functions carry out two different tasks and one of the two can invoke the other one for executing some required activity –replacement: the functions carry out the same task in possibly alternative ways, and one can be replaced by the other 14

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability DL Function Interoperability – Part 2 A digital library (DL A) is interoperable with another digital library (DL B) on a function (F) iff either DL A or DL B can invoke F and/or combine F with other functions, with or without the use of brokers 15

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability DL Product Compatibility Digital library B is product compatible with DL A with respect to functionality if –DL B provides all the functions DL A provides –DL B uses the same interface to invoke functions as DL A includes naming of functions, shape and color of buttons, screen layout, command names and syntax 16

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Interoperability Levels Achieving function interoperability facilitates/depends on –Syntactic Interoperability –Semantic Interoperability –Functional Interoperability –Behavioral Interoperability –Organizational/Business/Procedural Interoperability 17

DL FUNCTION INTEROPERABILITY ISSUES & SOLUTIONS 18

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability 19 Function Interoperability Issues Interface/API incompatibilities: Function interface includes information related to the input/output and the manners one should use to operate a function Pre/Post Condition differences: Pre- conditions & Post-conditions includes conditions that must hold prior to and after the invocation of a function Behavioral incompatibilities: Behavior specifications include information on the set of possible interactions supported by a specific function Composite Function Incompatibilities: Issues related to the interoperation of complex functions Ontology/Taxonomy Issues: Ontologies/Taxonomies provide a vocabulary for specifying the actual function semantics

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability API/Interface Incompatibilities Function API/Interface captures information related to the input/output and the manners one should use to operate a function –Interfaces could be either graphical or programming ones 20

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability API/Interface Incompatibilities (cont) 21 Fa Fb Fa : DL-A Search o a1: keyword (String) o a2: type of content (e.g. video, text) o o1: list of results (URIs) a1 a2 a1 a2 a3 o1 Fb : DL-B Search o a1: keyword (String) o a2: content age (e.g. >1990) o a3: list of personal preferences (e.g. movies, cartoons) o o1: list of results (content)

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Pre/Post Condition Incompatibilities Preconditions and Postconditions provide a specification of the conditions that hold for a function to be called and the ones that hold after its execution respectively 22

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Pre/Post Condition Incompatibilities (cont) 23 Fa Fb Fa : DL-A Search o pr.c1: a1 must be a single word o pr.c2: type of content must be {video, text, image} o ps.c1: results include forbidden material a1 a2 a1 a2 o1 Fb : DL-B Search o pr.c1: a1 may include sentences o pr.c2: type of content must be {video, audio, text} o pr.c3: user location must be in Greece o a1: keyword (String), a2: type of content (e.g. multimedia, text) o o1: list of results (URIs)

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Behavioral Incompatibilities Function behavior can be conceived as the set of possible interactions supported by a specific function –It expresses the perception of an external observer described in terms of supported input/output exchanges their (logical or time) ordering and constraints 24

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Behavioral Incompatibilities (cont) 25 Fa Fb a1 a2 a1 a2 o1 o a1: keyword (String), a2: preference filters (e.g. thrillers, cartoons) o o1: list of results (URIs) Fa : DL-A Search o a1, a2: are provided in the beginning and can not be changed afterwards o o1: results are returned in set of pages accessed one after the other (e.g. Google) Fb : DL-B Search o a1, a2: can be altered after first execution to refine results o o1: results are returned all at once (e.g Wikipedia)

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Composite Function Incompatibilities Function composition interoperability can be considered at two levels: –the level of constituent functions i.e. integration of simple (or atomic) functions –the level of composite functions i.e. interoperation of complex functions The concerns related to the interoperation of complex functions include issues such as the replaceability of complex functions or the compatibility of employed composition styles 26

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Composite Function Incompatibilities (cont) 27

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Function Ontology/Taxonomy Incompatibilities The precise specification of functions requires a very detailed typology or ontology i.e. a vocabulary for specifying the actual semantics The use of a common vocabulary for the description of functions provides the necessary basis upon which DLs may cooperate either in an automated or a 'manual' manner 28

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Function Ontology/Taxonomy Incompatibilities (cont) Ontology –Discover Navigate Browse Search –quick search –advanced search 29

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Function Ontology/Taxonomy Incompatibilities (cont) 30

SOLUTIONS 31

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Classification of Interoperability Approaches Agreement based / Static: Use of a set of principles (e.g. interfaces, etc) that achieve a limited amount of homogeneity among heterogeneous functions Mediation based : guarantee a high level of autonomy among the interacting functions, by isolating the interoperability machinery and implementing it in components which link the interacting functions 32

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Agreement-based Approaches A static definition of functions in terms of : –Interfaces e.g. I/Os –Behavior –Pre/Post –conditions An old & successfully applied solution –E.g. RosettaNet & e-Framework 33

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Agreement based Approaches (cont) 34 Fa a1 o1

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Mediation-based Approaches Static Mediation: Mediators are constructed in a static (non-automated) manner for specific cases Dynamic Mediation: Mediators are constructed in a dynamic (automated) manner based on the use of appropriate descriptions and formal methods 35

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Static Mediation Well tested and applied approach Used in many existing systems 36 Fa Fb a1 a2 a1 o1 Mediator Fc a1 a2 o1

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Dynamic Mediation Relies on the use of formal –Descriptions of functions (i.e. mathematical/logic based descriptions) and –Methods for the identification of mediators Used in research-based context 37 Fa a1 a2 o1 Fb a1 a2 o1 Fa Spec Fb Spec Constr. Mediator

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Composite Function Interoperation Formal approaches relying on the description of complex function choreographies Any other ideas ?????? 38

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Ontology/Taxonomy Interoperation Ontology mapping: involves the creation of a set of rules and axioms that precisely define how terms from one ontology relate with terms from the other ontology Ontology alignment: has the role of bringing the involved ontologies in a mutual agreement. The ontologies are kept separately but at least one of them has to be altered such as the involved ontologies are ”aligned” (i.e. they match) in their overlapping parts Ontology merging: results in creation of a new ontology that replaces the original ontologies. The merging can be done either by unification (all the terms from the involved ontologies are included and mismatches between the overlapping ones are resolved) or by intersection (only the overlapping terms are included and their mismatches reconciliated) 39

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability 2010 Odyssey in Athens Integrating what? – Search capabilities offered by Wikipedia, Europeana, Amazon To provide what ? –an account of the topic (taken from Wikipedia) –a list of resources in Europe related to the topic (Europeana) –a list of the available publications on the topic (Amazon) –the links between these three 40

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability 2010 Odyssey in Athens: Providing a Solution Have in mind the following: –Why do we need it ? –What are original/initial constraints ? –What will be our outcome? –Does it relate to any one of the presented issues/solutions? 41 DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Describing the Solution 1.Overview Context of the proposed approach including pointers to detailed description of it 2.Requirements Conditions under which the solution might be used 3.Results Changes resulting from the usage of the solution 4.Implementation guidelines How the changes are produced 5.Assessment Qualitative evaluation of the proposed solution 42

Information available at: Functionality WG Functionality Interoperability State-of-the-Art Report Functionality WG Functionality Interoperability State-of-the-Art Report

DL.org Autumn School Digital Libraries and Digital Repositories: Modelling, Best Practices & Interoperability Hands-On: Topics What are the discovery functions offered by your DLs? –Describe them in terms of the RM –Can they interoperate with Google Search? –Can they interoperate among them? Is the web a DL ? –Why not ? –Will it ever be ? 44