THE WEB SERVICE MODELING LANGUAGE WSML: AN OVERVIEW <s> Key Features of WSML <s> We propose a novel formalism, called Frame Logic (abbr., F-logic), that accounts in a clean and declarative fashion for most of the structural aspects of object-oriented and frame-based languages. These features include object identity, complex objects, inheritance, polymorphic types, query methods, encapsulation, and others. In a sense, F-logic stands in the same relationship to the object-oriented paradigm as classical predicate calculus stands to relational programming. F-logic has a model-theoretic semantics and a sound and complete resolution-based proof theory. A small number of fundamental concepts that come from object-oriented programming have direct representation in F-logic; other, secondary aspects of this paradigm are easily modeled as well. The paper also discusses semantic issues pertaining to programming with a deductive object-oriented language based on a subset of F-logic. <s> BIB001 </s> THE WEB SERVICE MODELING LANGUAGE WSML: AN OVERVIEW <s> Key Features of WSML <s> {PG,1 A tractor draft load monitoring system responsive to tractor and associated implement load changes. The system is particularly adapted for a tractor having an engine/transmission power unit coupled to its drive shaft. The power unit is mounted on the frame by resilient mounts that permit measurable angular displacement of the power unit relative to the frame about the drive shaft axis in reaction to changes in the drive shaft torque. The working depth of the implement, which may be tractor mounted, semi-mounted or a pull type implement, is raised or lowered by a hydraulic lift system that is controlled by a control valve assembly connected to a source of fluid under pressure. Interposed between the power unit and the control valve assembly is a transmission cable (Bowden wire type) and lever system that is operative to transmit angular displacement of the power unit to an actuating member of the control valve assembly to cause hydraulic actuation of the hydraulic lift device to change the working depth of the implement to compensate for changes in its draft load. <s> BIB002 </s> THE WEB SERVICE MODELING LANGUAGE WSML: AN OVERVIEW <s> Key Features of WSML <s> Abstract The OWL Web Ontology Language is a new formal language for representing ontologies in the Semantic Web. OWL has features from several families of representation languages, including primarily Description Logics and frames. OWL also shares many characteristics with RDF, the W3C base of the Semantic Web. In this paper, we discuss how the philosophy and features of OWL can be traced back to these older formalisms, with modifications driven by several other constraints on OWL. Several interesting problems have arisen where these influences on OWL have clashed. <s> BIB003 </s> THE WEB SERVICE MODELING LANGUAGE WSML: AN OVERVIEW <s> Key Features of WSML <s> We show how to interoperate, semantically and inferentially, between the leading Semantic Web approaches to rules (RuleML Logic Programs) and ontologies (OWL/DAML+OIL Description Logic) via analyzing their expressive intersection. To do so, we define a new intermediate knowledge representation (KR) contained within this intersection: Description Logic Programs (DLP), and the closely related Description Horn Logic (DHL) which is an expressive fragment of first-order logic (FOL). DLP provides a significant degree of expressiveness, substantially greater than the RDF-Schema fragment of Description Logic. We show how to perform DLP-fusion: the bidirectional translation of premises and inferences (including typical kinds of queries) from the DLP fragment of DL to LP, and vice versa from the DLP fragment of LP to DL. In particular, this translation enables one to "build rules on top of ontologies": it enables the rule KR to have access to DL ontological definitions for vocabulary primitives (e.g., predicates and individual constants) used by the rules. Conversely, the DLP-fusion technique likewise enables one to "build ontologies on top of rules": it enables ontological definitions to be supplemented by rules, or imported into DL from rules. It also enables available efficient LP inferencing algorithms/implementations to be exploited for reasoning over large-scale DL ontologies. <s> BIB004
There are a number of features which make WSML stand out from other language proposals for the Semantic Web and Semantic Web Services. These key features are mainly due to the two pillars of WSML, namely (1) a language independent conceptual model for Ontologies, Web Services, Goals and Mediators coming from WSMO  and (2) reuse of existing well-known logical language paradigms. More specifically, we see the following as the key features of WSML: One syntactic framework for a set of layered languages We believe different Semantic Web and Semantic Web Service applications need languages of different expressiveness. There already exist language recommendations for certain aspects, such as the Ontology languages RDFS  and OWL  . Already in the case of RDFS and OWL, we can see that layering languages on existing recommendations is not straightforward BIB003  ; either the layering is not strict, or certain desirable features of a language, such as the ability to use existing efficient reasoners, are lost. Normative, human readable syntax It has been argued that tools will hide language syntax from the user; however, as has been seen with the adoption of SQL, an expressive but understandable syntax is crucial for successful adoption of a language. Developers and early adopters of the language will have to deal with the concrete syntax. If it is easy to read and understand it will allow for easier adoption of the language. Separation of conceptual and logical modeling On the one hand, the conceptual syntax of WSML has been designed in such a way that it is independent of the underlying logical language an no or only limited knowledge of formal languages is required for the basic modeling of Web Services, Goals, Mediators and Ontologies. On the other hand, the logical expression syntax allows expert users to refine definitions on the conceptual syntax using the full expressive power of the underlying logic, which depends on the particular language variant chosen by the user. Semantics based on well known formalism WSML captures well known logical formalisms such as Datalog and Description Logics in a unifying syntactical framework, while maintaining the established computational properties of the original formalisms. Furthermore it allows the reuse of tools already developed for these formalisms. Notably, WSML allows to reuse efficient querying engines developed for Datalog and efficient subsumption reasoners developed in the area of Description Logics. Interoperation between the paradigms is achieved through a common subset, depicted by DLP BIB004 . WWW Language WSML has a number of features which integrate it seamlessly in the Web. WSML adopts the IRI  standard, the successor of URI, for the identification of resources, following the Web architecture. Furthermore, WSML adopts the namespace mechanism of XML and datatypes in WSML are compatible with datatypes in XML Schema BIB002 and datatype functions and operators are based on the functions and operators of XQuery  . Finally, WSML defines an XML syntax and an RDF syntax for exchange over the Web. When using the RDF syntax, WSML can be seen as an extension of RDFS and thus an integral part of the Semantic Web language stack. Frame-based syntax Frame Logic BIB001 allows the use of frames in logical expressions. This allows the user to work directly on the level of concepts, attributes, instances and attribute values, instead of at the level of predicates. Furthermore, variables are allowed in place of concept and attribute identifiers, which enables meta-modeling and reasoning over the signature. We believe the key features of WSML make it a flexible language for the description of Ontologies and Web Services.