alist of the representation formats supported by the service. Example: text/html, text/xml, application/json the version or release identifier of the service the default format used by the service unless otherwise specified the set of namespaces recognized by this service. Because many namespace identifiers tend to be cryptic (i.e. HL7 OIDs, BioPortal URL's, etc.), <i>knownNamespace</i> includes the namespace name, an optional URI \emph{and} a place to provide textual detail describing what the namespace references. Note that namespace names must be unique across an entire CTS2 implementation - the same namespace name cannot represent one namespace in code system A and a second in code system B. Note also that namespace names are \emph{local} to a service instance. Information that is communicated between service instances, recorded in data tables or client software \emph{must} use full URIs. a reference to the individual or organization that provides the service. the set of service profiles that are supported by this service implementation a description of the service, its use, etc. a short name that identifies the particular service and implementation the particular implementation type(s) supported by this profile the match algorithms that can be used in filters for this service instance the set of model attributes that can be referenced in filter instances for the given service implementation The set of properties that are used in one or more instances of the resource represented by this service. This list includes all properties that can be used in queries in this service, independent of the <i>entryState </i>or temporal state of the resource(s) being searched. Return the number of elements currently represented by the supplied directory URI. Return a <i>DirectoryURI</i> that references the set of all elements represented by <i>directory</i> that match the criteria specified in <i>filter.</i> Remove any of the elements in <i>elementsToRemove</i> from <i>initialSet </i>if present. Elements in <i>elementsToRemove</i> that are not in <i>initialSet</i> are ignored. Return a directory that represents the set of elements that are common to the two supplied directories. Note that both DirectoryURIs must represent resources of the same type. Return a directory that represents the combination of the contents of the supplied two supplied directories, with duplicate entries removed. Note that both of the directory URIs must resolve to entries of the same type. Return a <i>DirectoryURI</i> that resolves to the set of statements in <i>directory</i> that have subjects in <i>subjects</i>Return a <i>DirectoryURI</i> that resolves to the set of statements in <i>directory</i> that have subjects in <i>subjects</i> The supplied <i>directory</i> URI is not valid The type represented by the supplied <i>directory</i> URI is not the one required by the service invocation. The supplied namespace name is not one that is known to the service. The <i>EntityNameOrURI</i> is not known to the service Return a <i>DirectoryURI</i> that resolves to the set of statements in <i>directory</i> that have targets in <i>targets</i>. This includes both direct and any targets in BNODES. The supplied <i>directory</i> URI is not valid The type represented by the supplied <i>directory</i> URI is not the one required by the service invocation. The supplied namespace name is not one that is known to the service. The <i>EntityNameOrURI</i> is not known to the service restrict the list of statement to those in the supplied list of model attributesrestrict the list of statement to those in the supplied list of model attributes The supplied <i>directory</i> URI is not valid The type represented by the supplied <i>directory</i> URI is not the one required by the service invocation. Return a <i>DirectoryURI</i> that resolves to the set of statements in <i>directory</i> that have subjects in <i>subjects</i>Return a <i>DirectoryURI</i> that resolves to the set of statements in <i>directory</i> that have subjects in <i>subjects</i> The supplied <i>directory</i> URI is not valid The type represented by the supplied <i>directory</i> URI is not the one required by the service invocation. The supplied namespace name is not one that is known to the service. The <i>EntityNameOrURI</i> is not known to the service Return a <i>DirectoryURI</i> that resolves to the set of statements in <i>directory</i> that have targets in <i>targets</i>. This includes both direct and any targets in BNODES. The supplied <i>directory</i> URI is not valid The type represented by the supplied <i>directory</i> URI is not the one required by the service invocation. Return a <i>DirectoryURI</i> that resolves to the set of statements in <i>directory</i> that have subjects in <i>subjects</i> A CTS2 resource was referenced by name, URI or external identifier that was not known to the CTS2 service instance. The supplied <i>directory</i> URI is not valid The type represented by the supplied <i>directory</i> URI is not the one required by the service invocation. a DirectoryURI that resolves to the set of statements known to the service resolve a <i>StatementDirectoryURI</i> and return a directory summarizing the statements it referencesRetrieve a change set as an iterable resource - a handy function for viewing large change sets The supplied <i>directory</i> URI is not valid The type represented by the supplied <i>directory</i> URI is not the one required by the service invocation. The <i>referenceLanguage</i> is not supported by the service The change set specified could either not be read or located by the service. The <i>changeSetContext</i> is recognized by the service, but its state is not <i>OPEN</i>. One or more <i>changeSetContext</i> is not supported by the service Errors that can occur in sort and/or filter parameters The <i>format</i> is not supported by the service implementation The <i>timeLimit</i> was exceeded by the service. resolve a <i>StatementDirectoryURI</i> and return a list of the statements it referencesResolve a <i>DirectoryURI </i> that references a set of code system catalog entries and return the set of corresponding catalog entries Errors that can occur in sort and/or filter parameters The <i>format</i> is not supported by the service implementation The <i>timeLimit</i> was exceeded by the service. The supplied <i>directory</i> URI is not valid The type represented by the supplied <i>directory</i> URI is not the one required by the service invocation. The <i>referenceLanguage</i> is not supported by the service The change set specified could either not be read or located by the service. The <i>changeSetContext</i> is recognized by the service, but its state is not <i>OPEN</i>. One or more <i>changeSetContext</i> is not supported by the service <i>StatementQueryService </i>provides an ability to filter directories of statements by subject, predicate, target and/or model element. It should be noted that the functionality provided her has significant overlap with specifications such as SPARQL and the API4KB. It is not the intent of the CTS2 specification to compete with or offer alternatives to these specifications. The key differences between this API and those mentioned above is the <i>Statement</i> model. First, it differentiates between simple resource URIs and the namespace/name structure in entity references. Secondly it provides bridge information that identifies how CTS2 structures were derived from more atomic information. Finally, and perhaps most importantly, it provides provenance and history for the sets of assertions in statements. The query service itself could (and probably should) be implemented using triple stores, SPARQL, or other alternatives.