Motivated by formal models recently proposed in the context of XML, we study automata and logics on strings over infinite alphabets. These are conservative extensions of classical automata and logics defining the regular languages on finite alphabets. Specifically, we consider register and pebble automata, and extensions of first-order logic and monadic second-order logic. For each type of automaton we consider one-way and two-way variants, as well as deterministic, nondeterministic, and alternating control. We investigate the expressiveness and complexity of the automata and their connection to the logics, as well as standard decision problems. Some of our results answer open questions of Kaminski and Francez on register automata.
We formalize and study business process systems that are centered around "business artifacts", or simply "artifacts". Artifacts are used to represent (real or conceptual) key business entities, including both their data schema and lifecycles. The lifecycle of an artifact type specifies the possible sequencings of services that can be applied to an artifact of this type as it progresses through the business process. The artifact-centric approach was introduced by IBM, and has been used to achieve substantial savings when performing business transformations.
We study the inference of Data T ype De nitions DTDs for views of XML data, using an abstraction that focuses on document con tent structure.The views are de ned by a query language that produces a list of documents selected from one or more input sources. The selection conditions involve v ertical and horizontal na vigation, thus querying explicitly the order present in input documents. We poin t several strong limitations in the descriptive abilit y of curren t DTDs and the need for extending them with i a subtyping mechanism and ii a more pow erful speci cation mec hanism than regular languages, such a s c o n text-free languages. With these extensions, w e sho w that one can alw ays infer tight DTDs, that precisely characterize a selection view on sources satisfying giv en DTDs. We also sho w important special cases where one can infer a tight DTD without requiring extension ii. Finally we consider related problems such as verifying conformance of a view de nition with a prede ned DTD. Extensions to more pow erful views that construct complex documents are also brie y discussed.
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