Adaptable processes

We propose the concept of adaptable processes as a way of overcoming the limitations that process calculi have for describing patterns of dynamic process evolution. Such patterns rely on direct ways of controlling the behavior and location of running processes, and so they are at the heart of the adaptation capabilities present in many modern concurrent systems. Adaptable processes have a location and are sensible to actions of dynamic update at runtime; this allows to express a wide range of evolvability patterns for concurrent processes. We introduce a core calculus of adaptable processes and propose two verification problems for them: bounded and eventual adaptation. While the former ensures that the number of consecutive erroneous states that can be traversed during a computation is bound by some given number k, the latter ensures that if the system enters into a state with errors then a state without errors will be eventually reached. We study the (un)decidability of these two problems in several variants of the calculus, which result from considering dynamic and static topologies of adaptable processes as well as different evolvability patterns. Rather than a specification language, our calculus intends to be a basis for investigating the fundamental properties of evolvable processes and for developing richer languages with evolvability capabilities

Verifiable UML Artifact-Centric Business Process Models (Extended Version)

Artifact-centric business process models have gained increasing momentum recently due to their ability to combine structural (i.e., data related) with dynamical (i.e., process related) aspects. In particular, two main lines of research have been pursued so far: one tailored to business artefact modeling languages and methodologies, the other focused on the foundations for their formal verification. In this paper, we merge these two lines of research, by showing how recent theoretical decidability results for verification can be fruitfully transferred to a concrete UML-based modeling methodology. In particular, we identify additional steps in the methodology that, in significant cases, guarantee the possibility of verifying the resulting models against rich first-order temporal properties. Notably, our results can be seamlessly transferred to different languages for the specification of the artifact lifecycles.Comment: Extended version of "Verifiable UML Artifact-Centric Business Process Models" - to appear in the Proceedings of CIKM 201

Decidable Reasoning in Terminological Knowledge Representation Systems

Terminological knowledge representation systems (TKRSs) are tools for designing and using knowledge bases that make use of terminological languages (or concept languages). We analyze from a theoretical point of view a TKRS whose capabilities go beyond the ones of presently available TKRSs. The new features studied, often required in practical applications, can be summarized in three main points. First, we consider a highly expressive terminological language, called ALCNR, including general complements of concepts, number restrictions and role conjunction. Second, we allow to express inclusion statements between general concepts, and terminological cycles as a particular case. Third, we prove the decidability of a number of desirable TKRS-deduction services (like satisfiability, subsumption and instance checking) through a sound, complete and terminating calculus for reasoning in ALCNR-knowledge bases. Our calculus extends the general technique of constraint systems. As a byproduct of the proof, we get also the result that inclusion statements in ALCNR can be simulated by terminological cycles, if descriptive semantics is adopted.Comment: See http://www.jair.org/ for any accompanying file

Artifact-centric business process models in UML : specification and reasoning

Business processes are directly involved in the achievement of an organization's goals, and for this reason they should be performed in the best possible way. Modeling business processes can help to achieve this as, for instance, models can facilitate the communication between the people involved in the process, they provide a basis for process improvement and they can help perform process management. Processes can be modeled from many different perspectives. Traditional process modeling has followed the process-centric (or activity-centric) perspective, where the focus is on the sequencing of activities (i.e. the control flow), largely ignoring or underspecifying the data required by these tasks. In contrast, the artifact-centric (or data-centric) approach to process modeling focuses on defining the data required by the tasks and the details of the tasks themselves in terms of the changes they make to the data. The BALSA framework defines four dimensions which should be represented in any artifact-centric business process model: business artifacts, lifecycle, services (i.e. tasks) and associations. Using different types of models to represent these dimensions will result in distinct representations, whose differing characteristics (e.g. the degree of formality or understandability) will make them more appropriate for one purpose or another. Considering this, in the first part of this thesis we propose a framework, BAUML, for modeling business processes following an artifact-centric perspective. This framework is based on using a combination of UML and OCL models, and its goal is to have a final representation of the process which is both understandable and formal, to avoid ambiguities and errors. However, once a process model has been defined, it is important to ensure its quality. This will avoid the propagation of errors to the process's implementation. Although there are many different quality criteria, we focus on the semantic correctness of the model, answering questions such as "does it represent reality correctly?" or "are there any errors and contradictions in it?". Therefore, the second part of this thesis is concerned with finding a way to determine the semantic correctness of our BAUML models. We are interested in considering the BAUML model as a whole, including the meaning of the tasks. To do so, we first translate our models into a well-known framework, a DCDS (Data-centric Dynamic System) to which then modelchecking techniques can be applied. However, DCDSs have been defined theoretically and there is no tool that implements them. For this reason, we also created a prototype tool, AuRUS-BAUML, which is able to translate our BAUML models into logic and to reason on their semantic correctness using an existing tool, SVTe. The integration between AuRUS-BAUML and SVTe is transparent to the user. Logically, the thesis also presents the logic translation which is performed by the tool.Els processos de negoci estan directament relacionats amb els objectius de negoci, i per tant és important que aquests processos es duguin a terme de la millor manera possible. Optar per modelar-los pot ajudar a aconseguir-ho, ja que els models proporcionen nombrosos avantatges. Per exemple: faciliten la comunicació entre les parts involucrades en el procés, proporcionen una base a partir del qual millorar-lo, i poden ajudar a gestionar-lo. Els processos es poden modelar des de diferents perspectives. El modelat tradicional de processos s'ha basat molt en la perspectiva anomenada "process-centric" (centrada en processos) o "activity-centric" (centrada en activitats), que posa l'èmfasi en la seqüència d'activitats o tasques que s'han d'executar, ignorant en gran mesura les dades necessàries per dur a terme aquestes tasques. Per altra banda, la perspectiva "artifact-centric" (centrada en artefactes) o "data-centric" es basa en definir les dades que necessiten les tasques i els detalls de les tasques en si, representant els canvis que aquestes fan a les dades. El framework BALSA defineix quatre dimensions que haurien de representar-se en qualsevol model artifact-centric: els artefactes de negoci (business artifacts), els cicles de vida (lifecycles), els serveis (services) i les associacions (associations). Utilitzant diferents tipus de models per representar aquestes dimensions porta a obtenir diverses representacions amb característiques diferents. Aquesta varietat de característiques farà que els models resultants siguin més apropiats per un propòsit o per un altre. Considerant això, en la primera part d'aquesta tesi proposem un framework, BAUML, per modelar processos de negoci seguint una perspectiva artifact-centric. El framework es basa en utilitzar una combinació de models UML i OCL, i el seu objectiu és obtenir una representació final del procés que sigui a la vegada comprensible i formal, per tal d'evitar ambigüitats i errors. Un cop definit el procés, és important assegurar-ne la qualitat. Això evitarà la propagació d'errors a la implementació final del procés. Malgrat que hi ha molts criteris de qualitat diferents, ens centrarem en la correctesa semàntica del model, per respondre a preguntes com ara "representa la realitat correctament?" o "conté errors o contradiccions?". En conseqüència, la segona part d'aquesta tesi se centra en buscar una manera per determinar la correctesa semàntica d'un model BAUML. Ens interessa considerar el model com un tot, incloent el significat de les tasques (és a dir, el detall del que fan). Per aconseguir-ho, primer traduïm les tasques a un framework reconegut, DCDSs (Data-centric Dynamic Systems). Un cop obtingut, s'hi poden aplicar tècniques de model-checking per determinar si compleix certes propietats. Malauradament, els DCDSs s'han definit a nivell teòric i no hi ha cap eina que els implementi. Per aquest motiu, hem creat un prototip d'eina, AuRUS-BAUML, que és capaç de traduir els nostres models BAUML a lògica i aplicar-hi tècniques de raonament per determinar-ne la correctesa semàntica. Per la part de raonament, l'AuRUS-BAUML fa servir una eina existent, l'SVTe. La integració entre l'AuRUS-BAUML i l'SVTe és transparent de cara a l'usuari. Lògicament, la tesi també presenta la traducció a lògica que porta a terme l'eina

Artifact-centric business process models in UML : specification and reasoning

Business processes are directly involved in the achievement of an organization's goals, and for this reason they should be performed in the best possible way. Modeling business processes can help to achieve this as, for instance, models can facilitate the communication between the people involved in the process, they provide a basis for process improvement and they can help perform process management. Processes can be modeled from many different perspectives. Traditional process modeling has followed the process-centric (or activity-centric) perspective, where the focus is on the sequencing of activities (i.e. the control flow), largely ignoring or underspecifying the data required by these tasks. In contrast, the artifact-centric (or data-centric) approach to process modeling focuses on defining the data required by the tasks and the details of the tasks themselves in terms of the changes they make to the data. The BALSA framework defines four dimensions which should be represented in any artifact-centric business process model: business artifacts, lifecycle, services (i.e. tasks) and associations. Using different types of models to represent these dimensions will result in distinct representations, whose differing characteristics (e.g. the degree of formality or understandability) will make them more appropriate for one purpose or another. Considering this, in the first part of this thesis we propose a framework, BAUML, for modeling business processes following an artifact-centric perspective. This framework is based on using a combination of UML and OCL models, and its goal is to have a final representation of the process which is both understandable and formal, to avoid ambiguities and errors. However, once a process model has been defined, it is important to ensure its quality. This will avoid the propagation of errors to the process's implementation. Although there are many different quality criteria, we focus on the semantic correctness of the model, answering questions such as "does it represent reality correctly?" or "are there any errors and contradictions in it?". Therefore, the second part of this thesis is concerned with finding a way to determine the semantic correctness of our BAUML models. We are interested in considering the BAUML model as a whole, including the meaning of the tasks. To do so, we first translate our models into a well-known framework, a DCDS (Data-centric Dynamic System) to which then modelchecking techniques can be applied. However, DCDSs have been defined theoretically and there is no tool that implements them. For this reason, we also created a prototype tool, AuRUS-BAUML, which is able to translate our BAUML models into logic and to reason on their semantic correctness using an existing tool, SVTe. The integration between AuRUS-BAUML and SVTe is transparent to the user. Logically, the thesis also presents the logic translation which is performed by the tool.Els processos de negoci estan directament relacionats amb els objectius de negoci, i per tant és important que aquests processos es duguin a terme de la millor manera possible. Optar per modelar-los pot ajudar a aconseguir-ho, ja que els models proporcionen nombrosos avantatges. Per exemple: faciliten la comunicació entre les parts involucrades en el procés, proporcionen una base a partir del qual millorar-lo, i poden ajudar a gestionar-lo. Els processos es poden modelar des de diferents perspectives. El modelat tradicional de processos s'ha basat molt en la perspectiva anomenada "process-centric" (centrada en processos) o "activity-centric" (centrada en activitats), que posa l'èmfasi en la seqüència d'activitats o tasques que s'han d'executar, ignorant en gran mesura les dades necessàries per dur a terme aquestes tasques. Per altra banda, la perspectiva "artifact-centric" (centrada en artefactes) o "data-centric" es basa en definir les dades que necessiten les tasques i els detalls de les tasques en si, representant els canvis que aquestes fan a les dades. El framework BALSA defineix quatre dimensions que haurien de representar-se en qualsevol model artifact-centric: els artefactes de negoci (business artifacts), els cicles de vida (lifecycles), els serveis (services) i les associacions (associations). Utilitzant diferents tipus de models per representar aquestes dimensions porta a obtenir diverses representacions amb característiques diferents. Aquesta varietat de característiques farà que els models resultants siguin més apropiats per un propòsit o per un altre. Considerant això, en la primera part d'aquesta tesi proposem un framework, BAUML, per modelar processos de negoci seguint una perspectiva artifact-centric. El framework es basa en utilitzar una combinació de models UML i OCL, i el seu objectiu és obtenir una representació final del procés que sigui a la vegada comprensible i formal, per tal d'evitar ambigüitats i errors. Un cop definit el procés, és important assegurar-ne la qualitat. Això evitarà la propagació d'errors a la implementació final del procés. Malgrat que hi ha molts criteris de qualitat diferents, ens centrarem en la correctesa semàntica del model, per respondre a preguntes com ara "representa la realitat correctament?" o "conté errors o contradiccions?". En conseqüència, la segona part d'aquesta tesi se centra en buscar una manera per determinar la correctesa semàntica d'un model BAUML. Ens interessa considerar el model com un tot, incloent el significat de les tasques (és a dir, el detall del que fan). Per aconseguir-ho, primer traduïm les tasques a un framework reconegut, DCDSs (Data-centric Dynamic Systems). Un cop obtingut, s'hi poden aplicar tècniques de model-checking per determinar si compleix certes propietats. Malauradament, els DCDSs s'han definit a nivell teòric i no hi ha cap eina que els implementi. Per aquest motiu, hem creat un prototip d'eina, AuRUS-BAUML, que és capaç de traduir els nostres models BAUML a lògica i aplicar-hi tècniques de raonament per determinar-ne la correctesa semàntica. Per la part de raonament, l'AuRUS-BAUML fa servir una eina existent, l'SVTe. La integració entre l'AuRUS-BAUML i l'SVTe és transparent de cara a l'usuari. Lògicament, la tesi també presenta la traducció a lògica que porta a terme l'eina.Postprint (published version

Querying Visible and Invisible Information

We provide a wide-ranging study of the scenario where a subset of the relations in the schema are visible - that is, their complete contents are known - while the remaining relations are invisible. We also have integrity constraints (invariants given by logical sentences) which may relate the visible relations to the invisible ones. We want to determine which information about a query (a positive existential sentence) can be inferred from the visible instance and the constraints. We consider both positive and negative query information, that is, whether the query or its negation holds. We consider the instance-level version of the problem, where both the query and the visible instance are given, as well as the schema-level version, where we want to know whether truth or falsity of the query can be inferred in some instance of the schema

Separability in the Ambient Logic

The \it{Ambient Logic} (AL) has been proposed for expressing properties of process mobility in the calculus of Mobile Ambients (MA), and as a basis for query languages on semistructured data. We study some basic questions concerning the discriminating power of AL, focusing on the equivalence on processes induced by the logic $(=_L>)$. As underlying calculi besides MA we consider a subcalculus in which an image-finiteness condition holds and that we prove to be Turing complete. Synchronous variants of these calculi are studied as well. In these calculi, we provide two operational characterisations of $_=L$: a coinductive one (as a form of bisimilarity) and an inductive one (based on structual properties of processes). After showing $_=L$ to be stricly finer than barbed congruence, we establish axiomatisations of $_=L$ on the subcalculus of MA (both the asynchronous and the synchronous version), enabling us to relate $_=L$ to structural congruence. We also present some (un)decidability results that are related to the above separation properties for AL: the undecidability of $_=L$ on MA and its decidability on the subcalculus.Comment: logical methods in computer science, 44 page