Carlo Combi

AAMAS Conference 2026 Conference Paper

Centralized and Distributed approaches for restoring the Weak Controllability of Multi-Agent Interdependent STNUs

• Ajdin SUMIC
• Thierry Vidal
• Gauthier Picard
• Frédéric Maris
• Roberto Posenato
• Carlo Combi

This paper models the negative cycles that cause uncontrollability in Multi-Agent Interdependent Simple Temporal Networks with Uncertainty (MISTNU) as linear constraints, enabling (1) a fast centralized linear-programming repair and (2) a novel distributed constraint-reasoningapproachthattreatsthosecyclesasinter-agent DCOP constraints, preserving privacy, with a performance comparison between distributed solvers and a centralized baseline.

I&C Journal 2025 Journal Article

Modeling oracles in simple temporal networks with uncertainty

• Franziska S. Hollauf
• Roberto Posenato
• Carlo Combi
• Johann Eder

Simple temporal networks with uncertainty (STNUs) have achieved wide attention and are the basis of many applications requiring the representation of temporal constraints and checking whether they are conflicting. Dynamic controllability is currently the most studied notion to check whether a system can be controlled without violating temporal constraints despite uncertainties. However, dynamic controllability assumes that the actual duration of a contingent activity is known only when the end event of that activity occurs. The recently introduced notion of agile controllability considers the case where this duration is known earlier, leading to a more relaxed notion of temporal feasibility. We extend the definition of STNUs to STNUOs (Simple Temporal Networks with Uncertainty and Oracles) to represent the point in time at which information about a contingent duration is available. We formally define agile controllability as a generalization of dynamic controllability considering the timepoints of information availability. We propose a set of constraint propagation rules for STNUOs, leading to an algorithm for checking agile controllability.

TIME Conference 2024 Conference Paper

Agile Controllability of Simple Temporal Networks with Uncertainty and Oracles

• Johann Eder
• Roberto Posenato
• Carlo Combi
• Marco Franceschetti
• Franziska S. Hollauf

Simple temporal networks with uncertainty (STNUs) have achieved wide attention and are the basis of many applications requiring the representation of temporal constraints and checking whether they are conflicting. Dynamic controllability is currently the most relaxed notion to check whether a system can be controlled without violating temporal constraints despite uncertainties. However, dynamic controllability assumes that the actual duration of a contingent activity is only known when the end event of this activity takes place. The recently introduced notion of agile controllability considers when this duration is known earlier, leading to a more relaxed notion of temporal feasibility. We extend the definition of STNUs to STNUOs (Simple Temporal Networks with Uncertainty and Oracles) to represent the point in time at which information about a contingent duration is available. We formally define agile controllability as a generalization of dynamic controllability considering the timepoints of information availability. We propose a set of constraint propagation rules for STNUOs leading to an algorithm for checking agile controllability.

I&C Journal 2024 Journal Article

Predictive mining of multi-temporal relations

• Beatrice Amico
• Carlo Combi
• Romeo Rizzi
• Pietro Sala

In this paper, we propose a methodology for deriving a new kind of approximate temporal functional dependencies, called Approximate Predictive Functional Dependencies (APFDs), based on a three-window framework and on a multi-temporal relational model. Different features are proposed for the Observation Window (OW), where we observe predictive data, for the Waiting Window (WW), and for the Prediction Window (PW), where the predicted event occurs. We then consider the concept of approximation for such APFDs, introduce new error measures, and discuss different strategies for deriving APFDs. We discuss the quality, i. e. , the informative content, of the derived AFDs by considering their entropy and information gain. Moreover, we outline the results in deriving APFDs focusing on the Acute Kidney Injury (AKI). We use real clinical data contained in the MIMIC III dataset related to patients from Intensive Care Units to show the applicability of our approach to real-world data.

TIME Conference 2023 Conference Paper

Discovering Predictive Dependencies on Multi-Temporal Relations

• Beatrice Amico
• Carlo Combi
• Romeo Rizzi
• Pietro Sala

In this paper, we propose a methodology for deriving a new kind of approximate temporal functional dependencies, called Approximate Predictive Functional Dependencies (APFDs), based on a three-window framework and on a multi-temporal relational model. Different features are proposed for the Observation Window (OW), where we observe predictive data, for the Waiting Window (WW), and for the Prediction Window (PW), where the predicted event occurs. We then discuss the concept of approximation for such APFDs, introduce two new error measures. We prove that the problem of deriving APFDs is intractable. Moreover, we discuss some preliminary results in deriving APFDs from real clinical data using MIMIC III dataset, related to patients from Intensive Care Units.

AIIM Journal 2022 Journal Article

A manifesto on explainability for artificial intelligence in medicine

• Carlo Combi
• Beatrice Amico
• Riccardo Bellazzi
• Andreas Holzinger
• Jason H. Moore
• Marinka Zitnik
• John H. Holmes

The rapid increase of interest in, and use of, artificial intelligence (AI) in computer applications has raised a parallel concern about its ability (or lack thereof) to provide understandable, or explainable, output to users. This concern is especially legitimate in biomedical contexts, where patient safety is of paramount importance. This position paper brings together seven researchers working in the field with different roles and perspectives, to explore in depth the concept of explainable AI, or XAI, offering a functional definition and conceptual framework or model that can be used when considering XAI. This is followed by a series of desiderata for attaining explainability in AI, each of which touches upon a key domain in biomedicine.

I&C Journal 2021 Journal Article

Consistency checking of STNs with decisions: Managing temporal and access-control constraints in a seamless way

• Matteo Zavatteri
• Carlo Combi
• Romeo Rizzi
• Luca Viganò

A Simple Temporal Network (STN) consists of time points modeling temporal events and constraints modeling the minimal and maximal temporal distance between them. A Simple Temporal Network with Decisions (STND) extends an STN to model temporal plans with decisions. STNDs label time points and constraints by conjunctions of literals saying for which scenarios (i. e. , complete truth value assignments to the propositions) they are relevant. In this paper, we deal with the use of STNDs for modeling and synthesizing execution strategies. We propose an incremental hybrid SAT-based consistency checking algorithm for STNDs that is faster than the one previously proposed and allows for the synthesis of all consistent scenarios and related early execution schedules (offline temporal planning). We carry out an experimental evaluation with Kappa, a tool that we developed for STNDs. We also show that any STND can be easily translated into a disjunctive temporal network and vice versa.

AIIM Journal 2021 Journal Article

Publishing Artificial Intelligence Research Papers: A Tale of Three Journals

• Edward H. Shortliffe
• Mor Peleg
• Carlo Combi
• Anthony C. Chang
• Justyna Vinci

JAIR Journal 2019 Journal Article

Conditional Simple Temporal Networks with Uncertainty and Resources

• Carlo Combi
• Roberto Posenato
• Luca Viganò
• Matteo Zavatteri

Conditional simple temporal networks with uncertainty (CSTNUs) allow for the representation of temporal plans subject to both conditional constraints and uncertain durations. Dynamic controllability (DC) of CSTNUs ensures the existence of an execution strategy able to execute the network in real time (i.e., scheduling the time points under control) depending on how these two uncontrollable parts behave. However, CSTNUs do not deal with resources. In this paper, we define conditional simple temporal networks with uncertainty and resources (CSTNURs) by injecting resources and runtime resource constraints (RRCs) into the specification. Resources are mandatory for executing the time points and their availability is represented through temporal expressions, whereas RRCs restrict resource availability by further temporal constraints among resources. We provide a fully-automated encoding to translate any CSTNUR into an equivalent timed game automaton in polynomial time for a sound and complete DC-checking.

TIME Conference 2019 Conference Paper

Customizing BPMN Diagrams Using Timelines

• Carlo Combi
• Barbara Oliboni
• Pietro Sala

BPMN (Business Process Model and Notation) is widely used standard modeling technique for representing Business Processes by using diagrams, but lacks in some aspects. Representing execution-dependent and time-dependent decisions in BPMN Diagrams may be a daunting challenge [Carlo Combi et al. , 2017]. In many cases such constraints are omitted in order to preserve the simplicity and the readability of the process model. However, for purposes such as compliance checking, process mining, and verification, formalizing such constraints could be very useful. In this paper, we propose a novel approach for annotating BPMN Diagrams with Temporal Synchronization Rules borrowed from the timeline-based planning field. We discuss the expressivity of the proposed approach and show that it is able to capture a lot of complex temporally-related constraints without affecting the structure of BPMN diagrams. Finally, we provide a mapping from annotated BPMN diagrams to timeline-based planning problems that allows one to take advantage of the last twenty years of theoretical and practical developments in the field.

TIME Conference 2019 Conference Paper

Hybrid SAT-Based Consistency Checking Algorithms for Simple Temporal Networks with Decisions

• Matteo Zavatteri
• Carlo Combi
• Romeo Rizzi
• Luca Viganò 0001

A Simple Temporal Network (STN) consists of time points modeling temporal events and constraints modeling the minimal and maximal temporal distance between them. A Simple Temporal Network with Decisions (STND) extends an STN by adding decision time points to model temporal plans with decisions. A decision time point is a special kind of time point that once executed allows for deciding a truth value for an associated Boolean proposition. Furthermore, STNDs label time points and constraints by conjunctions of literals saying for which scenarios (i. e. , complete truth value assignments to the propositions) they are relevant. Thus, an STND models a family of STNs each obtained as a projection of the initial STND onto a scenario. An STND is consistent if there exists a consistent scenario (i. e. , a scenario such that the corresponding STN projection is consistent). Recently, a hybrid SAT-based consistency checking algorithm (HSCC) was proposed to check the consistency of an STND. Unfortunately, that approach lacks experimental evaluation and does not allow for the synthesis of all consistent scenarios. In this paper, we propose an incremental HSCC algorithm for STNDs that (i) is faster than the previous one and (ii) allows for the synthesis of all consistent scenarios and related early execution schedules (offline temporal planning). Then, we carry out an experimental evaluation with KAPPA, a tool that we developed for STNDs. Finally, we prove that STNDs and disjunctive temporal networks (DTNs) are equivalent.

JBHI Journal 2019 Journal Article

Normalizing Spontaneous Reports Into MedDRA: Some Experiments With <inline-formula> <tex-math notation="LaTeX">$\mathsf{MagiCoder}$</tex-math> </inline-formula>

• Carlo Combi
• Margherita Zorzi
• Gabriele Pozzani
• Elena Arzenton
• Ugo Moretti

Text normalization into medical dictionaries is useful to support clinical tasks. A typical setting is pharmacovigilance (PV). The manual detection of suspected adverse drug reactions (ADRs) in narrative reports is time consuming and natural language processing (NLP) provides a concrete help to PV experts. In this paper, we carry out experiments for testing performances of MagiCoder, an NLP application designed to extract MedDRA terms from narrative clinical text. Given a narrative description, MagiCoder proposes an automatic encoding. The pharmacologist reviews, (possibly) corrects, and then, validates the solution. This drastically reduces the time needed for the validation of reports with respect to a completely manual encoding. In previous work, we mainly tested MagiCoder performances on Italian written spontaneous reports. In this paper, we include some new features, change the experiment design, and carry on more tests about MagiCoder. Moreover, we do a change of language, moving to English documents. In particular, we tested MagiCoder on the CADEC dataset, a corpus of manually annotated posts about ADRs collected from the social media.

TIME Conference 2018 Conference Paper

Extending Conditional Simple Temporal Networks with Partially Shrinkable Uncertainty

• Carlo Combi
• Roberto Posenato

The proper handling of temporal constraints is crucial in many domains. As a particular challenge, temporal constraints must be also handled when different specific situations happen (conditional constraints) and when some event occurrences can be only observed at run time (contingent constraints). In this paper we introduce Conditional Simple Temporal Networks with Partially Shrinkable Uncertainty (CSTNPSUs), in which contingent constraints are made more flexible (guarded constraints) and they are also specified as conditional constraints. It turns out that guarded constraints require the ability to reason on both kinds of constraints in a seamless way. In particular, we discuss CSTNPSU features through a motivating example and, then, we introduce the concept of controllability for such networks and the related sound checking algorithm.

AIIM Journal 2017 Journal Article

Editorial from the new Editor-in-Chief: Artificial Intelligence in Medicine and the forthcoming challenges

• Carlo Combi

TIME Conference 2017 Conference Paper

Incorporating Decision Nodes into Conditional Simple Temporal Networks

• Massimo Cairo
• Carlo Combi
• Carlo Comin
• Luke Hunsberger
• Roberto Posenato
• Romeo Rizzi
• Matteo Zavatteri

A Conditional Simple Temporal Network (CSTN) augments a Simple Temporal Network (STN) to include special time-points, called observation time-points. In a CSTN, the agent executing the network controls the execution of every time-point. However, each observation time-point has a unique propositional letter associated with it and, when the agent executes that time-point, the environment assigns a truth value to the corresponding letter. Thus, the agent observes but, does not control the assignment of truth values. A CSTN is dynamically consistent (DC) if there exists a strategy for executing its time-points such that all relevant constraints will be satisfied no matter which truth values the environment assigns to the propositional letters. Alternatively, in a Labeled Simple Temporal Network (Labeled STN) - also called a Temporal Plan with Choice - the agent executing the network controls the assignment of values to the so-called choice variables. Furthermore, the agent can make those assignments at any time. For this reason, a Labeled STN is equivalent to a Disjunctive Temporal Network. This paper incorporates both of the above extensions by augmenting a CSTN to include not only observation time-points but also decision time-points. A decision time-point is like an observation time-point in that it has an associated propositional letter whose value is determined when the decision time-point is executed. It differs in that the agent - not the environment - selects that value. The resulting network is called a CSTN with Decisions (CSTND). This paper shows that a CSTND generalizes both CSTNs and Labeled STNs, and proves that the problem of determining whether any given CSTND is dynamically consistent is PSPACE-complete. It also presents algorithms that address two sub-classes of CSTNDs: (1) those that contain only decision time-points; and (2) those in which all decisions are made before execution begins.

TIME Conference 2015 Conference Paper

A Sound-and-Complete Propagation-Based Algorithm for Checking the Dynamic Consistency of Conditional Simple Temporal Networks

• Luke Hunsberger
• Roberto Posenato
• Carlo Combi

A Conditional Simple Temporal Network (CSTN) is a data structure for representing and reasoning about time-points and temporal constraints, some of which may apply only in certain scenarios. The scenarios in a CSTN are represented by conjunctions of propositional literals whose truth values are not known in advance, but instead are observed in real time, during execution. The most important property of a CSTN is whether it is dynamically consistent (DC), that is, whether there exists a strategy for executing its time-points such that all relevant constraints are guaranteed to be satisfied no matter which scenario is incrementally revealed during execution. Prior approaches to determining the dynamic consistency of CSTNs (a. k. a. , solving the Conditional Simple Temporal Problem) are primarily of theoretical interest, they have not been realized in practical algorithms. This paper presents a sound-and-complete DC-checking algorithm for CSTNs that is based on the propagation of constraints labeled by propositions. The paper also presents an empirical evaluation of the new algorithm that demonstrates that it may be practical for a variety of applications. This is the first empirical evaluation of any DC-checking algorithm for CSTNs ever reported in the literature.

AIIM Journal 2015 Journal Article

Spatiotemporal data visualisation for homecare monitoring of elderly people

• Jose M. Juarez
• Jose M. Ochotorena
• Manuel Campos
• Carlo Combi

Objective Elderly people who live alone can be assisted by home monitoring systems that identify risk scenarios such as falls, fatigue symptoms or burglary. Given that these systems have to manage spatiotemporal data, human intervention is required to validate automatic alarms due to the high number of false positives and the need for context interpretation. The goal of this work was to provide tools to support human action, to identify such potential risk scenarios based on spatiotemporal data visualisation. Methods and materials We propose the MTA (multiple temporal axes) model, a visual representation of temporal information of the activity of a single person at different locations. The main goal of this model is to visualize the behaviour of a person in their home, facilitating the identification of health-risk scenarios and repetitive patterns. We evaluate the model's insight capacity compared with other models using a standard evaluation protocol. We also test its practical suitability of the MTA graphical model in a commercial home monitoring system. In particular, we implemented 8VISU, a visualization tool based on MTA. Results MTA proved to be more than 90% accurate in identify non-risk scenarios, independently of the length of the record visualised. When the spatial complexity was increased (e. g. number of rooms) the model provided good accuracy form up to 5 rooms. Therefore, user preferences and user performance seem to be balanced. Moreover, it also gave high sensitivity levels (over 90%) for 5–8 rooms. Fall is the most recurrent incident for elderly people. The MTA model outperformed the other models considered in identifying fall scenarios (66% of correctness) and was the second best for burglary and fatigue scenarios (36% of correctness). Our experiments also confirm the hypothesis that cyclic models are the most suitable for fatigue scenarios, the Spiral and MTA models obtaining most positive identifications. Conclusions In home monitoring systems, spatiotemporal visualization is a useful tool for identifying risk and preventing home accidents in elderly people living alone. The MTA model helps the visualisation in different stages of the temporal data analysis process. In particular, its explicit representation of space and movement is useful for identifying potential scenarios of risk, while the spiral structure can be used for the identification of recurrent patterns. The results of the experiments and the experience using the visualization tool 8VISU proof the potential of the MTA graphical model to mine temporal data and to support caregivers using home monitoring infrastructures.

TIME Conference 2015 Conference Paper

The Price of Evolution in Temporal Databases

• Carlo Combi
• Romeo Rizzi
• Pietro Sala

Temporal Functional Dependencies (TFDs for short) are functional dependencies that predicate on temporal databases characterized by a special temporal dimension called valid time (VT). In [1] Combi et al. proposed a uniform framework that subsumes many of the TFDs proposed in literature and, by the combination of them, allow us to express finer constraints. Some interesting constraints are the Temporally Mixed Functional Dependencies (TMFD for short) that allow one to write constraints on the evolution of the data in the database. The problem of checking a TMFD against an instance of a temporal schema is polynomial. We will show that when approximation comes into play (i. e. , we look for TMFD holding for almost all database tuples) the problem turns out to be NP-Complete. Moreover we introduce a type of association rules build over TMFD called Temporally Mixed Association Rule (TMAR). We prove that verifying TMAR under approximation is still NP-Complete, by reducing it to a novel problem on directed acyclic graphs.

AIIM Journal 2015 Journal Article

Thirty years of artificial intelligence in medicine (AIME) conferences: A review of research themes

• Niels Peek
• Carlo Combi
• Roque Marin
• Riccardo Bellazzi

Background Over the past 30 years, the international conference on Artificial Intelligence in MEdicine (AIME) has been organized at different venues across Europe every 2 years, establishing a forum for scientific exchange and creating an active research community. The Artificial Intelligence in Medicine journal has published theme issues with extended versions of selected AIME papers since 1998. Objectives To review the history of AIME conferences, investigate its impact on the wider research field, and identify challenges for its future. Methods We analyzed a total of 122 session titles to create a taxonomy of research themes and topics. We classified all 734 AIME conference papers published between 1985 and 2013 with this taxonomy. We also analyzed the citations to these conference papers and to 55 special issue papers. Results We identified 30 research topics across 12 themes. AIME was dominated by knowledge engineering research in its first decade, while machine learning and data mining prevailed thereafter. Together these two themes have contributed about 51% of all papers. There have been eight AIME papers that were cited at least 10 times per year since their publication. Conclusions There has been a major shift from knowledge-based to data-driven methods while the interest for other research themes such as uncertainty management, image and signal processing, and natural language processing has been stable since the early 1990s. AIME papers relating to guidelines and protocols are among the most highly cited.

AIIM Journal 2013 Journal Article

Artificial intelligence in medicine AIME 2011

• Mor Peleg
• Carlo Combi

TAAS Journal 2012 Journal Article

Conceptual modeling of flexible temporal workflows

• Carlo Combi
• Matteo Gozzi
• Roberto Posenato
• Giuseppe Pozzi

Workflow technology has emerged as one of the leading technologies in modeling, redesigning, and executing business processes. The management of temporal aspects in the definition of a workflow process has been considered only recently in the literature. Currently available Workflow Management Systems ( WfMS ) and research prototypes offer a very limited support for the definition, detection, and management of temporal constraints over business processes. In this article, we propose a new advanced workflow conceptual model for expressing time constraints in business processes and we present a general technique to check different levels of temporal consistency for workflow schemata at process design time: since a time constraint can be satisfied in different ways, we propose a classification of temporal workflows according to the way time constraints are satisfied. Such classification can be used to successfully manage flexible workflows at runtime.

AIIM Journal 2012 Journal Article

Visually defining and querying consistent multi-granular clinical temporal abstractions

• Carlo Combi
• Barbara Oliboni

Objective The main goal of this work is to propose a framework for the visual specification and query of consistent multi-granular clinical temporal abstractions. We focus on the issue of querying patient clinical information by visually defining and composing temporal abstractions, i. e. , high level patterns derived from several time-stamped raw data. In particular, we focus on the visual specification of consistent temporal abstractions with different granularities and on the visual composition of different temporal abstractions for querying clinical databases. Background Temporal abstractions on clinical data provide a concise and high-level description of temporal raw data, and a suitable way to support decision making. Granularities define partitions on the time line and allow one to represent time and, thus, temporal clinical information at different levels of detail, according to the requirements coming from the represented clinical domain. The visual representation of temporal information has been considered since several years in clinical domains. Proposed visualization techniques must be easy and quick to understand, and could benefit from visual metaphors that do not lead to ambiguous interpretations. Recently, physical metaphors such as strips, springs, weights, and wires have been proposed and evaluated on clinical users for the specification of temporal clinical abstractions. Visual approaches to boolean queries have been considered in the last years and confirmed that the visual support to the specification of complex boolean queries is both an important and difficult research topic. Methodology We propose and describe a visual language for the definition of temporal abstractions based on a set of intuitive metaphors (striped wall, plastered wall, brick wall), allowing the clinician to use different granularities. A new algorithm, underlying the visual language, allows the physician to specify only consistent abstractions, i. e. , abstractions not containing contradictory conditions on the component abstractions. Moreover, we propose a visual query language where different temporal abstractions can be composed to build complex queries: temporal abstractions are visually connected through the usual logical connectives AND, OR, and NOT. Results The proposed visual language allows one to simply define temporal abstractions by using intuitive metaphors, and to specify temporal intervals related to abstractions by using different temporal granularities. The physician can interact with the designed and implemented tool by point-and-click selections, and can visually compose queries involving several temporal abstractions. The evaluation of the proposed granularity-related metaphors consisted in two parts: (i) solving 30 interpretation exercises by choosing the correct interpretation of a given screenshot representing a possible scenario, and (ii) solving a complex exercise, by visually specifying through the interface a scenario described only in natural language. The exercises were done by 13 subjects. The percentage of correct answers to the interpretation exercises were slightly different with respect to the considered metaphors (54. 4 – striped wall, 73. 3 – plastered wall, 61 – brick wall, and 61 – no wall), but post hoc statistical analysis on means confirmed that differences were not statistically significant. The result of the user's satisfaction questionnaire related to the evaluation of the proposed granularity-related metaphors ratified that there are no preferences for one of them. The evaluation of the proposed logical notation consisted in two parts: (i) solving five interpretation exercises provided by a screenshot representing a possible scenario and by three different possible interpretations, of which only one was correct, and (ii) solving five exercises, by visually defining through the interface a scenario described only in natural language. Exercises had an increasing difficulty. The evaluation involved a total of 31 subjects. Results related to this evaluation phase confirmed us about the soundness of the proposed solution even in comparison with a well known proposal based on a tabular query form (the only significant difference is that our proposal requires more time for the training phase: 21min versus 14min). Discussion and conclusions In this work we have considered the issue of visually composing and querying temporal clinical patient data. In this context we have proposed a visual framework for the specification of consistent temporal abstractions with different granularities and for the visual composition of different temporal abstractions to build (possibly) complex queries on clinical databases. A new algorithm has been proposed to check the consistency of the specified granular abstraction. From the evaluation of the proposed metaphors and interfaces and from the comparison of the visual query language with a well known visual method for boolean queries, the soundness of the overall system has been confirmed; moreover, pros and cons and possible improvements emerged from the comparison of different visual metaphors and solutions.

AIIM Journal 2011 Journal Article

Artificial Intelligence in Medicine AIME 2009

• Yuval Shahar
• Carlo Combi

AIIM Journal 2011 Journal Article

Mario Stefanelli, 1945–2010

• Riccardo Bellazzi
• Carlo Combi
• Silvana Quaglini

TIME Conference 2011 Conference Paper

Temporal Functional Dependencies Based on Interval Relations

• Carlo Combi
• Pietro Sala

In the last years the representation and management of temporal information has become crucial for several computer applications. In the temporal database literature, every fact stored into a database may be equipped with two temporal dimensions: the valid time, that describes the time when the fact is true in the modeled reality, and the transaction time, that describes the time when the fact is current in the database and it can be retrieved. Temporal functional dependencies (TFDs) add (transaction) valid time to classical functional dependencies (FDs) in order to express database integrity constraints over the flow of time. Currently, proposals dealing with TFDs adopt a point-based approach, where tuples hold at specific time points. Moreover, TFDs may involve the use of different granularities (i. e. , partitions of the time domain), to express integrity constraints as "for each month, the salary of an employee depends only on his role". At the best of our knowledge, there are no proposals dealing with interval-based temporal functional dependencies (ITFDs for short) where the associated valid time is represented by an interval. In this paper, we propose a set of ITFDs based on the Allen's interval relations, we analyze their expressive power with respect to other TFDs proposed in the literature and we propose an algorithm for verifying ITFDs in a database system.

TIME Conference 2010 Conference Paper

Towards Temporal Controllabilities for Workflow Schemata

• Carlo Combi
• Roberto Posenato

The modelling and management of temporal constraints over business processes has received some attention in the past years. Recently, we have introduced and discussed the concept of "controllability" for workflow schemata modelling real world business processes: controllability, originally introduced in the AI community for temporal constraint networks, refers to the capability of executing a workflow for all possible durations of all tasks. In this paper, we first extend the execution strategy proposed by Morris, Muscettola and Vidal in the context of temporal constraint networks, to deal with the execution of business processes in a more suitable way. Then, we discuss and propose a new algorithm to deal with the (dynamic) controllability of an overall workflow schema, where several, possibly disjoint, execution paths are possible, due to the presence of alternative paths in the workflow schema. We show that the presence of several controllable alternative execution paths in a workflow schema does not guarantee that the overall workflow schema is controllable.

TIME Conference 2009 Conference Paper

Building Logical Specifications of Temporal Granularities through Algebraic Operators

• Carlo Combi
• Sara Degani

Logical and algebraic approaches have been proposed in the literature for the definition and the management of time granularities. In the algebraic framework, a bottom granularity is assumed, and new granularities are created by means of suitable algebraic operators. In the logical framework, mathematical structures are used to represent time granularities, and logical formulae are used to specify meaningful properties between them. In this paper we extend the logical approach of Combi et al. for representing and reasoning about temporal granularities, defining logical formulae corresponding to calendar algebra operators. This approach allows one to define a large set of granularities, possibly corresponding to complex formulae, in a natural way. Indeed, it gives the possibility of specifying granularity-related formulae in an easier way through operators that are intuitive and natural as the algebraic ones, still maintaining the capability of reasoning on granularities through the (formal) techniques that have been deeply investigated for the logical framework.

AIIM Journal 2009 Journal Article

Temporal similarity measures for querying clinical workflows

• Carlo Combi
• Matteo Gozzi
• Barbara Oliboni
• Jose M. Juarez
• Roque Marin

Objective In this paper, we extend a preliminary proposal and discuss in a deeper and more formal way an approach to evaluate temporal similarity between clinical workflow cases (i. e. , executions of clinical processes). More precisely, we focus on (i) the representation of clinical processes by using a temporal conceptual workflow model; (ii) the definition of ad hoc temporal constraint networks to formally represent clinical workflow cases; (iii) the definition of temporal similarity for clinical workflow cases based on the comparison of temporal constraint networks; (iv) the management of the similarity of clinical processes related to the Italian guideline for stroke prevention and management (SPREAD). Background Clinical processes are composed by clinical activities to be done by given actors in a given order satisfying given temporal constraints. This description means that clinical processes can be seen as organizational processes, and modeled by workflow schemata. When a workflow schema represents a clinical process, its cases represent different instances derived from dealing with different patients in different situations. With respect to all the cases related to a workflow schema, each clinical case can be different with respect to its structure and to its temporal aspects. Clinical cases can be stored in clinical databases and information retrieval can be done evaluating the similarity between workflow cases. Methodology We first describe a possible approach to the conceptual modeling of a clinical process, by using a temporally extended workflow model. Then, we define how a workflow case can be represented as a set of activities, and show how to express them through temporal constraint networks. Once we have built temporal constraint networks related to the cases to compare, we propose a similarity function able to evaluate the differences between the considered cases with respect to the order and duration of corresponding activities, and with respect to the presence/absence of some activities. Results In this work, we propose an approach to evaluate temporal similarity between workflow cases. The proposed approach can be used (i) to query clinical databases storing clinical cases representing activities related to the management of different patients in different situations; (ii) to evaluate the quality of the service comparing the similarity between a (possibly synthetic) case, perceived as the good one with respect to a given clinical situation, and the other clinical cases; and (iii) to retrieve a particular class of cases similar to an interesting one.

TIME Conference 2008 Conference Paper

Towards a Formal Framework for Spatio-Temporal Granularities

• Alberto Belussi
• Carlo Combi
• Gabriele Pozzani

In the spatial context, the research community has not reached yet a widely accepted definition of granularity. There are relatively few papers about "spatial granularities " and many of them give different definitions and often refer to different interpretations of the term "spatial granularity". In this work we propose a formal definition of "spatial granularity" and other related terms involved in the spatial context, as happened for the temporal one. After that, we will merge together our framework for spatial granularity with the usual framework for temporal granularity, giving a definition of spatio-temporal granularity able to manage information about spatial granularities changing over time.

AIIM Journal 2008 Journal Article

Visual MRI: Merging information visualization and non-parametric clustering techniques for MRI dataset analysis

• Umberto Castellani
• Marco Cristani
• Carlo Combi
• Vittorio Murino
• Andrea Sbarbati
• Pasquina Marzola

Objective This paper presents Visual MRI, an innovative tool for the magnetic resonance imaging (MRI) analysis of tumoral tissues. The main goal of the analysis is to separate each magnetic resonance image in meaningful clusters, highlighting zones which are more probably related with the cancer evolution. Such non-invasive analysis serves to address novel cancer treatments, resulting in a less destabilizing and more effective type of therapy than the chemotherapy-based ones. The advancements brought by Visual MRI are two: first, it is an integration of effective information visualization (IV) techniques into a clustering framework, which separates each MRI image in a set of informative clusters; the second improvement relies in the clustering framework itself, which is derived from a recently re-discovered non-parametric grouping strategy, i. e. , the mean shift. Methodology The proposed methodology merges visualization methods and data mining techniques, providing a computational framework that allows the physician to move effectively from the MRI image to the images displaying the derived parameter space. An unsupervised non-parametric clustering algorithm, derived from the mean shift paradigm, and called MRI-mean shift, is the novel data mining technique proposed here. The main underlying idea of such approach is that the parameter space is regarded as an empirical probability density function to estimate: the possible separate modes and their attraction basins represent separated clusters. The mean shift algorithm needs sensibility threshold values to be set, which could lead to highly different segmentation results. Usually, these values are set by hands. Here, with the MRI-mean shift algorithm, we propose a strategy based on a structured optimality criterion which faces effectively this issue, resulting in a completely unsupervised clustering framework. A linked brushing visualization technique is then used for representing clusters on the parameter space and on the MRI image, where physicians can observe further anatomical details. In order to allow the physician to easily use all the analysis and visualization tools, a visual interface has been designed and implemented, resulting in a computational framework susceptible of evaluation and testing by physicians. Results Visual MRI has been adopted by physicians in a real clinical research setting. To describe the main features of the system, some examples of usage on real cases are shown, following step by step all the actions scientists can do on an MRI image. To assess the contribution of Visual MRI given to the research setting, a validation of the clustering results in a medical sense has been carried out. Conclusions From a general point of view, the two main objectives reached in this paper are: (1) merging information visualization and data mining approaches to support clinical research and (2) proposing an effective and fully automated clustering technique. More particularly, a new application for MRI data analysis, named Visual MRI, is proposed, aiming at improving the support of medical researchers in the context of cancer therapy; moreover, a non-parametric technique for cluster analysis, named MRI-mean shift, has been drawn. The results show the effectiveness and the efficacy of the proposed application.

TIME Conference 2007 Conference Paper

Conceptual Modeling of Temporal Clinical Workflows

• Carlo Combi
• Matteo Gozzi
• José M. Juárez
• Barbara Oliboni
• Giuseppe Pozzi

The diffusion of clinical guidelines to describe the proper way to deal with patients' situations is spreading out and opens new issues in the context of modeling and managing (temporal) information about medical activities. Guidelines can be seen as processes describing the sequence of activities to be executed, and thus approaches proposed in the business context can be used to model them. In this paper, we propose a general conceptual workflow model, considering both activities and their temporal properties, and focus on the representation of clinical guidelines by the proposed model.

TIME Conference 2006 Conference Paper

Representing trends and trend dependencies with multiple granularities

• Carlo Combi
• Rosalba Rossato

In this paper we propose a formal framework allowing the expression of temporal trends which involve multiple granularities. We first discuss the representation of trend dependencies and then we propose a characterization of trends according to different temporal features considering also the relationships with the specific temporal granularities involved in the trend definition. A suitable temporal logic is introduced to formally represent time-evolving relations, granularities and granular trends

TIME Conference 2006 Conference Paper

Task Scheduling for a TemporalWorkflow Management System

• Carlo Combi
• Giuseppe Pozzi

A workflow management system (WfMS) supports the coordinated execution of simple activities (tasks), assigning them to human or automatic executors (agents), to achieve the goal defined for a business process. The workflow scheduler performs task assignment policies: temporal aspects, such as availability time and skills of agents, deadlines for task completion, constraints over timestamps for task activation, periodic constraints cannot be neglected. By this paper we propose a temporal workflow scheduler which pervasively considers all the temporalities affecting task assignment policies

AIIM Journal 2006 Journal Article

Temporal representation and reasoning in medicine

• Carlo Combi
• Giuseppe Pozzi

AIIM Journal 2006 Journal Article

Temporal representation and reasoning in medicine: Research directions and challenges

• Klaus-Peter Adlassnig
• Carlo Combi
• Amar K. Das
• Elpida T. Keravnou
• Giuseppe Pozzi

Objective The main aim of this paper is to propose and discuss promising directions of research in the field of temporal representation and reasoning in medicine, taking into account the recent scientific literature and challenging issues of current interest as viewed from the different research perspectives of the authors of the paper. Background Temporal representation and reasoning in medicine is a well-known field of research in the medical as well as computer science community. It encompasses several topics, such as summarizing data from temporal clinical databases, reasoning on temporal clinical data for therapeutic assessments, and modeling uncertainty in clinical knowledge and data. It is also related to several medical tasks, such as monitoring intensive care patients, providing treatments for chronic patients, as well as planning and scheduling clinical routine activities within complex healthcare organizations. Methodology The authors jointly identified significant research areas based on their importance as for temporal representation and reasoning issues; the subjects were considered to be promising topics of future activity. Every subject was addressed in detail by one or two authors and then discussed with the entire team to achieve a consensus about future fields of research. Results We identified and focused on four research areas, namely (i) fuzzy logic, time, and medicine, (ii) temporal reasoning and data mining, (iii) health information systems, business processes, and time, and (iv) temporal clinical databases. For every area, we first highlighted a few basic notions that would permit any reader—including those who are unfamiliar with the topic—to understand the main goals. We then discuss interesting and promising directions of research, taking into account the recent literature and underlining the yet unresolved medical/clinical issues that deserve further scientific investigation. The considered research areas are by no means disjointed, because they share common theoretical and methodological features. Moreover, subjects of imminent interest in medicine are represented in many of the fields considered. Conclusions We propose and discuss promising subjects of future research that deserve investigation to develop software systems that will properly manage the multifaceted temporal aspects of information and knowledge encountered by physicians during their clinical work. As the subjects of research have resulted from merging the different perspectives of the authors involved in this study, we hope the paper will succeed in stimulating discussion and multidisciplinary work in the described fields of research.

TIME Conference 2005 Conference Paper

A Uniform Algebraic Characterization of Temporal Functional Dependencies

• Carlo Combi
• Angelo Montanari
• Rosalba Rossato

In the database literature, different types of temporal functional dependencies (TFDs) have been proposed to constrain the temporal evolution of information. Unfortunately, the lack of a common notation makes it difficult to compare, to integrate, and to possibly extend the various proposals. In this paper, we outline a unifying algebraic framework for TFDs. We first introduce the proposed approach, then we use it to give a uniform account of existing TFDs, and finally we show that it allows one to easily express new meaningful TFDs.

AIIM Journal 2005 Journal Article

Merging multimedia presentations and semistructured temporal data: a graph-based model and its application to clinical information

• Carlo Combi
• Barbara Oliboni
• Rosalba Rossato

Objective: In this paper, we focus on the issue of providing physicians with the capability of representing in a seamless way both temporal aspects of multimedia semistructured data and their temporal presentation requirements. Background: Semistructured data are data having some structure, that may be irregular or incomplete and does not necessarily conform to a fixed schema. Semistructured data often contain the description of histories of the considered real world. The eXtensible Markup Language (XML) is becoming a cross compatible and standardized means for representing semistructured clinical data. In the field of medical informatics, there are many ongoing activities concerning XML. In the field of multimedia database systems, the topic related to the integration of several media objects (with their temporal aspects) have been considered both for data modeling and querying issues and for modeling multimedia presentations. Methodology: We first propose the Multimedia Temporal Graphical Model (MTGM), by representing a clinical database for cardiology patients undergoing cardiac angiographies and then describe it in a formal way. We deal with the problem of expressing MTGM data by XML and of managing MTGM clinical data through an XML-based system. We provide both a technique for translating (a part of) an MTGM database into an XML document and some techniques allowing us to obtain presentations defined by means of the Synchronized Multimedia Integration Language (SMIL) from MTGM presentations. Results: MTGM allows one to represent and store clinical information in a semistructured, temporal, and multimedia database. The physician can define multimedia presentations based on the stored data. Multimedia presentations are then stored in the same MTGM database together with temporal clinical information and are thus represented according to the same data model. A prototype based on an XML native database system has been designed and implemented. Discussion and conclusions: In this work we have considered the theoretical and methodological issues concerning the definition of a general data model for describing temporal and multimedia features of semistructured clinical information. Other research and application oriented features, which have not been considered in MTGM, could be investigated for completing MTGM with regard to its applicability to clinical domains: MTGM does not allow one to express times at different levels of granularities, i. e. with different time units, or with indeterminacy; besides the considered valid time, it could be interesting to manage also other temporal dimensions such as the transaction and availability times. Besides being useful for managing multimedia data stored according to widely accepted standards as MPEG and DICOM, nowadays semistructured data, and XML in particular, are becoming the most important way for expressing and exchanging medical knowledge and data: MTGM can be considered as a data model allowing the seamless representation of both (multimedia and temporal) clinical data and knowledge.

TIME Conference 2002 Conference Paper

A Logical Approach to Represent and Reason about Calendars

• Carlo Combi
• Massimo Franceschet
• Adriano Peron

We propose a logical approach to represent and reason about different time granularities. We identify a time granularity as a discrete infinite sequence of time points properly labelled with proposition symbols marking the starting and ending points of the corresponding granules, and we intensively model sets of granularities with linear time logic formulas. Some real-world granularities are provided to motivate and exemplify our approach. The proposed framework permits to algorithmically solve the consistency, the equivalence, and the classification problems in a uniform way, by reducing them to the validity problem for the considered linear time logic.

TIME Conference 2001 Conference Paper

Representation of Temporal Intervals and Relations: Information Visualization Aspects and their Evaluation

• Luca Chittaro
• Carlo Combi

A crucial component for turning any temporal reasoning system into a real-world application that can be adopted by a wide base of users is given by its user interface. After analyzing and discussing the state of the art for the visualization of temporal intervals and relations, this paper proposes three new solutions, also evaluating them with a proper user study.

TIME Conference 2000 Conference Paper

Modeling Temporal Aspects of Visual and Textual Objects in Multimedia Databases

• Carlo Combi

We consider the problem of modeling temporal aspects of visual and related textual entities in multimedia databases, within the framework of an object-oriented temporal data model. We distinguish two different time aspects in multimedia visual data: intrinsic time, i. e. , the time managed according to the sequence of frames composing a visual data item, and extrinsic time, i. e. , the (valid) time of the real world represented by the visual data item. We also propose a three-layered approach for composing temporal visual data. Relationships between visual data and related textual data are then considered: we propose a taxonomy for temporal textural observations on visual data, based on their temporal properties. In relation to textural temporal data and visual data, we consider the existing contraints along their valid times, possibly given different granularities and with indeterminacy.

AIIM Journal 1999 Journal Article

Abstraction on clinical data sequences: an object-oriented data model and a query language based on the event calculus

• Carlo Combi
• Luca Chittaro

In this work, we deal with temporal abstraction of clinical data. Abstractions are, for example, blood pressure state (e. g. normal, high, low) and trend (e. g. increasing, decreasing and stationary) over time intervals. The goal of our work is to provide clinicians with automatic tools to extract high-level, concise, important features of available collections of time-stamped clinical data. This capability is especially important when the available collections constantly increase in size, as in long-term clinical follow-up, leading to information overload. The approach we propose exploits the integration of the deductive and object-oriented approaches in clinical databases. The main result of this work is an object-oriented data model based on the event calculus to support temporal abstraction. The proposed approach has been validated building the CARDIOTABS system for the abstraction of clinical data collected during echocardiographic tests.

TIME Conference 1997 Conference Paper

GCH-OSQL: A Temporally-Oriented Object-Oriented Query Language Based on a Three-Valued Logic

• Carlo Combi
• Giancarlo Cucchi

The need of managing temporal information given at different levels of granularity and indeterminacy is common to many application areas. Between them, we focus on the management of clinical data. Different time granularities are also needed in querying temporal databases. In this paper, we describe GCH-OSQL (Granular Clinical History-Object Structured Query Language), an object-oriented temporally-oriented extension of SQL. GCH-OSQL is based on an object-oriented temporal data model, named GCH-OODM. GCH-OODM allows storage of temporal information at different and mixed granularities. GCH-OSQL deals with the valid time of temporal data. The temporal extension of the SELECT statement includes the addition of the TIME-SLICE and MOVING WINDOW clauses, and the capability of referring to the temporal dimension of objects in the WHERE and SELECT clauses.

TIME Conference 1996 Conference Paper

Managing Time Granularity of Narrative Clinical Information: The Temporal Data Model TIME-NESIS

• Carlo Combi
• Francesco Pinciroli
• Giuseppe Pozzi

In the database field, the need of time management at different levels of granularity has been on for some years. It has been recently emphasized. Such a need is widespread when we have to manage medical clinical information. The temporal dimension is normally given at different granularities. In database systems based on the calendar time, granularity refers to uncertainty in specifying a temporal dimension as well as to use of different time-units. Thus, we need to set up modelling concepts and managing tools by which to establish temporal relationships between temporal clinical data. To manage the temporal dimension of data given at various and mixed levels of granularity, we defined the temporal data model TIME-NESIS (TIME in anamNESIS). The model provides temporal dimension to the data by using intervals that can be specified by different granularities. The model supports a three-valued logic, where True, False and Undefined are the truth values.