Maciej Syslo

University of Wrocław | WROC ·  Instytut Informatyki

The first books in Polish about the Pascal programming language appeared in the late 1970s, and were soon followed by a Polish translation of Niklaus Wirth’s book Algorithms + Data Structures = Programs. At that time, many efforts were made to prepare teachers to teach informatics in schools, and Pascal was one of the topics taught, often with no a...

In this article we examine key issues and tensions for developing and specifying Computing-related elements of curricula design, particularly the role of Computer Science in the curriculum. The article is based on a series of discussions and analyses of curriculum design across various countries with different approaches and traditions of Computing...

In this paper we have examined the position and roles of Computer Science in curricula in the light of recent calls for curriculum change and we have proposed principles and issues to consider in curriculum design as well as identifying priority areas for further research. The paper is based on discussions within and beyond the International Federa...

The first regular informatics lessons in schools in Poland were organised in the second half of the 1960’. Some of them were devoted to programming a mainframe computer (in Wrocław) and some to theoretical models of computers and computations (in Warsaw). Then, for more than last 30 years of formal informatics education in Poland we have been very...

Computational thinking, as coined by Jeannette Wing, is a fundamental skill for all to be able to live in today's world, a mode of thought that goes well beyond computing and provides a framework for reasoning about problems and methods of their solution. It has a long tradition as algorithmic thinking which within computer science is a competence...

We discuss here a number of algorithmic topics which we use in our teaching and in learning of mathematics and informatics to illustrate and document the power of logarithm in designing very efficient algorithms and computations – logarithmic thinking is one of the most important key competencies for solving real world practical problems. We demons...

We consider algorithmics for the jump number problem, which is to generate a linear extension of a given poset, minimizing the number of incomparable adjacent pairs. Since this problem is NP-hard on interval orders and open on two-dimensional posets, approximation algorithms or fast exact algorithms are in demand. In this paper, succeeding from the...

A children's university in Poland is a popular, organized form of inviting young children to activities which are offered and run by academic teachers. We have been involved in such initiatives whose goal is to introduce children to some concepts in computer science. According to Piaget (see [1]), children before the age of seven, can think abstrac...

In this paper we discuss a number of results and advices coming from our observations and didactical experience gathered when teaching about recursion in different contexts and on various education level (K-12 and tertiary). Knowing the difficulty in introducing, explaining and using recursion, we differentiate our approach, tools, and methods. Rec...

The first regular informatics lessons in schools were organised in Poland in the second half of the 1960s. Some of the lessons in Wrocław were devoted to programming a mainframe computer located at the university, and school students in Warsaw had a chance to learn theoretical models of computers and foundations of computations. In the mid-1970s, t...

Regional Computer Science Course is a novel approach to increasing programming skills among secondary school students in Poland. It is fully based on distance learning and individual work of students after regular school hours. In this project the achievements of students were monitored on-line through weekly programming contests. The standardized...

In this paper, which is a continuation of our works on informatics education in Poland presented at previous ISSEP meetings [16-18], we focus on informatics for all high school students, a new subject introduced to schools in September 2012 by the education reform of 2008. In Section 2 we shortly characterize informatics education in high schools i...

In this paper we first identify the main factors which influence the students' attitudes to study computer science related disciplines. Then various outreach initiatives and activities implemented in Poland are described and discussed. They range from changes in the national curriculum for middle and high schools to formal and informal lectures, co...

In this paper, a learning and teaching framework is described which is aimed at increasing student interest in studying computer science as a discipline, or at least in better understanding how a computer and its tools work and can be used in solving problems which may occur in different areas. In the beginning of information education in Poland, i...

Informatics Education – Supporting Computational Thinking contains papers presented at the Third International Conference on Informatics in Secondary Schools – Evolution and Perspective, ISSEP 2008, held in July 2008 in Torun, Poland. As with the proceedings of the two previous ISSEP conferences (2005 in Klag- furt, Austria, and 2006 in Vilnius, Li...

The paper deals with a subfamily of those planar graphs which have outerplanar intersection of their MacLane cycle basis. These graphs have been known as Halin graphs. Their connectivity properties, structure of cycles, and feasible embeddings in the plane are discussed here. This paper also presents some initial investigations of NP-complete probl...

We give necessary and sufficient conditions for a graph to be a centroid of another one as well as of itself. Then, we apply these results to some particular classes of graphs: chordal, Halin, series-parallel and outerplanar.

The paper deals with bases of the vector space associated with a graph. Section 2 presents two characterizations of the cycle basis which can be derived from a spanning tree of a graph, and Section 3 contains the counterexamples for the conjecture of Dixon and Goodman. Finally, some new problems are posed.

The scheduling and planning of a project can be represented by two types of networks, namely, by the activity networks and the event networks. For each project, there exists a unique activity network without redundant (transitive) arcs but since there is an infinite number of different-sized event networks, the problem is to find an event network w...

In this paper we deal with the page number of partially ordered sets (posets). In particular, we find the page number of some N-free posets whose root graphs form a family of planar posets with known page number.

We present the first polynomial-time algorithm for the problem of subgraph isomorphism for two-connected series-parallel graphs, using a new decomposition technique. We also show that this problem is in random NC, and that it is in NC if the input graphs are of bounded valence.

In this paper we discuss a number of topics which are usually considered as a part of informatics education and we show how they can enhance substantially mathematics education. The presented problems may be used as a bridge between both school subjects which can integrate them and help to better understand mathematics and informatics and the relat...

In this paper we deal with the page number of partially ordered sets (posets). We provide a lower bound in the terms of the jump number and then study posets with page number 2.

The reform of the Polish national education system started in the school year 1999/2000. One of the main features of it is the plan to integrate Information and Communication Technology (ICT) into almost all school subjects. The second important feature is preparing students to use computers and software in other subjects during separate ICT lesson...

We discuss the role of computers and informatics in school education in Poland; ‘informatics’ generally stands for ‘computer science’. Although, our investigations are based on the situation in Polish schools, the conclusions may apply to other countries. The main attention is paid here to didactical approaches in teaching and learning informatics...

In this paper we focus on the role schools should play in lifelong learning and on the use of IT in school environment. We report on some activities in these directions taken in Polish schools and in the Polish education system in general. Full Text at Springer, may require registration or fee

serwisy/ti/ STRESZCZENIE Przedstawiamy tutaj propozycję działań na rzecz kształcenia przyszłych nauczycieli, przygotowy-wanych w zakresie technologii informacyjnej zgodnie ze standardami w tej dziedzinie, które moż-na krótko ująć w następujący sposób: po pierwsze, w szkołach ponadgimnazjalnych, ogólne przy-gotowanie informatyczne uczniów wyniesione...

We review the situation in Polish schools (at the beginning of 1999) with regard to the role computers and information technology play in the curriculum and in school activities. A separate school subject, elements of informatics (EI), has been a part of the curriculum in Poland for the last thirteen years. It has been taught in elementary schools...

This paper is a concise description of the history of computers and Computer Science in Poland (mostly in Warsaw and Wrocław) till 1975.

 An amalgam is obtained from two Halin graphs having skirting cycles of the same length. We are interested in hamiltonicity of amalgams constructed from two identical Halin graphs without any shift along the skirting cycle. We establish hamiltonicity of amalagams constructed from cubic Halin graphs. We give a sufficient condition for hamiltonicity...

The bandwidth of a graph G is the minimum of the maximum difference between adjacent labels when the vertices have distinct integer labels. We provide a polynomial algorithm to produce an optimal bandwidth labeling for graphs in a special class of block graphs (graphs in which every block is a clique), namely those where deleting the vertices of de...

We consider different plane embeddings of partial 2-trees and give an efficient algorithm constructing a minimum cardinality cover of faces, where each face is covered by exactly one vertex. These tasks are facilitated by a unique tree representation of plane embeddings of 2-trees.

In this paper, we consider the jump number problem on interval orders and use arc-diagram representations of posets to provide an approximation algorithm for the problem in this case. First, a complete characterization of arc-diagrams of interval orders is presented. Then, based on the properties of such representations, it is shown that semi-stron...

Two new types of greedy chains, strongly and semi-strongly greedy, in posets are defined and their role in solving the jump number problem is discussed in this paper. If a poset P contains a strongly greedy chain C then C may be taken as the first chain in an optimal linear extension of P. If a poset P has no strongly greedy chains then it contains...

A subset W of vertices of a plane graph is said to be a perfect face-independent vertex cover (FIVC) if and only if each face-boundary contains exactly one vertex from W. We characterize maximal outerplanar graphs admitting plane embeddings with perfect FIVCs.

The concept of a branch weight centroid has been extended in [12] so that it can be defined for an arbitrary finite setX with a distinguished familyC of "convex" subsets ofX. In particular, the centroid of a graphG was defined forX to be the vertex setV(G) ofG andU V(G) is convex if it is the vertex set of a chordless path inG. In this paper, which...

A cycle in a graph is dominating if every vertex lies at distance at most one from the cycle and a cycle is D-cycle if every edge is incident with a vertex of the cycle. In this paper, first we provide recursive formulae for finding a shortest dominating cycle in a Halin graph; minor modifications can give formulae for finding a shortest D-cycle. T...

A cycle in a graph is dominating if every vertex lies at distance at most one from the cycle and a cycle is D-cycle if every edge is incident with a vertex of the cycle. In this paper, first we provide recursive formulae for finding a shortest dominating cycle in a Halin graph; minor modifications can give formulae for finding a shortest D-cycle. T...

A notion of anin-tree is introduced. It is then used to characterize and count plane embeddings of outerplanar graphs. In-trees have also been applied in the study of independent vertex covers of faces in outerplanar graphs.

In recent years, a generally accepted measure of a discrete optimization problem's difficulty became a worst-case, asymptotic growth complexity characterization. Because of the anticipated at least exponential complexity of any solution algorithm for members in the class of ΝΡ-hard problems, restricted domains of problems' instances are being studi...

A subset W of vertices of a plane graph G is said to be a face-independent vertex cover (FIVC) if each face-boundary contains exactly one vertex of W. A FIVC naturally corresponds to a vertex-independent face cover (VIFC) in the dual graph G * of G. In this paper we review the results on the existence of such covers in arbitrary planar graphs and i...

In this paper we initiate study of a new poset invariant, the page number, well-known for graphs. Lower and upper bounds are derived and then they are used to evaluate and to bound the exact value of the page number for some families of posets. Several problems are posed.

We comment in this note on the relations between sequential coloring and the Welsh-Powell upper bound for the chromatic number of a graph.

A subset of vertics W and a planer graph G is a face-independent vertex cover (FIVC) if there exists a plane embedding of G such that each boundary contains exactly one vertex from W. In general, verifying if a plane graph admits a VIFC is an NP-complete problem. If G is a maximal planar graph, then the existence of a FIVC in G can be efficiently t...

We comment in this note on the relations between sequential coloring and the Welsh-Powell upper bound for the chromatic number of a graph.

First, Cogis and Habib (RAIRO Inform. Théor. 13 (1979), 3–18) solved the jump number problem for series-parallel partially ordered sets (posets) by applying the greedy algorithm and then Rival (Proc. Amer. Math. Soc. 89 (1983), 387–394) extended their result to N-free posets. The author (Order 1 (1984), 7–19) provided an interpretation of the latte...

A subset U of vertices of a plane graph is said to be a perfect face-independent vertex cover (FIVC) if and only if each face has exactly one vertex in U. Necessary and sufficient conditions for a maximal plane graph to have a perfect FIVC are derived. A notion of an in-tree is used to study plane embeddings of maximal outerplanar graphs (mops) and...

The spatial configuration of polymer molecules in an Euclidean space depends on the adjacency of their units. The configuration dependent properties of the so called Gaussian polymer molecules of different structures can be expressed in terms of graph-theoretical categories such as the number of spanning trees, path lengths, generalized inverses an...

This paper is a continuation of another author’s work [Order 1, 7-19 (1985; Zbl 0564.06001)], where arc diagrams of posets have been successfully applied to solve the jump number problem for N-free posets. Here, we consider arbitrary posets and, again making use of arc diagrams of posets, we define two special types of greedy chains: strongly and s...

A skirted tree can be obtained from a Halin graph by subdividing some of its interior edges. We characterize Hamiltonian skirted trees and those trees which can be interior trees of Hamiltonian skirted trees. Both characterizations are algorithmic and provide polynomial-time recognition algorithms for Hamiltonian skirted trees.

Outerplanar graphs have been recently generalized in many directions. Almost all generalizations have been introduced to parameterize the family of planar graphs so that in consequence some of the decision problems which are NP-complete for planar graphs and easy (or trivial) for outerplanar graphs can be solved in polynomial time for every fixed v...

We consider total digraphs of digraphs and present: (i) a structural characterization, (ii) an algorithmic characterization based on a labeling procedure, and (iii) an efficient recognition algorithm. The computational complexity of the algorithm is dominated by the complexity of finding the square of a Boolean (adjacency) matrix of a digraph.

The problems of finding values of the chromatic number and the chromatic index of a graph are NP-hard even for some restricted classes of graphs. Every outerplanar graph has an associated tree structure which facilitates algorithmic treatment. Using that structure, we give an efficient algorithm to color the vertices of an outerplanar graph with th...

The length of a cycle basis of a graph G is the sum of the lengths of its cycles. Let c - and c + be the minimum and maximum lengths among all the cycle bases of G. Then G has the cycle basis interpolation property (cbip) if for all integers c between c - and c +, there exists a cycle basis of length c.We specify which blocks satisfy c - = c + and...

In the late 1920s several mathematicians were on the verge of discovering a theorem for characterizing planar graphs. The proof of such a theorem was published in 1930 by Kazimierz Kuratowski, and soon thereafter the theorem was referred to as the Kuratowski Theorem. It has since become the most frequently cited result in graph theory. Recently, th...

A maximal outerplane graph (mop) is a plane embedding of a graph in which all vertices lie on the exterior face, and the addition of an edge between any two vertices would destroy this outerplanarity property. Removing the edges of the exterior face of a mop G results in the interior graph of G. We give a necessary and sufficient condition for a gr...

The purpose of this paper is to discuss the jump number problem for partially ordered sets (posets) using their arc representations, in which poset elements are assigned to arcs. We present the solution of the jump number problem restricted toN-free posets. The Hasse diagram of anN-free poset is a line digraph, so it has a unique root digraph which...

Series-parallel graphs play a significant role in the analysis and synthesis of electrical networks, communication networks, and switching circuits. On the other hand, due to their very tractable structure, a number of algorithmic problems which are NP-complete for arbitrary graphs can be efficiently solved for the special case of series-parallel g...

The purpose of this paper is to present a graph-theoretic approach to the jump number problem for N-free posets which is based on the observation that the Hasse diagram of an N-free poset is a line digraph. Therefore, to every N-free poset P we can assign another digraph which is the root digraph of the Hasse diagram of P. Using this representation...

A graph F is called middle if there exists a graph G such that there is a one-to-one correspondence between the vertices of F and the vertices and edges of G such that two vertices of F are adjacent if and only if the corresponding elements (considered as subsets of the set of vertices) have a non-empty intersection.In this paper we present a linea...

The paper deals with optimal methods for finding a minimum homeomorph and a minimum split of a digraph which are line digraphs. The algorithms may be used as approximate methods for finding a PERT network with the minimum number of dummy activities.

It has been shown recently that the traveling salesman (TS) problem on Halin graphs can be solved by a polynomial-time algorithm. The purpose of this paper is to discuss two problems which result from this special case of the TS problem. One of the problems is a special case of the set-partitioning ( SP ) problem in which a set family consists of t...

This paper deals with the subgraph isomorphism problem for outerplanar graphs (SUBOUTISOM). In general, since trees and forests are outerplanar, SUBOUTISOM is NP-complete. We show that SUBOUTISOM remains NP-complete even when the strongest connectivity requirements are imposed on both graphs. The same results holds for the induced subgraph isomorph...

This paper contains the solution of the bandwidth problem for caterpillars. The method applied makes use of some lower bounds to the bandwidth of a graph in terms of subgraphs and their sizes and diameters. We introduce also several types of critical subgraphs related to the bandwidth problem and describe some of their properties.

In this short note we present a very efficient, linear time algorithm for the recognition of line digraphs. The algorithm is based on a reformulation of the characterization of line digraphs proved by Harary and Norman.

We prove that there exists a one-to-one correspondence between the spanning trees and the fundamental cycle sets of a graph G if and only if G is 3-edge connected. Then we define a fundamental cycle set graph and prove that such a graph is a tree graph. It follows, therefore, that every fundamental cycle set graph on at least three vertices is Hami...

The purpose of this note is to prove a counterpart of the Helly property for a family of non-trivial intervals on a tree.

All known cycle vector space algorithms for listing cycles of a graph are inefficient, and in the worst case they compute all vectors of the cycle space. This is a very significant drawback of the cycle space approach. In this paper, a cycle vector space algorithm for enumerating all cycles of a planar graph, which produces only cycles of a graph a...

Adominating cycle of a graph lies at a distance of at most one from all the vertices of the graph. The problem of finding the minimum size of such a cycle is proved to be difficult even when restricted to planar graphs. An efficient algorithm solving this problem is given for the class of two-connectedouterplanar graphs, in which all vertices lie o...