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In [[Graph (mathematics)|graph theory]], the '''modular decomposition''' is a decomposition of a [[Graph (mathematics)|graph]] into subsets of vertices called '''modules.'''  A module is a generalization of a [[Connected component (graph theory)|connected component]] of a graph.  Unlike connected components, however, one module can be a proper subset of another.  Modules therefore lead to a recursive (hierarchical) decomposition of the graph, instead of just a partition.
 
There are variants of modular decomposition for [[undirected graph]]s and [[directed graph]]s. For each undirected graph, this decomposition is unique.
 
This notion can be generalized to other structures (for example directed graphs) and is useful to design efficient algorithms for the recognition of some graph classes, for finding transitive orientations of [[comparability graph]]s, for [[Optimization (mathematics)|optimization problems]] on graphs, and for [[graph drawing]].
 
== Modules ==
 
As the notion of modules has been rediscovered in many areas, ''modules'' have also been called ''autonomous sets'', ''homogeneous sets'', ''intervals'', and ''partitive sets''.   Perhaps the earliest reference to them, and the first description of modular quotients and the graph decomposition they give rise to appeared in ([[Tibor Gallai|Gallai]] 1967).
 
A ''module'' of a graph is a generalization of a [[Connected component (graph theory)|connected component]]A connected component has the property that it is a set ''X'' of vertices such that every member of ''X'' is a [[Neighbourhood (graph theory)|non-neighbor]] of every vertex not in ''X''.  (It is a union of connected components if and only if it has this property.) More generally, ''X'' is a module if, for each vertex <math>v \not\in X</math>, either every member of ''X'' is a non-neighbor of ''v'' or every member of ''X'' is a neighbor of ''v''.
 
Equivalently, ''X'' is a module if all members of ''X'' have the same set of neighbors among vertices not in ''X''.
 
Contrary to the connected components, the modules of a graph are the same as the modules of its [[Complement graph|complement]], and modules can be "nested": one module can be a proper subset of another. Note that the set ''V'' of vertices of a graph is a module, as are its one-element subsets and the empty set;  these are called the '''trivial modules'''A graph may or may not have other modules.  A graph is called '''prime''' if all of its modules are trivial.
 
Despite these differences, modules preserve a desirable property of connected components, which is that many properties of the subgraph ''G[X]'' [[Glossary_of_graph_theory#Subgraphs|induced]] by a connected component ''X'' are independent of the rest of the graph.  A similar phenomenon also applies to the subgraphs induced by modules.
 
The modules of a graph are therefore of great algorithmic interest.  A set of nested modules, of which the modular decomposition is an example,  can be used to guide the recursive solution of many combinatorial problems on graphs, such as recognizing and transitively orienting [[comparability graph]]s, recognizing and finding permutation representations of [[permutation graph]]s, recognizing whether a graph is a [[cograph]] and finding a certificate of the answer to the question, recognizing [[interval graph]]s and finding interval representations for them, defining [[distance-hereditary graph]]s (Spinrad, 2003) and for [[graph drawing]] (Papadoupoulos, 2006).  They play an important role in Lovász's celebrated proof of the [[perfect graph theorem#Characterizations and the perfect graph theorems|perfect graph theorem]] (Golumbic, 1980).
 
For recognizing distance-hereditary graphs and [[circle graph]]s, a further generalization of modular decomposition, called the [[split decomposition]], is especially useful (Spinrad, 2003).
 
To avoid the possibility of ambiguity in the above definitions, we give the following formal definitions of modules.
<math>G = (V,E)</math>.
<math>M \subseteq V</math> is a '''module''' of <math>G</math> if:
* the vertices of <math>M</math> cannot be distinguished by any vertex in <math>V \backslash M</math>, i.e.
<math>\forall u,v \in M, \forall x\in V \backslash M</math>, either <math>x</math> is adjacent to both <math>u</math> and <math>v</math> or <math>x</math> is not adjacent to both <math>u</math> and <math>v</math>.
* the vertices of <math>M</math> have the same set of outer neighbors, i.e.
<math>\forall u,v \in M, N(u) \setminus M = N(v) \setminus M </math>.
 
<math>\emptyset</math>, <math>V</math> and all the [[Singleton set|singletons]] <math>\{v\}</math> for <math>v \in V</math> are modules, and are called '''trivial modules'''. A graph is '''prime''' if all its modules are trivial. [[connected component (graph theory)|Connected components]] of a graph <math>G</math>, or of its complement graph are also modules of <math>G</math>.
 
<math>M</math> is a '''strong module''' of a graph <math>G</math> if it does not overlap any other module of <math>G</math>:
<math>\forall M'</math> module of <math>G</math>, either <math>M \cap M' = \emptyset</math> or <math>M \subseteq M'</math> or <math>M' \subseteq M</math>.
 
== Modular quotients and factors ==
 
If <math>X</math> and <math>Y</math> are disjoint modules, then it is easy to see that either every member of <math>X</math> is a neighbor of every element of <math>Y</math>, or no member of <math>X</math> is adjacent to any member of <math>Y</math>.  Thus, the relationship between two disjoint modules is either ''adjacent'' or ''nonadjacent''No relationship intermediate between these two extremes can exist.
 
Because of this, '''modular partitions''' of <math>V</math> where each partition class is a module are of particular interest.  Suppose <math>P</math> is a modular partition.  Since the partition classes are disjoint, their adjacencies constitute a new graph, a '''quotient graph''' <math>G/P</math>, whose vertices are the members of <math>P</math>. That is, each vertex of <math>G/P</math> is a module of G, and the adjacencies of these modules are the edges of <math>G/P</math>.
 
In the figure below,   vertex 1, vertices 2 through 4, vertex 5, vertices 6 and 7, and vertices 8 through 11 are a modular partition. In the upper right diagram, the edges between these sets depict the quotient given by this partition, while the edges internal to the sets depict the corresponding factors.
 
The partitions ''{V}'' and  <math>\{\{x\}|x \in V\}</math> are the '''trivial modular partitions'''.  <math>G/\{V\} </math> is just the one-vertex graph, while <math>G/\{\{x\}|x \in V\}</math> = G.  Suppose <math>X</math> is a nontrivial module.  Then <math>X</math> and the one-elements subsets of <math>V \backslash X</math> are a nontrivial modular partition of <math>V</math>.  Thus, the existence of ''any'' nontrivial modules implies the existence of nontrivial modular partitions.  In general, many or all members of <math>P</math> can be nontrivial modules.
 
If ''P'' is a nontrivial modular partition, then ''G/P'' is a compact representation of all the edges that have endpoints in different partition classes of ''P''.  For each partition class ''X'' in ''P'', the subgraph ''G[X]'' induced by ''X'' is called a '''factor''' and gives a representation of all edges with both endpoints in ''X''.  Therefore, the edges of ''G'' can be reconstructed given only the quotient graph ''G/P'' and its factors. The term ''prime'' graph comes from the fact that a prime graph has only trivial quotients and factors.
 
When ''G[X]'' is a factor of a modular quotient ''G/P'', it is possible that ''G[X]'' can be recursively decomposed into factors and quotients.  Each level of the recursion gives rise to a quotient.  As a base case, the graph has only one vertex.  Collectively, ''G'' can be reconstructed inductively by reconstructing the factors from the bottom up, inverting the steps of the decomposition by combining factors with the quotient at each level.
 
In the figure below, such a recursive decomposition is represented by a tree that  depicts one way of recursively decomposing factors of an initial modular partition into smaller modular partitions.
 
A way to recursively decompose a graph into factors and quotients may not be unique.  (For example, all subsets of the vertices of a complete graph are modules, which means that there are many different ways of decomposing it recursively.) Some ways may be more useful than others.
 
== The modular decomposition ==
 
Fortunately, there exists such a recursive decomposition of a graph that implicitly represents all ways of decomposing it; this is the modular decompositionIt is itself a way of decomposing a graph recursively into quotients, but it subsumes all others. The decomposition depicted in the figure below is this special decomposition for the given graph.
 
[[File:ModularDecomposition.png|thumb|300px|A graph, its quotient where "bags" of vertices of the graph correspond to the children of the root of the modular decomposition tree, and its full modular decomposition tree: series nodes are labeled "s", parallel nodes "//" and prime nodes "p".]]
 
The following is a key observation in understanding the modular decomposition:
 
'''If ''X'' is a module of ''G'' and ''Y'' is a subset of ''X''''', then ''Y'' is a module of ''G'', if and only if it is a module of ''G[X]''.
 
In (Gallai, 1967), Gallai defined the modular decomposition recursively on a graph with vertex set ''V'', as follows:
 
# As a base case, if ''G'' only has one vertex, its modular decomposition is a single tree node.
# Gallai showed that if ''G'' is connected and so is its complement, then the maximal modules that are proper subsets of ''V'' are a partition of ''V''.  They are therefore a modular partition.  The quotient that they define is primeThe root of the tree is labeled a ''prime'' node, and these modules are assigned as children of ''V''.  Since they are maximal, every module not represented so far is contained in a child ''X'' of ''V''.  For each child ''X'' of ''V'', replacing ''X'' with the modular decomposition tree of ''G[X]'' gives a representation of all modules of ''G'', by the key observation above.
# If ''G'' is disconnected, its complement is connected. Every union of connected components is a module of ''G''. All other modules are subsets of a single connected component. This represents all modules, except for subsets of connected components. For each component ''X'', replacing ''X'' by the modular decomposition tree of ''G[X]'' gives a representation of all modules of ''G'', by the key observation above. The root of the tree is labeled a ''parallel'' node, and it is attached in place of ''X'' as a child of the root.  The quotient defined by the children is the complement of a complete graph.
# If the complement of ''G'' is disconnected, ''G'' is connected.  The subtrees that are children of ''V'' are defined in a way that is symmetric with the case where ''G'' is disconnected, since the modules of a graph are the same as the modules of its complementThe root of the tree is labeled a ''serial'' node, and the quotient defined by the children is a complete graph.
 
The final tree has one-element sets of vertices of ''G'' as its leaves, due to the base caseA set ''Y'' of vertices of ''G'' is a module if and only if it is a node of the tree or a union of children of a series or parallel node.  This implicitly gives all modular partitions of ''V''.  It is in this sense that the modular decomposition tree "subsumes" all other ways of recursively decomposing ''G'' into quotients.
 
==Algorithmic issues==
 
A data structure for representing the modular decomposition tree should support the operation that inputs a node and returns the set of vertices of G that the node represents. An obvious way to do this is to assign to each node a list of the ''k'' vertices of ''G'' that it represents.  Given a pointer to a node, this structure could return the set of vertices of ''G'' that it represents in ''O(k)'' timeHowever, this data structure would require <math>\Theta(n^2)</math> space in the worst case.
 
[[File:O n ModularDecompRep.pdf|thumb|An O(n) representation of the modular decomposition]]
 
An ''O(n)''-space alternative that matches this performance  is obtained by representing the modular decomposition tree using any standard ''O(n)'' rooted-tree data structure and labeling each leaf with the vertex of ''G'' that it represents.  The set represented by an internal node ''v'' is given by the set of labels of its leaf descendants.  It is well known that any rooted tree with ''k'' leaves has at most ''k-1'' internal nodes.  One can use a depth-first search starting at ''v'' to report the labels of leaf-descendants of ''v'' in ''O(k)'' time.
 
[[File:ModDecompQuotients.pdf|thumb|The modular decomposition, augmented with a quotient on the children of each internal node, gives a complete representation of ''G''.]]
 
Each node ''X'' is a set of vertices of ''G'' and, if ''X'' is an internal node, the set ''P'' of children of ''X'' is a partition of ''X'' where each partition class is a module.  They therefore induce the quotient ''G[X]/P'' in ''G[X]''.  The vertices of this quotient are the elements of ''P'', so ''G[X]/P'' can be represented by installing edges among the children of ''X''.  If ''Y'' and ''Z'' are two members of ''P'' and <math>u \in Y</math> and <math>v \in Z</math>, then ''u'' and ''v'' are adjacent in ''G'' if and only if ''Y'' and ''Z'' are adjacent in this quotient.  For any pair ''{u,v}'' of vertices of ''G'', this is determined by the quotient at children of the least common ancestor of ''{u}'' and ''{v}'' in the modular decomposition treeTherefore, the modular decomposition, labeled in this way with quotients, gives a complete representation of ''G''.
 
Many combinatorial problems can be solved on ''G'' by solving the problem separately on each of these quotients.  For example, ''G'' is a comparability graph if and only if each of these quotients is a comparability graph (Gallai, 67; Möhring, 85)Therefore, to find whether a graph is a comparability graph, one need only find whether each of the quotients is.   In fact, to find a [[comparability graph|transitive orientation]] of a comparability graph, it suffices to transitively orient each of these quotients of its modular decomposition (Gallai, 67; Möhring, 85).  A similar phenomenon applies for permutation graphs, (McConnell and Spinrad '94), interval graphs (Hsu and Ma '99), perfect graphs, and other graph classes.  Some important combinatorial optimization problems on graphs can be solved using a similar strategy (Möhring, 85).
 
[[Cograph]]s are the graphs that only have parallel or series nodes in their modular decomposition tree.
 
The first polynomial algorithm to compute the modular decomposition tree of a graph was published in 1972 (James, Stanton & Cowan 1972) and now linear algorithms are available (McConnell & Spinrad 1999, Tedder et al. 2007, Cournier & Habib 1994).
 
==Generalizations==
Modular decomposition of directed graphs can be done in linear time {{harv|McConnell|de Montgolfier|2005}}.
 
With a small number of simple exceptions, every graph with a nontrivial modular decomposition also has a [[skew partition]] {{harv|Reed|2008}}.
 
== References ==
*{{cite journal
  | last = Gallai | first = Tibor | authorlink = Tibor Gallai
  | title = Transitiv orientierbare Graphen
  | journal = Acta Mathematica Academiae Scientiarum Hungaricae
  | volume = 18
  | year = 1967
  | pages = 25–66
  | mr = 0221974
  | doi = 10.1007/BF02020961}}
*{{cite book
  | last1 = James | first1 = Lee O. | last2 = Stanton | first2 = Ralph G. | last3 = Cowan | first3 = Donald D.
  | contribution = Graph decomposition for undirected graphs
  | title = Proc. 3rd Southeastern International Conference on Combinatorics, Graph Theory, and Computing (Florida Atlantic Univ., Boca Raton, Fla., 1972)
  | publisher = [[Florida Atlantic University]]
  | year = 1972
  | pages = 281–290
  | mr = 0351909
}}
*{{cite book
  | last1 = Golumbic | first1=Martin C.
  | publisher = Academic Press
  | year = 1980
  | title = Algorithmic Graph Theory and Perfect Graphs
  | isbn = 0-444-51530-5}}
*{{cite journal
  | doi = 10.1137/S0097539792224814
  | last1 = Hsu | first1 = W.L. | last2 = Ma | first2 = T.
  | title = Fast and simple algorithms for recognizing chordal comparability graphs and interval graphs
  | journal = SIAM Journal on Computing
  | volume = 28
  | issue = 3
  | year = 1999
  | pages = 1004–1020}}
*{{cite journal
| last1 = McConnell | first1 = Ross M.
| last2 = de Montgolfier | first2 = Fabien
| doi = 10.1016/j.dam.2004.02.017
  | issue = 2
| journal = Discrete Applied Mathematics
| pages = 198–209
| title = Linear-time modular decomposition of directed graphs
| volume = 145
| year = 2005
| ref = harv}}
*{{cite journal
  | last1 = McConnell | first1 = Ross M. | last2 = Spinrad | first2 = Jeremy P.
  | title = Modular decomposition and transitive orientation
  | journal = [[Discrete Mathematics (journal)|Discrete Mathematics]]
  | volume = 201
  | year = 1999
  | pages = 189–241
  | url = http://www.cs.colostate.edu/~rmm/linto.pdf
  | mr = 1687819
  | doi = 10.1016/S0012-365X(98)00319-7}}
*{{cite journal
  | last1 = Möhring | first1 = Rolf H.
  | title = Algorithmic aspects of comparability graphs and interval graphs
  | journal = Graphs and Order
  | editor = I. Rival
  | publisher = D. Reidel
  | year = 1985
  | pages = 41–101}}
*{{cite journal
  | doi = 10.1007/BF02022041
  | last1 = Möhring | first1 = Rolf H.
  | title  = Algorithmic aspects of the substitution decomposition in optimization over relations, set systems and Boolean functions
  | journal = Annals of Operations Research
  | volume  = 4
  | year    = 1985
  | pages = 195–225}}
*{{cite book
  | last1 = Papadopoulos | first1 = Charis | last2 = Voglis | first2 = Constantinos
  | contribution = Drawing graphs using modular decomposition
  | title = [[International Symposium on Graph Drawing|Proc. 13th International Symposium on Graph Drawing (GD'05)]]
  | series = Lecture Notes in Computer Science
  | publisher = Springer-Verlag
  | volume = 3843
  | year = 2005
  | pages = 343–354
  | url = http://www.ii.uib.no/~charis/files/DrawModular.pdf
  | mr = 2229205
  | doi = 10.1007/11618058_31}}
*{{cite journal
| last = Reed | first = Bruce | authorlink = Bruce Reed (mathematician)
| doi = 10.1016/j.dam.2007.05.054
| issue = 7
| journal = Discrete Applied Mathematics
| mr = 2404228
| pages = 1150–1156
| title = Skew partitions in perfect graphs
| url = http://cgm.cs.mcgill.ca/~reedbook/papers/SkewPartitionsPerfectGraphs.pdf
| volume = 156
| year = 2008}}.
*{{cite book
  | last1 = Spinrad | first1=Jeremy P.  
  | series = Fields Institute Monographs
  | publisher = American Mathematical Society
  | year = 2003
  | title = Efficient Graph Representations
  | isbn = 0-8218-2815-0}}
*{{cite book
  | last1 = Tedder | first1 = Marc | last2 = Corneil | first2 = Derek | author2-link = Derek Corneil
  | last3 = Habib | first3 = Michel | last4 = Paul | first4 = Christophe
  | contribution = Simpler Linear-Time Modular Decomposition Via Recursive Factorizing Permutations
  | series = Lecture Notes in Computer Science
  | publisher = Springer-Verlag
  | volume = 5125
  | year = 2008
  | pages = 634–645
  | arxiv = 0710.3901
  | doi = 10.1007/978-3-540-70575-8_52
  | title = [[International Colloquium on Automata, Languages and Programming|Proc. 35th International Colloquium on Automata, Languages and Programming (ICALP 2008)]]}}.
 
== External links ==
* [http://www.lirmm.fr/~gambette/EnsDecompositionModulaireENG.php A bibliography of modular decomposition algorithms]
* A [[Perl]] [http://www.dns.net/dist/graph/ implementation of a modular decomposition algorithm]
* A Java [http://code.google.com/p/bpstruct/ implementation of a modular decomposition algorithm]
 
[[Category:Graph theory]]

Latest revision as of 23:22, 3 November 2013

In graph theory, the modular decomposition is a decomposition of a graph into subsets of vertices called modules. A module is a generalization of a connected component of a graph. Unlike connected components, however, one module can be a proper subset of another. Modules therefore lead to a recursive (hierarchical) decomposition of the graph, instead of just a partition.

There are variants of modular decomposition for undirected graphs and directed graphs. For each undirected graph, this decomposition is unique.

This notion can be generalized to other structures (for example directed graphs) and is useful to design efficient algorithms for the recognition of some graph classes, for finding transitive orientations of comparability graphs, for optimization problems on graphs, and for graph drawing.

Modules

As the notion of modules has been rediscovered in many areas, modules have also been called autonomous sets, homogeneous sets, intervals, and partitive sets. Perhaps the earliest reference to them, and the first description of modular quotients and the graph decomposition they give rise to appeared in (Gallai 1967).

A module of a graph is a generalization of a connected component. A connected component has the property that it is a set X of vertices such that every member of X is a non-neighbor of every vertex not in X. (It is a union of connected components if and only if it has this property.) More generally, X is a module if, for each vertex v∉X, either every member of X is a non-neighbor of v or every member of X is a neighbor of v.

Equivalently, X is a module if all members of X have the same set of neighbors among vertices not in X.

Contrary to the connected components, the modules of a graph are the same as the modules of its complement, and modules can be "nested": one module can be a proper subset of another. Note that the set V of vertices of a graph is a module, as are its one-element subsets and the empty set; these are called the trivial modules. A graph may or may not have other modules. A graph is called prime if all of its modules are trivial.

Despite these differences, modules preserve a desirable property of connected components, which is that many properties of the subgraph G[X] induced by a connected component X are independent of the rest of the graph. A similar phenomenon also applies to the subgraphs induced by modules.

The modules of a graph are therefore of great algorithmic interest. A set of nested modules, of which the modular decomposition is an example, can be used to guide the recursive solution of many combinatorial problems on graphs, such as recognizing and transitively orienting comparability graphs, recognizing and finding permutation representations of permutation graphs, recognizing whether a graph is a cograph and finding a certificate of the answer to the question, recognizing interval graphs and finding interval representations for them, defining distance-hereditary graphs (Spinrad, 2003) and for graph drawing (Papadoupoulos, 2006). They play an important role in Lovász's celebrated proof of the perfect graph theorem (Golumbic, 1980).

For recognizing distance-hereditary graphs and circle graphs, a further generalization of modular decomposition, called the split decomposition, is especially useful (Spinrad, 2003).

To avoid the possibility of ambiguity in the above definitions, we give the following formal definitions of modules. G=(V,E). MV is a module of G if:

  • the vertices of M cannot be distinguished by any vertex in VM, i.e.

u,vM,xVM, either x is adjacent to both u and v or x is not adjacent to both u and v.

  • the vertices of M have the same set of outer neighbors, i.e.

u,vM,N(u)M=N(v)M.

, V and all the singletons {v} for vV are modules, and are called trivial modules. A graph is prime if all its modules are trivial. Connected components of a graph G, or of its complement graph are also modules of G.

M is a strong module of a graph G if it does not overlap any other module of G: M module of G, either MM= or MM or MM.

Modular quotients and factors

If X and Y are disjoint modules, then it is easy to see that either every member of X is a neighbor of every element of Y, or no member of X is adjacent to any member of Y. Thus, the relationship between two disjoint modules is either adjacent or nonadjacent. No relationship intermediate between these two extremes can exist.

Because of this, modular partitions of V where each partition class is a module are of particular interest. Suppose P is a modular partition. Since the partition classes are disjoint, their adjacencies constitute a new graph, a quotient graph G/P, whose vertices are the members of P. That is, each vertex of G/P is a module of G, and the adjacencies of these modules are the edges of G/P.

In the figure below, vertex 1, vertices 2 through 4, vertex 5, vertices 6 and 7, and vertices 8 through 11 are a modular partition. In the upper right diagram, the edges between these sets depict the quotient given by this partition, while the edges internal to the sets depict the corresponding factors.

The partitions {V} and {{x}|xV} are the trivial modular partitions. G/{V} is just the one-vertex graph, while G/{{x}|xV} = G. Suppose X is a nontrivial module. Then X and the one-elements subsets of VX are a nontrivial modular partition of V. Thus, the existence of any nontrivial modules implies the existence of nontrivial modular partitions. In general, many or all members of P can be nontrivial modules.

If P is a nontrivial modular partition, then G/P is a compact representation of all the edges that have endpoints in different partition classes of P. For each partition class X in P, the subgraph G[X] induced by X is called a factor and gives a representation of all edges with both endpoints in X. Therefore, the edges of G can be reconstructed given only the quotient graph G/P and its factors. The term prime graph comes from the fact that a prime graph has only trivial quotients and factors.

When G[X] is a factor of a modular quotient G/P, it is possible that G[X] can be recursively decomposed into factors and quotients. Each level of the recursion gives rise to a quotient. As a base case, the graph has only one vertex. Collectively, G can be reconstructed inductively by reconstructing the factors from the bottom up, inverting the steps of the decomposition by combining factors with the quotient at each level.

In the figure below, such a recursive decomposition is represented by a tree that depicts one way of recursively decomposing factors of an initial modular partition into smaller modular partitions.

A way to recursively decompose a graph into factors and quotients may not be unique. (For example, all subsets of the vertices of a complete graph are modules, which means that there are many different ways of decomposing it recursively.) Some ways may be more useful than others.

The modular decomposition

Fortunately, there exists such a recursive decomposition of a graph that implicitly represents all ways of decomposing it; this is the modular decomposition. It is itself a way of decomposing a graph recursively into quotients, but it subsumes all others. The decomposition depicted in the figure below is this special decomposition for the given graph.

File:ModularDecomposition.png
A graph, its quotient where "bags" of vertices of the graph correspond to the children of the root of the modular decomposition tree, and its full modular decomposition tree: series nodes are labeled "s", parallel nodes "//" and prime nodes "p".

The following is a key observation in understanding the modular decomposition:

If X is a module of G and Y is a subset of X, then Y is a module of G, if and only if it is a module of G[X].

In (Gallai, 1967), Gallai defined the modular decomposition recursively on a graph with vertex set V, as follows:

  1. As a base case, if G only has one vertex, its modular decomposition is a single tree node.
  2. Gallai showed that if G is connected and so is its complement, then the maximal modules that are proper subsets of V are a partition of V. They are therefore a modular partition. The quotient that they define is prime. The root of the tree is labeled a prime node, and these modules are assigned as children of V. Since they are maximal, every module not represented so far is contained in a child X of V. For each child X of V, replacing X with the modular decomposition tree of G[X] gives a representation of all modules of G, by the key observation above.
  3. If G is disconnected, its complement is connected. Every union of connected components is a module of G. All other modules are subsets of a single connected component. This represents all modules, except for subsets of connected components. For each component X, replacing X by the modular decomposition tree of G[X] gives a representation of all modules of G, by the key observation above. The root of the tree is labeled a parallel node, and it is attached in place of X as a child of the root. The quotient defined by the children is the complement of a complete graph.
  4. If the complement of G is disconnected, G is connected. The subtrees that are children of V are defined in a way that is symmetric with the case where G is disconnected, since the modules of a graph are the same as the modules of its complement. The root of the tree is labeled a serial node, and the quotient defined by the children is a complete graph.

The final tree has one-element sets of vertices of G as its leaves, due to the base case. A set Y of vertices of G is a module if and only if it is a node of the tree or a union of children of a series or parallel node. This implicitly gives all modular partitions of V. It is in this sense that the modular decomposition tree "subsumes" all other ways of recursively decomposing G into quotients.

Algorithmic issues

A data structure for representing the modular decomposition tree should support the operation that inputs a node and returns the set of vertices of G that the node represents. An obvious way to do this is to assign to each node a list of the k vertices of G that it represents. Given a pointer to a node, this structure could return the set of vertices of G that it represents in O(k) time. However, this data structure would require Θ(n2) space in the worst case.

File:O n ModularDecompRep.pdf
An O(n) representation of the modular decomposition

An O(n)-space alternative that matches this performance is obtained by representing the modular decomposition tree using any standard O(n) rooted-tree data structure and labeling each leaf with the vertex of G that it represents. The set represented by an internal node v is given by the set of labels of its leaf descendants. It is well known that any rooted tree with k leaves has at most k-1 internal nodes. One can use a depth-first search starting at v to report the labels of leaf-descendants of v in O(k) time.

File:ModDecompQuotients.pdf
The modular decomposition, augmented with a quotient on the children of each internal node, gives a complete representation of G.

Each node X is a set of vertices of G and, if X is an internal node, the set P of children of X is a partition of X where each partition class is a module. They therefore induce the quotient G[X]/P in G[X]. The vertices of this quotient are the elements of P, so G[X]/P can be represented by installing edges among the children of X. If Y and Z are two members of P and uY and vZ, then u and v are adjacent in G if and only if Y and Z are adjacent in this quotient. For any pair {u,v} of vertices of G, this is determined by the quotient at children of the least common ancestor of {u} and {v} in the modular decomposition tree. Therefore, the modular decomposition, labeled in this way with quotients, gives a complete representation of G.

Many combinatorial problems can be solved on G by solving the problem separately on each of these quotients. For example, G is a comparability graph if and only if each of these quotients is a comparability graph (Gallai, 67; Möhring, 85). Therefore, to find whether a graph is a comparability graph, one need only find whether each of the quotients is. In fact, to find a transitive orientation of a comparability graph, it suffices to transitively orient each of these quotients of its modular decomposition (Gallai, 67; Möhring, 85). A similar phenomenon applies for permutation graphs, (McConnell and Spinrad '94), interval graphs (Hsu and Ma '99), perfect graphs, and other graph classes. Some important combinatorial optimization problems on graphs can be solved using a similar strategy (Möhring, 85).

Cographs are the graphs that only have parallel or series nodes in their modular decomposition tree.

The first polynomial algorithm to compute the modular decomposition tree of a graph was published in 1972 (James, Stanton & Cowan 1972) and now linear algorithms are available (McConnell & Spinrad 1999, Tedder et al. 2007, Cournier & Habib 1994).

Generalizations

Modular decomposition of directed graphs can be done in linear time Template:Harv.

With a small number of simple exceptions, every graph with a nontrivial modular decomposition also has a skew partition Template:Harv.

References

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    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

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    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
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  • 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

    My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
  • One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  • One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  • One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  • One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  • One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang
  • 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

    My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
  • One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

    In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

    Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

    Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

    A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

    The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

    There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang.
  • 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

    My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
  • 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

    My blog: http://www.primaboinca.com/view_profile.php?userid=5889534.