Chandrashekhar Khare

Jean-Pierre Wintenberger

INTERTWINING OF RAMIFIED AND UNRAMIFIED ZEROS OF IWASAWA MODULES

Introduction

Let F be a totally real field, p > 2 a prime, F ∞ ⊂ F (µ p ∞ ) the cyclotomic Z p -extension of F with Galois group Γ = Z p = γ . This short note is a sequel to [START_REF] Khare | Ramification in Iwasawa modules and splitting conjectures[END_REF]. The sole aim is to point out the ubiquity of a phenomenon dicussed in a particular case in our previous paper. Namely, the (arithmetic) eigenvalues of γ acting on Galois groups of maximal p-abelian unramified extensions of F (µ p ∞ ) intertwine with the eigenvalues acting on inertia subgroups of ramified p-abelian extensions of F (µ p ∞ ). We make this vague philosophy precise in the text below after alluding for mise-en-scène to the p-adic L-functions that lurk suggestively in the wings, but do not play an explicit role in the algebraic computations of this note.

Let ψ be an even Dirichlet character of F . Consider the p-adic L function ζ F,p (s, ψ) = L p (s, ψ), s ∈ Z p , which is characterised by the interpolation property L p (1-n, ψ) = L(1-n, ψω -n )Π v|p (1-ψω -n (v)N (v) n-1 ), for n ≥ 1 a positive integer. When ψ = 1, we denote the corresponding L-function by ζ F,p (s).

It is known that L p (s, ψ) is holomorphic outside s = 1, is holomorphic everywhere when ψ = 1, and otherwise has at most a simple pole at s = 1. This pole is predicted to exist by the conjecture of Leopoldt, which asserts the non-vanishing of the the p-adic regulator of units of F . The residue of ζ F,p at s = 1 has been computed by Pierre Colmez:

Res s=1 ζ F,p (s) = 2 d R F,p h F 2 √ D F ,
where R F,p is the p-adic regulator for F . The non-vanishing of R F,p is the Leopoldt conjecture for F and p.

We recall a folklore conjecture that is a very particular case of the general conjectures of Jannsen ([4]) about the non-vanishing of higher regulators. CK was partially supported by NSF grants. JPW is member of the Institut Universitaire de France.

1

As a supplement in the case m = 0, the case of "trivial zeros", the multiplicity of the zero at s = 0 of L p (s, ψ) is conjectured to be given by the number of v|p such that (1 -ψω -1 (v)) = 0.

We call the zeros of ζ F,p (s) unramified zeros following a similar usage in [START_REF] Wiles | The Iwasawa conjecture for totally real fields[END_REF].

The main conjecture of Iwasawa theory realises the zeros of the L-functions as roots of the characteristic polynomial of γ acting on "unramified arithmetic spaces". Nevertheless it gives no direct information about the zeros, belying the Hilbert-Polya philosophy in this case! Our basic observation, coming from [START_REF] Khare | Ramification in Iwasawa modules and splitting conjectures[END_REF] that we reinforce here, is that the unramified zeros (of the p-adic L-function) always intertwine with (the eigenvalues of γ acting on) ramification at p. Further the Leopoldt zeros, i.e. eigenvalues of Γ that correspond on a finite index subgroup to its action on p-power roots of unity, intertwine with ramification at Q, for finite sets of primes away from p, for a generic choice of Q.

This shows that the non-vanishing of p-adic regulators is equivalent to splitting of ramification in naturally occuring exact sequences of Iwasawa modules. The reader is referred to Theorems 4.2, 4.6 and 4.7 for precise statements.

The proofs of these theorems rely on numerical coincidences between -dimensions of certain Galois cohomology groups whose computation result from the work of Soulé and Poitou-Tate duality, -dimensions of Iwasawa modules that follow from theorems of Iwasawa describing the structure of inertia at p (resp. at a set Q of auxiliary primes) in the Galois group of the maximal odd abelian p-extension of F (µ p ∞ ) that is unramified outside p (resp. Q).

Galois cohomology

2.1. In our previous paper [START_REF] Khare | Ramification in Iwasawa modules and splitting conjectures[END_REF] we paid attention to integral questions, while here we work over Q p exclusively. We consider F a totally real field, an odd prime p. We consider a sufficiently large finite extension K of Q p with ring of integers O (that will contain values of the character under consideration).

Let S p be the set of places of F above p and ∞ and let S be a finite subset of places of F containing S p . Let G S be a Galois group of the maximal algebraic extension of F unramified outside S. We consider a potentially crystalline, or arithmetic, character χ of G S , of (parallel) weight m and thus of the form ηχ m p where χ p is the p-adic cyclotomic character, and η a finite order character. We impose that χ(c) is independent of the choice of complex conjugation c ∈ G F , and call it odd or even according as this value is either -1 or 1. We denote by ω the Teichmüller character. We consider the cohomology subgroup

H 1 (p)f (G S , K(ηχ m p )) of H 1 (G S , K(ηχ m p )) defined by imposing for v ∈ S, v /
∈ S p the condition to be unramified (although χ might be ramified at these v). We denote by H 1 f (G S , K(ηχ m p )) their Bloch-Kato subgroups, where for v primes over p, we impose the Bloch-Kato finiteness condition ( [START_REF] Bloch | L-functions and Tamagawa numbers of motives[END_REF]). We denote the dimensions over K of H 1 (p)f (G S , K(ηχ m p )) and

H 1 f (G S , K(ηχ m p )
) by h 1 (χ) and h 1 f (χ). We use h 1 split (χ) to denote dimensions of cohomology groups where we ask that the classes are split locally at all places above p and unramified at other primes. We have the tables.

2.2. Odd χ. χ = ηχ m p , χ odd m > 1 m = 1 m ≤ 0 h 1 (χ) d d + v|p h 0 (G v , η -1 ) -δ χ,χp d h 1 f (χ) d d -δ χ,χp 0
2.3. Even χ. χ = ηχ m p , χ even m > 1 m = 1 m ≤ 0 h 1 (χ) 0 v|p h 0 (G v , η -1 ) δ χ,id + h 1 split (χ p χ -1 ) h 1 f (χ) 0 0 0
Remark. The situation for even χ is thus not satisfactory as we do not have an explicit formula in all cases for h 1 (χ). The conjectures in [START_REF] Jannsen | On the -adic cohomology of varieties over number fields and its Galois cohomology[END_REF], concerning non-vanishing of higher p-adic regulators, predict the vanishing of h 1 split (χ p χ -1 ) for χ an even arithmetic character of G F (see also [START_REF] Bellaiche | An introduction to the conjecture of Bloch and Kato[END_REF] 5.2). This follows from the main conjecture of Iwasawa theory if the weight of χ is > 0.

Ingredients of the computation.

We justify the values in the tables. We need the following ingredients:

• (Bloch-Kato) h 1 f (χ) = dim K K(χ) G F + ord s=1-m L(η -1 , s) • (global duality) χ even: h 1 (χ) = h 1 split (χ p χ -1 ) + δ χ,id + v|p h 0 (G v , χ p χ -1 )
• (global duality) χ odd:

h 1 (χ) = d + h 1 split (χ p χ -1 ) -δ χ,χp + v|p h 0 (G v , χ p χ -1 )
The (global duality) equalities follow from Theorem 8.7.9. of [START_REF] Neukirch | Cohomology of Number fields[END_REF] and:

• (local Euler Poincaré characteristic) h 1 (G v , V ) = h 0 (G v , V ) + h 2 (G v , V ) + [F v : Q p ]dim K (V )
where v|p

• (local duality) h 0 (G v , V * (1)) = h 2 (G v , V )
The Bloch-Kato formula, which directly implies the bottom row of both tables, follows from a theorem of Soulé (Theorem 1 of [START_REF] Soulé | On higher p-adic regulators[END_REF]) and duality as we justify.

-The theorem of Soulé directly implies Bloch-Kato formula for h 1 f (χ) for m > 1.

-The case of m = 1 for the bottom rows follows from Kummer theory.

-We have the equality for m ≤ 0 and χ even:

h 1 f (χ) = h 1 f (χ p χ -1 ) -d + δ χ,id ,
and for m ≤ 0 and χ odd:

h 1 f (χ) = h 1 f (χ p χ -1
).

These equalities follow from Theorem 8.7.9 of [START_REF] Neukirch | Cohomology of Number fields[END_REF] and the fact that for m ≤ 0,

H 1 f (G v , χ) coincides with the unramified cohomology H 1 ur (G v , χ
). These two equalities allow us to deduce the case m ≤ 0 of the Bloch-Kato formula from the Theorem of Soulé (see also [START_REF] Bellaiche | An introduction to the conjecture of Bloch and Kato[END_REF], §4.3.1).

This checks the second rows of both the tables. Let us check the first row. For the first column in the case m > 1, we use the fact that

h 1 (G v , χ) = h 1 f (G v , χ).
The case m ≤ 0 even χ follows from (global duality) as h 0 (G v , χ p χ -1 ) = 0 for all v above p. For the case m = 1, we use global duality and that h 1 split (η -1 ) = 0 which follows easily from the fact that a Z p -extension of a number field has to be ramified at a place above p. For χ odd and m ≤ 0, we use global duality and the fact that

h 1 split (χ p χ -1 ) ≤ h 1 f (χ p χ -1 ) = 0.
2.5. Galois groups. We consider ε totally odd and ψ totally even finite order characters of G F , such that εψ = ω. We set ψ(n) = ψ(ω -1 χ p ) n := ψκ n , and likewise for ε(n). We consider characters ψ ζ of Γ that send a chosen generator γ of Γ to a p-power root of unity ζ and consider

ψ(n)ψ ζ , ε(n)ψ ζ .
We assume that ψ is of type S, i.e. we assume that the field F ψ cut out by ψ is linearly disjoint from the cyclotomic Z p -extension F ∞ of F . We denote by Γ the Galois group of F ∞ /F with choice of generator γ, consider Λ the completed group algebra Z p [[Γ]] that is isomorphic to Z p [[T ]] via the homomorphism which sends γ → 1 + T .

We let Λ K = Λ⊗K. We consider the Galois group

G ψ = G ε = Gal(F ψ (µ p )/F )× Gal(F ∞ /F ) of F ψ (µ p ∞ ) over F . A continuous character χ of G ψ with values in O * is
the product of a finite character χ ψ of Gal(F ψ (µ p )/F ) and a character χ Γ of Γ. The character χ Γ induces a K-algebra map Λ K → K. We denote by P χ the corresponding prime ideal of Λ K kernel of this map. It is generated by γ -χ(γ). The character χ ψ induces a morphism

f χ : Z p [Gal(F ψ (µ p )/F )] → O ⊂ K. The morphism Z p [[G ψ ]] → K induced by χ is the composite of the map Z p [[G ψ ]] → Λ K induced by f χ and the morphism Λ K → K.
We consider the maximal, abelian pro-p extension L ∞ of F ψ (µ p ∞ ) unramified everywhere: we denote its Galois group by X ∞ and set X ∞ = X ∞ ⊗ K. We set X ∞,ε to be the maximal quotient of X ∞ on which Gal(F ψ (µ p )/F ) acts by ε.

We also consider the analogous extensions L ∞,ε (Q) and corresponding Galois group X ∞,ε,Q when Q is any set of places of F and we allow ramification above Q. There are two natural cases to consider:

• Q is all the places above p, and then we replace Q by p in the notation; • Q is a finite set of places disjoint from the places above p.

Let F ψ,∞ be the cyclotomic Z p -extension of the totally real field F ψ . We denote by Y ∞ the Galois group of the maximal abelian prop-p extension of F ψ,∞ that is unramified outside p, and

Y ∞ = Q p ⊗ Y ∞ .
As above, we denote by Y ∞,ψ the related quotient on which Gal(F ψ (µ p )/F ) acs by ψ, and recall the perfect Γ-equivariant Iwasawa pairing

Y ∞,ψ × X ∞,ε → K(1).
Lemma 2.1. Let ψ be an even character of G F of type S and n ∈ Z.

(1) We have h

1 (ψ ζ ψ(n)) = dim K (Y ∞,ψ /P ψ ζ ψ(n) ) if ψ ζ ψ(n) is not trivial, and h 1 (ψ ζ ε(n)) = dim K (X ∞,ε,p /P ψ ζ ε(n) ). (2) We have that dim K ((X ∞,ε ) P ψ ζ ε(-n) /P ψ ζ ε(-n) ) = dim K ((Y ∞,ψ ) P ψ -1 ζ ψ(n+1) /P ψ -1 ζ ψ(n+1) ).
Proof. For (i) we use the inflation-restriction sequence relative to G S → G ψ .

Recall that the unramified condition for η ∈ H 1 (p)f (G S , K(εχ m p )) at v not above p and such that ψ is ramified at v (Section 2.1). We check that this condition is equivalent to that the restriction of η to the kernel of the map G S → G ψ is unramified at v.

For (ii), we invoke the pairing of Iwasawa. We use the cyclicity of Γ to identify dimensions of twisted invariants and covariants for Γ.

We rederive a standard result about trivial zeros of p-adic L-functions, usually proved using genus theory, which is a corollary to the lemma. Proposition 2.2. Suppose ε is an odd character of Gal(F ψ (µ p )/F ) as before. Then

dim K ((X ∞,ε ) P ψ ζ ε /P ψ ζ ε ) = h 1 (χ p ψ -1 ζ ε -1 ) = v|p h 0 (G v , ψ -1 ζ ε -1 ).
Proof. We deduce the first equality using (2) of Lemma 2.1 for n = 0 and the second equality using the above table for m = 1 even χ.

Note that v|p h 0 (G v , ψ -1 ζ ε -1
) is the number of places v|p such that the Euler factor (1 -ψ -1 ζ ε -1 (v)) is 0. It is conjectured by Greenberg that the trivial zeros occur semisimply i.e. dim K (X ∞,ε /P

ψ ζ ε ) = dim K (X ∞,ε ) P ψ ζ ε .

Main conjecture and higher regulators

We consider the Deligne-Ribet p-adic L-function ζ F,p (s, ψ) for an even character ψ of F of type S. It is defined on Z p when ψ is non-trivial, and on Z p \{1} when ψ is trivial. It is characterised by the interpolation formula that for integers n ≥ 1,

ζ F,p (1 -n, ψ) = L p (1 -n, ψω -n ),
where the superscript denotes that we have dropped the Euler factors at p. There is a power series W ψ (T ) in Λ K = Z p [[Γ]] ⊗ K (the latter by the isomorphism that sends a chosen generator γ of Γ = Gal(F ∞ /F ) to 1 + T and u := χ p (γ)), with the property that:

W ψ (u s -1) u 1-s -1 = ζ F,p (s, ψ)
when ψ is trivial, and

W ψ (u s -1) = ζ F,p (s, ψ)
otherwise. Furthermore we have :

W ψψ ζ (T ) = W ψ (ζ -1 (1 + T ) -1);
see the introduction of [START_REF] Wiles | The Iwasawa conjecture for totally real fields[END_REF], where the notation is G ψ (T ) for W ψ (u(1+T ) -1 -1).

Then the main conjecture asserts for characters ψ of type S that

(W ψ (T )) = char Λ K (X ∞,ψ -1 ω ),
i.e. the characteristic polynomial of the action of γ on the finite dimensional K-vector space X ∞,ε generates the same ideal as W ψ (T ). (We ignore µinvariants via this formulation.) When m is an integer = 0, Conjecture 1.1 is equivalent via the main conjecture to the statement that the generalised ζu m -eigenspace of X ∞,ψ -1 ω ⊗ Q p for the action of γ is trivial . When m = 0, via the main conjecture, we have that the generalised ζ-eigenspace is of dimension given by the number of v|p of

F such that (1 -ψ -1 ζ ε -1 (v)) = 0 4.
Intertwining of ramified and unramified zeros 4.1. Ramification at p. We consider the exact sequences:

0 → I Q → X ∞,ε,Q → X ∞,ε → 0,
of finitely generated Λ K -modules with Q = p (see 2.5).

Ramification at p and intertwining with non-trivial unramified zeros.

The next theorem follows from Th. 25 of [START_REF] Iwasawa | On Z -extensions of algebraic number fields[END_REF] :

Theorem 4.1.
We have an isomorphism of Λ K -modules

I p = {Λ d K ⊕ s j=1 Ind Γ G℘ j K(1)} K(1)
,

where G ℘ are the decomposition groups of the places ℘ above p in Γ.

We deduce from this and the computations in Galois cohomology earlier:

0 → (I p ) Pχ → (X ∞,ε,p ) Pχ → (X ∞,ε ) Pχ → 0,
of finitely generated Λ K -modules splits if and only if (X ∞,ε ) Pχ vanishes. This is equivalent to that ζ F,p (m, ψ -1 ζ ε -1 ω) = 0 when χ = χ p , and when χ = χ p , to that ζ F,p (s) has a pole at s = 1.

Proof. One direction is trivial. For the other direction, one notes by the theorem of Iwasawa that dim K ((I p ) Pχ /P χ ) is d if m = 1 and d+ v|p h 0 (G v , ε -1 )δ χ,χp if m = 1. We have the numerical coincidence : dim K ((I p ) Pχ /P χ ) = h 1 (χ).

Further one notes from Lemma 2.1 that h 1 (χ) = dim K (X ∞,ε,p ) Pχ /P χ . Thus if the exact sequence in the theorem splits, we deduce that (X ∞,ε ) Pχ /P χ = 0, which is equivalent to the vanishing of (X ∞,ε ) Pχ .

By the main conjecture proved by Wiles, the vanishing of (X ∞,ε ) Pχ /P χ is equivalent to the vanishing of W ψ at ζu m -1. It is equivalent to the vanishing of

ζ p (m, ψψ -1 ζ ) = ζ F,p (m, ψ -1 ζ ε -1 ω).
Remarks.

1. We also deduce that an equivalent formulation of the non-vanishing of the higher regulator conjecture is the conjecture that the exact sequence

0 → (I p ) Pχ → (X ∞,ε,p ) Pχ → (X ∞,ε ) Pχ → 0,
of finitely generated Λ K -modules splits for all odd arithmetic characters χ of G of non-zero weight.

2. As trivial zeros (in weight 0) do occur we get examples of Iwasawa modules in which ramification is allowed at p such that γ acts non-semisimply.

We have a conditional result for any character χ = εκ s of G ε not necessarily arithmetic, and that follows by similar arguments.

Proof. If Leopoldt conjecture is true, (X ∞,ω ) Pχ p = 0 and the exact sequence splits.

Let us prove the converse. For a finite dimensional vector space V over K endowed with a continuous action of G F that is unramified outside a finite set of places, and a set of Selmer conditions L = {L v } for L v ⊂ H 1 (F v , V ) where L v is outside a finite set of places the unramified subgroup, we have the formula :

h 1 L (F, V )-h 1 L ⊥ (F, V * (1)) = h 0 (F, V )-h 0 (F, V * (1))+ v (dim K L v -h 0 (F v , V )).
We apply this formula for V = K(1), and with the Selmer conditions L to be unramified everywhere. In particular the Selmer condition is trivial at places v above p V Iv = 0 for v above p. We get :

h 1 L (F, V ) -h 1 L ⊥ (F, V * (1)) = -1. Furthermore, we have h 1 L ⊥ (F, K) = 1 + δ. Consider the Selmer conditions L Q that arise when we allow ramification at Q, i.e., (L Q ) v = L v for v / ∈ Q and (L Q ) v = H 1 (G v , K(1)) for v ∈ Q. We get : h 1 L Q (F, V ) -h 1 L ⊥ Q (F, V * (1)) = -1 + r.
Furthermore, we have h 1

L ⊥ Q (F, K) = 1 + δ -r Q .
We see that :

h 1 L Q (F, K (1)
) = h 1 L (F, K(1)) + r -r Q . If the exact sequence splits, it remains exact after reduction modulo P χp , hence we have :

h 1 L Q (F, K (1)
) = h 1 L (F, K(1)) + r -1. Thus we get r Q = 1. As Q is generic and | Q |≥ 2, i.e., r Q = min(r, 1 + δ) with r ≥ 2, we get that 1 + δ = 1, thus δ = 0 and Leopoldt conjecture is true. Assume ε = ω or that ζ = 1. Then the sequence splits for all choices of primes q of F away from p, if and only if (X ∞,ε ) P ψ ζ εκ = 0.

Proof. We only sketch the proof as its very similar to the proof of Theorem 4.6.

By 2) of lemma 2.1, if (X ∞,ε ) P ψ ζ εκ = 0, the maximal abelian p-extension is unramified outside p, has Galois group that is of positive rank as a Z pmodule. Let q be a prime of F away from p, that splits in F ψψ -1

L of F ε -1 ψ -1 ζ ω = F ψψ

ζ

, such that the Frobenius at a prime above q of F ψψ ). With V = K(ψ ζ εκ) and the Selmer conditions as above, it follows that h 1 L ⊥ -h 1

L ⊥ q = 1.
Using the above formula, we get h 1 Lq -h 1

L ⊥ q -h 1 L + h 1 L ⊥ = 0.
If the exact sequence were to split, we would have h 1 Lq = h 1 L , which is a contradiction.

Conjecture 1 . 1 .

 11 (Non-vanishing of higher p-adic regulators) For an integer m = 0, L F,p (m, ψ) = 0 if either m = 1 or ψ = 1. Furthermore, ζ F,p (s) has a pole at s = 1.

Theorem 4 . 2 .

 42 Let χ = εψ ζ κ m be an odd arithmetic character of G ε of weight m, and let P χ be the corresponding prime ideal of Λ O for O such that χ is valued in O * . Then the exact sequence

4. 2 . 2 .

 22 Weight 1, ψ or ψ ζ non-trivial.

Theorem 4 . 7 .

 47 Consider the exact sequence0 → (I q ) P ψ ζ εκ → (X ∞,ε,q ) P ψ ζ εκ → (X ∞,ε ) P ψ ζ εκ → 0.

- 1 ζ

 1 on which Gal(F ψψ -1 ζ /F ) acts by ψψ -1 ζ and which

- 1 ζ

 1 is a non-torsion element in Gal(L/F ψψ -1 ζ

Proposition 4.3. Let χ = εκ s be any odd character of G ε . Assume further that H 1 split (G F,p , χ p χ -1 ) is trivial. Then the exact sequence 0 → (I p ) Pχ → (X ∞,ε,p ) Pχ → (X ∞,ε ) Pχ → 0, of compact finitely generated Λ K -modules splits if and only if (X ∞,ε ) Pχ = 0.

Remark: Note that the vanishing of H 1 split (G F,p , χ p χ -1 ) = 0 is predicted by Greenberg's conjecture that the p-part of the the class group of the cyclotomic Z p -extension F ∞ of F is finite. The above proposition suggests that there may be a formulation of the main conjecture using Ext Λ K (X ∞,ε , I p ).

The terminology is meant to reflect the fact that when δ > 0, the Frob q 1 , Frob q 2 will be linearly independent in Z 1+δ p = Gal(L ∞ /F ) for most choices of q 1 , q 2 . If r = 2 and we choose a prime q 1 freely, then for a density one set of primes q 2 , the set Q = {q 1 , q 2 } is generic.

We now show the intertwining of the Leopoldt zero u = u γ with the ramification at Q provided Q is a generic set of primes with |Q| > 1.

Proposition 4.5. Let Q be a finite set of primes of F away from p. Then the subgroup I Q of X ∞,ω,Q generated by the conjugacy class of the inertia groups

where G q is the decomposition subgroup at q in Γ = Gal(F ∞ /F ), and where we declare that Gal(F (µ p )/F ) acts by ω.

Proof. This follows from class field theory.

Note that when the primes q are inert in F ∞ /F then

splits if and only if (X ∞,ω ) Pχ p = 0, i.e., if and only if the Leopoldt conjecture is true.

Thus if there is a Leopoldt zero, then it intertwines with the ramified zeros at Q for a generic set of primes (away from p) with |Q| ≥ 2.


Erwan Flécher

Samir Amir
email: samir@ens.insa-rennes.fr2mbabel

Marie Babel

Olivier Déforges
email: odeforge@insa-rennes.fr

LAR VIDEO: Lossless Video Coding with Semantic Scalability

Baptized "LAR Video", method proposed in this paper describes a new lossless video coding algorithm with advanced semantic scalability. Motion estimation and compensation steps are first achieved to produce the well known displaced frame difference (DFD). The basic idea is to apply on this residual error a pyramidal decomposition based on an efficient scalable image compression technique, named LAR-APP. Resulting from a progressive data broadcasting, image-sequence can be scalably rebuilt in the decoder at different spatial resolution level. The given experimental results show that the proposed solution, in addition to the scalability, achieves good compression performances.

I. INTRODUCTION

Video coding is used by various applications requiring efficient and fast coding tools that allow high compression and low distorsion rate. These applications have to work with heterogeneous and time variable data network properties. To deal with this problem, a scalable video stream is commonly used [START_REF] Marquant | Représentation par maillage adaptatif déformable pour la manipulation et communication d'objets vidéo[END_REF]. Scalability defines compression algorithms that combine several processing levels [START_REF] Cammas | Codage vidéo scalable par maillages et ondelettes 2D[END_REF] in order to hierarchically describe the source. Low bit-rate video coding can be achieved with non-reversible tools. However, in some applications, resulting damages are unbearable especially in telemedicine and movies making context. Methods that combine both efficient lossless compression and scalability are still uncommon. In order to meet the requirement, a new scalable video coding algorithm, based on an efficient multiresolution approach for still image compression (LAR-APP) has been developped.

The LAR (Locally Adaptive Resolution) based on a variable block-size decomposition, leads to an efficient lossy image compression technique [START_REF] Déforges | Region of Interest Coding for Low Bit-Rate Image Transmission[END_REF]. Wrought on this coding assumption, three LAR-like pyramidal decomposition techniques namely LAR-APP [START_REF] Babel | Lossless and Lossy Minimal Redundancy Pyramidal Decomposition for Scalable Image Compression Technique[END_REF], Interleaved S+P [START_REF]Interleaved S+P Pyramidal Decomposition with Refined Prediction Model[END_REF] and RWHT+P [START_REF] Déforges | The RWHT+P for an improved lossless multiresolution coding[END_REF] followed it. Section II describes the LAR approach and pertinent features of the three succeeding approaches. Section III presents the foundation and the results of a lossless scalable video coder which takes advantage of the residual error coding by the LAR-APP. Finally, we conclude in section IV.

II. LOSSLESS LAR METHOD FOR STILL IMAGE A. Basic principle

Image can be represented as a superposition of a basic information and a local texture. Thus with the same scheme, a low bit rate image (basic information) can be transmitted with or without its additional error image. The LAR method is based on a two-layer coding that intrinsically gives at least two progressivity levels (Fig. 1). First stage of the image coding by LAR method is to generate a low resolution image (in terms of visual quality). This results in the construction of a locally-resolution image, determined by means of a quadtree data structure. Through this decomposition, the pixel size gives implicitly the nature of blocks: indeed, small ones are located on contours whereas large ones are situated on smooth areas. Now, let QP [Nmax..Nmin] represent the quadtree partition where N max and N min are respectively the upper and lower limit of square block size. Without the second layer, this coder clearly aims high compression ratio. The low bit-rate rebuilt image is visually acceptable thanks to quadtree partition that accommodates the variable block-size as a function of the original image context. For higher bit-rate, first stage is followed by a refinement layer that, if no quantification is applied, allows a lossless information compression. The semantic scalability property is enabled by a joint use of both the two-layer coding and the quadtree partitioning. This principle is heart of and was enriched by the following three scalable approaches.

B. Pyramidal approaches

LAR-APP [START_REF] Babel | Lossless and Lossy Minimal Redundancy Pyramidal Decomposition for Scalable Image Compression Technique[END_REF], Interleaved S+P [START_REF]Interleaved S+P Pyramidal Decomposition with Refined Prediction Model[END_REF] and RWHT+P [START_REF] Déforges | The RWHT+P for an improved lossless multiresolution coding[END_REF] are three methods for still images compression developped in our lab. They are unified algorithms of compression that combine prediction in a enriched context and scalability in terms of resolution and quality level. These methods take advantage of the two-layer LAR codec and add the multiresolution concept. The pyramidal decomposition is ordered by two successive descent processes. The first decomposition pass in the pyramid refines only small blocks located on contours and models homogeneous areas with larger blocks. The conditional spliting is illustrated by figure 2 [8..2] In this first pyramidal decomposition, semantic scalability is realised using grid information. The content-based local information increases the quality of the low bit-rate images which are rebuilt on each level of the pyramid. If the first decomposition intends to reconstruct the low resolution image (LAR-image), the second one processes the local texture information. All blocks at the current level which have not be encoded during the first pass are decomposed by the refinement layer.

Context modeling has become a key factor in lossless compression efficiency [START_REF] Said | An image multiresolution representation for lossless and lossy image compression[END_REF]. Global entropy can be reduced when different classes of symbols following the same law can be isolated. Our methods provide a straightforward separation of the laws at two different levels: block-sizes and decomposition level in each pass. Consequently, due to intrinsic property of our coder, an implicit context modelling is realised, leading to dramatically reduce the global entropy.

C. Decomposition methods

Previously we briefly explained the common working principles of the three pyramidal methods. The purpose of this section is to discuss their own way to reversibly split each block into four child-blocks. The scalable DPCM prediction of the LAR-APP method relies on successive descending processes that benefit from context-based information in the causal image (intra-level prediction) and the subsampled image (inter-level prediction). Contrary to LAR-APP, Interleaved S+P and RWHT+P methods work in a transform space which is more suitable to obtain high compression ratio. The main foundation of Interleaved S+P relies on a special implantation of S-Transform. Originality of this algorithm stands in its feature of efficiently predicting the transformation coefficients from two interleaved pyramids. The third method named RWHT+P, uses a reversible form of the formal Walsh Hadamard Transform applied on 2 × 2 blocks.

Interleaved S+P and RWHT+P are very efficient pyramidal solutions for lossless compression and outperform LAR-APP and states-of-the-art references CALIC [START_REF] Wu | A Context-based, Adaptive, Lossless/Nearly-Lossless Coding Scheme for Continuous-Tone Images (CALIC)[END_REF] and S+P [START_REF] Said | An image multiresolution representation for lossless and lossy image compression[END_REF]. In spite of that, because of its implementation simplicity, our video coder uses LAR-APP method for now. Results with better compression ratios utilizing Interleaved S+P and RWHT+P methods shall be reported in near future.

III. LOSSLESS LAR VIDEO CODING

In order to remove temporal redundancy between successive frames, both motion estimation and motion compensation are implemented in video coding standards. The common idea is to predict the current image by a motion compensated reference known to the decoder. A regular partition (MPEG-4) or a variable block-size decomposition (H.264 [START_REF] Ostermann | Video Coding with H.264/AVC: Tools, Performance, and Complexity[END_REF]) is first carried out. Then for each block, motion estimator seeks the best match in a reference image according to a similarity measure. The distance from the best-match block in the reference is represented by a motion vector that is coded and sent to the decoder. The difference between current and compensated image is usually named displaced frame difference (DFD) and has to be efficiently transmitted. In order to remove spatial redundancy, a transform is applied on this residual error. Commonly, tools used by video coding standard supply a robust compression but do not give an acceptable solution in the lossless coding context.

Joint use of the video coding scheme and the predictive pyramidal approach (section II) aims to meet two fundamental requirements. On one hand, a new algorithm with resolution and quality scalability is proposed. On the other hand, user has at his disposal a simple and unified solution for both lossless and lossy compression. Processing residual error with the LAR-APP method is the solution: a unique algorithm is used to perform in reversible and non-reversible manner (Fig. 3).

A. Motion estimation

Block matching algorithm (BMA) is a simple and efficient motion estimation method. Full search of the best matching provides optimal solution (in conformity with a similarity criterion) but proves to be very power consuming. Belonging to the zonal search family, EPZS (Enhanced Predictive Zonal Search) [START_REF] Tourapis | Enhanced predictive zonal search for single and multiple frame motion estimation[END_REF] overcomes this drawback with a priori knowledge of the block shift. Based on the blocks motion assessment in a causal neighbourhood and a motion reference memory, the displacement of the current block is predicted. Though DFD coding is already not precisely explained, it is nevertheless interesting to evaluate the influence of the motion model support on residual error entropic cost. Figure 4 illustrates the effect of the regular grid-size variation (block size: 16 × 16, 8 × 8 and 4 × 4) on the residual error coding by LAR-APP pyramidal approach. Resulting from lossless coding of Foreman image-sequence, mentioned entropies show that the best trade-off is given by a 8 × 8 block-size support.

Entropie de l'erreur pleine résolution par le LAR-AAP

Entropie des vecteurs de mouvement Naturally, the cost of decreasing DFD entropy with accurate prediction is the increased motion vector entropy. In the low bit-rate context, solutions similar to H.264 [START_REF] Ostermann | Video Coding with H.264/AVC: Tools, Performance, and Complexity[END_REF] approach, prove to be appropriate [START_REF] Zhang | Quadtree Structured Region-Wise Motion Compensation for Video Compression[END_REF]. Since there exists a trade-off between the costs of motion vectors and residual error, an optimal partition with variable block-size can be found. However in the reversible coding context, advantage provided by these methods, shall be mask in the error entropie dynamics. Consequently, adopted solution in our coder achieves a motion estimation on a grid of 8 × 8 block-size.

B. Residual error coding

In order to reap profit of the semantic scalability and the context modeling, quadtree partition (with spatial criterion) is here directly applied on images of the video sequence. Image partitioning and scalable decomposition of the bitstream can be described with a block diagram (Fig. 5). In accordance with the method described in section II, the lossless compression of the residual error is obtained by carrying out a full pyramidal decomposition. All blocks of the LAR grid are entirely split into the finest resolution. The coding with semantic scalability separates small blocks information and texture-based data. In this way, the first pass rebuilds an image with welldrawn contours. Thus global diagram defines for each pyramid level, a minimal block-size that conditions the decomposition process. Associated to QP [16..2] , the scheme (Fig. 5) shows this principle when the minimal block-size is equal to 2 n at pyramidal level n. Due to the similarity of evaluation process at the decoder, only inter/intra layer prediction errors are transmitted in a scalable bitstream. From the decoder point-of-view, reconstruction of the source image is a stage-work (Fig. 6). For each level of the pyramid, residual error is firstly decoded and added to the same-size compensated image. For this, pyramids of the compensated image and the residual error are formulated on the same base. Naturally, a coder with full scalability option requires a progressive stage of motion prediction/compensation. Though this step is not yet realised, somes applications can now be implemented. In the reversible context, pyramid has to be totally decoded in order to rebuild a lossless full resolution image. Therefore, browsing throught image-sequences at different resolution levels is one of our coder's functionalities. Through several exemples, we showed that its performances are encouraging for our futur works. In order to increase the compression ratio, a short aim is to substitute the LAR-APP by Interleaved S+P or RWHT+P method. Coding of the residual error with a pyramidal approach is not a sufficient condition to give our coder a global scalability. Thus, the second aim is to realise a method with full scalability which includes an hierarchical motion vectors coding.

LAR-APP decoding

Motion vectors

Fig. 1 .

 1 Fig. 1. Basic description of the LAR coder: two-layer coding

Fig. 3 .

 3 Fig. 3. Basic scheme of the lossless LAR video coder. N decomposition levels for the residual error compression by LAR-APP

Fig. 4 .

 4 Fig. 4. Effect of the motion model grid-size variation on the residual error coding by the lossless LAR-APP (Foreman sequence)

Fig. 5 .

 5 Fig. 5. Scalable coding of the residual error by the predictive pyramidal LAR-APP approach

Fig. 6 .Figure 7

 67 Fig. 6. Basic scheme of the lossless LAR video decoder. N decomposition levels for the residual error compression by LAR-APP

Fig. 7 .

 7 Fig. 7. (a) Progressive reconstruction of the source image from the pyramid of the residual error: lossless, full resolution: 3.80 bpp, level 1: 1.01 bpp, level 2: 0.37 bpp. Intermediate reconstruction from the residual error of the first pass: (b) error of the level 1 + interpolation (c) error of the level 1 + contours decomposition

  entropy of the residual error Entropy of the full resolution APP error

Fig. 8 .

 8 Fig. 8. Comparison between entropy of the lossless LAR-APP and the zero-th order entropy of the DFD on Football and MotherandDaughter sequences

  in which block-size devolves from 8 × 8 to 2 × 2.

	Level 3	Block 8x8 to be split
	Level 2	Block 4x4 to be split
	Level 1
	LAR Image	Quadtree Partition
	Blocks are splited into 4 child-blocks
	Blocks are copied out
	Fig. 2. Pyramidal decomposition of the LAR image conditionally to the
	quadtree partition QP

TABLE I INTRA

 I /INTER MODE COMPARISON OF THE LOSSLESS LAR-APP Figure 8 better describes the results presented in table I for Football and MotherandDaughter sequences. Both the zero-th order entropy of the DFD (named residual error in table) and that resulting from the lossless APP are showing in a temporal evolution context. Offering scalability function by level, LAR-APP also proves to be a efficient compression tool. IV. CONCLUSION Scalable video coder presented in this paper is an efficient solution for both lossless and lossy compression. Enriched


Jesús Díaz-Campo

Journalism ethics in a digital environment: How journalistic codes of ethics have been adapted to the Internet and ICTs in countries around the world

Keywords: journalism ethics, code of ethics, online journalism, the Internet, selfregulation Highlights

Journalism is facing new ethical issues because of the emergence of the Internet and Information and Communication Technologies (ICTs). In this article, we examine how journalistic codes of ethics have been updated to address this new reality. Three research questions are explored through a systematic analysis of 99 codes from around the world. Results show that, of the 99 codes analyzed, only 9 include references to the Internet and ICTs. We conclude with proposals for changes in the codes that would help journalists resolve these new moral issues.

Introduction

ICTs, in general, and the Internet, in particular, have created a fourth kind of journalism in addition to print, radio, and television journalism-the so-called cyber journalism, digital journalism, or online journalism. This new digital environment sets up a number of ethical dilemmas for journalists. While digital journalists still have the same dilemmas that journalists-and the journalism profession-have always faced, they now have some new dilemmas, as well.

The journalism process itself has changed radically, in fact, and we are in the middle of a changing media landscape [START_REF] White | The Ethical Journalism Initiative[END_REF]. We speak of a bidirectional process in which everyone may take part in producing and presenting the news. In another words, every individual becomes a potential publisher. This is only one of the several-and major-transformations that have taken place in journalism in recent years. Interactivity, hypertextuality, the use of multimedia, and immediacy are some of the main features of digital journalism, and each of these, of course, raises its own new ethical issues. As Evers (2001: 38) asks, -To what extent is a site owner legally or morally responsible for what is being posted?‖ (including anonymous comments). Is the site also responsible for links leading to offensive content? There are other new moral issues, as well, related to intellectual property, digital manipulation, and the process of gathering news and contrasting sources, for example, that stem from the use of multimedia and the need for immediacy.

So, the main question could be formulated as follows: are the current codes of ethics in journalism valid for the Internet, too? While there is agreement that the Internet has changed journalism, there is no consensus on the impact such changes have had [START_REF] Friend | Online journalism ethics[END_REF]. Consequently, responses to this question reveal two opposing points of view.

On the one hand, those who remember Belsey and Chadwick's statement (1994) that ethics and journalism are inseparable would argue that the existing ethical guidelines are equally effective for the new media. In other words, ethics is ethics-whether it is the new journalism or the old.

On the other hand, although the essence of journalism remains basically unchanged, it is obvious that the Internet "shapes and redefines a number of moral and ethical issues confronting journalists when operating online or making use of online resources," as Deuze and Yeshua (2001: 276) have stated.

There seems to be consensus that Deuze and Yeshua's statement is the most accurate; as many authors have pointed out [START_REF] Cooper | New Technology Effects Inventory: Forty Leading Ethical Issues[END_REF]Ess, 2008;[START_REF] Evers | New Moral Dilemmas in Online[END_REF][START_REF] Demir | Importance of Ethic, Credibility and Reliability in Online Journalism[END_REF][START_REF] García Capilla | From Postmodern Ethics to the New Ethics of the Me Generation: The Transition from Mass Media to the Internet[END_REF]Pavlik, 2001, Ward and[START_REF] Ward | Towards an Open Ethics: Implications of New Media Platforms for Global Ethics Discourse[END_REF]Whitehouse, 2010, among others), new media calls for new ethics because the issues online journalists are confronting are different from those that traditional journalists face. So, as Hayes, Singer, and Ceppos (2007, 275) remark, in the digital environment, -old assumptions about journalistic roles and values can no longer be accepted uncritically nor old approaches to them continued indefinitely.‖

In other words, new ethical issues require new ethical rules-or traditional ethical standards must be reformulated, at least. Journalists have met these challenges through self-regulation which, according to Evers (2001, 46), is -the only way to create online standards and to control the observation of moral rules.‖ According to Aznar (2005, pp. 13-14), the characteristics of this modality of regulation are 1) that its objective is to make effective use of or contribute to a particular activity's deontology, and 2) that it is created and sustained by the same agents who engage in that activity.

This second characteristic distinguishes self-regulation from legal regulation and, according to Mijatovic (2013, 5), represents one of its advantages in establishing rules of conduct for digital journalism: -self-regulation appears to be a solution to increase online accountability while offering more flexibility than state regulation.‖ Self-regulation is evidenced through a number of mechanisms, among which are deontological codes-documents that define the minimal expectations of moral activity, the ideal standards of conduct, and the accepted conventions of behavior [START_REF] Elliott-Boyle | A conceptual analysis of ethics codes[END_REF].

The codes set forth the principles that journalists, in keeping with their ethical conscience, must abide by as they carry out their work. As [START_REF] Bertrand | Media Ethics and Accountability Systems[END_REF] remarks, journalists around the world have found that, because the codes evidence a willingness to engage in self-regulation, they are an effective weapon against the threat of state intervention.

Even though the codes have sparked controversy on some occasions, a majority of academics and communications professionals still clamor for them because they are so effective [START_REF] Heinonen | Journalistic ethics in the age of net[END_REF].

Twenty years ago, Tina [START_REF] Laitila | Journalistic Codes of Ethics in Europe[END_REF] analyzed 30 journalistic codes of conduct in Europe, observing that most of them (21) had been adopted or revised in the 1990s. Laitila claims that the introduction of new information technologies-in addition to political changes, such as the fall of the Berlin wall and the European integration process-was one of the main reasons the journalism ethics debate was rekindled during those years. So, given the huge impact the Internet has had on the work of journalists, it would be interesting to know whether a similar debate has again surfaced and whether the emergence of digital journalism has translated to new ethical guidelines. Let us remember that, in terms of ethics, journalism has been among the most dubious professions in recent years. According to [START_REF] Mamonova | Area of activity of modern press councils in Europe[END_REF], most European press councils are actively involved with the Internet as well as print, radio, and television journalism.

So it was that, in an attempt to adapt self-regulation mechanisms and, more specifically, journalistic codes of ethics to that new reality, a working group organized in the United States by ASNE (American Society of Newspaper Editors) and the Poynter Institute drew up a new code of ethics in 1997 in which the following issues are addressed [START_REF] Mann | New Media‖ Bring a New Set of Problems[END_REF]:

1. Reliability of online content 2. Usage of database information 3. Linking 4. Editorial control of potentially hurtful or harmful content

Journalistic integrity and commercial pressure

The next question, then, would be: to what extent has the content of deontological codes around the world been adapted to the new digital scenario? This is a question that has been explored extensively with a focus on certain scenarios-for example, in the United States [START_REF] Whitehouse | Newsgathering and Privacy: Expanding Ethics Codes to Reflect Change in the Digital Media Age[END_REF], the Netherlands [START_REF] Deuze | Online Journalists Face new Ethical Dilemmas. Lessons from the Netherlands[END_REF], and Spain [START_REF] Ruiz | Una ética del ciberespacio o una ética en el ciberespacio? Análisis de los códigos de autoregulación de la profesión periodística[END_REF]-as well as in comparative studies of two countries [START_REF] Micó | La ética en el ejercicio del periodismo: credibilidad y autorregulación en la era del periodismo en internet[END_REF]. Until now, however, there has been no research of a global nature on this question. In contrast, in-depth studies on the current status and transformation of press councils have increased since the appearance of the Internet (Eberwein et al, 2011;Hulin & Stone, 2013).

Of all the research done on codes so far, probably the most ambitious is that of González Esteban et al (2011), which was conducted in Austria, Germany, Denmark, Estonia, Spain, France, and Poland; it examined other mechanisms, as well, such as press councils and the role of the ombudsman. These studies concluded that most of these countries lack any type of self-regulation mechanism for online journalism, in general, and all the initiatives that have appeared were spurred by individual media outlets.

No study to date, however, has systematically analyzed the degree to which journalistic codes around the world have been adapted to the new digital journalism reality. This study, therefore, seeks to determine the extent to which national journalistic codes of ethics have been adapted to the new online environment. To achieve this objective, we focused on three research questions: RQ 1. Are the codes most recently created and/or updated the ones that have the most Internet-related content in their articles?

As [START_REF] Laitila | Journalistic Codes of Ethics in Europe[END_REF] has pointed out, introduction of the new technologies was one of the driving forces behind an updating or reformulation of the codes of ethics in Europe during the 1990s. One objective of this study is to determine whether the continued development of these ICTs has been a driving force or a consideration in the updating of codes over the past decade, as well. RQ 2. What countries have modified their codes to the greatest extent in adapting them to the Internet's arrival?

Traditionally, countries in the West have been those most likely and among the first to develop the various self-regulation mechanisms, as several comparative studies have shown (in chronological order, [START_REF] Jones | Mass Media Codes of Ethics and Councils: A Comparative International Study on Professional Standards[END_REF][START_REF] Barroso | Principios fundamentales de deontología periodística[END_REF][START_REF] Villanueva | Códigos deontológicos de la prensa escrita en el mundo[END_REF][START_REF] Bertrand | Media Ethics and Accountability Systems[END_REF]Himelboim and Limor, 2008). So, another objective of this study is to examine whether this same pattern has been seen in the adaptation to digital journalism. RQ 3. What aspects of digital journalism and communications per se have the different countries incorporated into their codes?

The point of this question is to determine the extent to which elements specific to digital journalism have been integrated into their rules. What type of digital journalism-related content appears most frequently in the codes analyzed?

Material and methods

To conduct this study and achieve the stated objectives, codes that include standards pertaining to the Internet and to journalists' activity on the Internet were identified. In addition, the aspects of digital journalism governed by those codes were determined.

To be specific, 99 journalistic codes of ethics currently in force around the world were studied (see complete list in Appendix I). Two main sources were used:

EthicNet1 , a collection of deontological codes supported by the Department of Journalism and Mass Communication at the University of Tampere, and the database run by the Donald W. Reynolds Journalism Institute (RJI)2 . EthicNet and RJI list the names of all codes by their English translation.

Only generic codes used nationwide were included in the sample; regional or supranational codes were excluded. The sample also excluded thematic codes and self-regulation rules applicable only to certain topics or areas of journalism. So, codes like the Deontological Code from Catalonia (Spain), the Guidelines for News Embargoes from Belgium, and the Media and Sports Code from Italy, all of which can be found on the EthicNet website, were not included in the sample.

To find the codes that address digital journalism issues, a set list of terms (Table 1) was drawn up, and the entire text of the codes was searched for these terms. They were chosen on the basis of previous studies of a similar nature [START_REF] Deuze | Online Journalists Face new Ethical Dilemmas. Lessons from the Netherlands[END_REF]Hulin and Stone, 2013;[START_REF] Ruiz | Una ética del ciberespacio o una ética en el ciberespacio? Análisis de los códigos de autoregulación de la profesión periodística[END_REF] because they are terms used as synonyms for digital journalism (online, digital, or cyber journalism) or in referring to popular web features (site, website, email, social media, social networking sites) and services (Twitter, Facebook, etc.).

Results and discussion

According to the results of our study, only a small number of national journalistic codes of ethics include rules for online journalism. Of the 99 selfregulation codes included in the sample, those of only 9 countries mention the Internet and Information and Communication Technologies (ICTs): Bosnia and Herzegovina, Canada, Hungary, Luxembourg, the Netherlands, Norway, Poland, Romania, and the United Kingdom. In other words, 91% of codes around the world lack references to the digital landscape.

At the same time, only Canada's and Luxembourg's code-two of those nine codes-include a section on journalism and digital media, specifically. The remaining codes include different aspects of journalism and online activity in sections devoted to the key principles of professional deontology, such as the respect for privacy and the commitment to accuracy.

The considerations related to digital journalism that appear in the codes analyzed are primarily the management of user-generated content, the use of social media as vehicle and as source, and links to other websites.

The main trends found in these codes are discussed below.

General principles applicable to the online environment

Of the nine codes that make reference to these new forms of communication, seven of them (Albania, Cyprus, Hungary, the Netherlands, Poland, Romania, and the United Kingdom) mention the Internet, explicitly, as a medium they regulate, stating that online material enjoys the same rights and must comply with the same responsibilities as material in the traditional media. To what extent may journalists use messages that an individual-named or anonymous-posts on a social network? Clearly, then, this new paradigm raises particular issues that cannot be resolved simply by inserting adjectives into the existing traditional principles of ethics.

Mention of the Internet as a mass medium subject to the rights and ethical obligations addressed in the code constitutes the one and only reference to the online environment in the code of three countries: Hungary, Poland and Romania.

This fact implies that they consider new or specific rules for digital journalism to be unnecessary because all the generic rules for traditional media are directly adaptable to the new media. Under these three codes, then, digital journalists would be guided by the same general ethical principles as their colleagues in other media.

According to the Canadian code, blogging is a form of journalism subject to the same obligations as other content; it specifies that -The need for speed should never compromise accuracy, credibility or fairness. Online content should be reported as carefully as print content, and when possible, subjected to full editing.‖

This code places special emphasis on the accuracy of information and expressly prohibits the re-posting of rumors.

In contrast, other codes-the Norwegian code, for example-contain no statement whereby they take digital media, specifically, under their jurisdiction, although they do set rules for specific aspects of online journalism, as detailed later in this article.

Uses of social media

The Canadian code sums up several advantages that social networking sites offer journalists-providing an additional source, for instance. According to this code, -Journalists are increasingly using social networking sites to access information about people and organizations.‖

The code acknowledges that what individuals post on these networks loses its private message status and, generally speaking, allows these posts to be used as informative material: -When individuals post and publish information about themselves on these sites, this information generally becomes public, and can be used.‖ It also warns, however, that journalists must abide by certain rules for accessing messages on social networks, if their authors had no intention of making them public: -However, journalists should not use subterfuge to gain access to information intended to be private.‖ Likewise, even though the code stipulates that -We generally declare ourselves as journalists and do not conceal our identities, including when seeking information through social media‖, it adds that -journalists may go undercover when it is in the public interest.‖ Abiding by these stipulations in the Canadian code, a journalist would not be able to impersonate a third person or hack a user's account to access information. The code also instructs that -even when such information is public, we must rigorously apply ethical considerations including independent confirmation and transparency in identifying the source of information.‖ Under the Canadian code, using social networks to obtain information is subject to the same transparency obligations as traditional journalistic activity.

Within those considerations, the code makes special mention of children: -we take special care when reporting on children or those who are otherwise unable to give consent to be interviewed (…) we take special care when using any material posted to social media by minors, as they may not understand the public nature of their postings.‖

Linking

The use of links is another of the features unique to digital media and, as such, is addressed in the codes of Canada, Luxembourg, and Norway. These countries all concur in warning that the websites to which links point may be unreliable or fail to comply with ethical norms. Accordingly, the Norwegian code warns that -digital publication pointers and links could bring you to other electronic media that do not comply with the Ethical Code‖ and believes that users of the links must be informed that the links will direct them to other media: -See to it that links to other media or publications are clearly marked.‖

The Luxembourg code, in turn, states that journalists are obligated to confirm that the website they are creating a link to does not harbor illicit material: -Before proceeding to creating hyperlinks, the press agrees to verify that the sites concerned do not contain illicit material. If this is the case, the press shall refrain from creating any electronic link.‖ Likewise, the Canadian code states: -When we publish outside links, we make an effort to ensure the sites are credible; in other words, we think before we link.‖

User-generated content

The Internet has progressively facilitated the public's inclusion and participation in the communication process in such a way that user-generated content is ever more important. Comments was one of the early mechanisms through which the public could participate. The Dutch code has an entire section on -responses on websites,‖ according to which, the editorial office is ultimately responsible for the content appearing on the website, and although they -cannot be expected to check all these responses in advance,‖ they can decide to -remove previously placed responses.‖ In other words, this code requires that comments be moderated not beforehand but afterwards. The code stresses, in particular, that -If a response to an article on the website contains a serious accusation or a defamatory expression towards one or more known individuals, the editorial office, on the request of the person(s) involved, must investigate whether there are actual grounds for the accusation or allegation and, if this is not the case, remove the response.‖

To make this task easier for the editor, the Dutch code recommends that the website publish -the terms and conditions for selection and inclusion of responses.‖

This information lets users know what types of messages are acceptable and what

types will be filtered for violating ethical norms and could be deleted from the website.

The Norwegian code grants this authority and responsibility for deleting content in connection with digital chatting, as well, stating that -The editorial staff has a particular responsibility, instantly to remove inserts that are not in compliance with the Ethical Code.‖

There has also been controversy surrounding authorship and the right to quote material that users have uploaded to platforms like YouTube and Flickr. The Canadian code maintains that, in these cases, citing the website from which the material was obtained is not enough-the user who created the material must also be cited. -We try to obtain permission whenever possible to use online photos and videos, and we always credit the source of the material, by naming the author and where the photo or video was previously posted.‖ The code does not take into account, however, the possibility that an author might upload material under a pseudonym. It recommends, also, that user-created material be published solely with informative and not sensationalist zeal: -We use these photos and videos for news and public interest purposes only, and not to serve voyeuristic interests.‖

. Journalists' use of the Internet

Even though journalists' personal activity on the Internet is a thorny issue in the digital environment, only the Canadian code targets this for regulation. -Personal online activity, including emails and social networking, should generally be regarded as public and not private. Such activity can impact our professional credibility.‖ It recommends that -we take special caution in declaring our political leanings online." It is understood, then, that the perception of a journalist's independence could be damaged through his/her activity on Facebook and Twitter.

The Canadian code warns, moreover, that cyberactivism and civic engagement via social media could compromise the journalist's impartiality. It states: -As fair and impartial observers, we must be free to comment on the activities of any publicly elected body or special interest group. But we cannot do this without an apparent conflict of interest if we are active members of an organization we are covering, and that includes membership through social media.‖

Although the meaning of -active membership‖ here remains ambiguous, journalists are asked, further on in the text, to take into consideration their -political activities and community involvements-including those online-(…) if there is a chance we will be covering the campaign, activity or group involved.‖

The code suggests some ways to keep journalists' private online lives from being marred. -Our private lives online present special challenges. For example, the only way to subscribe to some publications or social networking groups is to become a member. Having a non-journalist subscribe on your behalf would be one solution, as would be joining a wide variety of Facebook groups so you would not be seen as favouring one particular constituency.‖

The code does acknowledge, however, that these services are useful not only as a source of information but also as a tool for establishing new contacts: -We encourage the use of social networks as it is one way to make connections, which is part of our core work as journalists.‖

Other aspects

The Internet affords the option to modify or delete content after it has been published. The Canadian code views these options as unlawful, however-even when it is at the request of the public or when the source of the information has requested it. The code stipulates, as the only exceptions, that this information may be deleted when it concerns -matters of public safety, an egregious error or ethical violation, or legal restrictions such as publication bans.‖ Furthermore, if corrections are made to -errors online, we indicate that the content has been altered or updated, and what the original error was.‖

The possibility of information available online being modified also has an impact on the reliability of the information sources and query tools to which journalists have access.

Conclusions

As this article has shown, the fact that a journalistic code of ethics has recently been adopted or updated is no guarantee that it will include rules for digital activity.

Since 2001, 31 codes have been written or revised, but only 9 of them have added specific references to the Internet and ICTs. In other words, in 22 instances of codes that were written or adapted in the twenty-first century, digital journalism was deemed not worth mentioning.

The 9 countries that do include references to it in their codes are in the West; so, as this type of document has been adapted to the new Internet reality, the historical pattern has continued, to some extent: in terms of journalistic selfregulation, countries in the West have always been the most advanced. Then again, there was one unexpected reality: many of the countries where the tradition of self-regulation is strongest-the United States and France, to name two-have not made the decision to modify their codes to adapt them to the Internet and ICTs.

Notable among the countries that have the most references to the Internet in their codes are Canada, the United Kingdom, and Norway.

The codes of ethics analyzed reflect an attitude toward the Internet and digital journalism that may be characterized, in short, as a widespread lack of interest and a lack of consistency. As pointed out earlier, in most of the 9 codes that do include references to ICTs, there is nothing more than a statement that online journalism is subject to the same principles as traditional journalism. There are no uniform trends as to how aspects specific to digital journalism are incorporated into the codes of ethics. Each country incorporates recommendations and isolated rules, stemming from the particularities of their national context, and there are hardly any themes or references that are common to all these codes. The only detectable trend is a concern about the website's and the journalist's responsibility with regard to creating links to other websites-an issue that, even so, is addressed in only 3 of the codes analyzed.

It seems reasonable, therefore, to suggest that an in-depth revision of the content of many of these codes is needed-like the revision accomplished 20 years ago [START_REF] Laitila | Journalistic Codes of Ethics in Europe[END_REF] and like the task undertaken by the Pew Project for Excellence in Journalism a few years ago (Kovach y Rosenstiel, 2003). Based on the testimony of more than 300 professionals and input from several public forums, that project attempted to redefine the existing basic principles upon which the practice of ethical and high-quality journalism should be founded. At that time, concentration of media ownership and sensationalism in content were the two primary incentives for reformulating the basic lines of consensus.

The point is that, even though many of these countries have written specific documents or guidelines to address digital journalism or some particular aspect of it (blogging, social media, etc.), the codes themselves also should be reformulated-for they are, after all, self-regulation's benchmark documents. This is exactly what happened back in the 1990s. Associations and/or press councils formulated a large number of recommendations to regulate very specific issues, such as publication of sensationalist content and news coverage on children, to mention two such issues-but that did not preclude a reformulation of the corresponding codes [START_REF] Laitila | Journalistic Codes of Ethics in Europe[END_REF]. In view of the advancement and consolidation of the Internet and ICTs, it only makes sense that something similar would happen now and the text of the codes would be revised in connection with tackling issues such as privacy, for example-an issue that, apart from the new technologies, is still handled in an archaic manner.

With reference to the ASNE and Poynter Institute criteria [START_REF] Mann | New Media‖ Bring a New Set of Problems[END_REF] mentioned at the beginning of this article, the conclusion is that the organizations responsible for adapting journalistic codes of ethics have not applied these criteria consistently. There are references, even though in a minority of cases, to four of the key established principles-reliability of online content, linking, editorial control of potentially hurtful or harmful content, and the uses of database information-and virtually no reference to the fifth-journalistic integrity and commercial pressure.

So, professional journalist organizations and associations around the world could work along these two lines when proceeding to update, as needed, the content of their codes of ethics. As we have seen, it is these very documents that set forth the standard moral criteria for all journalists. At the same time, however, they clearly define, for the public, the ground rules of the profession-a profession that will have a difficult time maintaining credibility, if those basic norms are obviously out-of-date and belong to a bygone reality.

Even though the ASNE and Poynter Institute criteria have not been applied consistently, it should be pointed out that, in the more than 15 years since those recommendations were made, the journalistic codes of ethics that did get updated an incentive for member countries of the organizations involved to undertake a similar revision of their own code.

  have incorporated other aspects of ICTs not addressed by the Poynter Institutefor instance, to mention only two examples, the use of information that users gather when accessing services on the web, and the function of social networks as a source for journalists. The pace at which new services and features are launched means that the Internet is a shifting reality that alters even the basic principles of traditional ethics, such as the respect for privacy: to what extent is a social network a public realm or a private realm?Journalist organizations around the world should try to keep pace with these changes, as best they can, and fine-tune the content and functioning of their selfregulation mechanisms to the new reality. One step in this direction that might be very useful would be to start revising some of the major supranational codes that were last updated many years ago now. The latest version of the International Federation of Journalists Code was approved in 1986; UNESCO's Principles of Professional Ethics in Journalism dates from 1983; and the European Code of Journalism Deontology dates from 1993. In theory, these revisions could serve as

Table 1 .

 1 Search terms used to locate self-regulation codes addressing issues related to

	Digital Journalism
	Blog	Chat
	Cyber	Database
	Digital	Email
	Facebook	Forum

Infographics Interactive Internet Link Online Site Social media Social networking sites Twitter Website

  Along the same line, the Canadian code-as assurance of media independencegrants the right to refuse to share unpublished material -such as notes and audio tapes of interviews, documents, emails, digital files, photos and video" with third parties. An exception to this rule could be made when -such sharing may be Adding the term -online‖ or -digital‖ to generic principles of journalistic ethics, however, does not resolve all ethical dilemmas that arise from this new journalism scenario. The United Kingdom Editors' Code of Practice may be cited as an example, for it stipulates, with regard to privacy, that -Everyone is entitled to respect for his or her private and family life, home, health and correspondence, including digital communications." This statement begs certain questions, however: would the use of social networks fall into the category of digital communications?

	necessary to check facts, gain the confidence of sources or solicit more
	information."
	material acquired by using hidden cameras or clandestine listening devices; or by
	intercepting private or mobile telephone calls, messages or emails‖ and that
	correspondence -including digital communications‖ must be respected.

For instance, the United Kingdom Editors' Code of Practice assures that -It is the responsibility of editors and publishers to apply the Code to editorial material in both printed and online versions of publications.‖ The Canadian code states that websites are another form of news organization, along with newspapers, magazines, radio, and television, and reminds us that -Ethical practice does not change with the medium.‖ Something similar happens with the British code's rules regarding privacy of communications. It reminds us that -The press must not seek to obtain or publish

  The Dutch code covers this point, stating that -The Internet, and search engines connected to it, has largely increased access to archive databases.‖ With regard to querying databases, this code states a preference for databases with archives that cannot be user-modified-as they can be on Wikipedia. Under this code, a Dutch journalist should not use this source, given that, -In principle, public interest in reliable archives, which are as complete as possible and the contents of which cannot be changed, outweighs any individual interest in removing or anonymizing archived articles, the contents of which may be displeasing to this individual. This socially important principle may be deviated from for reasons of private interest, in exceptional cases only.‖ Also, in a kind of self-referential way, the Luxembourg code speaks of the Internet as a vehicle to promote the visibility of the code itself, stating that -The Code is the object of a specific publication which will appear on the Internet site of the Press Council. This will also be the case of any update of the Code of

	Deontology.‖
	Another issue-this one related to privacy-is the gathering and use of users'
	personal information, normally through cookies or similar resources. The
	Norwegian code is the only one that addresses this issue, stating: -It is considered
	good press conduct to inform the users of interactive services on how the
	publication registers you, and possibly exploits your use of the services.‖ This code
	does not state that it is unlawful to collect such information but recommends that
	visitors to the website be informed as to what information is being gathered and
	how it will be used.
	Lastly, in the Bosnian code, the Internet is viewed as an additional tool to
	encourage and promote communication between media outlets and their public. It
	recommends that -every issue of each publication shall contain in an appropriate
	place the name, address, telephone, and if available, fax number and internet/e-
	mail address of the publisher and editor responsible to whom complaints can be
	addressed.‖

See http://ethicnet.uta.fi/ethicnet_collection_of_codes_of_journalism_ethics_in_europe

See http://www.rjionline.org/codes-ethics

Appendix I: List of Codes

Country Code Adopted/ Last revised in Albania Code of Ethics of Albanian Media 2006 Algeria Algerian Journalists' Charter of Personal and Professional Ethics 2000 Armenia Code of the Yerevan Press Club Member 2002 Australia Australian Journalists' Association Code of Ethics 1994 Austria Code of Ethics for the Austrian Press 1983 Azerbaijan Code of Professional Ethics for Journalists 2002 Bangladesh Press Council Code 2002 Belarus Journalists Ethics Code 1995 Belgium Code of Journalistic Principles 1982 Benin Press Code of Ethics 1999 Bosnia and Herzegovina Press Code of Bosnia and Herzegovina 2006 Brazil Code of Ethics of the National Federation of Brazilian Journalists 1987 Bulgaria Ethical Code of the Bulgarian Media 2004 Canada Canadian Association of Journalists Statement of Principles 2002 Colombia Code Of Ethics of the Journalists Circle of Bogota 1990 Democratic Republic of the Congo Code of Ethics of the Congolese Journalist 2004 Costa Rica Code of Ethics of the Journalists of Costa Rica 1991 Croatia Honour Codex of Croatian Journalists 2006 Cuba Code of Ethics of the Chilean Order of 1999 Appendix I Code of Ethics for Journalists in the Republic of Kazakhstan 1997 Kenya Code of Conduct for the Practice of Journalism in Kenya 2007 Kosovo Press Code for Kosovo 2005 Kyrgyzstan Code of the Association of Journalists of Kyrgyzstan 1999 Latvia Code of Ethics 1992 Liberia Code of Ethics of the Press Union of Liberia 1997 Lithuania Code of Ethics of Lithuanian Journalists and Publishers 2005 Luxembourg Code of Deontology 2004